Question about matching transformer (9:1 un-un)
 

Can the venerable 9:1 matching transformer (for matching a 500-ohm
random wire to a 50-ohm coaxial cable) also be used the inverse way,
that is, to match an incoming 50-ohm coax to a radio whose only
connection is a Hi-Z pair of screw terminals?

Further on, is there any reason why such a matching transformer could
not be installed inside said radio behind the screw terminal strip so
that a permanent SO-239 could be connected and mounted on the radio
chassis?

Thanks,
Bruce Jensen

Question about matching transformer (9:1 un-un)
 

bpnjensen wrote:
Can the venerable 9:1 matching transformer (for matching a 500-ohm
random wire to a 50-ohm coaxial cable) also be used the inverse way,
that is, to match an incoming 50-ohm coax to a radio whose only
connection is a Hi-Z pair of screw terminals?

Further on, is there any reason why such a matching transformer could
not be installed inside said radio behind the screw terminal strip so
that a permanent SO-239 could be connected and mounted on the radio
chassis?

Thanks,
Bruce Jensen

The improvement would be minimal.

Question about matching transformer (9:1 un-un)
 

On 1/23/10 01:28 , bpnjensen wrote:
Can the venerable 9:1 matching transformer (for matching a 500-ohm
random wire to a 50-ohm coaxial cable) also be used the inverse way,
that is, to match an incoming 50-ohm coax to a radio whose only
connection is a Hi-Z pair of screw terminals?

Further on, is there any reason why such a matching transformer could
not be installed inside said radio behind the screw terminal strip so
that a permanent SO-239 could be connected and mounted on the radio
chassis?

Thanks,
Bruce Jensen



A transformer impedance ratio is a function of the turns ratio
and the terminating impedances on each side. As long as the
impedances being transformed are the same ratio and the number of
turns on the core are the same ratio, the transformer doesn't care
one way or the other which direction it's used. So, there's no
reason you can't use a 9:1 in an inverse manner. Mounting it
internally, with proper care to minimize coupling to other hardware
within the receiver will work correctly.

The only consideration worth mentioning, is that a random wire
isn't exactly a 500 ohm impedance. Impedance of a random wire
changes with frequency. The 9:1 un-un is used to even those
variations out, more or less, to an impedance that's reasonably
uniform across the spectra in use for the receiver input to accept.

The application you're suggesting isn't going to have those
variations, and the 9:1 ratio is fairly close to the actual
impedance ratios being applied. Most screw terminal inputs are
actually closer to 300 ohm, and may or may not be balanced. And
radios so equipped, which also have a 50 ohm SO-239 are also
impedance matched from the S0-239 to the front end of the receiver
through a transformer, precisely as you describe.

So, with reservations, the answer to your questions a yes,
you can do it. And, no, there's no reason why you can't mount
internally.

The only reservations being that the impedances being
transformed are not precisely in the exact ratio as designed for the
9:1, which may result in irregular losses, and resonances--
comb filtering. Which you may or may not be able to discern in
casual listening.

Question about matching transformer (9:1 un-un)
 

On Jan 23, 5:06*am, "D. Peter Maus"
wrote:
On 1/23/10 01:28 , bpnjensen wrote:

Can the venerable 9:1 matching transformer (for matching a 500-ohm
random wire to a 50-ohm coaxial cable) also be used the inverse way,
that is, to match an incoming 50-ohm coax to a radio whose only
connection is a Hi-Z pair of screw terminals?

Further on, is there any reason why such a matching transformer could
not be installed inside said radio behind the screw terminal strip so
that a permanent SO-239 could be connected and mounted on the radio
chassis?

Thanks,
Bruce Jensen

* *A transformer impedance ratio is a function of the turns ratio
and the terminating impedances on each side. As long as the
impedances being transformed are the same ratio and the number of
turns on the core are the same ratio, the transformer doesn't care
one way or the other which direction it's used. So, there's no
reason you can't use a 9:1 in an inverse manner. Mounting it
internally, with proper care to minimize coupling to other hardware
within the receiver will work correctly.

* *The only consideration worth mentioning, is that a random wire
isn't exactly a 500 ohm impedance. Impedance of a random wire
changes with frequency. The 9:1 un-un is used to even those
variations out, more or less, to an impedance that's reasonably
uniform across the spectra in use for the receiver input to accept.

* * The application you're suggesting isn't going to have those
variations, and the 9:1 ratio is fairly close to the actual
impedance ratios being applied. Most screw terminal inputs are
actually closer to 300 ohm, and may or may not be balanced. And
radios so equipped, which also have a 50 ohm SO-239 are also
impedance matched from the S0-239 to the front end of the receiver
through a transformer, precisely as you describe.

* * So, with reservations, the answer to your questions a yes,
you can do it. And, no, there's no reason why you can't mount
internally.

* * The only reservations being that the impedances being
transformed are not precisely in the exact ratio as designed for the
9:1, which may result in irregular losses, and resonances--
comb filtering. Which you may or may not be able to discern in
casual listening.

Ah, thanks for this Peter - so, if the screw terminals are closer to
300 ohms, then a 6:1 transformer, with perhaps a 2.3:1 turns ratio,
could be a better choice?

The radio in question, BTW, is a simple DX-160 - it's front end is
pretty wide open anyway, but heck, why not? As long as I don't send a
big static charge through it, I figure I cannot do much damage :-)

BJ

Question about matching transformer (9:1 un-un)
 

On Jan 23, 4:59*am, dave wrote:
bpnjensen wrote:
Can the venerable 9:1 matching transformer (for matching a 500-ohm
random wire to a 50-ohm coaxial cable) also be used the inverse way,
that is, to match an incoming 50-ohm coax to a radio whose only
connection is a Hi-Z pair of screw terminals?

Further on, is there any reason why such a matching transformer could
not be installed inside said radio behind the screw terminal strip so
that a permanent SO-239 could be connected and mounted on the radio
chassis?

Thanks,
Bruce Jensen

The improvement would be minimal.

Well, that might be true - but if the noise could be reduced at all,
it would be worth it. I live in a VERY noisy place.

Bruce Jensen

Question about matching transformer (9:1 un-un)
 

On 1/23/10 12:14 , bpnjensen wrote:
On Jan 23, 5:06 am, "D. Peter
wrote:
On 1/23/10 01:28 , bpnjensen wrote:

Can the venerable 9:1 matching transformer (for matching a 500-ohm
random wire to a 50-ohm coaxial cable) also be used the inverse way,
that is, to match an incoming 50-ohm coax to a radio whose only
connection is a Hi-Z pair of screw terminals?

Further on, is there any reason why such a matching transformer could
not be installed inside said radio behind the screw terminal strip so
that a permanent SO-239 could be connected and mounted on the radio
chassis?

Thanks,
Bruce Jensen

A transformer impedance ratio is a function of the turns ratio
and the terminating impedances on each side. As long as the
impedances being transformed are the same ratio and the number of
turns on the core are the same ratio, the transformer doesn't care
one way or the other which direction it's used. So, there's no
reason you can't use a 9:1 in an inverse manner. Mounting it
internally, with proper care to minimize coupling to other hardware
within the receiver will work correctly.

The only consideration worth mentioning, is that a random wire
isn't exactly a 500 ohm impedance. Impedance of a random wire
changes with frequency. The 9:1 un-un is used to even those
variations out, more or less, to an impedance that's reasonably
uniform across the spectra in use for the receiver input to accept.

The application you're suggesting isn't going to have those
variations, and the 9:1 ratio is fairly close to the actual
impedance ratios being applied. Most screw terminal inputs are
actually closer to 300 ohm, and may or may not be balanced. And
radios so equipped, which also have a 50 ohm SO-239 are also
impedance matched from the S0-239 to the front end of the receiver
through a transformer, precisely as you describe.

So, with reservations, the answer to your questions a yes,
you can do it. And, no, there's no reason why you can't mount
internally.

The only reservations being that the impedances being
transformed are not precisely in the exact ratio as designed for the
9:1, which may result in irregular losses, and resonances--
comb filtering. Which you may or may not be able to discern in
casual listening.

Ah, thanks for this Peter - so, if the screw terminals are closer to
300 ohms, then a 6:1 transformer, with perhaps a 2.3:1 turns ratio,
could be a better choice?


That would be my thinking. Experimentation is the lifeblood of
the hobby, so I'd try it either way see what you get.



The radio in question, BTW, is a simple DX-160 - it's front end is
pretty wide open anyway, but heck, why not? As long as I don't send a
big static charge through it, I figure I cannot do much damage :-)

BJ


DX-160 is a pretty interesting radio to toy with. I've had two,
now, with dramatic inconsistencies in performance. Some, here, have
done extensive numbers of small modifications and gotten a pretty
decent radio out of it, so the raw material is there.

The front end of DX-160 is going to be close, but not really at,
any standard impedance. And it varies significantly from unit to
unit. It's very likely the scenario you first described in your
original post will be more than sufficient. Trial and error will get
you on target, but the practical differences in performance may be
trivial.

Question about matching transformer (9:1 un-un)
 

bpnjensen wrote:
[...]

The radio in question, BTW, is a simple DX-160 - it's front end is
pretty wide open anyway, but heck, why not? As long as I don't send a
big static charge through it, I figure I cannot do much damage :-)

BJ


I had a DX-150A in the early 1970s, and if I recall correctly, it
had an "antenna trim" control to peak up the input network for
maximum signal. The DX-160 may be the same -- the differences were
minimal, as I remember.

The trim adjustment would help match varying impedances to some
extent, but there could be cases where an input transformer would
help even more -- with a random impedance antenna on a wide range of
frequencies, it's hard to predict without making measurements.

Transformers work both ways, so one could add a switch for 1)
impedance step-up, 2) impedance step-down, and 3) direct connection.
Of course, an antenna coupler is another possible way to approach
the impedance issue.




With all good wishes,



Kevin, WB4AIO.
--
http://kevinalfredstrom.com/

Question about matching transformer (9:1 un-un)
 

On Jan 23, 2:09*pm, Kevin Alfred Strom
wrote:
bpnjensen wrote:

[...]



The radio in question, BTW, is a simple DX-160 - it's front end is
pretty wide open anyway, but heck, why not? *As long as I don't send a
big static charge through it, I figure I cannot do much damage :-)

BJ

I had a DX-150A in the early 1970s, and if I recall correctly, it
had an "antenna trim" control to peak up the input network for
maximum signal. The DX-160 may be the same -- the differences were
minimal, as I remember.

The trim adjustment would help match varying impedances to some
extent, but there could be cases where an input transformer would
help even more -- with a random impedance antenna on a wide range of
frequencies, it's hard to predict without making measurements.

Transformers work both ways, so one could add a switch for 1)
impedance step-up, 2) impedance step-down, and 3) direct connection.
Of course, an antenna coupler is another possible way to approach
the impedance issue.

With all good wishes,

Kevin, WB4AIO.
--http://kevinalfredstrom.com/

Mssrs. Maus and Strom, thank you! I think I will concoct a device
soon to see what happens with it.

Bruce Jensen

Question about matching transformer (9:1 un-un)
 

On Jan 23, 11:00*pm, bpnjensen wrote:
On Jan 23, 2:09*pm, Kevin Alfred Strom
wrote:





bpnjensen wrote:

[...]

The radio in question, BTW, is a simple DX-160 - it's front end is
pretty wide open anyway, but heck, why not? *As long as I don't send a
big static charge through it, I figure I cannot do much damage :-)

BJ

I had a DX-150A in the early 1970s, and if I recall correctly, it
had an "antenna trim" control to peak up the input network for
maximum signal. The DX-160 may be the same -- the differences were
minimal, as I remember.

The trim adjustment would help match varying impedances to some
extent, but there could be cases where an input transformer would
help even more -- with a random impedance antenna on a wide range of
frequencies, it's hard to predict without making measurements.

Transformers work both ways, so one could add a switch for 1)
impedance step-up, 2) impedance step-down, and 3) direct connection.
Of course, an antenna coupler is another possible way to approach
the impedance issue.

With all good wishes,

Kevin, WB4AIO.
--http://kevinalfredstrom.com/

Mssrs. Maus and Strom, thank you! *I think I will concoct a device
soon to see what happens with it.

Bruce Jensen

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

Again, my sincere thanks for the advice...

Bruce Jensen

Question about matching transformer (9:1 un-un)
 

bpnjensen wrote:
[...]
Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?




The latter course seems best to me, since the ideal core
characteristics are likely different for the two purposes.



Again, my sincere thanks for the advice...

Bruce Jensen



You're welcome; have fun with the DX-160.


With all good wishes,




Kevin, WB4AIO.
--
http://kevinalfredstrom.com/

Question about matching transformer (9:1 un-un)
 

On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?


Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

And DX-160 will drift.

Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.





p

Question about matching transformer (9:1 un-un)
 

In article ,
bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

The different core type comes from the fact that Amidon is reselling stuff
from different manufacterers. I've used both 77 and J for transformers.
They're pretty much the same. Whatever was on the pegboard at the
(then existing) local shops. Seems to work best from 3-15 Mhz, if
you want to go for higher frequencies, like CB, try a higher frequency
(lower perm.) core.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Question about matching transformer (9:1 un-un)
 

On Jan 25, 6:27*am, "D. Peter Maus"
wrote:
On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce

Question about matching transformer (9:1 un-un)
 

On Jan 25, 4:05*pm, bpnjensen wrote:
On Jan 25, 6:27*am, "D. Peter Maus"
wrote:





On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! *My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce- Hide quoted text -

- Show quoted text -
After changing just 2 or 3 ceramics in the audio stages has
improved enormously in my DX-160. Drift is somewhat moderate, compared
to other radios of similar design and era. But, the band switch is
VERY troublesome. Really kills gain and sometimes creates other
problems as well (requires incessant care,like a newborn). On the
positive note: the IF filter is actually of mechanical type,built
right into the IF coil ! Calibration is an over statement in this
receiver- it was never designed to be a precision gadjet,alas. Even
the model which preceded it , the SX/AX- 190 was miles ahead of it in
most respects. Radio Shack has been lowering it's standards
ever since...

Question about matching transformer (9:1 un-un)
 

On Jan 26, 1:54*am, wrote:
On Jan 25, 4:05*pm, bpnjensen wrote:



On Jan 25, 6:27*am, "D. Peter Maus"
wrote:

On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! *My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce- Hide quoted text -

- Show quoted text -

* * * * * *After changing just 2 or 3 ceramics in the audio stages has
improved enormously in my DX-160. Drift is somewhat moderate, compared
to other radios of similar design and era. But, the band switch is
VERY troublesome. Really kills gain and sometimes creates other
problems as well (requires incessant care,like a newborn). On the
positive note: the IF filter is actually of mechanical type,built
right into the IF coil ! *Calibration is an over statement in this
receiver- it was never designed to be a precision gadjet,alas. *Even
the model which preceded it , the SX/AX- 190 was miles ahead of it in
most respects. * * * * *Radio Shack has been lowering it's standards
ever since...- Hide quoted text -

- Show quoted text -

Hi, Anthony - when you changed the ceramics, did you change the values
too or just a like-for-like replacement with films?

My DX-160 freqs are so far off that it needs SOMETHING... :-O Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. Band 1 is so full of intermod products as to be useless
anyway...

How does the bandswitch kill gain? I have pretty good sensitivity on
all of the bands (sometimes too much!)...

Bruce

Question about matching transformer (9:1 un-un)
 

On 1/26/10 10:08 , bpnjensen wrote:
My DX-160 freqs are so far off that it needs SOMETHING... :-O Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. Band 1 is so full of intermod products as to be useless
anyway...




That's about normal for DX-160 at this age. And it will be prone
to intermod. The RF gain control is before the first gain stage, so
just turn it down until the intermod products start to decrease. Or
reduce the amount of antenna. A good ground will help, too.

Dial calibration is usually adjusted with LO for each band. The
upper bands will be further out of tolerance due to the greater
sensitivity to component value drift at higher frequencies.

Of course, if the bands are significantly out, you can well
assume with some certainty that the IF's are also out. Though likely
not by too much.

The bandswitch can be kind of flaky. Can spray cleaning may not
have the desired results. If you want to go bat**** crazy with this,
GoldPoint makes a really nice, configurable-to-purpose Swiss made
switch that can be applied to replace the flaky factory switch.
You'll never have bandswitch problems again. Cost more more than the
radio. More than a couple of them, actually, but anything worth
doing is worth overdoing.

They also make some detented step switch rotary faders for audio
(I put one in my C-26 preamp) they're amazing. But also not cheap.

I found the manual with schematic for mine. I can have a copy
made for you, if you need it.

p

Question about matching transformer (9:1 un-un)
 

On Jan 25, 11:18*am, (Mark Zenier) wrote:
In article ,

bpnjensen wrote:
Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

The different core type comes from the fact that Amidon is reselling stuff
from different manufacterers. *I've used both 77 and J for transformers..
They're pretty much the same. *Whatever was on the pegboard at the
(then existing) local shops. *Seems to work best from 3-15 Mhz, if
you want to go for higher frequencies, like CB, try a higher frequency
(lower perm.) core.

Mark Zenier *
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Thanks, Mark. I am really interested more in lower HF freq ranges,
such as 25 meters and up, especially the tropical bands. As luck
would have it, that's where most of my RFI is.

Bruce

Question about matching transformer (9:1 un-un)
 

On Jan 26, 8:30*am, "D. Peter Maus"
wrote:
On 1/26/10 10:08 , bpnjensen wrote:

My DX-160 freqs are so far off that it needs SOMETHING... :-O *Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. *Band 1 is so full of intermod products as to be useless
anyway...

* *That's about normal for DX-160 at this age. And it will be prone
to intermod. The RF gain control is before the first gain stage, so
just turn it down until the intermod products start to decrease. Or
reduce the amount of antenna. A good ground will help, too.

* *Dial calibration is usually adjusted with LO for each band. The
upper bands will be further out of tolerance due to the greater
sensitivity to component value drift at higher frequencies.

* *Of course, if the bands are significantly out, you can well
assume with some certainty that the IF's are also out. Though likely
not by too much.

* *The bandswitch can be kind of flaky. Can spray cleaning may not
have the desired results. If you want to go bat**** crazy with this,
GoldPoint makes a really nice, configurable-to-purpose Swiss made
switch that can be applied to replace the flaky factory switch.
You'll never have bandswitch problems again. Cost more more than the
radio. More than a couple of them, actually, but anything worth
doing is worth overdoing.

* *They also make some detented step switch rotary faders for audio
(I put one in my C-26 preamp) they're amazing. But also not cheap.

* *I found the manual with schematic for mine. I can have a copy
made for you, if you need it.

* * p

Thanks, Peter - what is "LO"?

I actually have a schematic and manual - I would not be surprised if
you were the one who copied it for me originally :-)

Bruce

Question about matching transformer (9:1 un-un)
 

On Jan 26, 1:54*am, wrote:
On Jan 25, 4:05*pm, bpnjensen wrote:



On Jan 25, 6:27*am, "D. Peter Maus"
wrote:

On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! *My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce- Hide quoted text -

- Show quoted text -

* * * * * *After changing just 2 or 3 ceramics in the audio stages has
improved enormously in my DX-160. Drift is somewhat moderate, compared
to other radios of similar design and era. But, the band switch is
VERY troublesome. Really kills gain and sometimes creates other
problems as well (requires incessant care,like a newborn). On the
positive note: the IF filter is actually of mechanical type,built
right into the IF coil ! *Calibration is an over statement in this
receiver- it was never designed to be a precision gadjet,alas. *Even
the model which preceded it , the SX/AX- 190 was miles ahead of it in
most respects. * * * * *Radio Shack has been lowering it's standards
ever since...

As I look at the schematic, I realize the band switch actually has
quite a bit to do - each time it is turned, about a half dozen
connections are mechanically made and broken simultaneously. Is this
the source of the trouble? Honestly, I don't think it is a problem in
my radio - but maybe I am missing something.

Bruce

Question about matching transformer (9:1 un-un)
 

On 1/26/10 20:29 , bpnjensen wrote:
On Jan 26, 8:30 am, "D. Peter
wrote:
On 1/26/10 10:08 , bpnjensen wrote:

My DX-160 freqs are so far off that it needs SOMETHING... :-O Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. Band 1 is so full of intermod products as to be useless
anyway...

That's about normal for DX-160 at this age. And it will be prone
to intermod. The RF gain control is before the first gain stage, so
just turn it down until the intermod products start to decrease. Or
reduce the amount of antenna. A good ground will help, too.

Dial calibration is usually adjusted with LO for each band. The
upper bands will be further out of tolerance due to the greater
sensitivity to component value drift at higher frequencies.

Of course, if the bands are significantly out, you can well
assume with some certainty that the IF's are also out. Though likely
not by too much.

The bandswitch can be kind of flaky. Can spray cleaning may not
have the desired results. If you want to go bat**** crazy with this,
GoldPoint makes a really nice, configurable-to-purpose Swiss made
switch that can be applied to replace the flaky factory switch.
You'll never have bandswitch problems again. Cost more more than the
radio. More than a couple of them, actually, but anything worth
doing is worth overdoing.

They also make some detented step switch rotary faders for audio
(I put one in my C-26 preamp) they're amazing. But also not cheap.

I found the manual with schematic for mine. I can have a copy
made for you, if you need it.

p

Thanks, Peter - what is "LO"?


Local oscillator. It generates the frequency used to beat against
the incoming frequency to create the IF.


I actually have a schematic and manual - I would not be surprised if
you were the one who copied it for me originally :-)


You're welcome.

I think?


p

Question about matching transformer (9:1 un-un)
 

On Jan 26, 11:08*am, bpnjensen wrote:
On Jan 26, 1:54*am, wrote:





On Jan 25, 4:05*pm, bpnjensen wrote:

On Jan 25, 6:27*am, "D. Peter Maus"
wrote:

On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! *My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce- Hide quoted text -

- Show quoted text -

* * * * * *After changing just 2 or 3 ceramics in the audio stages has
improved enormously in my DX-160. Drift is somewhat moderate, compared
to other radios of similar design and era. But, the band switch is
VERY troublesome. Really kills gain and sometimes creates other
problems as well (requires incessant care,like a newborn). On the
positive note: the IF filter is actually of mechanical type,built
right into the IF coil ! *Calibration is an over statement in this
receiver- it was never designed to be a precision gadjet,alas. *Even
the model which preceded it , the SX/AX- 190 was miles ahead of it in
most respects. * * * * *Radio Shack has been lowering it's standards
ever since...- Hide quoted text -

- Show quoted text -

Hi, Anthony - when you changed the ceramics, did you change the values
too or just a like-for-like replacement with films?

My DX-160 freqs are so far off that it needs SOMETHING... :-O *Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. *Band 1 is so full of intermod products as to be useless
anyway...

How does the bandswitch kill gain? *I have pretty good sensitivity on
all of the bands (sometimes too much!)...

Bruce- Hide quoted text -

- Show quoted text -

Arthur , not Anthony is the name here. Made some audio changes
several years ago according to www.mods.dk (excellent site, by the
way). If I remember correctly, it was C58 0.1uF became 5uF
(electrolytic) and C62 0.001 became 100pF. Audio became listenable at
this stage and I was never interested in making an eagle out of this
turkey. Stability is an old problem with most analog radios,whether
tubed or solid state ! Power supply, mixer/oscillator, variable
capacitors as well as regular component drift- all of these will
reflect in short/long term drift. The worst offender ,in my opinion is
S350 purchased from RShack. Under a Grundig label it was really a
Tecsun made portable. Never in my life did I see such abnormal drift!
Had something to do with temperature since it would get really freaky
in the summertime, especially pronounced at the higher HF frequencies.
DX-160's problems are nowhere near this bad. Oh, about that GoldPoint
bandswitch,Peter. What material is it made of ? If it has silver
contacts,then it is a real switch.

Question about matching transformer (9:1 un-un)
 

On Jan 26, 9:32*pm, wrote:
On Jan 26, 11:08*am, bpnjensen wrote:





On Jan 26, 1:54*am, wrote:

On Jan 25, 4:05*pm, bpnjensen wrote:

On Jan 25, 6:27*am, "D. Peter Maus"
wrote:

On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since..
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity..
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! *My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce- Hide quoted text -

- Show quoted text -

* * * * * *After changing just 2 or 3 ceramics in the audio stages has
improved enormously in my DX-160. Drift is somewhat moderate, compared
to other radios of similar design and era. But, the band switch is
VERY troublesome. Really kills gain and sometimes creates other
problems as well (requires incessant care,like a newborn). On the
positive note: the IF filter is actually of mechanical type,built
right into the IF coil ! *Calibration is an over statement in this
receiver- it was never designed to be a precision gadjet,alas. *Even
the model which preceded it , the SX/AX- 190 was miles ahead of it in
most respects. * * * * *Radio Shack has been lowering it's standards
ever since...- Hide quoted text -

- Show quoted text -

Hi, Anthony - when you changed the ceramics, did you change the values
too or just a like-for-like replacement with films?

My DX-160 freqs are so far off that it needs SOMETHING... :-O *Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. *Band 1 is so full of intermod products as to be useless
anyway...

How does the bandswitch kill gain? *I have pretty good sensitivity on
all of the bands (sometimes too much!)...

Bruce- Hide quoted text -

- Show quoted text -

* Arthur , not Anthony is the name here. *Made some audio changes
several years ago according to *www.mods.dk*(excellent site, by the
way). If I remember correctly, it was C58 0.1uF became 5uF
(electrolytic) and C62 0.001 became 100pF. Audio became listenable at
this stage and I was never interested in making an eagle out of this
turkey. Stability is an old problem with most analog radios,whether
tubed or solid state ! *Power supply, mixer/oscillator, variable
capacitors as well as regular component drift- all of these *will
reflect in short/long term drift. The worst offender ,in my opinion is
S350 purchased from RShack. Under a Grundig label it was really a
Tecsun made portable. Never in my life did I see such abnormal drift!
Had something to do with temperature since it would get really freaky
in the summertime, especially pronounced at the higher HF frequencies.
DX-160's problems are nowhere near this bad. Oh, about that GoldPoint
bandswitch,Peter. What material is it made of ? If it has silver
contacts,then it is a real switch.

Arthur, thank you, and please accept my apologies for erring on your
name!

Bruce

Question about matching transformer (9:1 un-un)
 

On Jan 27, 12:53*am, bpnjensen wrote:
On Jan 26, 9:32*pm, wrote:





On Jan 26, 11:08*am, bpnjensen wrote:

On Jan 26, 1:54*am, wrote:

On Jan 25, 4:05*pm, bpnjensen wrote:

On Jan 25, 6:27*am, "D. Peter Maus"
wrote:

On 1/24/10 11:55 , bpnjensen wrote:

Another question on this subject - what core should be used for this
application?

Amidon, among others, has cores of many materials including 43 and 77,
both of which seem to get use in these applications; however, for RFI
problems below 10 MHz, Amidon recommends cores of J material, and my
RFI problems (while not confined to under 10 MHz) are primarily below
that frequency. *Would use of J material be wise here, or for this
matching transformer would I be better using the old standbys 43 or
77, and then making lots of separate chokes from other materials such
as J?

* *Without specifics on the nature of your RFI, I'd build the
transformer from the recommended materials, 43 or 77, and then build
frequency specific chokes to purpose. That way, if your RFI changes,
as it often can, you're solution is to built another choke, not to
revise your receiver's input.

* *Kevin makes a good point about the antenna trim control at the
input of DX-160. That covers a multitude of sins. Not unlike my
Nationals, similarly equipped.

* *That control showed up on DX-120, and was the reason I got
interested in this line in the first place. I couldn't afford one
until DX-150. Bought one of those, and have had two DX-160s since.
Fun radios. Not quite as selective as my S-40 and S-53 Halli's but
good for program listening on the big guys. DX-160 had less hum in
the audio, and came on immediately. After more than a decade of
tubes, by that time, I thought that was bitchin' cool. Just couldn't
justify the money at the time.

* *DX-160 has pretty lifeless audio. Not much above 6k, and bottom
rolled of below 150hz. You can bring a little life back to that
bottom end, by changing a couple of the capacitors. One in the audio
circuit, and one bringing the audio from the detector to the audio
stage. Which ones at this point, specifically, I don't recall, but I
think one is on a trace on the extreme right of the PCB. It's out
there by itself, easy to replace. The other is further inboard, near
the audio IC. But you can cut-and-try with a .5ufd or a .1 ufd film,
across the any of the likely candidates listening for a change. Can
make quite a difference. Although with the fact AGC, and the
generally poor audio stage, don't expect Little Jewel audio.

* *You can clean up the woolly audio by replacing all the ceramic
capacitors on the board with films. Better definition and clarity.
Small films will fit right in the ceramic positions, and by
selecting your components carefully, for things like thermal
coefficient, you can mitigate some of the drift. Not all, but some.

* *And DX-160 will drift.

* *Further cleaning can be achieved by replacing the electrolytics.
Not only in the power supply, but those dispersed throughout the
board. After all these years, some will have become, or have begun
to become unformed. Some my be distended, indicating impending
failure. Some may even leak. Simple replacement procedure.

* *Touching up the alignment will also help, and using WWV as a
frequency standard, you can do a creditable job calibrating dial
positions.

* *Lastly, the dial lights have decent, but not remarkably long
life. You can find drop-in LED replacements at Digi-Key, or
SuperbrightLeds.com. The warm whites look just like incandescents,
and last 100 times longer. You may have to add a small series
resistor to the dial light circuit to limit current to the LED
replacements. That's a small matter, and dramatically improves life
of the lamp without significantly altering lumen output.

* *Now, if you REALLY want to make this rig over, you can install
Murata filters in the IF's. But that may be a long reach for such a
simple receiver.

* *p

Thank you once again, Peter and Kevin - great stuff! *My 160 does need
freq calibration pretty badly, and possibly (probably?) alignment as
well.

Bruce- Hide quoted text -

- Show quoted text -

* * * * * *After changing just 2 or 3 ceramics in the audio stages has
improved enormously in my DX-160. Drift is somewhat moderate, compared
to other radios of similar design and era. But, the band switch is
VERY troublesome. Really kills gain and sometimes creates other
problems as well (requires incessant care,like a newborn). On the
positive note: the IF filter is actually of mechanical type,built
right into the IF coil ! *Calibration is an over statement in this
receiver- it was never designed to be a precision gadjet,alas. *Even
the model which preceded it , the SX/AX- 190 was miles ahead of it in
most respects. * * * * *Radio Shack has been lowering it's standards
ever since...- Hide quoted text -

- Show quoted text -

Hi, Anthony - when you changed the ceramics, did you change the values
too or just a like-for-like replacement with films?

My DX-160 freqs are so far off that it needs SOMETHING... :-O *Band 3
is a disaster; 2 is quite good, 4 is pretty far off but usable, 5 is
not great. *Band 1 is so full of intermod products as to be useless
anyway...

How does the bandswitch kill gain? *I have pretty good sensitivity on
all of the bands (sometimes too much!)...

Bruce- Hide quoted text -

- Show quoted text -

* Arthur , not Anthony is the name here. *Made some audio changes
several years ago according to *www.mods.dk*(excellent site, by the
way). If I remember correctly, it was C58 0.1uF became 5uF
(electrolytic) and C62 0.001 became 100pF. Audio became listenable at
this stage and I was never interested in making an eagle out of this
turkey. Stability is an old problem with most analog radios,whether
tubed or solid state ! *Power supply, mixer/oscillator, variable
capacitors as well as regular component drift- all of these *will
reflect in short/long term drift. The worst offender ,in my opinion is
S350 purchased from RShack. Under a Grundig label it was really a
Tecsun made portable. Never in my life did I see such abnormal drift!
Had something to do with temperature since it would get really freaky
in the summertime, especially pronounced at the higher HF frequencies.
DX-160's problems are nowhere near this bad. Oh, about that GoldPoint
bandswitch,Peter. What material is it made of ? If it has silver
contacts,then it is a real switch.

Arthur, thank you, and please accept my apologies for erring on your
name!

Bruce- Hide quoted text -

- Show quoted text -

No problem,Bruce. After the audio modification it's frequency
response will improve substantially . Original design claimed 300Hz-
3 KHz. Ever tried to run it on 12VDC external power supply- may solve
some of the drift. N.B. The IF bandwith is 4 KHz,
if not mistaken. T16 is a coil with a mechanical filter, not very
spectacular at all- has rather broad attenuation skirts for such a
component. May be one day I will swap it with a Murata or NTT ,if they
match the holes. Wonder what impedances are involved here, sometimes
it makes a tremendous difference. No standard Collins (new or old)
filters that I know of will fit in here, thanks God !

Question about matching transformer (9:1 un-un)
 

On Jan 27, 12:53 am, wrote:


Oh, about that GoldPoint bandswitch, Peter. What material is it made of ? If it has silver
contacts,then it is a real switch.


Gold, actually.

Select the number of switch positions you want, stack the layers
you need, and wire it up. Pretty slick. Not cheap, but you'll never
have to screw around with a bandswitch again.

Truthfully, it's overkill for DX-160 and it's family. But then,
anything worth doing is worth overdoing.


http://www.goldpt.com/selector.html