48-482 FM antenna - Printable Version

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+--- Thread: 48-482 FM antenna (/showthread.php?tid=10138)

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48-482 FM antenna - mikethedruid - 07-26-2014

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/fe95abf5dc2118420d47a7b802012a5b/tumblr_n9cb2wFnMZ1sqxsgyo1_1280.jpg]

[Image: http://37.media.tumblr.com/a6f46cbc421447037f36a540e1430a74/tumblr_n9cb2wFnMZ1sqxsgyo2_1280.jpg]

[Image: http://38.media.tumblr.com/422aee0f3f7b57499813c416eee7c2c0/tumblr_n9cb2wFnMZ1sqxsgyo3_1280.jpg]

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RE: 48-482 FM antenna - Mondial - 07-26-2014

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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