How to find gangs ?
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thedelihaus
Nocturnal transmissions
thedelihaus
Nocturnal transmissions
When poking around in there, be careful not to get them dirty or DeOxit on them, as it will screw them up.
Pardons if you already knew that.
Pardons if you already knew that.
Attachments
Thanks was not aware of the deoxit bit
For "quartz" tuners you need to look at the schematic. A varactor is the solid state equivalent of a variable capacitor gang. The look like a pair of diodes with a connection between them. That connection is shared with all of the diode pairs.
They would be hard to spot for looking at the PCB.
They would be hard to spot for looking at the PCB.
clydeselsor
Lunatic Member
I found out the hard way!
dshoaf
That high voltage buzz
Following up to what Whitehall explained.....
Most of the 'digital' tuners over the years used a synthesized version of what the multi-gang variable cap once did for the local oscillator and first stage RF amp. This removed a lot of cost to the tuner as the mechanical, multi-gang capacitor was not cheap to produce. Synthezers are cheaper to produce, have no moving parts, and are more stable, frequency-wise than their old counterparts.
The problem, then, is that you cannot use the count of 'gangs' in the variable cap as a measure of the tuner's potential performance. Indeed, by the end of the old-school variable cap tuners, 3, 4 or 5 gang vari caps didn't really give it away as the IF strips had really become quite good. Today, most of this 80s vintage complexity has been boiled down to a handfull of chips on a small board, for the most part.
BTW, the ARRL/ham radio folks have plenty of good books on radio receiver designs in their annual ARRL Handbook. Check their website, www.arrl.org for books on all this RF theory.
Hope that helps a bit.
Cheers,
David
Most of the 'digital' tuners over the years used a synthesized version of what the multi-gang variable cap once did for the local oscillator and first stage RF amp. This removed a lot of cost to the tuner as the mechanical, multi-gang capacitor was not cheap to produce. Synthezers are cheaper to produce, have no moving parts, and are more stable, frequency-wise than their old counterparts.
The problem, then, is that you cannot use the count of 'gangs' in the variable cap as a measure of the tuner's potential performance. Indeed, by the end of the old-school variable cap tuners, 3, 4 or 5 gang vari caps didn't really give it away as the IF strips had really become quite good. Today, most of this 80s vintage complexity has been boiled down to a handfull of chips on a small board, for the most part.
BTW, the ARRL/ham radio folks have plenty of good books on radio receiver designs in their annual ARRL Handbook. Check their website, www.arrl.org for books on all this RF theory.
Hope that helps a bit.
Cheers,
David
