The forum is read-only currently.

Keep your ground connections short if you want them to work

Earlier today I got an email from an SWL with a KiwiSDR & AirSpyHF+. He was complaining about very high noise / RFI levels, even though he lives in a rural area much like myself (he was comparing his noise levels to what he sees when using one of my online KiwiSDR receivers).

We exchanged a few emails back and forth, so I could understand his setup. He has a 80 ft T2FD and 500 ft sky loop antenna, so comparable to some of my antennas. I asked him if the coax shields were grounded, he said yes. OK, I asked how. 

"I have a very nice ground it is a 8-ft rod into the ground and it is connected with the 12 gauge copper wire to the coax cables."

I explained that the connection from the ground rod to coax shield needs to be as short as possible. Ideally a few inches. How long is it? If it is many feet long, the inductance will be high, and it will not work as a good ground connection.

"Apx 12 feet". 

Hmm... So he shortened that to 9 inches, and reported the RFI levels dropped down to as low as if no antenna was connected to the radio. Ideal background noise levels.

He was pretty happy 😀

So the moral of the story is, if you want your ground to work, you need to keep the connection to it as short and low inductance as possible.

Paul_dbnut

Comments

  • I made some simple brackets that clamp to the ground rod and have 3/8" holes. I put "F" bulkhead barrels in the holes and that becomes a splice point, ground point, a bit of a lightning arrestor point. The ground is zero length.

  • I do nearly the same thing, I got a bunch of CATV F connector grounding blocks off eBay, attached directly to my ground rods. Short, direct, and low impedance.

  • I had grounding blocks and they weren't reliable outside, so I switched to the bulkheads, cheaper too

  • Those of us with shacks on the second floor have to make do! :-)

  • My shack is on a second floor as well. But all of my coax cables run at or below ground level between the shack and antennas, where they are grounded several times. It really does make an improvement. RFI issues, especially common mode, are often "death by a thousand cuts". Lots of additive problems that need to be addressed one by one. Fixing them can be time consuming, but it can also be the difference between clean reception and one of those RFI horror shows that you see on too many online receivers.

  • Same here Chris. Mine run outside thru 3" PVC pipe to the tower, but are grounded when they come to the surface (and that ground connected to my service entrance ground). It's the best I can do.

Sign In or Register to comment.