More SSB transmitter woes - Xtals.

I think ~ 20 kHz is likely too much to pull a crystal Maybe you can replace it with a 455 kHz ceramic resonator pulled to 450? Ed

I suppose there is some merit in building your own test equipment. For a low distortion and harmonic free two tone test signal on about 450 KHz, I suggest two low distortion RF signal generators, such as an old HP8640B, and a resistive combiner/divider. Basically a shielded box,

This photo is probably the last time my workbench was clean (about

Is this a BG7 crystal?

I couldn't find much on a "beehive" trimmer:

If lowering the frequency of one of the crystals would solve the problem you could open the top of the glass envelope and fill it with copper sulfate (sulphate) solution and electroplate copper onto the gold electrodes on the crystal. The extra mass should be affective at lowering the frequency buy a useful amount. A lot of trial end error would be needed to get it right. If you happen to have some gold potassium cyanide lying around then you could of course plate gold on instead of copper. John

I expect that a cheap FPGA and a dinky litle DAC could generate SSB.

Or even a 75-cent ARM, with its ADC for analog input, driving a parallel DAC for output. Figure a square inch of PCB. That might be a cool product.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It wouldn't be a restoration then, would it?

Jeroen Belleman

Hide it where nobody will see it.

But it would be an interesting problem, making an SSB generator in software.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

I believe many of the current amateur transceivers do it that way using the Weaver method.;

I had wondered about that - but would it be stable enough? The range of adjustment on the oscillator crystal is only about 10 c/s either way, so they are expecting the notch to be very narrow and the match between the oscillator and the notch crystal to be very stable.

The balanced mixer was very badly constructed with long screened leads running the length of the chassis; any changes in those leads (braided rubber-covered stranded wire) would throw the mixer out of balance and let carrier through. I have tidied it up and can get a carrier rejection of around 60dB using just the mixer alone - but I don't know how long it will retain that balance with temperature and component changes.

It might plate around the edges and short the electrodes. The old method of scribbling on the crystal with a pencil worked well (I have done it successfully) but that was on crystals that could be removed from their holders.

Strangely enough that is one of the few chemicals that I don't have lying around. :-)

By using a Marconi TF2016A signal generator with a Racal frequency meter (with an ovened crystal reference) I can get an accuracy of 1 c/s. Once the RF side is lined up. I have a home-made two-tone audio source for checking linearity. The harmonics of the RF can be checked with an ordinary receiver.

That looks so tidy and organised compared with mine.

By the way, the place for a fire extinguisher is low down near the doorway, so you can reach it on the way out or on the way in without raising your head into the hot and smokey zone.

That's it. The ones in this set are long and thin because of the shape of the quartz bar.

It is a multiple concentric screw piston trimmer made by Philips. They were very popular in the UK and Europe for HF and VHF equipment but there was also a giant version made for a push-button tuned radio set where the elements were wound as opposite-handed spirals and shaped to give a semi-logarithmic characteristic.

. . so you measured the oscillator crystal under the same conditions, or are you assuming from performance?

Are you sure they were intended to operate in the modes quoted? These glass crystals were never cheap, so it seems an illogical design intention.

RL

The manual filter alignment section of the manual (6-6) cites

RL