Old & unusual Marconi Sig Gen

[Oldmadham]

Has anyone run into a Marconi VHF signal generator which had a "bonus" HF range as well?

The VHF ranges were built like the proverbial brick toilet, & were accordingly stable, but the "add on " HF range was obtained with a self excited fixed VHF oscillator, which was mixed with the normal output to produce HF------the resultant HF signal drifted like it was going out of fashion!

Date of manufacture would have been from the late 1950s to the mid 1960s.

I have never seen one of that particular design since 1967, but I have always wondered why Marconi added a range as a sort of "afterthought".

I've never seen one on the 'Net, either--------a few look like it, but just have normal ranges.

[turretslug]

Do you have a number for this particular device? ISTR the TF995 does some stirring-down on its lowest range to get an HF span that would be an unfeasible number of octaves by simple single oscillator means. Having done it once, they obviously liked the idea, picked it up and ran with it, the later solid-state TF2008 is a banquet of multiplying and mixing of crystal and VFO in all sorts of ratios to derive its coverage.

[trh01uk]

Its possibly a "special" produced for some specific requirement. Maybe MOD. Does it have a CTxyz type model number? Can you post some photos of the front panel?

Richard

[Oldmadham]

Originally Posted by trh01uk

Its possibly a "special" produced for some specific requirement. Maybe MOD. Does it have a CTxyz type model number? Can you post some photos of the front panel?

Richard

No, too long ago.
I had to work with it to test HF receivers back in 1967 in the remote tropical North of Western Australia, so no photos, no nothing.

I just remember the strange way of obtaining a HF range.
If they had taken the same trouble with the fixed oscillator as with the main generator, it probably would have been OK, but it was just "out in the breeze", with no real attempt at screening, temperature stabilisation, etc.

The little old Advance generator we had (in a light green case) was much more stable but didn't have proper level calibration, attenuators, etc.

Re: the specific requirement.

This is a definite possibility, as I was with the old Australian "Postmaster General's Dept", who did buy a lot of gear, so maybe they really only bought it for the VHF links we had there, & the HF range was their "afterthought".

Over the years, I have run into a number of different strange devices, the details of which seem to have disappeared into the mists of time.