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Author Topic: 30L-1 RF INPUT CABLE  (Read 28012 times)
W9NVN
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Posts: 12




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« Reply #60 on: August 09, 2016, 12:36:59 AM »

Tom, Thought I would chime in and say   congratulations on the Yasme Excellence Award, and as W9IQ said, very well deserved and thank you for sharing your knowledge and expertise and your very informative web site. As I have observed your many posts, it is clear to me you have always striven to
be accurate and always explaining in a concise easy to understand manner.. I wish you the very best!

               VY 73 W9NVN
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K3VO
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Posts: 31




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« Reply #61 on: August 12, 2016, 02:20:22 PM »

RE cable for 30L1. I used about three feet of RG 8X from my Transceiver  to the amp. It worked perfectly on all bands  including 17 and 12 meters. As I recall Bill Orr W6SAI wrote a lot about the 30L1  and influenced me as to how I set it up. Make sure  you use a relay for the PTT with a modern trancseiver.
Ed K3VO
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K9AXN
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Posts: 441


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« Reply #62 on: August 12, 2016, 03:10:23 PM »

Ed,

It's nice to hear a success story for the 30L1.  What are you driving it with?

Kindest regards Jim
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K3VO
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Posts: 31




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« Reply #63 on: August 14, 2016, 08:35:57 AM »

I used a IC-746 when I had it. Managed to work 275 countries with this setup. I sold  everything when moved to Nv with HOA restrictions. Now just a dipole and a transceiver
ED
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K5PB
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Posts: 27




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« Reply #64 on: August 15, 2016, 01:04:15 AM »

Some 30 years ago on a visit to Cedar Rapids, I was told by some amateurs working at Collins that the original 30L1 approach was done by one of the amateurs as a home brew item, and when seen, the commercial possibilities were recognised and so the 30L1 appeared. How true this is, I don't know.

Pete, you are absolutely correct about the origin of the 30L-1.  I was there.  It started out as what we called an "Under the Lab Bench" project (i.e. not formally funded), and was designed by Gene Senti W0ROW (now SK), who was head of the Amateur Design Group at that time.  It was intended to match the 32S/KWM-2 and 2A in size and drive requirements.  There was also high interest at the time by the USAF and some of the "dark" agencies in an easily transportable station of greater power than the KWM-2A by itself.  Art Collins saw it one day and said "Let's get it into production."  Thus, it got to be somewhat of a rush job.  I was assigned to write the original manual for it.

The main purpose of the so-called Super Cathode circuit design was primarily to provide a better match between exciter RF output level and amplifier drive requirements.  The 20.5-foot RF interconnect cable shippped with earlier production I think was mainly a spillover from the 30S-1; it was later dropped. I used a 30L-1 on many bands using good antennas with no sign of instability, but I don't doubt that with a lousy, highly reactive load it could be problematic.

By the way, Warren Bruene designed the 30S-1 but had nothing to do with the 30L-1.  I worked with him personally for many years, and he was truly a gifted engineer.  One does not get elected a Senior Fellow in the IEEE by being incompetent.  I find some of the comments elsewhere in this thread to be offensive and patently untrue.

Best to all,
Stu, K5PB
Collins Radio, Ret.
« Last Edit: August 15, 2016, 01:40:08 AM by K5PB » Logged
G3RZP
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Posts: 1165




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« Reply #65 on: August 15, 2016, 03:31:06 AM »

Stu,

Thanks for that info - it must have been about 30 years ago I was told that, when I went to Cedar Rapids to present two papers at the IEEE Fallcon convention. Rockwell actually asked for me and paid the air fare from Chicago! The last time I was there was in 1988 when in two days, I went to Rolling Meadows IL (the old Hallicrafters plant), Cedar Rapids IO, Kansas City KS, Fort Wayne IN and ended in Boca Raton FL at 0200...

Do you know why the 30L1 had such a low value of plate choke inductance - 40 microhenries? On 3.5 MHz, it needs an extra 52 pF of plate tuning capacity, and has about an amp of RF in it in addition to the DC. That puts around 9 volts across the plate choke bypass capacitor and still 2 volts across the electrolytics.

The other question is about the handbook. Mine at least says that for 230 volt operation, the  two 115 volt primaries are in series and the junction of the two goes to the neutral. This seems highly dubious to me, because if the two phases aren't exactly balanced, the transformer could get very hot trying to do that. Plus of course, for operation in countries having a 230 volt supply, it would blow the fuse as 230 volts got put across the 115 volt section.

I understand it was a very long time ago, but I figured you might know. I doubt anybody else does!

I never met Warren Bruene, but his book with Pappenfus is a classic, and he contributed a lot to QST.

73

Peter G3RZP
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K9AXN
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« Reply #66 on: August 15, 2016, 09:08:24 AM »


By the way, Warren Bruene designed the 30S-1 but had nothing to do with the 30L-1.  I worked with him personally for many years, and he was truly a gifted engineer.  One does not get elected a Senior Fellow in the IEEE by being incompetent.  I find some of the comments elsewhere in this thread to be offensive and patently untrue.

Best to all,
Stu, K5PB
Collins Radio, Ret.


Stu,

Good of you to support Bruene's legacy!

Kindest regards Jim
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K5PB
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Posts: 27




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« Reply #67 on: August 15, 2016, 10:58:52 AM »

Hi Peter, G3RZP,

The 30L-1 was just going into production when I joined Collins on 1 Feb 1961 (wow, some 50+ years ago). I never discussed the plate choke value with Gene, but I suspect it may have been partly space but probably more a matter of avoiding series resonances.  The military and other agencies used the KWM-2A/30L-1 combination on many frequencies other than the ham bands, so choke resonance was definitely a consideration.  For ham-band only use, of course, you could increase the value and park the series resonance somewhere outside of those frequencies.  Tom, W8JI, has some great info on plate chokes on his web site.

To Jim, K9AXN,

Thanks for the kind words re Warren Bruene.  He was not only a colleague but a good friend for decades.  He was endowed with perhaps the best quality in an engineer, an inquiring mind, and he was mentally sharp right up to his passing in his 90s.  I think his legacy is very much worth being highly respected.

Have to go out of town for several days, but will respond to anything further when I get back.

Best to all,
Stu, K5PB


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K9AXN
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Posts: 441


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« Reply #68 on: September 06, 2016, 10:36:17 AM »

You can find a more detailed description of the cable length issue at

http://collinsradio.org/Signal/newsletters/Issue%2071%203rd%20Quarter%20of%2013%20Post%20War%20(PDF).pdf

See page 16 and the bibliography for several other sources.

As you review the details from the sources it becomes apparent that the cable length had differing effects on the 5 bands it was meant affect.  The net effect that I came away with is it was meant to improve the IMD one or two db to offset the distortion caused by phase modulation in the 32S and KWM exciters. 

It was also apparent, but unstated, that the 32S and KWM series radios were vulnerable because they implemented two stage feed back from the final plate to the driver cathode reintroducing the phase disturbance from the plate.

Was it simply a marketing hype conspiracy or an effort to get the last drop of functional improvement from the technology --- You decide.

One thing jumps out --- the 30L1 was not the problem; any GG amp would have had the same effect on the 32S and KWM radios.

Last thought.  There were 17,000 30L1 amps sold to a variety of people with a variety of technical expertise.  It had some forward thinking unique design ideas. 

Regards Jim
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K5PB
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Posts: 27




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« Reply #69 on: September 09, 2016, 11:37:17 PM »


Was it simply a marketing hype conspiracy or an effort to get the last drop of functional improvement from the technology --- You decide.


Jim, I can say with assurance that it was mostly the latter.  We had an in-house developed spectrum analyzer, the 478R-1 that was quite advanced for it's day.  It was housed in a 6-foot high cabinet, had a 17" CRT, and could "see" -70 to -80 dB down.  Many an hour was spent in the labs tweaking our amps and their drivers to eke out a few more dB of IMD suppression.  The goal of ultra-clean signals was a Collins mantra.

Naturally, the marketeers made as much of this as possible, but it was based on substance, not smoke.

73,
Stu, K5PB
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KD6VXI
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Posts: 177




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« Reply #70 on: September 10, 2016, 09:58:27 AM »

Stu,

It shows.   Unless running class A or predistortion,  today's crap isn't as clean as what you guys turned out.

Quality is job one.   

--Shane
KD6VXI
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G3RZP
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Posts: 1165




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« Reply #71 on: September 10, 2016, 04:26:06 PM »

Shane,

Three years ago, I gave a lecture at the RSGB Convention entitled 'Spreading the Sewage', in which I analysed the degradation in high order IMD products following the introduction of solid state PA stages in amateur equipment. After the last generation of tube PAs, it has got very bad with anything up to 11th order now being significant, whereas before, anything above 5th order wasn't worth worrying about - were it Yaesu, Kenwood, Collins, Drake....

I offered the talk to W9DXCC the other year but never got a response......neither yea or nay, just silence.


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K9AXN
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« Reply #72 on: September 10, 2016, 07:15:10 PM »

Shane, Stu,

Your right!  If I was in the market for an amplifier that used 811A's I would not be looking for a current production amp --- It would be hands down the 30L1.  The amp has been shaken down and modified to eliminate instability and that includes leaving the negative feedback active.  I don't believe any of the directly grounded grid 811 amps could get close to the IMD numbers of the 30L1.

Stu, after going through that material it was obvious that the cable did make a minimal difference --- when your chasing excellence, every drop counts.  Also, found nothing that infers that it affected all bands equally or that it had anything but a minimal effect.  Actually it stated that it had little if any affect on the 20 Metre band.  Couldn't find anything that reeked of invalid hype.  

The folks that suggested the conspiracy theory and denigrating comments directed at Bruene were like nails on a chalkboard.  I look at Bruene of Collins, Stanford and Orwin of Hallicrafters and many others that were truly great and innovative engineers who never blew their horns.    

A super day to you--- Regards Jim  
« Last Edit: September 12, 2016, 06:57:54 PM by K9AXN » Logged
KE7YD
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Posts: 100




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« Reply #73 on: September 11, 2016, 12:17:42 AM »

Todays amps are built to a price point, just as everything else is.  I ran a couple of Collins products through the BLS inflation calculator. Here are the results.  KWM-2, introduced in 1959 for $1150. Now it would be $9575. The 30L1 amp, introduced in 1961 for $550. Now it would be $4185.  The 30S1 amp was introduced in 1958 for $1550. Now it would be $12,906.

Ken
KE7YD
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W3RSW
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Posts: 604




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« Reply #74 on: September 11, 2016, 02:10:12 PM »

That really puts it in perspective. I think if I were going to get one of Ameritron's amps I'd go for the single 3cx800a7 model. Doesn't over stress the lesser product line output network and power supply like the twin tube model and can be slightly modified to amplify a K3 or similar radio running only 20 or 30 watts at much better IM products at those reduced levels.

 Run the Amer. at 750 to 900 watts output. The Eimac original 3cx800 rating was for 1200 out so I'd try to find a decent used Eimac for a spare if doubting the lifetime of the included Chinese copy.

Hey, better yet a new 3cx obtained somehow, --estate, surplus from someone having too many spares   Grin or whatever .

Peter, RZP, my admiration of you keeps growing.  Just the other day I ran across an article in August 2011 "QST" about you attending a standards conference.  Your comment about studied ignorance of cleaning up dirty noise floors is ... Well, your right, "the silence is deafening."

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Rick, W3RSW
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