Sg230 Smartuner

[ve7hfr]

I had an SGC 230 given to me from an estate.

http://www.sgcworld.com/230ProductPage.html

I followed the instructions and installed it as follows.
I have a 1/2 size G5RV so I disconnected and jumpered the centre feed cable connections at the antenna. I attached the output post of the SG230 to one end of the long wire I now had. It was a total of about 62 feet and one end is 25' above ground the other is approx. 10'

Since the SG230 requires a 12vdc supply to operate it, I bought a laptop adapter with a 12vdc 5 amp rating. The SG requires only .9 A so power is no problem.

I checked the supply to make sure the ground side was actually on the low side of the power line (120 VAC with a 2 wire plug)

All the antenna wire was #14 enameled wire.

The ground is critical with this system so I connected the RF GRD post to the water line for the house. This is grounded to the incoming gas line and all the heating ducts in the house. So I have a large area counterpoise.

Now to the problem. When I tune up, I get squealing in all the speakers in the house. The RF protection in the home theatre system kicks in an puts up the protection warning on the screen. I noticed the incoming noise level was very high, in fact S9 was typical on most bands. I heard only strong stations.

I know the SG230 is tuning as I can see the output power jump when it's properly tuned on any freq.

When I reverted back to the G5RV it works well as it always does.

Any ideas how to solve this problem ?

[5B4AJB]

Shorten your ground, you want as short a connection as possible to real earth.

Bash into the ground a couple of feet of copper pipe with a heavy, braided wire soldered onto it (on the gas stove, of course .

[edit] Using the gas mains is not a good idea...

[ve7hfr]

I live on the side of a mountain and it's solid rock in most places. Driving a pipe into the ground is impossible. I've tried it with a 6' length of Rebar in several places and it went in about 6"

I have not connected directly to the gas mains. I checked connections around the house (water,gas,ducts) and it shows continuity between them all. My actual Grd. connection is to the heating duct work that runs under the floors.

The SG230 insists that good grounding is imperative for proper operation of the system. Radials longer than the antenna are recommended but impossible here.

I have a fellow ham who thinks the laptop power adapter I'm using is causing the problem because it's not clean power.

So I may try a battery or regulated base power supply I have for 2M but it's a bit of trouble to hook it up on the mast.

[John_D]

I noticed the incoming noise level was very high, in fact S9 was typical on most bands.

What you have is a vertical with top inductance (the original G5RV horizontal bit). Vertical are notorious for picking up noise although great for txing.Tuning such a short antenna for top band will really require an ATU for that specific band. Preferably a manual one. Auto ATUs can only cater for a small VSWR. With such a short antenna you are actually getting maximum current in the auto ATU itself. Hence the radiation into the house.

[ve7hfr]

Thanks for the input. I had a long discussion with a retired radio engineer the other day. RF Grounding seems to be the problem as suspected. When the weather warms enough to thaw the ground I'll try the copper pipe or steel rods in the flower beds. The second level terrace in the yard is about 25'x 15' of top soil 2 to 3 feet deep, so that will become the ground field. I'm thinking perhaps 10 rods ? With the price of copper very high, steel rebar looks attractive.

So I'm on hold for at least a month.

[5B4AJB]

Steel is a poor conductor at RF, aluminium would be a better choice.
The actual diameter (of conductor) won't matter much, unless you have hundreds of metres of it.

Solder a tag to the end of your earth wire and bolt it together if you can't solder the wire on (to aluminium)...

If you're going to dig a trench for ali tubing, consider drilling holes every metre or so, you can pour (hot?) water down it to reduce the earth resistance further.