RF coil has resistor - Printable Version

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+--- Thread: RF coil has resistor (/showthread.php?tid=7253)

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RF coil has resistor - marty - 08-17-2013

Hi All;
Can anyone tell me WHY the Primary coil of the RF transformer has a 10K Resistor accross it ?? The primary coil measures 38.6 ohms and the secondary coil measures 4.6 ohms.. The Primary coil is wound inside of the coil form in that cross hatch type of winding.. The Secondary coil is wound on the outside of the coil form..
The other set that has the same type of Mixer Tube 1C6, a Philco 39, which is a two band set against this which is a four band set.. The circuit is easier to follow on the two band set, and it looks like the Oscillator circuit is the same between the two, except that one is a four band set and the other a two band set..
THANK YOU Marty

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RE: RF coil has resistor - codefox1 - 08-17-2013

Please post schematic or link. Cold be limp attempt as a "fusister."

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RE: RF coil has resistor - marty - 08-17-2013

Hi All;
Codefox, I would think that this is too old of a set to have a fusistor..
Here is the link for the Philco 34
http://www.nostalgiaair.org/Resources/185/M0013185.htm
And here for comparison here is the link for the Philco 39
http://www.nostalgiaair.org/Resources/265/M0013265.htm
My guess is for when the signal would be too strong, so as not to overload the RF transformer.. Or possibly some kind of Damping effect..
THANK YOU Marty

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RE: RF coil has resistor - exray - 08-17-2013

That's often done to knock off the Q of the coil. Sometimes good RF selectivity is not a good thing since its variable across the band. And in a production environment it can create alignment headaches.

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RE: RF coil has resistor - marty - 08-17-2013

Hi All;
Exray, Thank You, that is exactly what I needed to know.. I just fired up the set, with the Resistor disconnected on one side, just to see If it would make any difference.. I still just get a hum, my set doesn't know the Tune, either..
I will re attach it and try again..
I also will look at the Oscillator with my scope and see what I get..
Thank You Marty

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