Re: East, West, and in between on 160m
Matthew King - AK4MK
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Hmmm.... at 30ft, that antenna is about 0.07~ above the ground on 160m. That's the equivalent of a 20m dipole about FOUR FEET off the ground. I think we all have an idea of how well that'd work for anything other than very close-in communications.
An end-fed antenna really likes to be right at 1/2~ long at the lowest frequency of interest, so that'd be about 255' on 160. A true "long wire" antenna is a full wavelength or longer at the lowest frequency of interest, or just over 500 feet.
As Carr says in the Practical Antenna Handbook regarding an end-fed antenna (an inherently unbalanced antenna), " ...the user must realize the most important thing he or she can do to improve the antenna is to make sure there is an excellent RF ground system attached to the chassis of the ATU (tuner) or transmitter where the wire connects." The emphasis is mine, and is meant to indicate that a piece of #6 wire to an 8 foot ground rod isn't an effective RF ground. That's a safety ground. An effective RF ground is a counterpoise or radial field.
Right now, with no counterpoise, your feedline is being forced to be the counterpoise, or at least it would be without the isolator on it. I'm of the opinion that you're much better off WITH the isolator so that you're not bringing RF into the shack on the feedline, but I'm also of the opinion that you NEED a counterpoise, especially with the isolator on the feedline. No matter how productive the antenna may have been to this point, an effective counterpoise would make it much more so, especially on 160 where it's already very low and very short. There's not going to be a whole lot of efficiency there either way, but the counterpoise should help quite a bit.
In effect, you have three things you can do to improve your antenna:
Get it higher
Make it longer
Give it an effective counterpoise system
Several radials (8-16) just as long as you can make them and fanned out equally (as obstacles allow) hooked to the ground post on your matchbox should make a real difference in the performance of your antenna on all bands. More radials are better, if you can do it, up to a point of diminishing returns of about 40 radials. If the isolator is currently at the feedpoint, you could move it to the shack entry point instead and that'd make your feedline radiate and be a very minimalist counterpoise. It may well bring common mode current close enough to your shack to make weird things happen to speakers, computers, monitors, TV's, etc... as well, though. If absolutely NOTHING else can be done, at least do a short piece of #6 wire to a fully driven ground rod with a well-biting clamp on it. That might make some difference, but nothing approaching that of a real counterpoise.
Good luck with it, friend Jim - I'll be out spreading more radials myself in the spring!
On Thu, Feb 1, 2018 at 2:11 PM, Jim K5SP <jinnis@...> wrote: