Topband: GAP VERTICAL QUESTION

[D. S. Coleman]

GD all,

I thought I would weigh-in on the GAP discussion, as I have a
Challenger that has
been standing in my backyard for just over  twelve years now and
continues to be a useful antenna.  When I moved to my present QTH in
2000, I wanted to get on the air with a multiband antenna and I had no
trees for supports for antennas and no options for a radial system for
verticals.  The Challenger covered a lot of bands, had a relatively
small footprint, and didn't cost too much, so I bought a GAP
Challenger as my first commercially made antenna in thirty years as a
radio amateur.  I had to prune its three radials to adjust the SWR on
a couple of bands and I added about a foot of rod to the lower tuning
rod, but in the end I had an antenna that worked on 10, 12, 15, 17,
20, 40, and 80-meters.  The soil conductivity at my QTH is pretty good
and the antenna worked, netting DXCC on all those bands with
100-watts.  As time went on, I was able to build ground mounted
verticals with good radial systems under them and I was able to do
some useful comparisons with the GAP Challenger, which was something
over 100' away from the other antennas.  The comparisions were pretty
interesting.

10 & 12-meters:  On both bands, the Challenger gave virtually
identical performance to quater-wave ground mounted verticals.  There
was no significant difference between the short grounded mounted
vertical and the elevated feed of the GAP, despite advertising claims.

15M:  On 15-meters, the Challenger was usually inferior to a ground
mounted quarter-wave vertical, often by about an S-unit.  I do not
recall ever seeing an instance where the GAP vertical was better than
the ground mounted vertical on 15-meters.

17M:  On 17-meters the GAP was usually equal to the grounded mounted
quarter-wave vertical.  Sometimes one would be a few dB better than
the other, but overall there was little or no difference between the
two.

20M:  The GAP Challenger worked very well on 20-meters and would from
time to time beat the ground mounted vertical.  The antennas were very
similar in performance, but subjectively I suspect the GAP Challenger
may have a slight edge over the other antenna in general use.

40M:  I think the Challenger is actually at its best on 40-meters,
although it is not as good as the Battle Creek Special that is located
about 250' away and has nearly 2-miles of radials under it. The BCS
has several dB advantage in signal strength, but then again, the GAP
doesn't require two acres of land and two miles of radials.

80M:  The GAP Challenger works on 80-meters, but the loss is
substantial.  I did work my first P2 using the Challenger on 80M, but
the Battle Creek Special has been at least 10-dB better in all cases.
The Challenger is probably in the mobile antenna class in terms of
signal strength and loss, but it is useful on 80M.

6M & 2M:  I had to test the Challenger on 6M and 2M, being as the
antenna is advertised to work on those bands.  The length of the
antenna suggested an extremely high radiation angle on those bands and
very little radiation laterally.  Well, that is apparently correct.
Compared to simple ground planes, the Challenger is down by 8-10
S-units on both bands. No, I'm not kidding.  If the station you are
trying to work is just about overhead, then the story may be
different, but  I did not evaluate that condition.  I think that this
test illustrates the point that low SWR does not an antenna make.

I will close with a current summary as to the antenna situation at
AB4I.  We had a derecho storm to come through with 90 MPH winds in the
summer and I lost my Battle Creek Special, my 80M horizontal loop, and
all my Beverage antennas.  The only antenna left standing was the GAP
Challenger and it still works.  It is currently my only antenna, but I
have another low band antenna under construction.  It's hard not to
like an antenna that covers a lot of bands, is simple, and just seems
to work.  It is not the best antenna in any category, but there is a
lot to like about it.  If I could have only one antenna, I would
probably choose an 80M horizontal loop.  If I had no way of supporting
the loop, then antennas like the GAP Challenger definitely have some
advantages.  The older I get, the more I appreciate practical points
such as that.

Do be advised that my experiences are all over ground that has fairly
good conductivity.  The results could be different if situated over
very poor ground.  As always in matters of antennae, YMMV.

73,
Steve
AB4I