Normal Noise Floor

[chrissim]

Assuming that incidental noise from any extraneous source is always present, when I detach my antenna from the back of my reference radio, I have a noise floor of S1 to S2. Connect antenna and it rises sharply to S6 to S8 on an empty frequency. Antenna for this purpose is a Pixel loop. The S6 to S8 occurs regardless of nulling feature (rotating). The antenna is located far from the house.

My question is: in such circumstances as those of an average American neighborhood, what would you expect the noise floor to be using an arbitrary frequency with (1)antenna detached from radio and with (2)antenna attached? Also, must be an unused frequency.

I ask because I have recently switched from Direct TV to cable, and am quite confident that there is an additional noise factor involved with the switch over.
I refuse to have any modems in the room where I listen and have been sure to remove any device deemed not pertinent to my survival : )

However, my wife has to have her Ancient Aliens nightly fix, therefore I can’t demand that she turn the tele off, now can I?

In the “listening station,” I have a computer, the radios, and a run of RG45 (never presented much of an issue before the cable TV installation) along with accompanying equipment necessary to use the radios.

No, I don’t ground the radios due to the 22 feet of space between my second story room and the ground below, but I do ground the antennas. Again I have to stress that the grounding shouldn't be an issue noise wise as it’s never been an issue before. Now, before someone responds with the usual “always ground your radios,” I’ve read a number of articles that stress grounding at such a height negates the benefits of grounding itself. So there’s that!

Finally, the new noise occurs on all antennas and radios. The noise itself can be described as a more audible hiss than normal. I only use the radio attached to the Pixel as an example (Ten Tec RX 350) because it has historically always been the quietest receiver of the lot.

Oh yeah, I should add that the massive coax they connected to the junction box or whatever they call it is sitting, unburied, right beneath all of my coax leading upstairs. Nice of them, eh?

Okay, there it is. Please respond so that I might compare.
Thanks!

 

[k9rzz]

No antenna there should be NO noise. Hsssssssss Typical suburban lot ... prob S2 - S3 (esp. in the summer with distant lightning crashes).

 

[SCPD]

There are too many variables to make an intelligent reply. One thing to do is to get a portable AM radio (with a telescopic whip antenna) and move it around the house.

The important thing to know is that if you hear RFI it doesn't necessarily mean it's being picked up by your antenna -- however it's a start -- then you can remove any offenders one at a time.

Since you just had cable service installed, it's very possible the RG-6 coax is acting as an antenna and putting out RFI garbage. You can confirm this by disconnecting the coax and unplugging all connections to any cable TV equipment. The modems they use to give digital phone service can be noise generators.

If you can identify that the RG-6 coax lead is the main offender then the cable TV company is required to address any RFI. They should be able to fix it for you.

They will likely use something like this to ground your lead. This can be important if you have a lot of connection points and coax running through the house: http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?ctn=SDW5003O/17&scy=us&slg=en

Since your noise level is only S6 it's very possible you're just picking up a neighbor's plasma TV or outdoor flood lights. There are several (too many) possibilities.

 

[majoco]

There's something wrong with your 'reference' radio if you have S1 to S2 with no antenna connected.

Both of my desktop receivers ( NRD515 and a Kenwood R2000) read the same - resting on the stop below S1 with no antenna connected. Connect the antenna (through a splitter to both receivers) and the noise rises considerably but both meters show S1. They were both set up according to the service manuals and despite different setup figures both show almost identical deflections of S8 to 9 on a known local signal.

 

[chrissim]

Thanks for the replies. Not sure if I should have used the term noise floor, but I thought it fitting in the circumstances. I'm going out the the box on the side of the house and will detach the main coax coming into the house. Second step will be to unplug all cable receivers

I did walk around with my portable and got the usual. It doesn't seem to be the coax from the cable installation itself, nor does it seem to be the power cables from the modem and receiver boxes - it's the boxes themselves. Man those things are noisy.

majoco - I don't think there's anything wrong with the reference radio. I just fired up the Drake and it's the same thing as is the Excalibur. I suppose it's possible there's something wrong with all three. Perhaps it's just ambient noise creeping in.

Thanks again for the replies!