Marconi 2955a RF signal generator problem

[Proeletrotech]

Hi guys, can someone help me? my marconi 2955 has this problem:

The RF signal generator doesn't have frequency stability, I've put a external GPSDO on 1MHz input, but doesn't change anything, when you measure the frequency with a frequency counter, you cannot see any problems, but, when use a HF radio in SSB mode it's so clear the instability, I tested the HF radio with other RF signal generator and there's no problem at all.

Does anyone already had this problem?
Or a suggestion to solve it?

Thanks.

[George Edmonds]

Hi

Please keep in mind that the Marconi 2955, is it a 2955 or a 2955A, was never designed for use with SSB communications links, it’s primary role is for use with private FM radio links.

It sounds that you are hearing phase noise from the Rx side signal generator, but from your description I cannot be certain.  Without access to measurements from a modulation meter such as a Marconi 2305 or a HP8901/A/B it is impossible to say if the 2955/A meets its specifications or not.

It is normal that if you listen to the 2955’s signal generator with a modern HF radio or HF transceiver you will hear all sorts of burbling noises.

George G6HIG Dover UK

[Kim Christensen]

Not an insult, but just in case: Are you sure that it is in CW mode and all modulation is turned off?