Terrible problems with noise persist.. suggestions?

[TassieJay]

Here's my suggestions to try, in order:
1) Try a temporary run of coax from the loop to the power injector direct. Run it in through a door or window, using one unbroken length of coax, just for testing. This will have the coax & loop 'floating' with respect to earth, and eliminate any problems that might be being introduced by your adaptors & grounding of the coax. If it works significantly better... you're well on the way to sorting the problem.
2) Set up a radio that can be battery powered. Use it for a while and get used to how the noise sounds in this configuration. Then figure out a way to power the Wellbrook loop power injector from battery also - just make double sure the polarity is right! Now go ahead and turn off all mains power to your house, running the radio and loop from battery. Has the noise gone? If so, the noise source is in your house somewhere. If there was no change to the noise, it might be time to look for a better place to mount the loop. Generally, as far away from power lines and neighbouring houses is best - assuming your own house is not producing any RF noise.
3) Use that CATV or quad shield cable with some caution. They can only be used with crimp/compression connectors, as the aluminium braid can't be soldered to. Andy did recommend against using this sort of cable long term, as if any moisture get in, it can induce noise in the cable. Having said that, I have used a double shield 75 ohm cable - though with a real solid copper core and real tinned copper braid - without problems for over a year now.

And not that it should matter in this instance, but if you're looking for a simple way to improve your existing earth, just let a water hose drip some water around the ground where your earth stakes are located for a few days. Get the ground good & moist - that'd be the easiest & quickest way to improve its effectiveness.

Hope you get the problem sorted out... and share your solution once you have nailed it.

 

[mstephens741]

That's impressive! Ok, I am going to see where I can locate something less than 500 feet! - - Thanks.

 

[nanZor]

I have to ask: is that R1000 that is kind of long in the tooth actually working ok on it's own? No dried out ac power supply caps - bad display boards etc. Does it work on dc?

I'm also suspect of the adapters not making a good enough connection possibly leading to a voltage drop at the loop amp.

Your noise source may not be localized - that is if it is being radiated from power lines etc surrounding your property, you won't be able to obtain a pointing null. When my neighbors went bpl inside their homes (multiple neighbors arghhh), my loops were useless since they couldn't obtain a null.

Test your loop's ability to actually null a localized noise source - enlist the aid of a helper armed with a battery-powered drill motor half way across the yard. Do not use an ac powered drill motor as the ac cord will act as an antenna de-localizing the noise.

Hopefully as you swing the loop you should get two very distinct nulls on the drill motor as you swing all the way around. If you get something else, like a weird cardiode pattern, or only one null on one side, the loop is unbalanced and something else (usually the feedline) is now part of the antenna. Since your loop is up a few feet, perhaps have your help *safely* operate the drill motor on top of a ladder, since the nulls are deepest perpendicular to the plane of the loop. If properly constructed, you should be able to obtain two nulls on each side of the loop.

Try it without an rf-ground! Some of my early loop experiments were less than successful when I had multiple antennas sharing the same ground on a common antenna-switch. Because I had a poor ground to begin with, this ultimately meant that the shield of the feedline to the loop was also shared with the shields from all my other antennas, severely unbalancing my loop.

In the end, my grounds are so noisy that I run from deep-cycle optima batteries / solar / chargers, but that's another story....

 

[modrachlan]

Interesting stuff, herzian! That is a good question about the R-1000. I'm not sure- I bought it used and some days it seems great. But in order to eliminate it I think I will conduct that drill test with an RTL-SDR dongle that I just got in the mail, plus my trusty Icom IC-R2.

Unfortunately I suspect neighborhood noise because one day recently, there was practically no noise. So either something that was causing racket was turned off or unplugged by someone else in the house, or the thing that is causing problems was turned off by a neighbor.

 

[modrachlan]

Update: the LMR-240 made with BNC connectors on each end has arrived. Noise levels are down, but not gone. However, for lack of a better way of expressing it, more reception is making it to the receiver. Even my Sony 2010 is enjoying a boost.

My noise problems are not gone, but I feel assured it's not self-generated anymore. with the old cable, engaging the rotor (the rotor wire and the antenna lead come in to the house next to each other) caused all kinds of racket across the spectrum. Now there is no noise at all caused by the rotor. So I think the lead is definitely sufficiently isolated from picking up junk on the way in!

 

[nanZor]

I also note that the R1000 does not have a gain control - only attenuation. Although the loop has a compensating amplifier, you may want to try activating the receiver's 20db attenuator believe it or not.

For example, at night with a reasonably decent antenna, there is usually no need for a preamp for 10mhz and below. Without a preamp on/off option or variable gain control on the '1000, all you can do is attenuate.

The secret to loops is to look for the best signal-to-noise ratio, rather then pegging the S-meter. So, generally if you can null most of the noise, but still have a signal strong enough to copy comfortably, then you are in business. If the 20db attenuator still allows for comfortable copy, this also helps push the noise down below the noise floor.

Coming to terms with a quality loop can sometimes be strange when one is used to hammering the S-meter, and then suddenly switching to listening for the best signal-to-noise ratio instead.

In my case, I had to actually put tape over my s-meter to train myself to listen, and not *look* at a signal.

Your system may still need improvement, but compliment this with the search for SNR instead of S-meter banging.

 

[lanbergld]

You could try what works for me on my Icom IC-R75. Suddenly, in the past month, I'm plagued with horrific noise that buries utility stations which normally come in good. I suspect I have new neighbors that have some kind of noise making equipment, but really I dont know the cause.

Anyway, I removed my random wire antenna and replaced with just a telescopic whip. Put right into the R75's SO-239 jack. Yes, just a Radio Shack rod that I think is meant for scanners. The noise disappears, well, 80% of it does. Kicking in the R75's preamp compensates for the loss of anetnna length. The reception is now fantastic. I should note that I put the random wire into my GND terminal, to act as a counterpoise of sorts for the telescopic rod. Perhaps this will only work on a highly sensitive receiver, I can't guarantee it will on the Kenwood R-1000.

I surmise that the nasty, sudden RFI I'm getting is horizontally polarized and that's why this works for me. I just know it fixed my problem. You could try it. Sometimes simpler is better.


Larry