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eHam Forums => Boat Anchors => Topic started by: W9KDX on September 01, 2011, 06:07:04 AM



Title: Power ratings on 1960s transceivers
Post by: W9KDX on September 01, 2011, 06:07:04 AM
I was looking through some of my old electronics catalogs from the 1960s and I noticed that virtually all of the transceivers, (Drake, Swan, Hallicrafters, Hammarlund) had a minimum of 250 watts PEP on SSB transmitting power.  Most had 400-500 watts.  It seems that today the standard is 100 watts and I was just curious as to whether the rating system changed like it did for stereo equipment, or if there was some other reason that today's equipment was lower powered.

Thanks guys.


Title: RE: Power ratings on 1960s transceivers
Post by: AC5UP on September 01, 2011, 07:15:07 AM
Older tube gear was typically rated by DC WATTS INPUT to the finals since watt meters were relatively rare back in the day but almost every Ham had a VOM. If a pair of 6146's ran 600 volts on the plates and pulled a quarter amp key-down CW that would be 600 x .25 = 150 watts at DC.

Efficiencies varied depending on the tubes used and the band, but the rule of thumb was RF Out = 50% of DC In. In the example above our "150 watt" transmitter would be good for approximately 75 watts into the coax on 40 and 20 Meters. As recently as the mid 70's it was not unusual for a three tube hybrid rig to output 110 watts on 80 Meters and 80 watts on 10 Meters as HF tubes tend to run out of steam toward the upper bands. The advertising was all ballpark numbers, but a good Ham knew the other side of the circuit won't hear the difference between 100 watts and 85 watts.

If you made the Q you were running enough power......  ;)


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 01, 2011, 07:50:27 AM
Not only was it input power (Hallicrafters had a lot of 144 watts plate input SSB rigs), but the higher power ones were using (abusing?) sweep tubes.

Also 100 watts out still allows a reasonable size heatsink.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 01, 2011, 08:33:11 AM
Everything AC5UP wrote is true. Here's a bit more:

RCA released the 6146 in the early 1950s. Its design was partially based on comments from hams and ARRL about what the ideal amateur transmitting tube would be, and the shortcomings of existing transmitting tubes such as the 807.

The 6146 was very popular from the start, for a whole bunch of reasons, and pretty soon most manufactured and ham rigs beyond the economy class ran either one or two 6146s in the final. The EFJ Valiant ran three, modulated by another pair. A pair of 6146s could provide 100 watts of plate-modulated AM RF output without strain, and a bit more on CW. They could do SSB just as well.

In 1959-1960 Collins released the KWM-2. While it was not the first amateur HF SSB transceiver, nor the first to cover all 5 HF bands of the time, it became very popular despite its over-$1000 price. About the same time, Collins released the 32S-1 and 75S-1 matched-pair transmitter-receiver set, which cost even more yet were also very popular.

The KWM-2 and 32S-1 both ran a pair of 6146s in the final, with 800 volts on the plates. 180 watts PEP input, about 100 watts output (depending on band).

The KWM-2 and 32S-1/75S-1 became the gold standard for ham gear well into the 1970s. Competing manufacturers looked to those rigs as the ones to match or beat. They used the basic Collins paradigms, but had to figure out ways to compete.

The most obvious way to compete was to offer lower-priced rigs, which almost all did. The usual method was to offer fewer bands and/or less-costly circuitry and parts. The Collins PTO, mechanical filters, 200-kHz-segment heterodyne scheme and 6146 finals were all subject to cost-cutting scrutiny. Heathkit and a few others went the kit route, too.

In that same era hams began to use grounded-grid linear amplifiers for high power SSB and CW. The venerable 811A,  new tubes specifically designed for "zero-bias Class B" service such as the T-160L/572B and 3-500Z, plus the newly-introduced high voltage silicon rectifiers, made such amplifiers smaller, simpler and less expensive than anything hams had seen before. In particular they made high-power 'phone within the reach of many hams who could only dream of it before.

Such amplifiers had low gain compared to their predecessors; a typical GG amp like the Heath SB-200 required over 50 watts of RF drive. A "100 watt" transceiver or transmitter was a perfect match - buy the rig first, then add the amp when the budget had recovered. Nothing wasted along the way.

(Ironically, Collins never made a matching amplifier using the T-160L/572B or 3-500Z).

All these factors were the prime reasons so many hams went to SSB in the 1960s and left AM behind. They were also part of the reason many hams stopped homebrewing (but google "LWM-3" for an example of what some hams did).

Some rigmakers tried to compete by offering rigs with higher power ratings at a competitive price. This would reduce/eliminate the need for a linear amplifier. Such rigs used tubes designed for color TV sets in their finals - up to four of them in parallel. Because the TV "sweep tubes" were produced in much greater quantities, their price was lower, so the overall cost was less than a pair of 6146s. Unfortunately, such tubes became hard to find when tube-type TVs began to disappear.

When the change to solid-state came to amateur radio in the 1970s, the first step was the "hybrid" rigs such as the TS-520, with solid-state low-level and tubes for the final and driver, because the cost of a solid-state final was still too high. When the hybrids achieved acceptance and the cost of a solid-state final became low enough, the natural standard was a power level that matched the classic "pair of 6146s" .

And it still is.

73 de Jim, N2EY



Title: RE: Power ratings on 1960s transceivers
Post by: AD4U on September 01, 2011, 09:56:09 AM
Since I love boat anchor radios and have a room full of them, I will chime in.

All boat anchor radios were rated for power input, as already posted.  Power output was usually around 50% of power input.

Many rigs of that era used a pair of 6146 tubes - Collins S line and Heathkit SB and HW rigs to name a few.  These rigs were rated for 180 watts input and around 100 watts output.  Others like Drake and some of the National rigs used sweep tubes (6JB6), but the power rating was generally about 200 watts input and 100 watts output.  100 watts was the power needed to drive the linear amps of the era.

Then there was Swan, Galaxy, Yaesu, and some of the National rigs (and others).  They used (abused) color TV sweep tubes and were rated at 500-700 watts input.  These rigs were aimed at the hams who wanted a strong signal without having to buy an amp.  Two sweep tubes could be had for less than $10 and at that price it did not matter if they had to be replaced every 6 months or so.

I have a Swan 700CX (2-8950 tubes) that will put out 400++ watts PEP on SSB.  My Galaxy GT-550A (2-6LB6 tubes) and my Yaesu FTDX-570 (2-6KD6 tubes) will put out 300+ watts PEP.  

Hallicrafters even sold a transceiver (SR-2000 Hurricane??) that was rated at 2000 watts.

These rigs were not real fussy about having a 1:1 SWR and they did not seem to care if you used a balun or not and you generally did not need a "tuner".  I use these rigs regularly and get good reports.

Dick AD4U


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 01, 2011, 11:08:01 AM
Slight thread drift here...

What was the 572B/T-160L designed for? I cannot believe it was for grounded grid RF, becasue of when it appeared - 1953 or so is it first appearance in a ARRL handbook, and then it's Class B audio ratings. My suspicion is that it was originally intended for modulating a 500 Watt output AM BC station. Back in those days, not many amateurs were using 'slop bucket' as it was termed, so there was no demand for GG amplifiers. Some years later were the days for really extravagant claims for SSB - for example, it gave 20dB advantage over AM, so a 10 watt SSB station was as effective as kilowatt of AM!


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 01, 2011, 12:38:14 PM
What was the 572B/T-160L designed for? I cannot believe it was for grounded grid RF, becasue of when it appeared - 1953 or so is it first appearance in a ARRL handbook, and then it's Class B audio ratings. My suspicion is that it was originally intended for modulating a 500 Watt output AM BC station. Back in those days, not many amateurs were using 'slop bucket' as it was termed, so there was no demand for GG amplifiers. Some years later were the days for really extravagant claims for SSB - for example, it gave 20dB advantage over AM, so a 10 watt SSB station was as effective as kilowatt of AM!

I didn't know the 572B/T-160L went back that far! All the references I see are to the very late 1950s and early 1960s, but will check my Handbooks.

It is quite possible that it was designed originally for Class B modulator use. There were a number of triodes designed for "zero bias class B" (actually AB2 because the plate current is not zero at no-signal). The TZ-40 and 811 are two examples. Such tubes greatly simplify the modulator because there is no bias supply and no screen supply. They do require a few watts of audio drive, and in some cases require neutralization (!)

A few hams were using SSB in the 1930s, but the cost and complexity precluded widespread amateur use until after WW2. The development of practical audio phase shift networks and crystal lattice filters made amateur SSB relatively easy by the late 1940s, but relatively few hams went for SSB back then because:

1) It required equipment that was more complex than AM, and required a higher degree of stability.

2) Most existing rigs could not be made to work on SSB without considerable modification.

3) Most existing receivers, when adusted for SSB, lost the AVC and S-meter functions. Few had suitable selectivity settings.

4) "Zero beating" for net or round-table operation required real skill.

The development of the SSB transceiver and matched-pair transmitter-receiver changed all that. An SSB transceiver was actually easier to use than AM "separates" - and could cost less. The development of the table-top GG amplifier drove the final nail.

In AM days, running high power meant Big Iron and a serious amount of space, power and money. AFAIK, there were only two transmitters ever made for the amateur market that could run the USA legal limit of 1000 watts DC input, plate modulated. They were the WEFJ Desk Kilowatt ($1700 in the late 1950s, without exciter!) and the Collins KW-1 (if you have to ask the price, you can't afford it). A homebrew AM KW took up at least a 6 foot rack, and twice that space was not unusual. Power requirement was measured in kW, weight in hundreds of pounds, and everything had to be rated for continuous duty. Such stations were common in the late 1950s.

Jump ahead just 5 years, and a ham could have an SSB transceiver and 1200 watt amp on a card table (SB-100/200 combo). And the SSB station often cost less.

btw, the actual advantage of SSB over AM is about 14 dB. This is due partly to the elimination of the carrier, partly to using all the power in one sideband, and partly to the ability to use a narrower receiver.

73 de Jim, N2EY


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 01, 2011, 01:23:27 PM
Jim,

the advantage assumes a receiver improvement that is equally achievable on AM. If you take that away, then 6 dB is the advantage.

The cheapest high power AM must undoubtedly have been a surplus BC610 at about 400/500 watts DC input. Otherwise, as you say, heavy iron. But even 1 kW CW input was not a simple job. I remember in the early '60s, W1JFG was there first thing every morning (EST) on 20m AM. I seem to remember he had a Johnson....

And in those days, hams had at least a knowledge of Ohm's law, which doesn't seem to be the case now...

And I am not getting only at US hams - it seems to be world wide.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 01, 2011, 01:30:54 PM
Peter,

No argument from me on any of that.

Yes the '610 was surely a way to a couple of hundred watts of AM, but you had to do some work to get the rig behaving decently. The Globe King and Viking Five Hundred were other options - not cheap, but they did the job. And of course homebrewing in all its glory.

73 de Jim, N2EY


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 01, 2011, 02:35:42 PM
Jim,

the provenence of the BC610 is the somewhat amusing thing. It was a ham rig - the Hallicrafters HT4.

So was the HRO as a military piece of kit, and several Hammarlund receivers.

One wonders, without the US ham radio industry and American amateur radio operators in the services, how long it would have taken to win WW2.

The strange thing is that although the British at an early stage recruited amateurs to act as a an intercept service, the US never did the same.  Here, we had  people over age for call up, people with disability, still able to do intercept work at home - and very valuable it turned out.

Sorry, thread drift.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 01, 2011, 03:13:24 PM
the provenence of the BC610 is the somewhat amusing thing. It was a ham rig - the Hallicrafters HT4.

So was the HRO as a military piece of kit, and several Hammarlund receivers.

Yes, and several other pieces of ham gear went to war. IIRC, the Hallicrafters S-36 was used for a time in Great Britain to listen for enemy radars - it was the best available receiver for the frequency range.

The HT-4 -> BC-610 story is a bit more than simply rebadging, though. The original HT-4 needed lots of reengineering to meet the vibration, shock and humidity specs of the HT-4. In one early road test, the plates of the final amp variable cap were found on the bottom of the cabinet - it had shaken to bits!

The HT-4 also used some rather odd tubes, and had to be redesigned to use tubes on the JAN VT list of approved types. Interesting how many types on that list were made by General Sarnoff's RCA, and how few by other companies....

One wonders, without the US ham radio industry and American amateur radio operators in the services, how long it would have taken to win WW2.

Yes, they served in many roles. Recently I saw a documentary about the proximity fuze in which one of the administrators said that he would intentionally pair up hams with theoretical physicist types in the research teams. The theory folks knew the formulas and laws while the hams would push for practical solutions.

The strange thing is that although the British at an early stage recruited amateurs to act as a an intercept service, the US never did the same.  Here, we had  people over age for call up, people with disability, still able to do intercept work at home - and very valuable it turned out.

Never realized that, but quite true. I don't know if amateur intercepts fed Bletchley Park, but anything intercepted could have a potential use.

Of course being on this side of the pond, and more than 2 years behind in getting into the fray, some things got missed. the US role was somewhat different. I suspect the US brass considered intercept not so important here, except perhaps for U-boat comms. Or maybe they were afraid of leaks.

OTOH US hams not in uniform played roles in industry, research, WERS (a form of civil defense), radio instruction, and other ways. One particular unofficial service was figuring out ways to keep BC receivers working with available parts and tubes.

Even the ARRL Handbook went to war, in a special "Defense Edition" used for training.

btw, after WW2 it was discovered that the Germans had made copies of the HRO for their own use. I think the Japanese did too. High praise, in a way, and a foreshadowing of things to come.

To get back to the subject, WW2 military BA designs are sometimes considered rather odd by hams, particularly in power level. For example, the popular AN/ART-13 uses an 813 modulated by a pair of 811s. Most hams would consider that combo good for 450-500 watts input, yet the AN/ART-13 runs them at less than half that power. Of course this was done because the set might have to work under very trying circumstances (cold, heat, humidity, altitude, improper tuning, failed antenna) without failing, and without operator attention.

73 de Jim, N2EY



Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 02, 2011, 03:17:05 AM
Jim,

Intercepts were posted to P.O.Box 23, Barnet, from where they went to Wandsworth prison (!) where a special unit sorted them: a lot went on to Bletchley after that. The listeners were issued with receivers and headphones: the HRO my father had was fitted with a vernier scale for more accurate logging. That never went back with the HRO after the war - it's on my HRO today. The headphones didn't go back, either.

The RSGB took delivery of 3000 copies of their 'Amateur Radio Handbook' the day before war was declared. They worried about selling them - but they needn't have done. By the war's end, they had printed and sold 181,500! Because of its use in training the military, the paper controller specially released paper for it.

Strange that after the war, there was a lot of surplus gear around , but at least in the first few years, it wasn't cheap - a BC348 would cost two week's pay for the average ham.

BC610 - Have you seen  http://www.archive.org/details/VoiceofV1944  and 
http://www.archive.org/details/VoiceofV1944_2


Title: RE: Power ratings on 1960s transceivers
Post by: WA0ZZG on September 02, 2011, 06:07:17 AM
Those of you that like the old Collins gear will like this.  A couple of year ago, I ended up sitting with an old gentleman that was the designer of the KWM-2 PA cage and had a chance to chat with him.  He was personally hired by Art Collins because he showed up in the factory parking lot with a 5-band home made SSB transciever running in his car. He was using a pair of 6146's for finals. Nobody had done this before.   His first job was to make a pair of 6146's very linear.  These tubes were actually designed for VHF-FM radios and class C service.  They were not the most linear.  He ended up beating his brains out, until he came up with the concept of RF negative feedback.  That cleaned them up.
He is now in his 90's.  This was his first job as a young man. He was self trained and still lives in Cedar Rapids.
By the way......
The Collins 30L-1 was designed by a Collins Ham in his basement.  811A's are actually modulator tubes in 1KW AM broadcast transmitters, but were used because they could be put on their side and the case made the same size as a KWM-2.  They could also meet Art Collins demand for extreme linearity.

Dave  WA0ZZG


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 02, 2011, 07:13:39 AM
Collins were using negative RF feedback in the early 1950's - Bruene wrote it up in both Electronics and the IRE journal some years later.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 02, 2011, 04:56:20 PM
Fascinating stuff! Thanks for the link to the BC-610 video.

Some historic bits:

- The Collins KWM-2 (1959) was preceded by the KWM-1 (1957). The KWM-1 only covered 14 to 30 MHz, and required a heterodyne crystal for each 100 kHz segment (!) Both rigs used a pair of 6146s in the final.

- The Hallicrafters HT-32 SSB transmitter (1957) also used a pair of 6146s in the final.

- The first manufactured all-HF-band SSB transceiver was the Cosmophone 35. It had many advanced features and predated the KWM-2 by some time. However it was only produced in small numbers for a short time. It used a single 6146 in the final.

- The Collins 30L-1 appeared in 1961.

- I am not sure when the T-160L/572B tube appeared. My 1957 ARRL Handbook does not list it but my 1964 edition does. Since it was not an RCA tube my RCA Transmitting Tube manuals are no help.

- The best clue to the origin of the 572 that I could find is an article in QST for May, 1961. It shows an amp using a pair of United Electronics UE572 tubes, and says the tube is a new type. If so, it explains why Collins didn't use them; the 30L-1 design was probably already frozen before the '572 appeared.

- Like the 811-A, the T-160L/572B can be horizontally mounted (the SB-200/201 did so). Why Collins stuck with 811As is a mystery; perhaps they figured it wasn't worth redesign and retooling.

73 de Jim, N2EY


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 02, 2011, 05:59:22 PM
The 30L1 is also notoriously unstable. It is one of the few 4x 811 style tube amplifiers without neutralization. The only other commercial 4 x 811 amp I'm aware of that did not neutralize was a Dentron.


Title: RE: Power ratings on 1960s transceivers
Post by: AC5UP on September 02, 2011, 06:34:02 PM
Since this thread is hopelessly adrift...

The comments regarding WW II intelligence in the UK reminds me of an interesting conversation I had with an uncle many years ago. He was in the Army quartermaster's corps and stationed in England prior to D-Day. Said he had never seen so much stuff in one place and will never see anything like that again. It was that far over the top. Seems that Unca' Sam routinely double and triple shipped orders as Liberty ships didn't always make it to port and the invasion of an occupied continent is a very big deal requiring a buttload of stuff.

We're not talking about jeeps and guns exclusively. We're talking about everything that goes along with everything else from shoelaces to spare cotter pins to bulldozer mufflers.

The interesting part (to me) was that not everything made it to where it was supposed to go. The Brits had been on severe rations for several years and certain items like spark plugs and radio tubes tended to grow feet and walk away in the dark of night with great regularity. And of all the stuff that disappeared the weirdest thing of all, as far as my uncle was concerned, was the British obsession with gasoline powered lawn mowers. Even more peculiar was how the locals pinched them with total disregard for the Catch 22 nature of the crime... Boost a lawnmower and then what? You can't mow with it anywhere off the Army base because it's obvious what it is, where it came from, and the probable sequence of events that put it in your hands.

D'oh!

Didn't matter. The British take great pride in their gardens and nothing spiffs up a lawn like a proper mowing with a sharp blade.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 02, 2011, 06:40:34 PM
The 30L1 is also notoriously unstable. It is one of the few 4x 811 style tube amplifiers without neutralization. The only other commercial 4 x 811 amp I'm aware of that did not neutralize was a Dentron.

I always wondered about that. It's not as if adding neutralization to a 4x 811A amp is all that complex.

There's an article in QST for June, 1961 that shows a 4x811A GG amp with neutralization, so it wasn't a big secret at the time. The author says the amp was stable on all bands except 10 meters before neutralization was added.

73 de Jim, N2EY



Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 03, 2011, 02:03:32 AM
I am slowly rebuilding a 'bargain' 30L1. There were 3 Chinese 811s in it and the plates were horizontal for the filaments to sag into the grid, and one Russian 811 with the plate at 45 degrees! Several of the feedthroughs were broken, the power transformer had been rewound since it no longer had dual primary, only a 230 volt one, the 25k equalising resistors just flap about on wires, and the usual problem, at least on 230 volt 50 Hz, is the power switch had destroyed one of its contacts. And several of the electrolytics have seen better days, judging by the encrustation around the leads.

The rebuild has 4 572Bs, with the grids hard wired to ground, and a neutralising winding of Teflon insulated wire over the filament choke. I've planned the neutralising cap which will be coaxial cylinders with Teflon insulation. There's a hefty 22 ohm HV glitch resistor. The original plate choke is 44 microhenries, so that has about an amp of RF in it on 80: I've a 1 mH choke out of a TU5B (Tuning unit for the BC191) in series, and for the rectifier for metering, I've made a fully shielded (piece of 15mm copper tube) arrangement with a 300pf feedthrough cap for the input: there's a 4pf cap made from 5mm copper tube and Teflon insulated wire from the pi tank input. Plus step start on the AC input and a relay to actually switch the power. Bias in the filament centre tap, as is the send - receive arrangement.

I'd never have bought the thing had I been able to see what it was like inside...


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 03, 2011, 02:10:57 AM
Talking of things walking from Army stores in WW2.

The late GC3KAV was on Guernsey during the war: his wife and son got away on the last boat, but as the only plumber on the island, he stayed to fix a problem at the hospital. He was jailed for having a radio, but let out to do a plumbing job, and went back to jail with all the bits for a crystal set in his pockets. He and the jailer laid an antenna in the sewer, and thus the BBC news was distributed...Later, he stole a German Staff car by building a haystack over it when one unit moved out and before another moved in, and in the end he had a stock of over 10,000 gallons of stolen petrol in an underground tank intended originally as a septic tank. He also had a good collection of German WW2 radios that he 'liberated'.


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 03, 2011, 03:23:34 AM
The 30L1 is also notoriously unstable. It is one of the few 4x 811 style tube amplifiers without neutralization. The only other commercial 4 x 811 amp I'm aware of that did not neutralize was a Dentron.

I always wondered about that. It's not as if adding neutralization to a 4x 811A amp is all that complex.

There's an article in QST for June, 1961 that shows a 4x811A GG amp with neutralization, so it wasn't a big secret at the time. The author says the amp was stable on all bands except 10 meters before neutralization was added.

73 de Jim, N2EY



No matter how well the amp is laid out and built with four tubes, it is impossible to get unconditional 10 meter stability and sometimes 15 meter stability without neutralizing. That's why Collins came up with that silly 20 foot coax and phase of reflections nonsense. The long cable in effects adds an attenuator on the amp input.

All that NFB stuff does is make the problem or repeatability worse. Feedback capacitors across a couple stages that are tuned will not have consistent phase shift.  The stable way to do NFB when user adjustable tuned circuits are present is lifting the cathode through a resistance.

73 Tom


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 03, 2011, 05:58:58 AM
You can do feedback over two or three tuned stages if you are very careful and use phase detectors and servo loops to do the tuning, with some presetting from some form of memory. You also have to do a lot of Bode or Nyquist plots. Even so, there were various transmitters in the late 50's and early 60's of this sort using tetrodes where they had resistors in the filament circuit for feedback as well.

As Tom says, doing it by hand is recipe for disaster.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 03, 2011, 08:05:34 AM
Tom and Peter,

Great stuff on the 30L-1. I've always wondered what really went on with that design.

It's not as if Collins was aiming for the lowest possible price, or had to avoid patent infringement. They even had the Heathkit HA-10 Warrior amp as a guide (it's neutralized, btw). Maybe Collins had a warehouse full of 811As?

Heathkit saw the light in the SB-200, which replaced the Warrior after only a few years.

I can think of only three explanations:

1) By the early 1960s, Collins had spent a lot of time and $$ on ham gear development and took a break from it. Consider how many amateur products Collins introduced between, say, 1952 and 1962.   

2) Tied into 1) above is the relatively short time many Collins products of those days were on the market. For example the KWM-1 came out in 1957, and in just 2 years was replaced by the KWM-2. I bet more than a few KWM-1 buyers weren't all that thrilled, particularly when they saw the resale value of their KWM-1s drop. Same for those who bought a KWS-1. (Note that once Collins had the 75S-3/32S-3/30L-1/KWM-2 line done, there was no new HF ham gear from them until the KWM-380)

3) The T-160L/572B was brand-new in the early 1960s and for several years only made by one manufacturer. 811A was a common, well known bottle made by many companies. Even though the cost of a pair of 572s could be less (when you count the savings in sockets, plate caps, small parts, etc.),  cost was not as much of a major factor to Collins.

Thoughts? Guesses? Stories?

73 de Jim, N2EY



Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 03, 2011, 09:01:27 AM
I'm sure that somewhere, I saw a reference to the 572B in the mid 1950s, but of course, I can't find the reference. I find it hard to believe that it was originally designed for HF SSB service though. By 1960, better structures were well known - a pressed glass base like a 7094 would have given a far shorter grid lead. Even if you kept a UX4 type base, you could significantly shorten the grid lead with a pressed glass base. If you went to a 7 pin septar like the 832, you could have multiple grid leads, and reduce the propensity to parasitics. As Class B audio modulator for a 500 watt BC rig, I can see it, but for RF, it is a bit of a compromise.

My previous experience with them gave me troubles in stopping parasitics: we will see if this time, it's any better. No Tom, no nichrome!! Or any other snake oil charm....

I was told on a visit to Collins some years back on business that 30LI was originally an amp built by a Collins ham at home, and Art was so impressed he had it put into production. That jibes with what Dave, WA0ZZG heard. Haven't been to Cedar Rapids for years but I can still remember the smell from the corn processing plant!


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 03, 2011, 09:26:41 AM
I always wondered about that. It's not as if adding neutralization to a 4x 811A amp is all that complex.

There's an article in QST for June, 1961 that shows a 4x811A GG amp with neutralization, so it wasn't a big secret at the time. The author says the amp was stable on all bands except 10 meters before neutralization was added.

Collins had stabilitly isses in the 30L1 and several of the later transmitters because they hung their hats on that silly negative feedback system. That issue was the root source of the Collins part of a big white paper on how 6146B's were poorly engineered by RCA. KWM2's for example would break into oscillation and blow up the little RF feedback trimmer in that silly circuit.

RCA never planned of people misusing feedback and having stages running right on the edge of stability.

I suspect Collins thought floating the 811A grid on the small mica caps was a reliable cure for not neutralizing the 811's. On a bench, I am sure there are cases where it could work.

73 Tom


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 03, 2011, 12:28:31 PM
Tom,

Wasn't that a W6SAI (or similar call) idea to get 'pseudo super cathode driven' operation?

I can see it being useful for a fixed frequency amp at a frequency where the caps series resonate the grid inductance. Not otherwise - or am I missing something?


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 03, 2011, 03:00:22 PM
Tom,

Wasn't that a W6SAI (or similar call) idea to get 'pseudo super cathode driven' operation?

I can see it being useful for a fixed frequency amp at a frequency where the caps series resonate the grid inductance. Not otherwise - or am I missing something?

I think Orr lifted the idea from Collins. Unfortunately it was a bad idea no matter where it started.


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 03, 2011, 11:01:20 PM
The RCA Transmitting Tubes handbook has four 811 amp in it with 220pF capacitors from grid to ground BUT it does have neutralisation. But I do think they are too small.


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 04, 2011, 02:58:54 PM
The RCA Transmitting Tubes handbook has four 811 amp in it with 220pF capacitors from grid to ground BUT it does have neutralisation. But I do think they are too small.

They are too small for 160 and 80 meters, that's for sure!


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 04, 2011, 03:20:06 PM
The RCA Transmitting Tubes handbook has four 811 amp in it with 220pF capacitors from grid to ground BUT it does have neutralisation. But I do think they are too small.

I found that scnematic in TT-5, dated 1962. It is schematic 5-13. It does not appear in TT-4. The amp is for 80-10, so the caps may be adequate.

As far as I can tell, it is simply a copy of the K6SNO amp from QST for June, 1961. (Also appears in "Single Sideband for the Radio Amateur", 4th edition, 1965. And possibly elsewhere.)

But in both the ARRL publications and the Transmitting Tube book, the grid bypasses are 0.01 uf disks., and there is one for each grid. It looks to me as if the reason the grids aren't directly grounded to chassis is for grid metering and the application of cutoff bias through an external connection. Of course it is possible to perform both of those functions with directly-grounded grids (by not grounding the negative HV*) but K6SNO didn't do it that way for some reason. (Perhaps it didn't occur to him, and with .01 uF from each grid to ground they were pretty close to RF ground anyway.

* Methods of measuring grid and plate current in amplifiers with directly-grounded grids appeared in amateur designs of 1962 and probably earlier.

btw, the 4th edition of "Single Sideband for the Radio Amateur" makes no mention of the T-160L/572B, either in projects nor tube data. But the 1964 and later editions of the ARRL Handbook show data on the tube.

73 de Jim, N2EY


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 06, 2011, 09:14:48 AM
The RCA Transmitting Tubes handbook has four 811 amp in it with 220pF capacitors from grid to ground BUT it does have neutralisation. But I do think they are too small.

I found that scnematic in TT-5, dated 1962. It is schematic 5-13. It does not appear in TT-4. The amp is for 80-10, so the caps may be adequate.

220 pF is 206 ohms on 80 meters. The grid impedance is less than 50 ohms when conducting heavily, and higher with less G-K voltage.

How could placing 200 ohms of reactance in series with a time-varying resistance that gets less than 50 ohms over part of the cycle be adequate bypassing?

High reactance grid bypasses add a level of non-linearity to the system. Grid impedance varies greatly over the RF cycle, voltage division is obviously not constant over the RF cycle. It is also not constant with frequency. It is certainly not negative feedback like Collins and Orr said.

It is the polar opposite of what we actually want. I think it is an inexcusable design error. They acted like the tube has infinite grid-cathode impedance. Obviously they forgot it was a sub-2 class that draws grid current over a large portion of the RF cycle, with a wildly varying G-K impedance. 

73 Tom


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 06, 2011, 09:46:07 AM
The RCA Transmitting Tubes handbook has four 811 amp in it with 220pF capacitors from grid to ground BUT it does have neutralisation. But I do think they are too small.

I found that scnematic in TT-5, dated 1962. It is schematic 5-13. It does not appear in TT-4. The amp is for 80-10, so the caps may be adequate.

220 pF is 206 ohms on 80 meters. The grid impedance is less than 50 ohms when conducting heavily, and higher with less G-K voltage.

How could placing 200 ohms of reactance in series with a time-varying resistance that gets less than 50 ohms over part of the cycle be adequate bypassing?

Ya didn't read far enough, Tom.

The schematic I found in TT-5 shows .01 uF grid bypasses, not 220 pF. That's less than 5 ohms per bypass, and there are four of them, one for each grid.

The TT-5 schematic is identical to a 1961 QST article by K6SNO.

High reactance grid bypasses add a level of non-linearity to the system. Grid impedance varies greatly over the RF cycle, voltage division is obviously not constant over the RF cycle. It is also not constant with frequency. It is certainly not negative feedback like Collins and Orr said.

It is the polar opposite of what we actually want. I think it is an inexcusable design error. They acted like the tube has infinite grid-cathode impedance. Obviously they forgot it was a sub-2 class that draws grid current over a large portion of the RF cycle, with a wildly varying G-K impedance. 

I agree that 220 pF is too small, but that's not what was used.

73 de Jim, N2EY


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 07, 2011, 12:52:26 AM
220pF on each grid is what is used in the RCA book that I have. Don't know which one it is, as it is about 700 miles away at the moment - I'm at a meeting in Switzerland.


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 07, 2011, 02:49:13 AM
I was referring to the 220 pF. I read the .01 uF.



Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 07, 2011, 06:21:02 AM
I wonder if this was a copy of a copy of a circuit diagram and although the 220pF was supposed to be changed, it didn't actually happen. It is not unknown for the published circuit diagram to not match the equipment because of upgrades, or even errors in the original.

I'm not totally convinced that 0.01 mFd is as good as a very short piece of copper tape...


Title: RE: Power ratings on 1960s transceivers
Post by: W8JI on September 07, 2011, 01:06:08 PM
I wonder if this was a copy of a copy of a circuit diagram and although the 220pF was supposed to be changed, it didn't actually happen. It is not unknown for the published circuit diagram to not match the equipment because of upgrades, or even errors in the original.

I'm not totally convinced that 0.01 mFd is as good as a very short piece of copper tape...

A short piece of copper tape would be good, but there is sooo much thin lead from the socket up to the actual grid the overall fifference is pretty small. The only problem with small caps is at lower HF, at 20 MHz and above nothing can change very much. The long thin lead to the grid dominates.

I tried to get manufacturers to change how the grid lead is configured in both the 811 and 572. They really stink for RF. The Chinese didn't understand the idea, and the Russians were not even making the tubes any longer. Everything was existing stock.


Title: RE: Power ratings on 1960s transceivers
Post by: N2EY on September 07, 2011, 02:47:27 PM
Tom & Peter,

Well, there's a mystery! Because the original schematic and all the reprints I can find show .01 uF from each grid to ground. Maybe there was a typo in early TT-5s and they fixed it; I think the Transmitting Tube Manuals went through several printings each.

Oddly enough, the SB-200 schematic I have shows 220 pF from each 572B to ground! And a little RF choke in series.

The design has the power supply right on the same chassis (866As and choke-input filter; bet that thing was heavy!) so there's no reason not to just ground the grids directly and change the metering circuits slightly.

----

Too bad they wouldn't listen to you, Tom. I can think of several tube designs that would be a lot better with "disc seal" bases (or whatever the proper name is).

For example the 807 is IMHO a great lower-power tube except for the very long grid, screen and cathode leads. (Yes, the 807W/5933 is an improvement, but they could have used an octal base and made it really sweet.

And it's not like this stuff was unknown; the 2E26 and 6146 have much shorter leads and multiple cathode connections.

Could it be that the serious development work was going into external-anode tubes for VHF/UHF? One impression I get from my limited reading of RF stuff from the late 1960s onward is that the focus mostly seemed to be on VHF/UHF, with HF being a sort of backwater.   

73 de Jim, N2EY


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 08, 2011, 12:28:51 AM
Jim,

The 807 was a 'high frequency' tube for its time. In fact, there was an RAF aircraft tx that used a selected version, the 8018, at 120 Mc/s. Class C, but not very, with grid modulation of the previous stage, which probably explains why to this day, aircraft comms always sound horribly distorted to me! The tx got replaced fairly quickly: the new one had the design taken to the US where they probably had two fits, and built the SCR522 instead - a far superior device. Although the slide bars for doing the tuning were the same.The 807 did come out in 1936 or so, too.....


Title: RE: Power ratings on 1960s transceivers
Post by: G3RZP on September 08, 2011, 01:32:40 AM
There was an 807 family on a pressed glass Loctal base, with much shorter leads, made in the UK. The basic 807 equivalent was the STC 5B/254M: a wire ended version was the 5B/254G, while a single ended version was the 5B/255M (effectively a 6L6 on a Loctal base) . The 5B/257M was a 5B/255M with a 12.6 volt heater, and the 5B/258M was a 19 volt 0.3 amp heater version of the 5B/254M.

Strangely, in spite of the much shorter internal leads, it was still rated to 60MHz for full power and 125MHz at reduced power.

It first appeared in the early 1950s.


Title: RE: Power ratings on 1960s transceivers
Post by: K4EJQ on September 13, 2011, 10:45:52 AM
Jim, Tom and Peter; I must say I have enjoyed reading your "drifty" thread. Thanks for sharing it with me. 73, Bunky, K4EJQ