Re: [TenTec] The problem with directly end fed wires

[Joe Giacobello <k2xx@swva.net>]

Stuart, I don't disagree with a word you've said.   However, keeping the 
ground lead shorter than a 1/4 wave on the highest frequency band you're 
using will minimize the RF in the shack problem.  Obviously, this 
becomes much easier as the operating frequency is lowered.  I rarely 
have RF problems on 30, 40 and 80M.

You can also use an artificial ground and tune the reactance out of the 
ground lead, but that requires an additional piece of equipment.  It was 
always my understanding that using a 1/4 wave counterpoise on the 
band(s) of interest was also effective in minimizing RF in the shack by 
moving the high voltage point outside the shack.  I really haven't tried 
this technique very often, but I have been advised that it really is 
more effective in reducing ground losses than it is in minimizing RF in 
the shack.

I have used end fed wires at my home station over the years, especially 
when I was renting, and I have had very good experiences with them.  
However, they were rarely over 170 feet long and were used primarily on 
the lower frequencies.

73, Joe

Stuart Rohre wrote:

> Joe,
> Well, some of you are lucky enough to have used end fed antennas in
> situations where the ground conditions helped your need to ground.   My two
> very bad end fed wires were 1) in the desert where there is no good RF
> ground, and 2) in the Tropics where the rainforest zone has no good RF
> ground.
> Both suffered from unidirectional response and from high RF levels in the
> shack where I could draw sparks off the metal chassis of transmitter.
>
> That tropics problem was the most surprising until a power engineer for
> Malaysia explained to me the daily rain leaches out all conductive salts
> from the earth, and they long ago washed down jungle rivers to the seas.
> They find they have to put down 10 earth rods for grounding and only get it
> down to 10 ohms.
>
> In USA, the standard for a "good" ground is usually done with one or two
> earth rods and is 5 ohms.
> The bottom line is that a balanced (dipole) antenna escapes needing to rely
> on earth ground, and any single ended fed antenna needs counterpoise or good
> RF earth or both for optimum results.
>
> The balanced antennas (dipoles), have a more easily obtained omnidirectional
> response, which is good when you are looking for any contacts as a new ham,
> both DX and closer in.  They automatically supply the missing half of the
> Marconi antenna single wire.   Later, when one is faced with camping or
> hiking in areas with few or no supports, more simple wires may be the way to
> get something working, but is not the easiest antenna to use.
>
> I just saw a number of new hams, when I first came into the game, get bum
> starts with random wires; of course, we all lived in the desert and did not
> know about RF grounds then.
> 73,
> Stuart
> K5KVH
>
>
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>  

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