The AM Forum

I had the occasion today to unhook and re hook my ground system in JS clip lead fashion to the radio during the middle of the daytime while listening to some very weak signals out of 2 land on 85. The antenna was one of the 450 ohm feeders just stuck into the center of the bnc and the other feeder screwed under the screw of the johnson low pass filter.

The ground system is 6 10ft ground rods 10ft apart connected with #6 splitnutted together to enter the house thru a PVC pipe, maybe 4 ft length to the outside nut breakout and another 5 ft to each ground rod, all propane torch soldered. there is a 7th rod connected with #6 going back to the service entrance, a length of 20 ft with 2 10 ft rods at the end of that run.

there was/is a solid repeatable 1/2 s unit difference when the ground system is connected on all signals as well as a increase in background noise with no signal. I was always told that ground systems could not effect ground wave signals like this on 75 meters.

has anyone else ever seen this effect on a "non-ground system" antenna like a dipole? I just found it curious.

Hola Derb,

My guess is that your balanced open wire fed antenna is now unbalanced by connecting it across the hot and gnd. It may be exhibiting some feedline radiation resulting in some vertical polarization.  A good ground will always help antennas like that.

Try the same test with a coaxial fed horizontal dipole antenna that has a balun/choke or use the new Derb Johnson antenna tuner on that balanced open wire antenna when it's done.

As you've said, it should make little difference with a horizontal balanced dipole if the ground is connected or not, signal strength-wise..

I guess my point is you really need a full-blown radial field matrix under the antenna and out a few wavelengths to make up for poor Earth ground RF-wise. A few rods in the ground are really meaningless for minimizing RF ground losses and have no effect on pattern formation. The lower the desired final angle, the farther out the radials must go, otherwise it's depending on pure Earth. Otherwise the lowest angles are eaten up my Earth losses leaving higher angles. At some point, Earth dictates your outcome. This is especially important for verticals.

Rods are good for safety reasons, RF in the shack, etc., of course.

In case you're interested, here's a short article I wrote after talking with a number of 160M DX gurus about grounds and radials:
http://amfone.net/ECSound/K1JJ16.htm


Hope youse if feeling good and have a smooth holiday, there BJB!

T

hey Tom same to you.  8)

I'm doing ok fine. Going to a local fester on Sunday, gonna see JN and Slab and pal around for a while and get some junkbox junk.  Keeping busy in the shack rebuilding stuff upon more stuff. the news about Kennedy hit me hard as you can imagine. The fact that they did not operate on him tells me he's not going be around much longer. Where they took the biopsy from means his is not operable unlike mine was/is. His age is going to work against him bad as well.

the radio work is helping me out a lot. The days were pretty long - now all I can think of is what I need to do tomorrow to get this or that going. I cant do as much as I want but I do as best as I can. It's filling my days up and I'm pretty happy.  :D Hammy Hambone is keeping the costs low and I'm glad Hambones abound.

have a great weekend OM.