N9NEO wrote:
Is anyone here interested in collaborating on a small pc board with a
precision detector and an elliptic filter? and maybe even a small
amplifier too. This would be a retrofit to existing radio. I have
heard it is almost as good as a sync detector- better than some. I
have heard others say it is smoke and mirrors so I expect to get to the
truth here.

I am looking for two other people to help out. Board will cost you
maybe 30 bucks. I use PCB express. You get three small boards no silk
no solder mask for about 60bucks. I am in-between consulting jobs now,
so that I have a little time but watching my funds. I think with smd
parts maybe only half a board is needed so that each will cost even
less.


Idea has been around for quite some time but recently brought to my
attention by Terry. I am looking at that Redsun RP2100 unit as the
platform to run with.

regards,
NEO

For an interesting thread see:
http://amfone.net/Amforum/index.php?topic=3857.0

Terry

For an interesting thread see:
http://amfone.net/Amforum/index.php?topic=3857.0

Terry

Yea, those guys over there got a lot on the ball with High Perfromance
detectors and such. Frank, GFZ, is a friend of mine and does a lot
with the Racal units.

I'm not looking for anybody to do any hands on work that will take up a
lot of time. Just a few who I can bounce Ideas off of and help if I
get stuck. Like I said - I'm in between jobs so I got the time to lay
out a board. When boards done whoever wants one can have.

Looks like the board will have the detector, amplifier and filter on
it. I want to drive a set of phones with the thing and am not really
too concerned with driving a speaker. I will have a line out connector
to drive directly into my Marantz so I don't think amplifier will be so
critical for me. I notice that Dallas Lankford set up his filters to
drive into 8 ohms. I think I'm going to drive into a higher impedance
- probably near 100 ohms and then just a buffer to drive the phones.

So question for now is about headphone impedance. I'll post that
seperate and see what others are using for phones.

Below is link to paper. it's the one about improved eliptic filters.
I have the filters in switchercad just to see how impedance effects
filter response.

http://www.kongsfjord.no/dl/dl.htm

73
NEO

N9NEO wrote:

For an interesting thread see:
http://amfone.net/Amforum/index.php?topic=3857.0

Terry

Yea, those guys over there got a lot on the ball with High Perfromance
detectors and such. Frank, GFZ, is a friend of mine and does a lot
with the Racal units.

I'm not looking for anybody to do any hands on work that will take up a
lot of time. Just a few who I can bounce Ideas off of and help if I
get stuck. Like I said - I'm in between jobs so I got the time to lay
out a board. When boards done whoever wants one can have.

Looks like the board will have the detector, amplifier and filter on
it. I want to drive a set of phones with the thing and am not really
too concerned with driving a speaker. I will have a line out connector
to drive directly into my Marantz so I don't think amplifier will be so
critical for me. I notice that Dallas Lankford set up his filters to
drive into 8 ohms. I think I'm going to drive into a higher impedance
- probably near 100 ohms and then just a buffer to drive the phones.

So question for now is about headphone impedance. I'll post that
seperate and see what others are using for phones.

Below is link to paper. it's the one about improved eliptic filters.
I have the filters in switchercad just to see how impedance effects
filter response.

http://www.kongsfjord.no/dl/dl.htm

73
NEO

I have found Dallas' LP fitle to be a very usefull addition to my
system.
When I first posted a link to his filter I took some hits because some
people think that active is either easeier or better. An active fitler
would
clearly lend it self to easier adjustments. The active circuit at the
link I
posted has a slight advantage for those with radios will less then
ideal IF
filters. The 5KHz, 9KHz, and 10KHz notches will be very usefull. I
built a
set for my DX398 for use on mini-dxpeditions.

For normal adjsutments I like the Tone Tilt that I first experienced in
a Kiwa
MAP SAD.

One simple circuit for which I do not have a link is a "ear protector".
I listen with earphones a lot of the time. My wife is very supporting
but doesn't understand my fascination with utility reception. Nothing
worse then trying to dig out a weak signal, with the AF gain cranked
up,
and a loud static "pop" rolls in. Or even worse, another signal comes
on frequency.

OUCH!

My hearing has suffered enough and have no desire to damage them
any more!

So I built a device that consists of a series resistor, a pair of two
1N400X
wired as a clamp to limit the voltage to a maximum of ~1.4V. Since my
two choices of earhphones are a 40 year old set of Sennheiser HD424, 2K
each side, and a set of Byer's with ~600 Ohms each side. The Sennheiser
are of the "opne air" desing and I can wear them for hours.The Beyers
are
of the clsoe design and I were them when there is too much back ground
noise. They also have a built in boom mic so on those odd occasions I
actually use my ham gear, they are nice for hands free. A foot PTT or
VOX are very usefull.

The earphone protector has a Lo-Z to high Z (8:600 ohms) transformer,
but
it will work great with every radio I have tried it with without
thetransformer.
I use sereis resistors of 470 Ohms, and have a 1K pot across the diodes
to
allow the level to be adjusted. This pot is a screwdriver and even
though the
Beyers and the Sennheisers have over a 2:1 difference, the sound levels
are matched to within a few dB. I can't measure earphone output better
then
about +/- 2dB.

Terry

I have found Dallas' LP fitle to be a very usefull addition to my
system.
When I first posted a link to his filter I took some hits because some
people think that active is either easeier or better. An active fitler
would
clearly lend it self to easier adjustments. The active circuit at the
link I
posted has a slight advantage for those with radios will less then
ideal IF
filters. The 5KHz, 9KHz, and 10KHz notches will be very usefull. I
built a
set for my DX398 for use on mini-dxpeditions.

For normal adjsutments I like the Tone Tilt that I first experienced in
a Kiwa
MAP SAD.

One simple circuit for which I do not have a link is a "ear protector".
I listen with earphones a lot of the time. My wife is very supporting
but doesn't understand my fascination with utility reception. Nothing
worse then trying to dig out a weak signal, with the AF gain cranked
up,
and a loud static "pop" rolls in. Or even worse, another signal comes
on frequency.

OUCH!

My hearing has suffered enough and have no desire to damage them
any more!

So I built a device that consists of a series resistor, a pair of two
1N400X
wired as a clamp to limit the voltage to a maximum of ~1.4V. Since my
two choices of earhphones are a 40 year old set of Sennheiser HD424, 2K
each side, and a set of Byer's with ~600 Ohms each side. The Sennheiser
are of the "opne air" desing and I can wear them for hours.The Beyers
are
of the clsoe design and I were them when there is too much back ground
noise. They also have a built in boom mic so on those odd occasions I
actually use my ham gear, they are nice for hands free. A foot PTT or
VOX are very usefull.

The earphone protector has a Lo-Z to high Z (8:600 ohms) transformer,
but
it will work great with every radio I have tried it with without
thetransformer.
I use sereis resistors of 470 Ohms, and have a 1K pot across the diodes
to
allow the level to be adjusted. This pot is a screwdriver and even
though the
Beyers and the Sennheisers have over a 2:1 difference, the sound levels
are matched to within a few dB. I can't measure earphone output better
then
about +/- 2dB.

Terry

Ok on the phones. You had mentioned them in your email to me in
September. You had also sent me a diagram of an op-amp with a pair of
emitter followers that I could use to drive the filter. Like I said,
I'm probably going to design the filter to run into a hundred or so
ohms. I'll probably stick an op-amp on the output of the filter to act
as a buffer - although 2k probably wouldn't move the filter response
much. Then of course I'll have to have a baxandall /bandaxall style
tone control so the project grows some. Yes, active filters would
probably be ok and LT has some very nice filter chips that would work
too - and I haven't ruled them out.

More later.
NEO

N9NEO wrote:



Ok on the phones. You had mentioned them in your email to me in
September. You had also sent me a diagram of an op-amp with a pair of
emitter followers that I could use to drive the filter. Like I said,
I'm probably going to design the filter to run into a hundred or so
ohms. I'll probably stick an op-amp on the output of the filter to act
as a buffer - although 2k probably wouldn't move the filter response
much. Then of course I'll have to have a baxandall /bandaxall style
tone control so the project grows some. Yes, active filters would
probably be ok and LT has some very nice filter chips that would work
too - and I haven't ruled them out.

More later.
NEO

Before trying a baxandall /bandaxall tone circuit, you owe it to
yourself to
at least bread board the circuit at
http://members.tripod.com/roymal/ReverbTone.htm.

I like baxandall for "HiFi" audio but in 40+ years of SWL I have never
needed
to boast the highs, lows and mids seperately. I played with a
professional
1/3 octave EQ unit, that had variable shelving etc last winter and
except for
the complexity it had some minor advantages. But all in all the single
Tone-Tilt
won the test. A tuneable AF notch is a nice addition.

There have been times when I found a very sharp 60Hz notch filter to
very usefull with
older tube radios with less then perfect power supply filtering. These
days I mainly
operate radi from a well regulated and very well filtered 12V. [13.67V
which is
also the proper voltage to float charge a Gell Cell/PbSO4 battery] So
60/120/180
Hz hum is seldom an internal issue.

At some point I am going to have to redesign my system to seperate the
audio from the outboard detector. When I built it I didn't plan on
adding radio
that didn't have 455KHZ as the IF. Best laid plans and all of that.

There are paradoxes or logical conflicts in my statements and the
operation
of my audio chain. I want smooth response out to say 15KHz. But I add
filtering to chop out the highs and lows. I found it better to use a
set of JBL
speakers designed for "Home Theater" 5.1 (or 7.1) side speakers that
naturally
roll off at about 6K. By 10KHz they are mute. I found this works better
then
adding a low level AF filter. The Minimus 7's almost worked with the
tweeter
switched off. Then when I get the harmonic distortion during bad fades
with ths
SADs, I kick in Dalla's ELP AF filter. When an unwanted het pops up I
use
a low level tuneable notch.

When I look at my system I sometimes want to scream. This was supposed
to
be simple! I designed and built a true hifi system that is flat, +/1
1dB from
~30Hz to above 20KHz. With the minimuis speakers and an added tweeter
and
subwoofer it is flat +/- 4 or 5dB from 60Hz to above 15KHz. [It is very
hard to come
up with accurate measurements that relfect reality in a room!] When
doing serious,
IE money making, audio work on the PC I really need the full bandwidth
with the
subwoofer. But for SWL I chop it to something like ~100Hz to maybe
7KHz.
Simply nuts. No wonder my wife insisted on her own radio.

Since my "far field"/ ISM/HiFer beacon is toast, lightning, I have to
be content with
running my test audio from a high bit rate MP3 into my system and
mixing real radio background noise and measuring the result. Since I
can't, and never could, really
duplicate any of the effedts sfading and selective fading introduced,
this isn't really
that much different then my prior test. As a general rule, it is better
to control BW
with the correct IF filter, a speaker with natural roll off or lastly
low level or high
level filters. Conversly the more filtering you add, the quicker you
get listening
fatigue. Listening to AM through a 1.8KHZ SSB fitler will tire you out
pretty fast.
More later when my brain untangles.

And this is all for fun.


Terry

wrote:
N9NEO wrote:



Ok on the phones. You had mentioned them in your email to me in
September. You had also sent me a diagram of an op-amp with a pair of
emitter followers that I could use to drive the filter. Like I said,
I'm probably going to design the filter to run into a hundred or so
ohms. I'll probably stick an op-amp on the output of the filter to act
as a buffer - although 2k probably wouldn't move the filter response
much. Then of course I'll have to have a baxandall /bandaxall style
tone control so the project grows some. Yes, active filters would
probably be ok and LT has some very nice filter chips that would work
too - and I haven't ruled them out.

More later.
NEO

Before trying a baxandall /bandaxall tone circuit, you owe it to
yourself to
at least bread board the circuit at
http://members.tripod.com/roymal/ReverbTone.htm.

I like baxandall for "HiFi" audio but in 40+ years of SWL I have never
needed
to boast the highs, lows and mids seperately. I played with a
professional
1/3 octave EQ unit, that had variable shelving etc last winter and
except for
the complexity it had some minor advantages. But all in all the single
Tone-Tilt
won the test. A tuneable AF notch is a nice addition.

There have been times when I found a very sharp 60Hz notch filter to
very usefull with
older tube radios with less then perfect power supply filtering. These
days I mainly
operate radi from a well regulated and very well filtered 12V. [13.67V
which is
also the proper voltage to float charge a Gell Cell/PbSO4 battery] So
60/120/180
Hz hum is seldom an internal issue.

At some point I am going to have to redesign my system to seperate the
audio from the outboard detector. When I built it I didn't plan on
adding radio
that didn't have 455KHZ as the IF. Best laid plans and all of that.

There are paradoxes or logical conflicts in my statements and the
operation
of my audio chain. I want smooth response out to say 15KHz. But I add
filtering to chop out the highs and lows. I found it better to use a
set of JBL
speakers designed for "Home Theater" 5.1 (or 7.1) side speakers that
naturally
roll off at about 6K. By 10KHz they are mute. I found this works better
then
adding a low level AF filter. The Minimus 7's almost worked with the
tweeter
switched off. Then when I get the harmonic distortion during bad fades
with ths
SADs, I kick in Dalla's ELP AF filter. When an unwanted het pops up I
use
a low level tuneable notch.

When I look at my system I sometimes want to scream. This was supposed
to
be simple! I designed and built a true hifi system that is flat, +/1
1dB from
~30Hz to above 20KHz. With the minimuis speakers and an added tweeter
and
subwoofer it is flat +/- 4 or 5dB from 60Hz to above 15KHz. [It is very
hard to come
up with accurate measurements that relfect reality in a room!] When
doing serious,
IE money making, audio work on the PC I really need the full bandwidth
with the
subwoofer. But for SWL I chop it to something like ~100Hz to maybe
7KHz.
Simply nuts. No wonder my wife insisted on her own radio.

Since my "far field"/ ISM/HiFer beacon is toast, lightning, I have to
be content with
running my test audio from a high bit rate MP3 into my system and
mixing real radio background noise and measuring the result. Since I
can't, and never could, really
duplicate any of the effedts sfading and selective fading introduced,
this isn't really
that much different then my prior test. As a general rule, it is better
to control BW
with the correct IF filter, a speaker with natural roll off or lastly
low level or high
level filters. Conversly the more filtering you add, the quicker you
get listening
fatigue. Listening to AM through a 1.8KHZ SSB fitler will tire you out
pretty fast.
More later when my brain untangles.

And this is all for fun.


Terry

Yes, this is all for fun.

Tone circuit link you provided should be fine. I don't intend to do
any breadboarding before I fab a pc board. I don't have the eyesight
or the steady hand that I had as a kid, but my circuit design is
ten-fold better so that I can usually do up a board that can be shipped
first go around.

I was thinking of using that Red Sun radio (RP2100 I think it's called)
for a platform cause it has IF out. Also thinking of a Rad Shack
DX-394 I think it is. Looks like I got my RA17L sold so that should
finance this project. I'm out of work and on a tight budget so I have
to sell this to pay for that.

73
NEO

There looks like a typo in schematic.

http://www.amwindow.org/tech/htm/alowdisdet.htm

Amplifier inputs have to be swapped at the two rectifiers.

later
NEO

There looks like a typo in schematic.

http://www.amwindow.org/tech/htm/alowdisdet.htm

Amplifier inputs have to be swapped at the two rectifiers.

later
NEO

N9NEO wrote:
There looks like a typo in schematic.

http://www.amwindow.org/tech/htm/alowdisdet.htm

Amplifier inputs have to be swapped at the two rectifiers.

later
NEO

I don't remember any errors, but it has been 8 months since I built one
of these. I will open up my outboard detector and verify the design. It
will
have to wait until Sunday night at the earliest.

Terry

wrote:
N9NEO wrote:
There looks like a typo in schematic.

http://www.amwindow.org/tech/htm/alowdisdet.htm

Amplifier inputs have to be swapped at the two rectifiers.

later
NEO

I don't remember any errors, but it has been 8 months since I built one
of these. I will open up my outboard detector and verify the design. It
will
have to wait until Sunday night at the earliest.

Terry

No big deal there Terry, it's really a minor issue and probably would
work no problem anyway. What I found is just that the way the detector
is shown the output will be negative. I simulated it in
SwitchercadIII. (That's my secret to designing pc boards that work
without breadboarding.) I would appreciate if you look at and comment
on a couple of things with the circuit though. I am a power supply guy
and I don't know too much about detectors.

Rob uses a RC filter on the output of this thing so that the output is
an avaraging operation rather than responding to the peak of the
waveform. It looks like the pole is set for near 5kHz so some phase
distortion is going to be introduced - probably not a big deal. Rob
goes out of his way to do a full wave rectification, but that doesn't
make much sense to me with the filter he sticks on the end.
What do you think about just doing a detector that responds to the peak
of the waveform in a half-wave type rectifier? By the time this signal
goes through a 4kHz elliptic filter there isn't going to be a microvolt
of 455kHz signal to be found. Gain the IF signal up so that any error
due to diode matching will be minimized. I have a circuit that uses 3
schottkys in Spice that should do a nice job. I can send it to you if
you run Switchercad. It's a free download.

regards,
Bob