One for the tech heads.

[mudnut]

G'day All.
As some of you may know, I have had a bit of a problem with our TV reception since a storm wrecked our antenna a few months ago.

To repair it, I used some inch gal water pipe with two parallel braces as the upper part, and three pieces of gal pipe welded together as the base.

The base is mounted to three brackets that are welded to the steel veranda pole, which is concreted into the ground. I have modified the middle bracket as a swivel point so I can lower the whole set up, very easily.

After a week of bad reception I drove an earth stake into the ground and got a very small improvement for my work.

Before the storm, we had the antenna mounted on a piece of 1 inch gal pipe, that was attached to a 4 metre long piece of 3 inch, thick-walled mild steel pipe, that was painted.

After fitting the new pole with the original antenna, and spending ages tuning and adjusting the system, I could get most channels perfectly, but about a 1/2 of them would drop out. Some worse than others.

I bought a new phased antenna array and enough quad shielded coax to reach the TV without any inline connections.

Long story short: I got only marginal improvement, and eventually found that I had to insulate the array from the pole. The reception is now perfect in dry mild wind. Yet to find out if rain and high winds will affect it.

I was curious to find out what caused the problem. With the earth disconnected I discovered a .402 volt (2.3 millamp) between the steel frame of the house and the earth stake. On the oscilloscope, a miniscule 50hz power cycle was apparent at the top of the dc voltage.

I turned the main circuit breaker off and the 50hz disappeared, but the .402 volts remained. Also I found that the voltage takes about

5-6 seconds to build up when the earthed out and then disconnected.


I can understand there being a few millivolts of 50hz AC being apparent as we are on a Single Wire Earth Return (SWER) system

Where is the 402 millivolts coming from. It was definitely wiping out the TV signal every 5-6 seconds when the pole was earthed, but not all of the time and it did get worse as the ground dried out.

I have checked all of the neutral and earth connections in the house too.

[Beni C]

Hi Mudnut, what area are you in and what antenna did you buy?
Do you have line of site to the transmitter?

[mudnut]

I have fixed the reception (all good so far).

I am just wondering where the voltage from our house to ground is coming from.

I bought a wisi 02MM-EE06-1 UHF phased array TV antenna, from a Jaycar distributor.

It has the flat grid to deflect the signal to four small receptors. I had to do a modification on a bracket and tighten all the fasteners. I posted in the angry thread about the terrible build quality of the unit.

[threedogs]

do you run an internal 240v amplifier as well.
Did jay Car suggest that antenna for your area, you may need those sideways mounted jobs?
what are your max Db's

[mudnut]

No amp needed so far TD. The TV is working. I am curious as to where the voltage that was wiping out the TV signal before I fixed it, is coming from.

[the evil twin]

Hiya mudnut,

If I understand how you are wired up and where you are taking your reading that small earth current is normal.
It is the neutral to earth differential between where you are taking the reading and earth.
That is why it disappears when you earth out then slowly builds up and also why it is different when the ground is wet.

Google 'Earth Neutral voltage' and see if that matches the symptoms you are seeing.

[mudnut]

This is a D.C. voltage that takes 5-6 seconds to appear after the earth wire to the stake I put in is disconnected. The main power circuit breaker is Off. The orange between the antenna and pole is what I did to make the TV work properly.

[MuddyTroll]

So the current still remains ATM and you have just insulated the antenna to get it going?

I've done a dozen or more antenna installs and have felt slight tickles when touch the antenna when it's mounted. Always use rubber gloves now

I was going to suggest-
Static generation from the antenna?
Or possible power output from the TV itself?

[kevin07]

my head hurts

[Hodge]

How far are you from another nearest property / power supply? And how far is your house / antenna from the tin can ? Could be the neighbors stray currents. If all else fails, I'd get Powercor to come and test the SWER, main earth, just in case.