On 5/8/2023 2:11 PM, Big Al wrote:
On Monday, January 10, 2005 at 2:19:35 PM UTC-5, Dave Platt wrote:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4672&item=5743095997&rd=1
He might be making the J-Pole one-wavelength long which would
indeed result in about 3 dB of gain but at a relatively useless
take-off-angle.
I suspect that he's comparing a standard half-wave-radiator J-pole to
a typical "ground plane" antenna (a quarter-wave monopole, with one
set of quarter-wave radials, possibly tilted downwards for an
impedance match).
The latter sort of antenna falls somewhat short of behaving like
a true infinite-ground-plane antenna, as the radials are neither
horizontal nor infinite in extent. If I recall correctly, the
radiation pattern will be tilted upwards from the horizon by
a significant amount.
The J-pole will be close to 0 dBd, while the "ground plane" will
probably fall a few dB short of that figure out at the horizon.
--
Dave Platt <dpl...@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
I built a copper pipe j-pole a number of years ago for 11 meters. It hangs almost at the top of a large oak; just low enough not to take a lightning strike (so far). It's a real bear to put up or down, but it really doesn't require any maintenance. I
do use a choke balun at the feedpoint and about 75 feet of LMR400 into the shack. It took some time to get the swr into good range, but at 1.2:1 I can't ask for much better and it never changes. I haven't had heavy ice for quite a while. Performance is
much better than expected. I wanted to build a decent homebrew to save up for a ground plane vertical. Haven't spent the savings yet. Gets a lot of comments when they ask what I'm using!
Well, the subject is: "Re: Does a j pole need grounding and/or a balun?"
Okay, if you don't ground it, what happens? Some say that you are
leaving them floating. If they are floating, they will drift away
skyward and you will lose them. Like a child's balloon.
Forget the balun. It will go up with the antenna anyway. No need to
increase your losses.
You will be a happier camper if you just go ahead and tether your
antenna. Check it from time to time to make sure its tether is still
sturdy. If the antenna runs out of "floatness" in the future, you may
dispense with the tether.
Don't forget: You heard it here first!
--- SoupGate-Win32 v1.05
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