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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 25th Jan 2012, 4:04 pm   #1
davidgem1406
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Default Information for AM/FM alignment in general

This is in the way of a couple of general questions regarding AM/FM alignment that has been brought about by some work on a Roberts R700 where I replaced all the AF114 and AF117 transistors using replacement types. The R700 is working OK. But I need to check the alignment on both AM and FM.

The first question is what constitutes an RF coil used to couple the generator to a receiver ferrite aerial, the service data talks about a wobbulator but we don't need that for AM alignment.

Next is the FM. Do we really need a wobbulator to check the FM alignment or does an AM/FM signal generator do the same thing? such as an Advance SG63F that I am interested in buying (as it's cheap) and in good condition but working order is unknown.

It does have the frequency ranges to do the job on FM. The .pdf document is attached.

Regards,
Dave
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File Type: pdf Advance 63E sig gen.pdf (1.01 MB, 143 views)
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Old 6th May 2012, 5:18 pm   #2
radiobloke
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Default Re: Information for AM/FM alignment in general

Going backwards through the post, the generator looks like it covers all of the bases.

The question is whether the wobbulator or sweep function generator will be needed. Probably for FM if the radios that you want to repair have it but also some Roberts (as I have found to my cost - having to buy a very fancy RF generator) also need the sweep function, because they just wont work without a flat peaking. (If you see what I mean)
The RT8, for instance, which is on the bench at the mo needs one, and it's only MW and LW.

The coil I had to experiment with. A few kind souls suggested various diameters and amounts of winding. The best for both AM, LW, SW and FM anded up as being 3 loops of standard hook up wire (any kind really) wrapped around a six inch diameter tube, with a 50 ohm resistor attached to save the output of the RF gen from seeing a dead short. Good quality shielded cable to a plug appropreate for the generator.

Phew, hope that helps a bit,
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