[Collins] 32S-1 unknown mod

[Dr. Gerald N. Johnson]

AM. RTTY was sometimes mentioned using an added shifter in the PTO or 
changing the bias drive on the USB/LSB shifter in the PTO. Sometimes the 
added shifter was connected using a tube socket test extender under the 
PTO tube. I'm sure not beneficial to frequency stability. W5USI says it 
was suggested at Collins. I know it was published in RTTY magazine in 
those days. I have a copy somewhere.

Most RTTY was run using audio tones, for 850 shift the tones users were 
2125 and 1275 because the RTTY standard high tone of 2975 wouldn't pass 
through the SSB filter and without taking out the capacitor on the plate 
of the receiver audio output tube 2975 was weak. Hence the "Collins 
tones" of 1275 and 2125. 2125 and 2975 were used for AFSK beginning in 
amateur RTTY on FM (the first mode it was allowed on) using pairs of 
surplus telephone company filters. Now with 170 shift most common saving 
spectrum and usually working better and with computers doing the copying 
and creating the transmit tones, any tone pair that passes through the 
filters works, though its probably worth the slight bother to keep the 
tones above 1/2 the upper audio cutoff frequency through the transmit 
filter to minimize spurious outputs if the transmit tones have harmonics 
or the audio is over driven.

Long about 40 years ago I created the audio tones using a unijunction 
transistor oscillator with equal rise and fall slopes srranged so that 
keying changed only the slope (and hence the frequency) with no other 
keying transients. The triangular wave form compared to a square wave or 
sawtooth had only 8% total harmonic distortion which was cleaner than 
those more common digital waveforms. Keying an LC audio oscillator 
tended to have some envelope transients at the time of the keying that 
caused splatter when used for transmitting RTTY through a SSB transmitter.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 3/8/2014 3:43 PM, Carl wrote:
> AM or RTTY?
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Bill Riches" <bill.riches at verizon.net>
> To: <collins at mailman.qth.net>
> Sent: Saturday, March 08, 2014 4:12 PM
> Subject: [Collins] 32S-1 unknown mod
>
>
>> Just obtained a clean 32s-1 that has a mod in it that I have not seen. I
>> have not fired up the unit yet. Pin 6 of v2 plate of BFO osc is connected
>> to a 100 k pot thru a 51 pf cap. The wiper of the pot is connected to
>> p7 of
>> V4 first mixer through a 100 pf cap in series with a 22k resistor. The
>> 100
>> k pot is mounted on the same type of add-on bracket that is used for
>> the vox
>> time const control mod. The knob on this control is identical to the
>> other
>> knobs on the other three controls. Workmanship is first class. Is this a
>> Collins mod? What is it for? Inquiring mimes want to know!
>>
>>
>>
>> 73,
>>
>> Bill, WA2DVU
>>
>> Cape May, NJ
>>
>>
>>
>> .
>>
>>
>>
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