Here is the proposed HP-117A Modification Board. The board is meant to sit in the open slot of the 117A and will require a little bit of rewiring to the back plane on the underside of the chassis. But what we have here is two MC1496s set up as frequency doublers to strip off the BPSK data from the front end and also the local 60 kHz comparison signal which will be inserted before the A3 Phase Comparitor. There are also op-amps buffers that will allow additional gain as needed. Both signals will then be 120 kHz instead of 60 kHz but I believe the A3 module should be able to work with the faster frequency and the rest of the unit should function as normal.

Status Update: It turns out the MC1496 is actually quite sensitive and really doesn't like seeing a 60 volt peak to peak signal from the front end or a 30 volt square wave. So after adding some 100K resistors in front of the 1K level pots and increasing the op-amp gain to 10, I was able to get the mixers happy enough to get what appears to be a phase lock using a function generator. But the square wave mixer gives me sawtooth on the output when it balance, not sure if I nuked it with excessive signal level or it it's op-amp voltage skew. It seems to work but I'm not really happy with it and thinking about using a 1:1 SMPS transformer and diodes to make a doubler for the RF side may try the same for the reference or some sort of doubler based on a XOR gate and transistor buffer. On Sun, Apr 16, 2023, 22:39 Matt Krick <dcflux@gmail.com> wrote: > Here is the proposed HP-117A Modification Board. The board is meant to > sit in the open slot of the 117A and will require a little bit of rewiring > to the back plane on the underside of the chassis. > > But what we have here is two MC1496s set up as frequency doublers to strip > off the BPSK data from the front end and also the local 60 kHz comparison > signal which will be inserted before the A3 Phase Comparitor. There are > also op-amps buffers that will allow additional gain as needed. > > Both signals will then be 120 kHz instead of 60 kHz but I believe the A3 > module should be able to work with the faster frequency and the rest of the > unit should function as normal. >

Matt indeed 30V is far far too much and you have dropped it down. Good. I think possibly the saw tooth is due to the function generator not actually locking. As such you are drifting through the phase. Total guess. Regards Paul On Mon, May 8, 2023 at 1:18 PM Matt Krick via time-nuts < time-nuts@lists.febo.com> wrote: > Status Update: > > It turns out the MC1496 is actually quite sensitive and really doesn't like > seeing a 60 volt peak to peak signal from the front end or a 30 volt square > wave. > > So after adding some 100K resistors in front of the 1K level pots and > increasing the op-amp gain to 10, I was able to get the mixers happy enough > to get what appears to be a phase lock using a function generator. > > But the square wave mixer gives me sawtooth on the output when it balance, > not sure if I nuked it with excessive signal level or it it's op-amp > voltage skew. > > It seems to work but I'm not really happy with it and thinking about using > a 1:1 SMPS transformer and diodes to make a doubler for the RF side may try > the same for the reference or some sort of doubler based on a XOR gate and > transistor buffer. > > On Sun, Apr 16, 2023, 22:39 Matt Krick <dcflux@gmail.com> wrote: > > > Here is the proposed HP-117A Modification Board. The board is meant to > > sit in the open slot of the 117A and will require a little bit of > rewiring > > to the back plane on the underside of the chassis. > > > > But what we have here is two MC1496s set up as frequency doublers to > strip > > off the BPSK data from the front end and also the local 60 kHz comparison > > signal which will be inserted before the A3 Phase Comparitor. There are > > also op-amps buffers that will allow additional gain as needed. > > > > Both signals will then be 120 kHz instead of 60 kHz but I believe the A3 > > module should be able to work with the faster frequency and the rest of > the > > unit should function as normal. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

On 5/8/2023 8:03 AM, Matt Krick via time-nuts wrote: > Status Update: > > It turns out the MC1496 is actually quite sensitive and really doesn't like > seeing a 60 volt peak to peak signal from the front end or a 30 volt square > wave. IMHO, the MC1496 would be my last choice for a mixer. Practically anything else would be better. It is not just "quite" sensitive, but it is sensitive to the point of being nearly unusable. And the noise figure is nothing great. Rick N6RK