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48-482 FM antenna
mikethedruid
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Posts: 1,824
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City: Sneedville, TN
#1

07-26-2014, 07:25 PM
While waiting for my caps to arrive, I have been looking into the FM antenna situation on my radio. I have the "line cord antenna" which connects to pin 2 of the little plug on the chassis back. I have seen pictures of these radios with a very different FM antenna setup, a wire running in a single loop around the very back of the cabinet, but attached to the same pin 2. Having read Philco's instruction sheet for the radio, I see they say it should NOT be externally grounded. Looking at the schematic, I was thinking that using the present "line cord antenna" as a virtual ground, attached to pin 1 of the little plug, and a single loop antenna attached to pin 2 might give good results. Attached are the relevant schematics. Any thoughts ?

[Image: http://33.media.tumblr.com/fe95abf5dc211...1_1280.jpg]

[Image: http://37.media.tumblr.com/a6f46cbc42144...2_1280.jpg]

[Image: http://38.media.tumblr.com/422aee0f3f7b5...3_1280.jpg]
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Mondial
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City: Irvington, NY
#2

07-26-2014, 07:36 PM
Leave the antenna connected to the line cord as is, it works very well. The location on the power cord is located 1/4 wavelength at FM broadcast freqs from the internal line to chassis caps which act as a ground to chassis. Therefore, 1/4 wavelength down the power cord, you are at a relative signal voltage maximum and this is where the capacitive coupling to the antenna input is located.

When operating correctly, the reception with the line antenna is excellent.
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  1. The PHILCO Phorum
  2. Philco Radio Discussions
  3. Philco Electronic Restoration