ChrisSmolinski

The diurnal changes in SNR scores are interesting to observe, below is the KiwiSDR with a 400 ft south directed Beverage antenna. Somewhat different results on the other KiwiSDRs with different antennas, as expected the 11/10m dipole is pretty dismal by comparison

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.