Terrible problems with noise persist.. suggestions?

[modrachlan]

I hope someone can help me with this. I have had persistently bad problems with noise all the way from longwave to the 10 meter band. Across the board. I bought a Wellbrook loop because I have read about using the magnetic portion of the signal reduces noise, allowing you to hear weak signals. I am mostly interested in MW DX and tropical band DX but also want decent performance on the ham and broadcast bands, so the Wellbrook seemed like a good choice. Nothing doing, only the strongest signals can make it through the noise.

I can tell you how I set up the loop. It's on a mast on the southeast corner of my home about 15 feet in the air and about 10 feet from the corner of my house. There is a rotator. I used RadioShack 50-Ft. RG-58 Coax for the antenna, which goes to a grounding block. the block is grounded into two rods hammered into the ground (though the ground is so hard they protrude a foot or so). The two rods are coupled together the best I can. more RG-58 connects the block to the antenna interface inside. the lead goes to a Kenwood receiver and sometimes I couple it inductively through a copper loop to a Sony AN=LP1 so I can use it with portables. But this setup is not very successful.

One thing I was told to try but have not yet is rock salt buried next to the rods. It seems like an extreme measure but I am about to go there.

I have tried eliminating fluorescent lighting and getting everything away from power and internal power wiring. Nothing seems to help.

I have been told to try different cable. I will need to buy about $60 worth of the recommended cable. I am willing to do this, but just wanted a second opinion before splurging. I also worry that I've got too many converters in the path (bnc to pl-259 back to F for the grounding block, etc). I assume they are all opportunities for RF to leak in.

Should I try the cable? A different antenna to test? Move it indoors? Is there a way to test and measure the noise problem in order to isolate it? Do I need an antenna phaser or preselector? (I am also considering a second loop in conjunction with the first to null out the noise.) I am really tearing my hair out here!

Thanks for any and all advice.

 

[Boombox]

What kind of noise is it? Power line hash? A neighbor's plasma TV?

Have you tried to pinpoint the noise with a portable SW receiver?

 

[modrachlan]

Thank you for your reply. I have not. Do I just listen on a frequency and see where it's the loudest? Is there a good freq to use for typical sources?

The noise sounds mainly like very strong static plus humming in the upper bands. But I will make a note of what I hear where when I go home at lunch.

 

[modrachlan]

I've found a few things on my own that list some things to try: a thread here about finding the source of noise (http://forums.radioreference.com/hf-mw-lw-general-discussion/241501-how-find-rf-noise-culprit.html) and this page (http://radiojayallen.com/combatting-am-and-sw-interference/). The following suggests grounding the wire at the antenna, burying the cable, and re-grounding it where it goes into the house: Grounding is key to good reception -- antenna special on hard-core-dx.com

I hope it's ok for me to post these things here, I think Radio Reference is the best radio site on the Internet, and I would love for this thread to be where I put a stop to me just being frustrated and actually doing all I can to reduce interference. Seems like the best place to share these links, then.

 

[popnokick]

Record the noise and post the sound file here. There are many people reading who have had similar problems and may recognize the interference immediately, allowing you to focus your troubleshooting.

 

[SCPD]

Wait you grounded the coax shield on a Wellbrook Loop? You do realize this is a powered loop..?

I think the grounding is causing the interference. Perhaps a ground loop.

Remove everything except the necessary connections for now. What receiver do you have? How is it powered?

 

[modrachlan]

It's a Kenwood R-1000, powered through a surge suppressor.

I guess I should clarify, I am grounding the loop in the sense that it's outside and the lead goes to a grounding block on the windowsill via PL259 to F adapter.

I was wondering if treating the shield in any other way than just plugging it in along with the lead would help, though.

As far as making a recording.. I will absolutely post something here later today.

Thanks for the interaction guys, I really appreciate it.

 

[SCPD]

Okay I'm confused. The loop coax goes to a dc-powered box. The radio lead goes from that to the radio. Is this what you grounded -- the radio lead?

Did you try removing the ground connection to see if that helped any?

 

[modrachlan]

Maybe this will help. This is my signal path.

Outside

Loop-->BNC to PL-259 connector-->RG58 with PL-259 connectors-->PL-259 to F connector-->Grounding Block

Inside
Grounding block-->F to PL-259 (premade)-->Antenna interface-->PL-259 (premade)-->radio

Antenna interface is getting DC power, yes.

Is this a bad way to do it?

I have experimented with a bare wire lead to the receiver and the shield to a ground in the house- this is where I messed with grounding it. but right now I don't remember the outcome, so I don't think it made much difference.

 

[SCPD]

Maybe this will help. This is my signal path.

Outside

Loop-->BNC to PL-259 connector-->RG58 with PL-259 connectors-->PL-259 to F connector-->Grounding Block

Inside
Grounding block-->F to PL-259 (premade)-->Antenna interface-->PL-259 (premade)-->radio

Antenna interface is getting DC power, yes.

Is this a bad way to do it?

Well, there's 12v DC on the shield of the antenna coax. So you're grounding that out. You might be causing issues with the Wellbrook interface box by grounding out the shield. Since the 12v DC wall wart is grounded to your AC then you're likely creating a ground loop somewhere.

Eliminate the grounding block. The interface box should only have the coax. You generally don't ground an active antenna.

Also those "adapters" are horrible for the antenna connection. I highly recommend getting a length of LMR-240 made with BNC connectors on each end.

Another obvious thing to try is to run your radio off DC if possible.

 

[modrachlan]

Thanks for this info! I wish I had asked more questions here before setting things up on my own!

 

[SCPD]

No problem. Here is my thread:

http://forums.radioreference.com/receive-antennas-below-30mhz/222770-we-have-nulls.html

Latest picture:

 

[chrissim]

If I may add: I use RCA to F adapter which in turn connects to an F to RCA female (connected to the power inserter) which eventually leads to an antenna splitter using a Pixel loop. I've noticed no discernible difference using this method over an outright connection which omits any adapter at all.

Although as has been suggested, your adapters may be contributing to your issue, adapters have been used successfully. I used LMR 400 with a shorter run and abandoned that when I went for a longer run and now use RG6 quad (Pixel supplied). Using an extremely high tech empirical method of measurement (my wife makes the changes outdoors while I bark out instructions from the second story window), I've noted no difference at all between LMR and RG6 and adapters/no adapters.

What made the biggest difference was moving everything out of the room in which the radio equipment is in that wasn't necessary, such as wireless routers, installing snap on ferrite chokes around cables/wires, and 1:1 current baluns .

A Pixel rep informed me that there was no need for a ground with these types of loops. Just disconnect whichever coax you eventually go with when storms roll in.

I ask plenty of elementary questions and I'm certainly not a source of wisdom, but I don't think your issue is with adapters or type of coax, unless you're involving really long distances.

As a disclaimer, I have certainly found that what works for one doesn't necessarily work for another. So you never know.

Perhaps that will help you some in your investigation.

 

[mstephens741]

I'm happy to hear that at least for one person "adapters and type of coax" made no difference in noise. I have been concerned about these connectors, and having used RG-6 from Lowes (quite cheap). DX Engineering in it's instructions recommends a "flooded" RG6 - mostly because it is self healing. But I am sure more expensive too.

I've set my SDR up in the computer room (of course) that is loaded with noise makers, I know, I have three power strips to handle all the gadgets. I am going to try to isolate some of these, but seriously, there's not much that can be done about monitors and PCs when they are needed to run the SDR!

"I think" (translate: I hope), my Excalibur is protected to some degree by its own cast aluminum enclosure. I have lifted it up and waved it over various devices with no particular increase in noise.

MY UNDERSTANDING (testing my knowledge here) of the noise problem is that the antenna itself is picking up these noise signals in the air just like they pick up radio waves. Noise and Signal are indistinguishable from each other. My sewing machine or TV screen is a "broadcast tower" just like the 100kW SW tower. If the antenna is immersed in a noisy field it will be hard to eliminate.

 

[Token]

Well, there's 12v DC on the shield of the antenna coax. So you're grounding that out. You might be causing issues with the Wellbrook interface box by grounding out the shield. Since the 12v DC wall wart is grounded to your AC then you're likely creating a ground loop somewhere.

Eliminate the grounding block. The interface box should only have the coax. You generally don't ground an active antenna.

Nick, the 12 VDC is on the center conductor of the coax, not on the shield. The shield carries only the negative or “ground” side of the +12 VDC, and that can be at ground potential no problem. The 12 VDC wall wart provides no ground at all (note it is not a three prong plug) so the 12 VDC consist of a plus and a minus and is floating until something else takes it to ground.

Also, since the outer conductor has continuity all the way from the receiver plug to the BNC at the antenna, it does not appear to be DC blocked as the center conductor naturally is, applying a ground anyplace along the outer conductor would have no more impact on the 12 VDC than having your radio grounded, and grounding the radio is not a bad idea and something everyone should have, unless you have a hot chassis. Also, grounding the chassis of the radio, and thus the antenna coax outer shield, will happen whether you want it or not if the radio has a 3 prong plug, I don’t think I have seen a radio with an isolated UHF connecter in many years.

You do not ground these kinds of antennas for performance, such as a counterpoise, so they do not need a ground to work, but that does not mean you cannot ground them. I see no particular problem with the use of a grounding block at the entry point of the house in this situation, in fact I would say it is preferred with a thought towards lightning protection. That does not mean this is adequate for lightning, it only means it is better than no grounds at all.

For the record, my setup is somewhat electronically similar to the one described with the grounding block, and the Wellbrook works as advertised, quite well indeed (for a small antenna). My setup (Wellbrook mounted on Yaesu G-450 rotor, 12 feet above ground level, 60+ feet from house):

Wellbrook antenna BNC -> 120 feet of RG214 ->PL-259 -> UHF type feedthrough on aluminum patch panel at wall of house

Patch panel is grounded just like the ground block described (all antennas come through this patch panel in some way).

Patch panel UHF -> PolyPhaser (also grounded) -> UHF-BNC adapter -> RG-58 patch cord (10 feet), BNC each end -> Wellbrook antenna interface -> shack antenna distribution system


T!

 

[SCPD]

You do not ground these kinds of antennas for performance, such as a counterpoise, so they do not need a ground to work, but that does not mean you cannot ground them. I see no particular problem with the use of a grounding block at the entry point of the house in this situation, in fact I would say it is preferred with a thought towards lightning protection. That does not mean this is adequate for lightning, it only means it is better than no grounds at all.

Hmm okay thanks for the clarification. When I asked Andy Ikin at Wellbrook he said you don't want to ground it. Perhaps he was referring to the performance benefit rather than the safety aspect.

The Pixel has a separate grounding point for lightning protection. It doesn't "protect" the coax entry.

 

[SCPD]

I'm happy to hear that at least for one person "adapters and type of coax" made no difference in noise.

Just to be clear, I wasn't calling out RF adapters. I use them all the time. If I didn't have these I'd be in trouble. I have about 5 of each of the more popular adapters.

What I was saying though is that RF adapters can cause other issues. For my Wellbrook install, they added too much weight. They also were not very secure -- even with electrical tape. I just didn't trust them to make a consistent connection.

Yes convenience can be costly but it's also peace of mind.

 

[SCPD]

I have been concerned about these connectors, and having used RG-6 from Lowes (quite cheap). DX Engineering in it's instructions recommends a "flooded" RG6 - mostly because it is self healing. But I am sure more expensive too.

Did you at least get the "quad shield" RG6? You do not want the super cheap RG6 as it's prone to picking up all kind of EMI. Ask any CATV installer!

 

[mstephens741]

Quad shield?

"Digital Satellite Cable RG/6 CATV 2300 Mhz 18AWG 75*C E232510" is printed on the cable. It has a foil shield surrounded by silver braid. I thought the braid looked skimpy IME.

 

[SCPD]

Quad shield?

"Digital Satellite Cable RG/6 CATV 2300 Mhz 18AWG 75*C E232510" is printed on the cable. It has a foil shield surrounded by silver braid. I thought the braid looked skimpy IME.

Yeah the quad shield has double the layers, hence the "quad" name.

This cable is constructed with 75 ohm RG-6 coax, which uses two layers of copper braiding and two layers of aluminum foil to protect the data integrity from any stray RFI or EMI signals.

Here's an example: Southwire 56918445 500-Feet Quad Shields Type RG 6/U 18 AWG Coaxial Cable, Black - Amazon.com