[Collins] KWM-1 neutralization procedure

AI2Q ai2q at roadrunner.com
Sat May 21 17:36:06 EDT 2011


I will study the schematics, Jerry.

What is the RCA phono jack for on top of the chassis on the KWM-1?

Also, does anyone have a schematic for the late model KWM-1s, like mine?

== Alex


----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at weather.net>
To: "AI2Q" <ai2q at roadrunner.com>
Cc: <collins at mailman.qth.net>
Sent: Saturday, May 21, 2011 4:37 PM
Subject: Re: KWM-1 neutralization procedure


> The 32S and the KWM-1 techniques should produce the same settings and the 
> same effect, a stable PA and driver. Both try to get the feedback to zero, 
> the 32S by measuring leak through with no tube gain and the KWM-1 
> technique measuring reverse leak through with no tube gain. When the tubes 
> aren't contributing gain the circuits are bilateral and so either 
> technique should work fine.
>
> I've come to the conclusion that there was a sloppy draftsman making 
> schematics and he wasn't checked closely. I wish we had access to the 
> entire collection of component specifications those are what purchasing 
> bought by and the components department tested incoming parts by.
>
> 73, Jerry, K0CQ
>
> On 5/21/2011 2:59 PM, AI2Q wrote:
>> Thank you, Jerry.
>>
>> Yes, I didn't take too seriousl;y the need for a 60-uA meter!
>>
>> I think I will try the old tried and true method before tinkering with
>> the Collins diode detector and sig gen.
>>
>> Vy 73, AI2Q, Alex
>>
>> ----- Original Message ----- From: "Dr. Gerald N. Johnson"
>> <geraldj at weather.net>
>> To: "AI2Q" <ai2q at roadrunner.com>
>> Cc: <collins at mailman.qth.net>
>> Sent: Saturday, May 21, 2011 1:53 PM
>> Subject: Re: KWM-1 neutralization procedure
>>
>>
>>> That is a good technique. If you leave a path for screen or plate
>>> current your dip will not be exact neutralization. You have to
>>> disconnect those supply lines from the driver to neutralize it. I'm
>>> not so sure about the feedback neutralization. There is a procedure in
>>> the KWM-1 manual using signal generator and detector. And on the
>>> detector schematic I see the draftsman missed a digit on his Leroy
>>> lettering kit and calls for a 60 microamp meter that was never made,
>>> better to use a 50 microamp meter, they can be bought without having
>>> it made special. Just like the schematic for wattmeters shows a 390
>>> microamp meter when it was really 300 microamps.
>>>
>>> Now compare the KWM-1 manual technique to that in the 32S-1 manual
>>> which uses transmitted signal with plate and screen disconnected (and
>>> there the driver neutralization will work better with both plate and
>>> screen of the driver tube disconnected, opening the screen alone lets
>>> there be a little tube gain yet) and then neutralizes the feedback so
>>> that plate and grid current dips coincide as you tune the pat plate
>>> tuning. Without checking, I think that the transmitter circuits of the
>>> KWM-1 and 32S are very similar so the neutralization should work well
>>> with either manual technique.
>>>
>>> 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
>>>
>>> On 5/21/2011 12:16 PM, AI2Q wrote:
>>>> What is the best way to neutralize the (a) driver, (b) feedback 
>>>> trimmer,
>>>> and (c) PA of my KWM-1?
>>>>
>>>> My late model KWM-1 has a screen-off slide switch as well as an RCA
>>>> phono socket on the chassis for the grid.
>>>>
>>>> I am used to neutralizing by removing B+ from plates and screens,
>>>> applying drive, and adjusting for minimum output on my scope placed
>>>> across (a 50-ohm load) after peaking the pi-L network on the 6146s.
>>>>
>>>> Any help or suggestions appreciated.
>>>>
>>>> Vy 73, AI2Q, Alex
>>>> Member: ARRL, FOC, RSGB, CWops, QRP-L, Antique Wireless Association,
>>>> Wide Area Amateur Radio Network
>>>> http://home.roadrunner.com/~alexmm
>>>>
>>
>> 



More information about the Collins mailing list