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Philco 90 High Resistance Antenna Coil? - Printable Version

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Philco 90 High Resistance Antenna Coil? - Joe - 02-04-2012

Hello Ron

Continuing to try to analyze the low reception on some weaker stations, I measured the resistance of the antenna coil at the coil lugs themselves, which is about 10.7 ohms. The other side of the coil measured 6.8 ohms. Is this too high? Was under the impression that they should be about 3 ohms.

Reception improved almost 10 fold when I put the antenna lead on the grid of the RF, with no distortion throughout the dial, and with the volume control working perfectly. I'm not really comfortable removing the coil and was thinking of leaving the antenna lead hook up at the RF grid.

Any harm in doing this? The 90 has been playing set up with antenna to grid for 6 hours now with no ill effects, and the number of stations received like this is unbelievable!

Thanks for your thoughts or opinion on this. Joe

Re: Philco 90 High Resistance Antenna Coil? - Radioroslyn - 02-04-2012

So just for laughs take your ohm meter and measure the resistance from chassis ground and the ANT post. What do you get?
The set doesn't care where you connect the antenna. Sometimes you can get some 60cy modulation mixed in with the incoming signal if there isn't a ground return for the grid.
Terry

Re: Philco 90 High Resistance Antenna Coil? - LASJayhawk - 02-05-2012

I assume your model 90 has 1 #47 output tube by the volume control works comment.

My best guess is that the radio is our of alignment, if the antenna coil tuning isn't tracking the oscillator it attenuates the signal (the radio is trying to receive say 900 but the front end is tuned to say 870) if the if coils are tuned to the wrong frequency the same thing will happen.

Re: Philco 90 High Resistance Antenna Coil? - Joe - 02-05-2012

Hello 7etatdef

Thanks for the reply...I measure 11.1 ohms resistance from chassis ground and the ANT post, so I'm assuming no open. Is this ok or too high? If it is an antenna coil issue, I'm not sure if I want to attempt to pull it out and check or rewind it. This especially if you think the problem is worse than that.

If as you say, if the set doesn't care where you connect the antenna, can I keep it on the RF grid? (BTW...The set is one with one #47 tube)

Thank you again for your reply!

Joe

Re: Philco 90 High Resistance Antenna Coil? - Joe - 02-05-2012

Hello LASJayhawk...Thanksfor the reply

You assumed right. Ther model 90 has 1 #47 output tube. I'm a novice, and judging by your reply, I don't know anywhere near what you know about the issue. What I can tell you though as far as alignment is that every station I pull in matches where it should be on the dial. In other words for example, station 600, 770, 880, 1010, 1130, 1400, 1500, etc tune in on the money with the dial numbers. This is so whether I have the antenna lead at the antenna lug, or at the RF grid. Only difference is, at the RF grid they tune in much stronger, and I get in many more weaker stations. Also, there is no drift or distortion, even with the antenna lead at the RF grid. Would the radio be out of alignment if this is the case? Any further thoughts?

Thank you very much again for your reply.

Joe

Re: Philco 90 High Resistance Antenna Coil? - codefox1 - 02-05-2012

Yes, the antenna section is out of alignment. Please close the other thread on the same subject.

Re: Philco 90 High Resistance Antenna Coil? - Joe - 02-05-2012

I'm not sure how to close the other thread Codefox. However, how do I align the antenna section? Looking at a schematic, I think it is the section to the left (before) the RF tube. Looking at the schematic I see what looks like variable capacitors. Are they the trimmers that are on the 4 gang tuner assembly on the chassis? If so, which trimmer or trimmers are they, if I am looking at the chassis from the front, with the dial facing me?

If they are not the trimmers involved, where are they and how do I adjust them? (I don't have a tool that looks like it will fit them).

Thank you for helping a novice...Joe

Re: Philco 90 High Resistance Antenna Coil? - Ron Ramirez - 02-05-2012

Joe Wrote:I'm not sure how to close the other thread Codefox.
This can only be done by a moderator or by the site admin (me). It has now been done.

Re: Philco 90 High Resistance Antenna Coil? - LASJayhawk - 02-05-2012

Joe, Yes. The forward 2 adjustments on the big tuning gang are both antenna adjustments (i think!)....My riders shows the 1 47 tube version from the bottom, and the 2 45's from the top. Icon_eek

Here is one way to make the 1/4" tuning tool:

http://philcoradio.com/phorum/showthread.php?tid=242

Tune to a station as high on the dial as you can 1400 to 1500 if possible then adjust the 2 trimmers for max signal

Good Luck

Re: Philco 90 High Resistance Antenna Coil? - Joe - 02-07-2012

Hello Ron

You can close this thread. I am past this issue now thanks to everyone, but I have another issue on want to post on a different thread.

Thanks....Joe