Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Noise in the a/c line
#16

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.

Pete AI2V
#17

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?
#18

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. Icon_wink
#19

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/
#20

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




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
My Philco 37-116 Restore
Hello MrFixr55, Thank you for taking the time to explain. I measured 50 volts where you say. Today the 370 volts at ...dconant — 12:51 PM
462ron
Oh that sucks. It’s something easily overlooked. Hopefully it’s nothing more than a resistor! Ron462ron — 08:08 AM
Philco 46-480 Electronic Restoration
Just confirmed that you are correct. It’s the function generator. I connected the signal output probe to one of the inpu...jrblasde — 07:52 AM
Philco 46-480 Electronic Restoration
Ouch, you may be right. Yes, it is solid state. It’s the signal output of my oscilloscope. May be time to crack that ...jrblasde — 07:27 AM
462ron
If you didn’t put a DC blocking cap between the signal generator probe and the plate of the 1st IF it’s possible you ble...462ron — 07:07 AM
My Philco 37-116 Restore
Hi DConnant, The reason why C127 is isolated from ground is because sets of this vintage did not have the center tap...MrFixr55 — 01:07 AM
Philco 46-480 Electronic Restoration
The shield is on the 6H6. It was, in fact, a missing jumper to connect the main chassis ground to the RF chassis grou...jrblasde — 10:58 PM
Zenith H725
When dealing with noise on power lines, time to get my Jackery 240 out. Talk about clean can hold a portable am radio ne...David — 08:52 PM
Zenith H725
Arran - I bet you're right probably vinyl, there was no rubber smell when desoldering it, which you often get with the o...EdHolland — 08:23 PM
Zenith H725
Ed; It was very likely vinyl covered wire given the vintage of the set, there was some rubber/gutta percha wire used ...Arran — 06:34 PM

[-]
Who's Online
There are currently no members online.

>