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Author Topic: SSB adapters for vintage receivers  (Read 28107 times)
K1YTG
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Posts: 486




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« on: January 22, 2012, 01:04:37 PM »

I have noticed many ssb adapters for vintage rigs.  Isn't the idea on the vintage rig to experience the way it used to be?  Learn to use the BFO to tune in the ssb?
If you want the ease of a modern rig, I assume there is a modern rig available.
Changing the old rig around may make it easier but easier is available whenever you want it.
Experiencing the way it used to be is part of owning the vintage piece?
Or should I break down and spend the money to try out a product detector on one of the old rigs, such as r-388?
Perhaps I would use it more often?
What has been you experience with inboard or outboard ssb units?
Norm
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AC5UP
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« Reply #1 on: January 22, 2012, 04:24:12 PM »

Detecting an SSB signal on an AM/CW receiver with a BFO has its limitations... And that's why your Uncle Sam spent large amounts of money to buy pallets full of these for the DoD: http://bama.edebris.com/download/tmc/cv591a/cv591a.pdf

10 tubes plus rectifier and voltage regulator. We're talking about a serious piece of gear. The book is a quick download and the theory of operation / circuit description might be useful to appreciate the value of the adapter.

The other common unit was the CV-1694 / GRC-129 made by Manson Laboratories. It's something of a stripped down converter compared to the CV-591 from TMC. I have both, and the CV-1694 appears to need the last IF and ~455 KC BFO signal from a modified R-390A along with B+ and 6.3vac filament power. Never found any tech manuals or confirmation on whether B+ is 150, 180 or 250 vdc so I check the web occasionally to see if anything new has been published. Nice little rack mount box, someday I might add a non-functioning switch marked "Helter Skelter".

As for the CV-591... Almost fully self contained and all it needs is the last IF signal from the back panel of a GPR-90 or R-390A. I have seen comments on the web claiming that NOTHING sounds better on SSB than an R-390A / CV-591 combo but you know how some Collins collectors are prone to exaggeration..........  Cool
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W4OP
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« Reply #2 on: January 22, 2012, 04:55:46 PM »

I partially agree. I have restored a beautiful RME-4350 (http://www.parelectronics.com/vintage-radio-restoration.php)

AM is simply wonderful on it and that beautifully smooth dial is a luxury. I use  the receiver a lot while I am working. However, listening to a CW net or SSB roundtable takes constant attention to the RF Gain control in order to hear the weak and loud stations.
I designed a product detector for the rig (which already has 455KHz IF out and audio in ports on the rear apron).
So now the RX is also a joy to use on CW/SSB. No holes, easily reversable- the ONLY way I do mods.

Dale W4OP
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AA4HA
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« Reply #3 on: January 22, 2012, 07:32:34 PM »

I have an R-390A and a CV-591 SSB unit. While it does sound nice there are also some solid state devices from Sherwood Engineering that sound much better.

Since the CV-591 takes off from the 455 KHz IF it bypasses the somewhat imperfect audio system of the R-390A. For AM reception you can accomplish the same tap-off of the R-390A at the diode load lead and an external high quality audio amplifier.

No receiver is perfect (but the R-390 and R-390A are about as close to that perfection you will get with a tube based radio).

Another good adapter is the Hammarlund HC-10 SSB adapter. While I do not have one it would go along great with an SP-600.

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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K8AC
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Posts: 1897




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« Reply #4 on: January 25, 2012, 09:31:52 AM »

Quote
I have noticed many ssb adapters for vintage rigs.  Isn't the idea on the vintage rig to experience the way it used to be?  Learn to use the BFO to tune in the ssb?
Remember that before approximately the mid 1950s, there was very little SSB on the amateur bands.  I recall hearing very few SSB signals even in 1960 in my part of the country.  There was a huge resistance to SSB in the beginning because of how difficult it was to tune in on a typical receiver of the day.  Even after acquiring some skill in tuning the BFO for SSB, the results were quite poor and AMers were certain that SSB would die an early death.  My recollection is that my fellow hams just avoided listening to SSB completely and so the assumed experience of "the way it used to be" in tuning SSB just didn't exist.

I've restored a ton of boatanchor receivers over the years, and have usually gone the route of using an external home brew product detector, although some of the receivers were constructed such that an internal product detector could be used with no holes drilled.  I used to use a MC1496 module and I see that's still available in a more modern form, the LM1596.  Such a product detector can easily be built on a small piece of perf board, and all you have to do is feed the IF signal and BFO to the module and route the detected audio to the receiver audio chain.  For receivers with an external connector for a product detector, those connections are readily available.  Another challenge to using the vintage receivers for SSB is that many of the receivers killed the AVC when the BFO was on.  In many cases, that's a fairly easy modification that involves not grounding the AVC line when the BFO is on, and just adding capacitance to the AVC circuit to slow things down a bit. 

The Hammarlund HC-10 is a nice unit that essentially takes the IF signal from the receiver (was it only for 455 KHz IFs?) and the remaining signal processing occurs entirely within the HC-10.  So, you gain some nice selectivity along with a product detector and audio stages. 

I recall one National HRO-60 to which I added the product detector, AVC modification and a Collins mechanical filter resulting in a very nice sounding SSB receiver (and I had the side benefit of better CW operation with AGC).
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G3RZP
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« Reply #5 on: January 26, 2012, 12:23:20 AM »

Part of the problem was that the BFO injection to the diode was low, to reduce noise. In fact, I seem to remember one pre war rx had a control to vary the BFO level. In order to get good AM performance from a diode detector, you want 10 volts or more of carrier: to demodulate SSB, you would need at least 10 volts of BFO, probably more, and still need to back off the RF gain control. But then you hit problems with insufficient audio. The large voltage needed for the diode was part of the reason for the popularity at one time of the infinite impedance detector, plus it didn't load the last IF transformer as much as a diode. But it didn't provide AGC either, so that had to come from somewhere - often the plate of the last IF amplifier. The 6B8 double diode, semi-remote cut off pentode was sometimes used for that.

One method I've used succesfully is to apply the high level IF signal that you have anyway via a few pf to the suppressor grid of something like a 6SJ7, with the rest of 6SJ7 used as an electron coupled oscillator for the BFO. The advantage of this is that low mu of the suppressor grid is able to take a fair amount of volts, while the coupling to the AGC diode is so low that the AGC still works. It also quite often allows the original tube to be used!
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N2EY
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« Reply #6 on: January 26, 2012, 10:07:12 AM »

Remember that before approximately the mid 1950s, there was very little SSB on the amateur bands.  I recall hearing very few SSB signals even in 1960 in my part of the country.  There was a huge resistance to SSB in the beginning because of how difficult it was to tune in on a typical receiver of the day.  Even after acquiring some skill in tuning the BFO for SSB, the results were quite poor and AMers were certain that SSB would die an early death.  My recollection is that my fellow hams just avoided listening to SSB completely and so the assumed experience of "the way it used to be" in tuning SSB just didn't exist.

Opinion question:

From what I have read and heard, SSB in amateur radio didn't really take off until the introduction of SSB transceivers such as the KWM-2, SB-100, etc., and similar transmitter-receiver pairs that could transceive.

The reason I have come up with is that tuning in an SSB signal, zero-beating, and similar tasks was a pain in the neck, compared to AM, when using typical gear of the 1950s and earlier. Even setups intended for SSB, such as the HT-32/SX-101 pair, weren't that easy to use. (And they cost a fortune!)

But when the SSB transceivers arrived, everything changed, because they were so much easier to use. And they cost less than separates.

Your opinion?

73 de Jim, N2EY 
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G3RZP
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« Reply #7 on: January 26, 2012, 12:30:11 PM »

Jim,

Don't forget things like the products under the names of Swan, National, Galaxy and so on. They were cheaper, smaller, lighter and easier to use (except for the drift of the Swans!) than oether the separates or many of the AM set ups. Over here, the KW2000, a sort of copy of a cross between the KWM2 and the KWM1. On A Saturday morning, G8KW who started KW Electronics was there with guys lining up to pay cash - and it was around $500 for the transceiver. He used to literally sell around 15 each week!

But you are right.
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KQ6Q
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Posts: 1003




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« Reply #8 on: January 28, 2012, 08:45:52 PM »

Back in the 50's, I lived down the street from W6VX, and we both had HRO Sr's.
I copied his hot-up mods on mine -
6AG7 1st RF, 6DC6 2nd RF, 6BA7 mixer, added a collins mech filter after the mixer,
and a 6BA6 to make up for the filter loss, and replaced the Detector/1st audio
module with a Vector plug-in unit where I built a copy of the product detector
from the 75A4 with a 12AU7, and used a miniature 7-pint to emulate the original
audio and AM detectors. It worked VERY well. It might still be floating around
out there in Antique-boat anchor land - I sold it after I was married and being
moved around in the military - with the speaker, external PS and plug in coils,
it was just too bulky. Before I got the mech filter, I even had a BC-453 Q-5'er on it.

Those were the days!
Fred, KQ6Q
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K8AC
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Posts: 1897




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« Reply #9 on: January 29, 2012, 02:38:50 PM »

N2EY question:

I suspect that one's recollection of what drove the move to SSB will be different depending on your age and financial situation while the change was in progress.  I grew up in a blue-collar community and was a teenager at the time, so state-of-the-art gear was a bit beyond my reach.  The guys in the club who were out of high school and had jobs went for Drake gear - R4/T4 originals.  The problem in getting on SSB wasn't so much the receiver, as there were some decent Hammarlunds such as the HQ-170, but rather there were not many choices in SSB transmitters.  A bit later, when the Heathkit transceivers and receiver/transmitter pairs came on the market, that was the entry to SSB for those of us with not much money.  Collins gear was out of reach for just about everyone that I knew. 

One big difference between then and now was that there were virtually NO collectors of ham gear and the prices of used stuff was low.  Once something new came out, the price of the older stuff tumbled and that's where the young hams without much money got their rigs.  My first SSB transmission capability came in the form of a Heathkit HW-100 that I bought for $150.  After that, it was Drake gear for many years. 

Interesting the Fred mentioned the BC-453 Q5'er.  I had a friend in 1959 who assembled a receiver using command sets with a BC-453 as a Q5'er and that was my introduction to a smooth-tuning CW receiver with selectivity.  At that time, you could pick up command sets for $10 or so each.  Today, the collectors have driven the prices out of sight.
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G3RZP
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« Reply #10 on: January 30, 2012, 02:43:33 AM »

I picked up a virgin BC453 Q Fiver rx, without dynamotor, for $15  3 years ago. Figured it was bargain then.
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AB7KT
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Posts: 158




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« Reply #11 on: January 30, 2012, 05:48:01 PM »

"What has been you experience with inboard or outboard ssb units?"

I came into the ham radio game long after SSB was standard issue. But, I like the old rigs and own a number of them. I recently bought an outboard SSB unit off of eBay for my R-390A. Not because I needed it, but because I buy all kinds of junk I don't need. This is a solid state, modern manufacture, small black box with a single three position switch on the front for LSB OFF USB. It connects to the 455 IF BNC connector on the back of the R-390 receiver. You have to also use an amplified speaker for the audio output.

After hooking it up, I found it somewhat easier to tune in a SSB station. Not enough so that I thought it was worth buying if I had to do it over again though. It isn't hard to tune in a SSB signal with the R-390 to begin with.
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I thought you said this was a weak signal mode ? I HAVE a weak signal and he still didn't hear me.

FWIW: My callsign is AB8KT
N2EY
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Posts: 5067




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« Reply #12 on: February 02, 2012, 03:07:23 PM »

I suspect that one's recollection of what drove the move to SSB will be different depending on your age and financial situation while the change was in progress.  I grew up in a blue-collar community and was a teenager at the time, so state-of-the-art gear was a bit beyond my reach.  The guys in the club who were out of high school and had jobs went for Drake gear - R4/T4 originals.  The problem in getting on SSB wasn't so much the receiver, as there were some decent Hammarlunds such as the HQ-170, but rather there were not many choices in SSB transmitters.  A bit later, when the Heathkit transceivers and receiver/transmitter pairs came on the market, that was the entry to SSB for those of us with not much money.  Collins gear was out of reach for just about everyone that I knew.

That's pretty much what I recall from the 1960s. Collins was for doctors, lawyers and well-heeled business types.

Point is, what really got SSB rolling was rigs that made it easy to use and less expensive overall than AM separates of the same power.

One big difference between then and now was that there were virtually NO collectors of ham gear and the prices of used stuff was low.  Once something new came out, the price of the older stuff tumbled and that's where the young hams without much money got their rigs.  My first SSB transmission capability came in the form of a Heathkit HW-100 that I bought for $150.  After that, it was Drake gear for many years.

I remember that most hams couldn't afford to collect rigs - they represented too much of an investment! And with prices dropping, it made sense to unload the old stuff fast. A lot of us beginners started out with used stuff because of that. 

Interesting the Fred mentioned the BC-453 Q5'er.  I had a friend in 1959 who assembled a receiver using command sets with a BC-453 as a Q5'er and that was my introduction to a smooth-tuning CW receiver with selectivity.  At that time, you could pick up command sets for $10 or so each.  Today, the collectors have driven the prices out of sight.

Early on I struggled with various homebrew, surplus and used commercial receivers, winding up with an SX-99.

Then I discovered the idea of putting a crystal-controlled converter in front of a BC-453 for 80 and 40 CW. The result was amazing! I sold the SX-99 and used the BC-453/converter combo for quite a while, until I learned to build a better receiver.

IMHO Command sets today aren't any more expensive than they were back then, once you adjust for inflation, unless you want a mint example. I figure that $10 back in the mid-1960s equates to $60-70 today. What really costs a mint are Command set accessories, because nobody kept them!

Thanks for the reply

73 de Jim, N2EY



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K0KHZ
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« Reply #13 on: February 24, 2012, 12:36:01 PM »

Jim,

Don't forget things like the products under the names of Swan, National, Galaxy and so on. They were cheaper, smaller, lighter and easier to use (except for the drift of the Swans!) than oether the separates or many of the AM set ups. Over here, the KW2000, a sort of copy of a cross between the KWM2 and the KWM1. On A Saturday morning, G8KW who started KW Electronics was there with guys lining up to pay cash - and it was around $500 for the transceiver. He used to literally sell around 15 each week!

But you are right.

Transceivers were a big "leap ahead" in the SSB growth curve, but please do not lose sight of the historical process involving the GE series about homebrew SSB generation....  that was at the core of early SSB on the bands. 

That technology evolved to a firm called Central Electronics, where the transmitters model 10A and 10B (plug-in coils!!) both kit and manufactured put many hams on SSB, and the Sideband Slicer receive adapter tapped the IF from your existing receiver provided fine sideband rejection from your AM bandwidth receiver.  Even today we find homebrew using the phasing technique of sideband processing, both transmit and receive.  Even in the solid state environment.  Look, no SSB Filter !!

Let us Not Forget......
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W9GB
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« Reply #14 on: February 24, 2012, 01:56:25 PM »

Quote from: w4op
I designed a product detector for the rig (which already has 455KHz IF out and audio in ports on the rear apron).

Dale, is that the PC board mounted under the meter on the front panel (right side)??

greg, w9gb
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