Collins 30L1 design questions

Discussion in 'Amateur Radio Amplifiers' started by K9AXN, Feb 16, 2018.

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  1. W1BR

    W1BR Premium Subscriber QRZ Page

    You are kidding, right??? TC-2, 30pF. Neutralization is from the pi-net output.
    Did you even look at the website? Instead of adding an out of phase link on the filament choke like Heath, B&W and others did, they are assuming a perfect 18o degree phase shift of constant amplitude occurs across the tank. Poor engineering at best.
    Last edited: Feb 17, 2018
  2. KA9JLM

    KA9JLM Ham Member QRZ Page


  3. K9STH

    K9STH Platinum Subscriber Platinum Subscriber QRZ Page


    I have absolutely no idea as to what the "fix" was for the 30L-1. Those circuit changes happened several years before I was employed at Collins Radio. Also, virtually all of the amateur radio equipment was built in the Cedar Rapids, Iowa, area and I was several hundred miles south in Richardson, Texas. A relatively few 75A-4 receivers were built in Toronto, Ontario, Canada, and 500 KWM-2- series were built, under license, in Japan.


    A lot of the design features, in the 30S-1, were dictated by the United States military. The placement, of the heat exhaust, may have been one of those features. Frankly, I have no idea as to if this was a military requirement or not. The 30S-1 was designed 9-years before I went to work for Collins (April 1967).

    CW, in the 32S-1, 32S-2, KWM-2, and KWM-2A was definitely an "afterthought"! That equipment was originally designed for SSB operation only. Again, I suspect but do not have any real information on this, since all that equipment was used by the military, there might have been a military requirement for some sort of CW operation. Collins corrected the very poor CW design with the 32S-3 and 32S-3A. With the KWM-2- series Collins did try to eliminate the multiple CW signals by increasing the tone frequency from 1350 Hz to 1550 Hz and finally to 1750 Hz. Although that did help, somewhat, with the 2nd harmonic of the tone frequency causing additional pseudo CW signals, it did not help with the signal on the opposite sideband and the suppressed carrier.

    It is possible to very closely align the 32S-1, 32S-2, and KWM-2- series so that the unwanted signals are so far down that they cannot be heard less than a mile away. However, that close alignment only lasts a day, or so, and the multiple signals are back. I have aligned my 32S-1 so that another amateur, who lived less than 1/2-mile from me, could not detect any signal except for the desired signal. Unfortunately, by late the next afternoon the additional signals were back.

    As a result, I do not even think of using my 32S-1 or KWM-2A on CW. For SSB, they do an excellent job. But, for CW, no dice!

    It was Art Collins nature to over-design things and this was echoed in his relationship to his employees. Yes, there were errors made in the production of equipment by Collins Radio. However, considering the reputation that Collins had in the telecommunications field for decades, the triumphs greatly outweighed the failures.

    Glen, K9STH
  4. K9AXN

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    Please read the bottom right box! It says FL-=2100Z. That neutralizing method was added to the Z model. Roger is correct!!! Interestingly there is no evidence that the design was unstable except from the one person who condemned it.

    Regards Jim
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Beats me, I have no idea. It just seems "silly," since I'd think in most cases, people take big, heavy gear like that (it weighs about 175 lbs or so, as I recall) and push it against a wall to get it out of the way. Doing so with a 30S-1 can cause serious problems unless you modify the cooling system (which I did).

    Even more interesting is what Heath did with the SB-200, really not long after the 30L-1 was for sale (I think about 4-5 years later?). They packaged an amp with the same band coverage as the 30L-1 but using two better tubes, and made it just about the same size, with the same output power, in a far easier to service and much less expensive appliance. An SB-200 is "wide open" everywhere and even someone with poor eyesight can get inside and service it. The 30L-1 isn't like that.

    I heard 17K 30L-1s were sold over its time. I can't confirm that, but sounds reasonable. I think more Ameritron AL-811Hs have been sold in its market time, and it's still being produced and sold. The AL-811H since 2011 uses directly grounded grids and is stable as a rock. Tube failures always exist since nobody makes 811As quite as good as they were made in the 1950s-60s, but that's not an amp design issue.:p

    For "collecting," a 30L-1 is pretty and a nice thing to own. For "operating," I'd rather have an AL-811H.:)

    I'll bet you're right, but that's curious since back in those days, CW was still heavily used by the military. Today, of course, it's not. But I "sat in" on Morse instruction at Ft. Monmouth in 1973, so the Army was still teaching it then -- and I noted their teaching method absolutely sucked, so I volunteered to change it. My method was about ten times more effective, in that the begrudged students all had it nailed in four classes, compared with the Army way that was about 80% pass rate after ten classes.:p But that was a gorgeous place to visit and do this -- walnut-paneled rooms and hallways, really a first-class taxpayer-funded set of classrooms.:)

  6. K9AXN

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    Pete, please read the mfgr's schematics. 8JI had an agenda.

    Regards Jim
  7. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Regards Jim
  8. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Need to finish one issue then go on to the next regarding the 30L1 ----please.

    The first issue was whether the grids were floated when the capacitors were added.

    Waiting for WIK to come back with calculations for series resonance using 70nH for the grid lead in the tube plus 30nH for 1.5 inches of lead for the capacitors --- which is high.

    We will get to the reason for the cable issue later. There is a lot of ground to cover before we can connect the dots. Thanks.

    Regards Jim
  9. W1BR

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  10. K9AXN

    K9AXN Premium Subscriber QRZ Page

    Correct, I believe Roger was referencing earlier models which had no neutralizing circuitry.
    I'm hoping we can get back to a friendly technical conversation limiting the subject matter to the 30L1 design ---- should be interesting.


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