Noise reduction: To ground or not to ground?

[W4KRR]

I'm using a Grundig Satellit 750 with a Par EF-SWL antenna. I have noticed that if I ground the radio using a length of wire from the ground post to an 8 foot ground rod, the noise floor drops on some frequencies, but increases on other frequencies. (The Par is also grounded at the EF-SWL Box).

So, any suggestions? Ground the rig or not?

BTW: Radio is running on batteries; in a room with two PC's, LCD TV, several Wall Warts, UPC battery back-ups, printer, etc. Unplugging these things, one at a time, removes some of the noise, but not all.

BTW#2: Moving the radio into another room, away from other electronics, using a ground plane antenna designed for scanner frequencies, results in almost no noise, with clear signals. So either the PAR antenna is introducing noise, or the other electronics, or a combination of both. Was thinking of a loop antenna, but I don't want to shell out for one only to discover my reception is no better (or worse)!

Tips or suggestions welcomed.

 

[SCPD]

So, any suggestions? Ground the rig or not?

No.

BTW: Radio is running on batteries; in a room with two PC's, LCD TV, several Wall Warts, UPC battery back-ups, printer, etc. Unplugging these things, one at a time, removes some of the noise, but not all.

Welcome to the digital society.

...using a ground plane antenna designed for scanner frequencies, results in almost no noise, with clear signals. So either the PAR antenna is introducing noise...

Negative. Your scanner antenna is just providing you with less signal. The PAR antenna is just picking up RFI because it is designed for the HF spectrum.

A loop would likely help but only if you can get it outside away from the house. A loop will not *CURE* RFI however. You need to find the sources of RFI and eliminate them.

 

[ka3jjz]

With the PAR did you try the different combinations on the transformer? There are several variations.

I suspect that the path to ground isn't all that short (as it should be) - because if the path is too long, it might end up acting as another antenna for noise (which is part of what you seem to be experiencing)....Mike

 

[W4KRR]

Thanks Nick and Mike for the replies.

I do have one of the studs on the PAR transformer connected to a ground; I will have to check to see which one. I have not yet tried other combinations, but I will. The ground wire length is about five feet or so to a ten foot copper clad ground rod.

My next step will be to shut off the circuit breaker to the room to see how that affects the noise level. Of course if it solves the noise issue, it will return as soon as the power is restored! Unplugging an LCD TV, and a Wifi router, as well as a few other wall warts didn't seem to affect anything much.

I did fine one particularly noisey wall wart used to charge my Panasonic Toughbook. As soon as I unplugged it, the noise level dropped by about 50%.

 

[ka3jjz]

5 foot should be OK...do experiment with those transformer connections. Every installation is different, and there's no way for any of us to say 'combination x will work' - it will be a bit of trial and error

Mike

 

[nanZor]

Your 750 could just be suffering from major overload, and that is why it seems to work on HF ok with a small scanner antenna.

Note that while the 750 looks the part, inside is a single Toshiba receiver chip intended for consumer boom boxes basically, with some supporting external tuning, and rf attenuation and whatnot. You'll probably need a LOT of rf-attenuation to get that EF-SWL antenna under control, which could include not only the pot, but also the push-button ones as well.

 

[ka3jjz]

Or even better, put together the little project below, and gain a bit with some static protection as well...

http://forums.radioreference.com/receive-antennas-below-30mhz/295299-great-first-timer-project.html

Mike