Noise in the a/c line - Printable Version
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Re: Noise in the a/c line- COAXIAL NO-NO - AI2V - 12-07-2008
Using coaxial cable on the input to most 1930's radios, especially Philco's, isn't a good idea unless you use a ferrite balun transformer at the antenna terminals; even using a balun will have mixed results. If you look at the input schematic you will see that the capacitance of the coax will go directly across the input input tuning stages; all of this added capacitance will kill reception. You will find that you won't be able to adjust the input stages when using coax.
A hand-wound 1:1 balun of a few turns might reduce background noise but at the cost of some sensitivity.
Re: Noise in the a/c line - codefox1 - 12-12-2008
Some of the worst noise generators are chargers for phones and cameras, as well as ac adaptors for computers and other electronic gear. Of these, the imports you get for just a couple of dollars on Ebay are the worst of the worst.
And don't forget about lamp dimmers, especially the older ones. Either turn the lamp off, or all the way up.
If your television is as old as your Philco, there's another source of agony. But then again, you don't watch tv and listen to the radio at the same time, do you?
Re: Noise in the a/c line - Robert - 12-13-2008
He may have to live with the noise until summer time when the pellet stove is not running.
He is getting a lot of ooohs and awwws on the radio I restored for him. I will try to get a pic of the radio on the board.
Bob.
Re: Noise in the a/c line - radiomikee - 12-15-2008
With all due respect to AI2V, I (AB3CX) have been using coax fed amatuer radio antennas to feed various antique radios including all the usual Philco 1930's sets for years. They work great this way. Believe me, you never heard so many stations. There is no special need for a balanced line in, or a balun. Baluns are important in certain transmitting settings to prevent common moder currents on the braided shields of feedlines, or for impedance matching in going from 50-72 ohm coax to 300-600 ohm balanced feedlines. No way are antique radio receivers on HF fussy enough to be susceptible to issues in this area. In fact, the typical longwire random length antenna is completely unbalanced as most folks use it, which is as a direct feed with no ground. My point in all this was that the person who started this thread assumed he had line interference which he does not have, he has RF interference. If he wants to avoid it he can use an outdoor antenna with shielded cable feedline, away from the source of the RFI, which he already documented is inside his house. Further attempts to deal with the power line are a distraction and waste of time/
Re: Noise in the a/c line - exray - 12-16-2008
radiomikee Wrote:, he has RF interference. If he wants to avoid it he can use an outdoor antenna with shielded cable feedline, away from the source of the RFI, which he already documented is inside his house. Further attempts to deal with the power line are a distraction and waste of time/
I don't know about a waste of time. You can often keep the garbage from radiating into the air so much by bypassing AT THE SOURCE if the source can be identified.
-Bill