Gem Quad (or other quads) HF
Feroz & Pam Ghouse
If there are any folks who use the Gem Quad...I would like to get
information on its, practical performance. I am interested in their 4
element triband quad.
Questions I ask are
1. SWR specs
2. Can the quad be tuned to any frequency (within limits - favor the
CW, DX or SSB portions ) on the band for which the loop is cut ?
3. Is tuning the quad a long procedure.
4. Can some of the WARC bands be added to the triband
configuration...and what will the effects be?
Any information is greatly appreciated....we can even start a
thread.....
Feroz, 4S7FG/WU9N
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Duncan Clark
In article <34D352A5...@centuryinterX.net>, Feroz & Pam Ghouse
<fgh...@centuryinterX.net> writes
>If there are any folks who use the Gem Quad...I would like to get
>information on its, practical performance. I am interested in their 4
>element triband quad.
>
>Questions I ask are
>1. SWR specs
>2. Can the quad be tuned to any frequency (within limits - favor the
>CW, DX or SSB portions ) on the band for which the loop is cut ?
>3. Is tuning the quad a long procedure.
>4. Can some of the WARC bands be added to the triband
>configuration...and what will the effects be?
>
I put together a quad from second hand GEM quad spreaders and spiders
based on info from the Quad handbook.
I use 2ele on 20m and 4ele on 17, 15, 12 &10 and 5ele on 6m. My boom
length is 14ft. I use the boomless spider in the middle of the boom and
use the single spiders at either end of the boom so my array is balanced
weight wise. I only use 2ele on 20m because trees close by wouldn't let
me use 4ele. I cut 2 feet off the ends of the 2nd director and reflector
spreaders.
I cut my loop lengths straight from the book formulas and feed each
driven element using 1/4 wavelength 75 ohm (or 50ohm if it is a good
match) coax. They all go to a relay switch box and are individually
switched from the shack. Loops use aluminium welding wire and the boom
height is 10m. I did very little adjustment (except for 17m - see later)
of the loops as it was pretty much impossible once the loops were
attached.
Results:
As I cut the lengths from the book values I am slightly out on lowest
SWR on various bands. I only operate ssb but use the 20m and 15m across
the whole of the ssb portions without noticing any real difference in
performance. My SB1000 linear hasn't complained yet. An Autek SWR
analyser paid for itself alone with this beast and was really helpful in
making sure that I was close enough.
20m is a little low at 14.12 but F/B >20dB
17m best at 18.120 F/B about 10dB
15m best at 21.150 F/B >20dB
12 spot on >20dB F/B
10m 28.5 >20dB F/B
17m is an enigma. I can't get the F/B any better and I've done a lot of
adjustment! Possibly the spacing is too close, however I put out a very
loud signal on this band. The poor F/B is a pain as at times. On the
other bands I do very well and am more than competitive against locals
with yagis at 40-50ft (except for the guy with 3-5ele at 120ft!) and
have no complaints with the antenna at all.
It's been up 2 years and survived strong winds without any problem. Ice
is not a problem here in southern UK and I have never seen any on any
element.
Things I want to change. Replace tilt over mast with tilt over 55ft.
tower moved 10ft. further from trees and increase boom length to 20ft.
This will allow me to go up to 4ele on 20m and hopefully do something
about the 17m F/B. I'd love to try adjusting the reflector remotely from
the shack (whilst continually listening) with a variable capacitor then
replacing this with a fixed value later.
Remember this beast is a 3D structure and takes a lot of handling. It's
not heavy just very very unwieldy. Some sort of tilt over mast/tower I
would say is a must.
Good luck
Duncan
G4ELJ
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Duncan Clark