[TowerTalk] Multiband End Fed
ve4xt at mymts.net
Fri Apr 21 14:31:30 EDT 2017
You have good, and multiple, reasons to be a doubter.
A good match doesn't necessarily have a thing to do with performance. A dummy load has a good match. And wide bandwidth, too!
Do you really want all that RF emanating inside your shack? And using the chassis of every piece of equipment as a counterpoise? Good luck with trying to cope with RF burns.
Also, the wire will be a magnet for noise, so forget about using a computer, plasma tv, air conditioning, furnace, etc., while operating.
At lower frequencies, the wire will behave kinda like you expect; at higher frequencies, look for really weird patterns.
Not to mention the lightning issue.
Coax affords much greater likelihood of keeping the RF inside the coax as it enters the house. You can't put a common-mode choke on a wire...
Random wires are OK for portable and QRP portable, but you're asking for trouble in a fixed station, imho.
73, kelly, ve4xt
Sent from my iPhone
> On Apr 21, 2017, at 11:28, Wilson Lamb <infomet at embarqmail.com> wrote:
> I’m a doubter.
> Is there any way you could put up a wire ending in the shack?
> Feed it with a little MFJ tuner and you can match on ANY frequency, with higher efficiency.
> The fact that they show such good matches on such a bunch of non harmonically related freq’s shows there’s more going on than they talk about.
> Note that some freqs are phone, some CW and that small excursions in the bands can make large changes in SWR. Where do you want to be?
> B%W sold a magic antenna to the military. It got a fair match because it had resistors at the feedpoint!
> The logic was that if you fed it enough RF enough would get out to make your contact.
> You can find it in the QST archives.
> The impedance of an end fed varies from thousands to under a hundred Ohms. The low Z magnitudes depend more on ground quality than the high Z ones.
> A really good shack ground is a good thing.
> A reading of the Antenna Book or Handbook would be very useful for you.
> There is still no free lunch,
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