One's up for auction on Ebay right now:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

Has anyone owned one of these receivers? I'm not bidding on it, but I'm
curious about how it would stack up against one of the better
commercial receivers, like an R8B or 7030+.

Steve

wrote:

One's up for auction on Ebay right now:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

Has anyone owned one of these receivers? I'm not bidding on it, but I'm
curious about how it would stack up against one of the better
commercial receivers, like an R8B or 7030+.

Never had one, never will. Not even necessary for DX'ing...

dxAce
Michigan
USA

I swear by, not at, Drake receivers.©
Drake R7, R8, R8A and R8B

http://www.iserv.net/~n8kdv/dxpage.htm

dxAce wrote:
wrote:

One's up for auction on Ebay right now:


http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3D576 83=
29816&rd=3D1&ssPageName=3DWDVW

Has anyone owned one of these receivers? I'm not bidding on it, but
I'm
curious about how it would stack up against one of the better
commercial receivers, like an R8B or 7030+.

Never had one, never will. Not even necessary for DX'ing...

dxAce
Michigan
USA

I swear by, not at, Drake receivers.=A9
Drake R7, R8, R8A and R8B

http://www.iserv.net/~n8kdv/dxpage.htm

I had one several years ago, worked ok, nothing to write home about. I
agree, the Drake R8 series is better as are many other receivers. Guy
Atkins, a well known mw dx'er sold his and kept a Kiwa modified Icom
R75.

Les

Les is correct. After much comparison on the tropical bands and foreign MW
DXing, I found the modded R-75 essentially equal to a fine example of a
RA6790GM (with various new parts, and tweaked, serviced, and refurbished by
the Racal guru Gary Wingerd).

At one point I installed a very desireable upgrade to the front end roofing
filters, by changing them from a 20 kHz bandwidth to a 10 kHz bandwidth,
using two 40.455 MHz modules from a Cubic R-3030 RF board. This made the
Racal better at tough MW split-frequency DXing with strong signals nearby in
frequency.

Still, the R-75 was so much easier to operate-- smaller, lighter, cooler
running, and has the advantage of working off 12vdc for power when needed at
DXpeditions. In addition, the Twin PBT control in the R-75 is a great tool
for DXing-- a feature sorely missing in the Racal. The RA6790GM model fit
its commercial/military monitoring purpose well, at a reasonable cost in its
day for organizations and governments. It was never intended to meet the
specific needs of DXers.

One example of the awkwardness of the RA6790GM for DXing is in the choice of
filters for SSB. To use anything other than the default SSB filter (normally
3.0 kHz), you need to switch to CW mode, adjust the BFO offset to achieve
natural speech, and then choose one of the other installed bandwidths. This
is VERY inconvenient during changing DX reception conditions, particularly
during dawn enhancement of signals when you need a flexible, quick-to-adjust
receiver.

My R-75 has these Kiwa mods: Synchronous AM module, Kiwa CLF-D2K filter (no
longer made), and the Kiwa audio upgrade. I also have two 1.8 kHz INRAD
filters in the 2nd IF , ECSS volume mod, Dr. Phil's high fidelity audio
upgrade, and a number of other smaller mods. The radio doesn't need these
mods to perform very well, but I to tinker with my gear...

The R-75 is now my secondary radio. The main and best performing rig in the
shack now is a ICOM IC-756Pro transceiver. In all but one DXing situation
over the last 4 or 5 months, the 756Pro has noticeably outperformed the
R-75. There is not a huge difference, but big enough that I can often times
make out more words and IDs in a foreign language on a static-riddled, weak
station on the 756Pro compared to the R-75.

However, the R-75 is the best value in a new receiver these days (while they
last...I wonder how many R-75's Universal Radio still has in their dwindling
stock?)

Guy Atkins
Puyallup, WA USA


"Les" wrote in message
ups.com...

SNIP

I had one several years ago, worked ok, nothing to write home about. I
agree, the Drake R8 series is better as are many other receivers. Guy
Atkins, a well known mw dx'er sold his and kept a Kiwa modified Icom
R75.

Les

"Has anyone owned one of these receivers? I'm not bidding on it, but
I'm
curious about how it would stack up against one of the better
commercial receivers, like an R8B or 7030+."

Well, remember the Racal is a commercial grade receiver designed for
specific applications ranging from laboratory work to fixed frequency
monitoring, etc. It was not built as a hobbyist radio. There are
several interesting reviews that go into detail about it's strong
points and several limitations: http://www.eham.net/reviews/detail/488


On the other hand, the R8B and 7030, R75, etc., are consumer grade
receivers for serious hobbyists. All three are known for for having
numerous very useful features that allow the user to manipulate the
signal in a variety of ways. Unlike the Racal they all have memories,
a feature that is basic to swling.

Fully expect that you would hear the same signals on the Racal as you
would with the three consumer receivers. The Racal does look the
serious receiver with the rack mount case, handles and austere design.

Pete G on this group raves about how great it is.

however it does not mean it is fun to use. commercial receivers are not
always fun to use.

I have a Drake maritime 5000 dollar receiver, I find it no fun at all to use
compared to the satellit 800 or a modded DX-394 or similar fun to use
receiver.




wrote in message
ups.com...
One's up for auction on Ebay right now:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

Has anyone owned one of these receivers? I'm not bidding on it, but I'm
curious about how it would stack up against one of the better
commercial receivers, like an R8B or 7030+.

Steve

"mike maghakian" wrote in message
...
Pete G on this group raves about how great it is.

however it does not mean it is fun to use. commercial receivers are not
always fun to use.

I have a Drake maritime 5000 dollar receiver, I find it no fun at all to
use compared to the satellit 800 or a modded DX-394 or similar fun to use
receiver.


The 6790 is a good receiver........if you want all of the "creature
comforts", this isn't the receiver to use. It is my favorite as far as
performance, but it is so DEEEEEEEEEEEEEEEEEEEEEEPPPPPPPPPPPPPPPP! We are
talking about over 20 inches of depth.
The gain of the I.F. system is higher than any of my other receivers. The
MDS measures less than .1uV over the whole tuning range, which is in line
with just about every other receiver being sold today.
My favorite receiver? My Lowe HF-150.
I also have the HF-225, but it doesn't compare with the 150 for MW
reception, because of the lossy duplexer that it uses on the MW range (why
they don't use a bandpass filter for this range, I don't know).
My 2nd favorite is my NRD-515, followed by the Palstar R30, Yaesu FRG-100,
Icom R75, AOR7030, SW-8, and all of the others (I lost count).
Many folks are concerned about getting ahold of parts for the 6790, but the
same could be said about the Cubic, WJ, Collins, and all of the other
premium receivers. The main advantage of the super high end receivers is
that most of them can be used for shipboard operation, where they will be
co-located with high power transmitters.
An example is the Collins HF-2054 or the 851S-1 receiver............these
receivers can handle 100V of RF at the antenna input without damage to the
receiver, whether it is powered on or turned off.
Is this kind of robustness needed for the home receiver. Probably not. The
ESD protection that these receivers afford would be helpful, as evidenced by
the number of Lowe receivers that I have replaced the 1st mixer in recently.
Somebody made a comment about how cool the Icom R-75 runs..........I bet
that you haven't attempted to touch that internal 5V regulator.
There have been some failures with this regulator recently. The failure
mechanism is caused by the fact that Icom chose to use an 18V supply to
power the radio. Dave Zantos has modified his power supply by adding a
pre-regulator that brings the voltage down to 13.5V before it enters the
radio.
My advice? Either modify that Icom power brick or replace it with a
regulated 13.5V power supply.
Looking inside of that supply, you will find spots on the circuit board for
adding bypass caps across each rectifier diode.
Add .01uF caps in these places and it will prevent the diodes from
rectifying RF. Another good mod for this power supply is to add a 1uF NP cap
from each leg of the SECONDARY of the power transformer to ground. This
snubs the switching noise from the rectifier diodes.
I have heard mention on this NG that purchasing a good regulated supply gets
rid of these emissions........this is not really the case. Any power supply
can be made quiet by using the aforementioned techniques.
The AOR7030s power supply can also benefit from these mods.

Pete

Hi Pete,

I was the one who mentioned the cool-running R-75. I should have also
mentioned I *only* power it by a 13.5vdc Astron supply. I've never used the
ICOM power brick.

Guy


"Pete KE9OA" wrote in message
...

"mike maghakian" wrote in message
...
Pete G on this group raves about how great it is.

however it does not mean it is fun to use. commercial receivers are not
always fun to use.

I have a Drake maritime 5000 dollar receiver, I find it no fun at all to
use compared to the satellit 800 or a modded DX-394 or similar fun to use
receiver.


The 6790 is a good receiver........if you want all of the "creature
comforts", this isn't the receiver to use. It is my favorite as far as
performance, but it is so DEEEEEEEEEEEEEEEEEEEEEEPPPPPPPPPPPPPPPP! We are
talking about over 20 inches of depth.
The gain of the I.F. system is higher than any of my other receivers. The
MDS measures less than .1uV over the whole tuning range, which is in line
with just about every other receiver being sold today.
My favorite receiver? My Lowe HF-150.
I also have the HF-225, but it doesn't compare with the 150 for MW
reception, because of the lossy duplexer that it uses on the MW range (why
they don't use a bandpass filter for this range, I don't know).
My 2nd favorite is my NRD-515, followed by the Palstar R30, Yaesu FRG-100,
Icom R75, AOR7030, SW-8, and all of the others (I lost count).
Many folks are concerned about getting ahold of parts for the 6790, but
the same could be said about the Cubic, WJ, Collins, and all of the other
premium receivers. The main advantage of the super high end receivers is
that most of them can be used for shipboard operation, where they will be
co-located with high power transmitters.
An example is the Collins HF-2054 or the 851S-1 receiver............these
receivers can handle 100V of RF at the antenna input without damage to the
receiver, whether it is powered on or turned off.
Is this kind of robustness needed for the home receiver. Probably not. The
ESD protection that these receivers afford would be helpful, as evidenced
by the number of Lowe receivers that I have replaced the 1st mixer in
recently.
Somebody made a comment about how cool the Icom R-75 runs..........I bet
that you haven't attempted to touch that internal 5V regulator.
There have been some failures with this regulator recently. The failure
mechanism is caused by the fact that Icom chose to use an 18V supply to
power the radio. Dave Zantos has modified his power supply by adding a
pre-regulator that brings the voltage down to 13.5V before it enters the
radio.
My advice? Either modify that Icom power brick or replace it with a
regulated 13.5V power supply.
Looking inside of that supply, you will find spots on the circuit board
for adding bypass caps across each rectifier diode.
Add .01uF caps in these places and it will prevent the diodes from
rectifying RF. Another good mod for this power supply is to add a 1uF NP
cap from each leg of the SECONDARY of the power transformer to ground.
This snubs the switching noise from the rectifier diodes.
I have heard mention on this NG that purchasing a good regulated supply
gets rid of these emissions........this is not really the case. Any power
supply can be made quiet by using the aforementioned techniques.
The AOR7030s power supply can also benefit from these mods.

Pete

Ok, that makes sense..............on 13.5V, the Icom runs great. I still
have to do the audio mods to mine one of these days. It is a super
performer, RF wise.
Right now, I am revamping a McKay Dymek DR-33C. I just measured the LO
injection from the synthesizer. At +17dBm, I would expect much better IM
performance. LW is laden with multiple MW signals.
I am going to replace that whole kludge of a 1st mixer with a Mini-Circuits
TAK-3H. This device has an IP3 of +29dBm.
The 2nd mixer is getting a Siliconix E431..............this device has an
IP3 of +30dBm.
It should be a very good receiver when I get through with it. I used the
TAK-3H when I upgraded my KWM-380. With a wide open front end on MW / LW, no
IMD products were noted.
These mods should improve the MDS of the DR-33C. I will post my results.

Pete

"Guy Atkins" wrote in message
...
Hi Pete,

I was the one who mentioned the cool-running R-75. I should have also
mentioned I *only* power it by a 13.5vdc Astron supply. I've never used
the ICOM power brick.

Guy


"Pete KE9OA" wrote in message
...

"mike maghakian" wrote in message
...
Pete G on this group raves about how great it is.

however it does not mean it is fun to use. commercial receivers are not
always fun to use.

I have a Drake maritime 5000 dollar receiver, I find it no fun at all to
use compared to the satellit 800 or a modded DX-394 or similar fun to
use receiver.


The 6790 is a good receiver........if you want all of the "creature
comforts", this isn't the receiver to use. It is my favorite as far as
performance, but it is so DEEEEEEEEEEEEEEEEEEEEEEPPPPPPPPPPPPPPPP! We are
talking about over 20 inches of depth.
The gain of the I.F. system is higher than any of my other receivers. The
MDS measures less than .1uV over the whole tuning range, which is in line
with just about every other receiver being sold today.
My favorite receiver? My Lowe HF-150.
I also have the HF-225, but it doesn't compare with the 150 for MW
reception, because of the lossy duplexer that it uses on the MW range
(why they don't use a bandpass filter for this range, I don't know).
My 2nd favorite is my NRD-515, followed by the Palstar R30, Yaesu
FRG-100, Icom R75, AOR7030, SW-8, and all of the others (I lost count).
Many folks are concerned about getting ahold of parts for the 6790, but
the same could be said about the Cubic, WJ, Collins, and all of the other
premium receivers. The main advantage of the super high end receivers is
that most of them can be used for shipboard operation, where they will be
co-located with high power transmitters.
An example is the Collins HF-2054 or the 851S-1 receiver............these
receivers can handle 100V of RF at the antenna input without damage to
the receiver, whether it is powered on or turned off.
Is this kind of robustness needed for the home receiver. Probably not.
The ESD protection that these receivers afford would be helpful, as
evidenced by the number of Lowe receivers that I have replaced the 1st
mixer in recently.
Somebody made a comment about how cool the Icom R-75 runs..........I bet
that you haven't attempted to touch that internal 5V regulator.
There have been some failures with this regulator recently. The failure
mechanism is caused by the fact that Icom chose to use an 18V supply to
power the radio. Dave Zantos has modified his power supply by adding a
pre-regulator that brings the voltage down to 13.5V before it enters the
radio.
My advice? Either modify that Icom power brick or replace it with a
regulated 13.5V power supply.
Looking inside of that supply, you will find spots on the circuit board
for adding bypass caps across each rectifier diode.
Add .01uF caps in these places and it will prevent the diodes from
rectifying RF. Another good mod for this power supply is to add a 1uF NP
cap from each leg of the SECONDARY of the power transformer to ground.
This snubs the switching noise from the rectifier diodes.
I have heard mention on this NG that purchasing a good regulated supply
gets rid of these emissions........this is not really the case. Any power
supply can be made quiet by using the aforementioned techniques.
The AOR7030s power supply can also benefit from these mods.

Pete

In article
,
"Pete KE9OA" wrote:

Snip

Somebody made a comment about how cool the Icom R-75 runs..........I
bet that you haven't attempted to touch that internal 5V regulator.
There have been some failures with this regulator recently. The
failure mechanism is caused by the fact that Icom chose to use an 18V
supply to power the radio. Dave Zantos has modified his power supply
by adding a pre-regulator that brings the voltage down to 13.5V
before it enters the radio. My advice? Either modify that Icom power
brick or replace it with a regulated 13.5V power supply. Looking
inside of that supply, you will find spots on the circuit board for
adding bypass caps across each rectifier diode. Add .01uF caps in
these places and it will prevent the diodes from rectifying RF.
Another good mod for this power supply is to add a 1uF NP cap from
each leg of the SECONDARY of the power transformer to ground. This
snubs the switching noise from the rectifier diodes. I have heard
mention on this NG that purchasing a good regulated supply gets rid
of these emissions........this is not really the case. Any power
supply can be made quiet by using the aforementioned techniques. The
AOR7030s power supply can also benefit from these mods.

You are right about the 5V regulator. These are series regulator
elements and the higher the input voltage the more power they must
dissipate to regulate the voltage down to the lower voltage.

People don't seem to get the diode rectifier concept here though. The
diode in the power supply passes current when the voltage polarity is in
the right direction and blocks it in the reverse. This is the
rectification function. When the diode switched from on to off the
circuit goes to high impedance. This results in a voltage spike that can
damage the diode if the voltage goes above the PIV rating. PIV stands
for Peak Inverse Voltage. It is this voltage spike every time the diode
switches off that causes EMI/RFI depending on the path. It could be
either or both but is usually mostly EMI.

If it is mostly EMI, the usual case, then a common mode choke will block
the majority of the diode switching noise on the cord to the radio.

The power supply terminology to reduce the PIV voltage across the diode
so as to not damage it is a "snubber" circuit. This is usually made of a
cap and resistor across the diode. The cap/resistor time constant value
is determined by the duration of the reverse spike it design to absorb.
The resistor burns the power.

If the spike is small and you want to suppress it for RF reasons only
then it can be just a cap. The capacitor will circulate the current from
the voltage spike around the diode, which is a small RF current loop,
instead of allowing it to propagate away from the diode through the rest
of the power supply circuit up the power cord and into your radio and
make a buzz at 60 or 120 Hz.

You can use a cap to the AC outlet ground on the secondary side of the
transformer but it might not be the best thing to do as it or a pair on
either side on the secondary will generate a continuous current down the
AC mains ground lead at 60 Hz. It might be better to use one cap on the
negative side of the DC output to ground in order to reduce this common
mode switch noise. Alternatively you might try a cap on the positive
output to ground in addition to the one one the negative side. Here you
will only be sending the noise currents down the AC mains leads and not
the 60Hz components.

--
Telamon
Ventura, California