The PHILCO Phorum
40-120 Antenna Loop - Printable Version

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40-120 Antenna Loop - TonyJSenior - 12-11-2007

Picked up a sad looking 40-120 off of eBay (as if I need another project to work on Icon_lol ) Remembering the Charlie Brown holiday special from my youth, I told my wife "it's not a bad radio, it just needs a little love". Not sure how many more times that's going to work with her though.

Havent removed the chassis from the case and probably won't do so for awhile, but it appears that a loop antenna is wound on a wooden frame in the back of the cabinet, possibly mounted to the chassis. There also appears to be antenna loop wires also that are sort of draped across this coil as if they were pulled out or whatever. Does anyone have specifics on what the loop should be / look like as I'm sure that Philco wouldn't have put out a radio looking like this. Thanks in advance (will be placing an order with Chuck soon for prints)

- Jim Dutridge - 12-12-2007

Tony, I can snap a picture of mine this afternoon and send it to you.

Jim

- TonyJSenior - 12-12-2007

Thanks Jim - that would be appreciated. It appears almost like another loose wound coil that is perpendicular to the one on the frame, but with some turns that are cut. What a mess...

- TonyJSenior - 12-12-2007

Well I decided to pull the chassis out and trace out what was what with the mess of wiring around the loop frame. As far as I can tell, there were two thin wires that both terminated to a lug on the antenna terminal strip that ultimately connects to the chassis. I am assuming that each of these wires were wound around the antenna frame perpendicular to the antenna loop and basically were fastened at each end to a hole in the frame. Since this wire was cut in several places and some sections missing, that's what I can gather. Am I correct in this, and if so, is this some sort of 'ground plane' that is required for this antenna setup? When it comes time to work on this chassis I want to replace it - any help with the number of turns etc. would be helpful.

Another thing I discovered is that this unit has a mixture of cloth covered wire and the dreaded rubber insulated style. Some of the rubber pieces are deteriorating and I'll replace them. As far as the others, what is typical with the rest of you who work on these type chassis - do you typically replace all of the rubber wiring to be sure to nip future problems in the bud?

One last thing I noticed in looking at this one - the multi sectioned electrolytic was rated at 120v and the print shows a voltage measurement of 120V on one section. Nothing like working right at the rating of the unit - my cap looks like it has expanded out both ends of the cardboard tube.

- Jim Dutridge - 12-13-2007

Tony, sorry but the radio I was thinking of is actually a 41-220, a little bit different animal than yours.

- TonyJSenior - 12-13-2007

Thanks for checking Jim - I found a few pictures on the web that shows this setup. Hopefully between them I'll get a better idea on how to replace the 'mess'.

- TonyJSenior - 12-14-2007

Think I stumbled on to what this extra loop is supposed to be. According to another website that showed a Philco Transitone TH-16, this extra looped coil perpendicular to the antenna loop is supposed to serve as an 'electrostatic shield'. This is supposed to reject waves electrostatic in nature, therefore improving signal to noise ratio. Based on pictures of other 40-120's I've come across, looks like around 20 turns are present. Probably not too critical, but now I've got a better grasp on what it is.