GAP TITAN DX info
"hambone"
I have decided on a GAP, Titan DX, would appreciate any info (pro & con),
anyone can give me.
Thanks for all your help.
hambone e-mail: uniq...@gte.net
Robert Walling
side of my house. I guyed it with their guy kit they sell, but it only
comes with 2 guys. (I contacted GAP and discovered that the two 100 ft.
guys are supposed to be cut in half to give four 50 ft. guys) These pictures
show what happens with only 2 guys on a telescopic mast! But the pictures
show the strength of the antenna, which is VERY heavy and awkward to handle
with only one person. The antenna is nearly indestructible and performs
very well on all specified bands. But the size and weight of the antenna
requires heavy duty support and guying. Also, having someone to help would
be a big benefit!
http://www.connect.net/rwalling/gap/gap.html
Bob
KD7EX/5
Bob Duncan
>I have a GAP Titan mounted on a radio shack telescopic mast attached to the
>side of my house. I guyed it with their guy kit they sell, but it only
I bought my GAP Challenger when they first came out and mine was recently
nuked in an icestorm. I had gotten wobbly over the years, even
though I had it guyed. Mine was roof-mounted. It was a royal pain
to mount (31.5') and I installed it in a Radio Shack tripod, then
raised it up and bolted it to roof rafters. I never would
have thought that raising something so light would have been
so very difficult.
Nevertheless, I got great performance from mine, particularly on
40m. I'm definitely going to buy another GAP and I was looking
into the Titan. In fact, I'm thinking about mounting the next one
like yours, on a telescoping mast next to the house. I figured
that with the mast and the Titan being 6' shorter than the
Challenger, that mounting would be easier. However, I'm not
encouraged from your post.
Also, I sent GAP an email asking about the relative performance
on 40m of their main antennas and it seems (as I suspected) that
performance was proportional to overall length. They
rated the Titan just a notch below the Challenger on 40m.
Bob, KC4TEO
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Bob Duncan
. ...They rated the Titan just a notch below the Challenger on 40m.
>Bob, KC4TEO
Don, W6JL wrote:
> Just how much is a "notch", anyway? Must be a marketing term :-)
Here are the exact words from GAP...
"The Titan is just about a match to the Challenger. The Challenger is
a slight bit better on 40 meters and 80 meters because of the heigth.
The Eagle is okay on 40 meters, but not like the Challenger."
Don W6JL
snip >
. ...They rated the Titan just a notch below the Challenger on 40m.
>Bob, KC4TEO
Bob OM,
Just how much is a "notch", anyway? Must be a marketing term :-)
73,
Don, W6JL
David Butler
Having seen some messages about the GAP Titan DX vertical
I thought you might be interested in reading my review of that
antenna I wrote for Practical Wireless in 1998.
I hope you enjoy it.
73
David Butler G4ASR
VHF Columnist (but qrv 1.8MHz - 10GHz!)
*********************************
The GAP Titan DX multi-band Vertical Antenna. David Butler G4ASR
No doubt you are one of many radio amateurs who own an h.f. transceiver and are
looking for an antenna that will cover all frequency bands from 3.5MHz through
to 30MHz. It's quite likely that you'll want to chat to the locals and at other
times try your hand at working some DX stations. You may be interested in
operating exclusively on c.w. or maybe s.s.b. or perhaps even both modes. But
let me tell you that the perfect antenna that exhibits a wide bandwidth and has
variable high and low angle radiation patterns to suit all propagation paths
just doesn't exist. I wonder how many of you have looked longingly at the large
antenna arrays that adorn the covers of amateur radio handbooks and magazines
and wished you had the space for such radiators. Indeed how many of you are
lucky enough to have a suitable location or are able to get planning permission
for a tower adorned with a multi-band Yagi. Some operators might even find it
difficult to erect a simple trapped dipole covering the 3.5MHz to 28MHz bands.
So, instead of thinking horizontal why not think vertical.
Verticals are very popular antennas for the low frequency (l.f.) and high
frequency (h.f.) bands as they can produce low-angle radiation without requiring
the very high supports needed for horizontal antennas to produce the same
low-angle radiation. Verticals are designed to work in a limited space and make
a perfect compliment to a horizontal dipole or any other type of antenna you may
be using.
However there some significant problems associated with verticals in general and
multi-band versions in particular.
A ground-mounted vertical antenna ideally requires a perfect ground consisting
of an infinitely large, perfect reflector. In the real world however the ground
is far from perfect with varying degrees of conductivity. Near the antenna there
is a need for a good ground system to collect the antenna return currents
without incurring losses. A good earth system normally employs a considerable
number of buried wires or radials extending out to at least a quarter wavelength
from the base of the antenna. Note that a ground rod or base post, although
achieving a good d.c. ground, contributes very little to the r.f. ground system.
In the case of a multi-band vertical it is conventional practice to use traps,
coils or transformers to achieve auto-switching between the various frequency
bands. Traps are problematical insofar that they must have a high Q to operate
efficiently. Unfortunately this very process means that they also have a very
narrow bandwidth thus restricting the overall antenna bandwidth. No doubt you've
heard the stories about the use of trapped antennas during snowy and icy
weather. On many occasions users have reported the snow melting from the traps.
That's because traps can be lossy and the transmitter power heats them up.
Loading coils and transformers also possess similar unwelcome characteristics
and of course the more components parts there are in an antenna the less
reliable it becomes.
GAP Technology
Recently GAP Antenna Products have implemented a revolutionary new antenna
design which eliminates the inefficiencies and losses associated with radials
and traps. Ironically, the premise for the GAP principle was the result of an
anomaly of a quality assurance test. The test was to determine r.f. leakage from
what was supposed to be a "sealed" box. Fortunately, one of the technicians
responsible for securing the cover, had failed to fully tighten one of the
screws. This resulted in small slit or GAP. Since the box was not tight, when
energised, the r.f. literally screamed through this tiny opening. A few years
ago the President of GAP Antenna Products George Henf KK4CW remembered this and
wondered what would happen if he put a slit in a piece of coaxial cable. He hung
the cable, cut for the 14MHz band, from a tree and made a slit where
electrically he felt he would find a match at 50 ohms. His thinking was that if
the feed point impedance of a full size vertical is 36 ohms and the top goes to
infinity, then somewhere in between should be 50 ohms. Thus if the proper
elevation is selected, the radiation resistance will be 50 ohms, a perfect match
to the feedline. It was also found that elevating the feed point also reduced
the earth losses. Technically, earth loss results from the capacitance of the
antenna to ground, from above the feed point. Reducing the earth loss eliminates
the need for a radial system. Instead a simple counterpoise system is all that
is required. There are no traps in a GAP antenna. The elevated feed and the
unique tuner rods enable the GAP to operate as a vertical dipole even though it
is grounded. Eliminating traps makes the antenna more reliable and increases its
operating bandwidth. This is the principle behind the GAP antenna.
GAP Antenna Products manufacture a range of verticals including the 4-band
Voyager DX (1.8MHz, 3.5MHz, 7MHz and 14MHz), the 6-band Eagle DX (7MHz, 14MHz,
18MHz, 21MHz, 24MHz and 28MHz) and the 8-band Challenger DX (3.5MHz, 7MHz,
14MHz, 21MHz, 24MHz, 28MHz, 50MHz and 144MHz.) However the antenna I'm reviewing
this time around is the Titan DX shown in the photograph Fig.1. This is an
8-band centre-fed vertical using the GAP technology and requiring no radials.
The antenna covers the 3.5MHz, 7MHz, 10MHz, 14MHz, 18MHz, 21MHz, 24MHz and 28MHz
bands, stands a respectable 8M tall and weighs in at 25 pounds. It can handle up
to 1500W of r.f. on all bands with the exception of the 3.5MHz band where the
use of such high power is not recommended for continuous duty cycle modes such
as r.t.t.y. or Amtor. Of course it will comfortably handle the UK limit of 400W
on any band no matter what the transmission mode.
As can be seen in the photograph Fig.2 tuning rods are located around the
central mast section. Lengthening or shortening these will raise or lower the
resonant frequency but as the lengths have been determined at the factory there
is no requirement to adjust them. These rods act as vertical dipoles and are
predominant for the majority of bands that the Titan functions on. The only
exception to this is on the 3.5MHz band. To achieve resonance here a length of
coaxial cable is used to compensate for the missing portion of the antenna. This
cable is terminated in a capacitor, referred to by GAP as a CAP unit. Various
CAP units are available to allow the user to select where they want their lowest
band resonance to fall. Therefore before you purchase the antenna you must
specify in which 100kHz slot of the 3.5MHz band you wish to operate in. For
European usage you have to choose between 3.5-3.6MHz, 3.6-3.7MHz or 3.7-3.8MHz.
This option only applies to the 3.5MHz band simply because the antenna is not
tall enough to cover the entire band. On all other bands that the Titan DX
antenna operates on the s.w.r. is under 2:1 and no adjustments are necessary.
Simply turn the v.f.o. and go!
The antenna is designed to mount easily on a 11/4 " heavy gauge steel pipe which
can be any length of your choosing. That's because the Titan has an integral
counterpoise system and as the feedpoint is elevated you can mount the vertical
anywhere you wish. It can be located close to the ground, on top of a tall pole
or even above the roof of a house. Although the Titan is designed to withstand
substantial winds unguyed both GAP Antennas and the importers Vine Antenna
Products recommended the use of guys as a form of insurance. (I bought three
lengths of nylon guy very cheaply from a local camping store.) If you're going
to ground mount the Titan then GAP recommend that the pipe is mounted in a 50cm
diameter hole 1M deep or more and filled with concrete. I guess this is
necessary if you don't want to use guys but as my QTH is 233M a.s.l. on the
foothills of the Black Mountains the use of guys are obligatory. Before pushing
in the steel pipe I laid the four rigid counterpoise rods on the ground to see
what physical size they take up. In my opinion this is quite important as the
counterpoise arrangement does sterilise 9 square metres of area. If I'd had more
time I would have mounted the antenna just above the flat roof of my garage but
for the purposes of this review I located it at ground level.
Assembly
The Titan arrives in a box measuring 7cm x 24cm x 2.5M. Inside you'll find all
the necessary aluminium tubing, coaxial cable and associated hardware. The main
sections and tuner rods are all made of double-drawn 6063-T832 aluminium tubing.
This is an excellent material and much better than the less expensive extruded
tubing. All of the antenna components have a real quality feel to them and even
the coaxial cable is a special type that is rated for very high power operation.
A 14-page installation and assembly booklet is also included. I'm pleased to
say that this gives clear unambiguous instructions and contains many line
drawings and diagrams to help with the construction.
To get started with the assembly you'll need a flat space approximately 10M in
length. A driveway or patio surface is ideal as it will provide a surface which
allows you to find the screws that you drop!
Assembly is really quite simple as all the holes are factory drilled and all you
have to do is simply line up a big hole over a little hole and insert a self
tapping stainless steel screw with a nut driver which GAP conveniently provide.
The only other tools you'll need are a 1/4" screwdriver (and a soldering iron
and cutters to connect a provided PL259 plug onto the end of the cable). Unlike
other antennas where the tube sections are slit and held together by a hose
clamp the main sections of the Titan are designed to telescope into each other
and are simply held in place by a steel screw. The CAP unit which dictates the
lowest working frequency on the 3.5MHz band slips inside one of the sections and
cannot be changed (easily) once the antenna completed. All the plastic tuner rod
standoff insulators are pre-positioned on the various mast sections. It's only
necessary to loosen their clamps, twist them into the correct plane and then
re-tighten. The tuner rods simply slip into holes provided in the insulators and
are held in place by a locking screw. The assembly was very straight forward and
I encountered no problems whatsoever. It took me a leisurely three hours to read
through the instruction booklet, identify all components and assemble the
antenna. Now it was time to place the Titan onto the ground post. Although the
Titan is 8M tall I accomplished this task single-handedly, although it may be
useful for another hand to be available during this operation. Because of it's
size it's not recommended that the counterpoise hoop assembly, shown in the
photograph, Fig.3, is fitted until the antenna is in an upright position. A
bracket is fitted to the lower mast section by use of a hose clamp and then it's
a simple matter of slipping in the four counterpoise rods. A length of copper
wire is then threaded through plastic caps placed on the end of the rods to make
a large square approximately 3M each side. The exact length of the wire affects
the centre frequency on the 7MHz band but I just set it to the length given in
the assembly booklet and left it at that.
Measurements
Now it was time to check the voltage standing wave ratio (v.s.w.r. but commonly
termed s.w.r) of the antenna on the various bands. The s.w.r. is a measure of
how well the feed-point impedance of the antenna is matched to the
characteristic impedance of the feed line. (As an aside I should mention that in
my opinion the use of s.w.r. as an important evaluation criteria is actually
wrong. After all a dummy load will exhibit an excellent s.w.r. match across all
frequencies! More meaningful would be measurements of antenna efficiency and
radiation characteristics but these are far more difficult to measure.) To
measure the s.w.r. match I used a Kenwood TS690S all-band transceiver and a
Daiwa CN-410M cross-needle s.w.r. meter. The tests were very easy to perform and
the results are shown in the table Fig.4. On all bands between 7MHz to 30MHz the
s.w.r. was no worse than 2:1 and in many cases it was considerably better than
this. This is excellent as it allows solid-state transceivera to work from one
end of the band to the other without the s.w.r. protection cutting in. For the
3.5MHz band I had chosen the CAP unit which would allow the lowest frequency of
operation to be 3.700MHz. I measured an s.w.r. of 2:1 at 3.675MHz, dipping to
1.2:1 at 3.743MHz and rising again to 1.8:1 at the top end of the band. The 2:1
s.w.r. bandwidth therefore was some 125kHz which is very good for a vertical
antenna on this band. However it was probably more than this but my TS690S is
programmed to stop transmitting exactly at 3.8MHz! Judging by the way the s.w.r.
was rising though I reckon the actual (2:1) bandwidth would be more like 135kHz.
After performing these measurements I then had a completely wacky idea of
checking the s.w.r. on the 50MHz band. At the bottom end of the band the s.w.r.
was very high (>5:1) however much to my surprise the s.w.r. improved further up
the band and measured a comfortable 2:1 between 50.980MHz to 51.780MHz.
Co-incidentally this covers all of the f.m. telephony channels centred on
51.510MHz. This was quite a revelation to me but not as much as the surprise I
got when speaking to a GAP engineer about this added feature. He said they
already knew about this and asked if I had measured the Titan on the 144MHz band
as well! When I checked it showed a very good match across the entire band,
with an s.w.r. of 1.5 at 144MHz rising to 1.7 at 146MHz. Of course these were
the findings of the review antenna at my QTH so there's no guarantee these are
reproducible elsewhere.
Results
It's often difficult to quantify how well an antenna performs during a short
review period as there is limited time available for playing with it and of
course the state of the sun-spot cycle and the prevailing propagation at the
time play an equally important part. At it's lowest frequency of operation
(3.5MHz) the performance didn't seem 'hot' at all. That's not really surprising
as it's only 8M tall. It gets you around Europe reasonably well but DX signals
from much further afield were many S-points weaker compared to my dipole.
However once you move up to the 7MHz band and above the performance really
starts to become quite impressive for such a relatively low profile antenna.
Using the TS690S barefoot (100W) and resisting the temptation of turning on the
amplifier I made a number of contacts on all bands. Highlights are difficult to
assess (and possibly meaningless to other operators) but as an example of the
antennas potential I made DX contacts on all bands including JA on 7MHz c.w.,
VK2 on 14MHz s.s.b. and PY and LU (also on s.s.b.) on the 28MHz band. And don't
forget that it works on the 50MHz and 144MHz bands as well. A quick excursion
onto these bands one evening produced three f.m. contacts on the 50MHz band, the
furthest being at 90km. Up on the 144MHz band two f.m. contacts were quickly
made, one station being 50km away.
Bottom Line
If you need an efficient vertical antenna that takes up very little ground space
and covers all bands from 3.5MHz to 30MHz then the GAP Titan DX could be the
antenna for you. It uses quality materials, is very easy to assemble and needs
no tuning adjustments. Apart from the 3.5MHz band it covers the entirety of all
h.f. bands with a low s.w.r. I worked some good DX with it on all h.f. bands
and don't forget that although not in the specifications the Titan appears to
work on the 50MHz and 144MHz bands as well. Actually the real bottom line is
that I thought it was so good I actually bought the review model and you can't
say better than that!
Acknowledgements
My thanks to Ron Stone GW3YDX of Vine Antenna Products for supplying the review
model.
Ron can be contacted at The Vine, Llandrinio, Powys, SY22 6SH.
Tel. (01691) 831111 Fax. (01691) 831386
GAP Antenna Products
Tel. 001 561 571 9922
http://www.gapantenna.com
**********************
V.S.W.R. data
Band###Frequency###vswr###Frequency###vswr###Bandwidth
80M###3.675MHz###2.0###3.800MHz###1.8###125kHz###*
40M###7.000MHz###1.4###7.100MHz###1.3###Entire band
30M###10.100MHz###1.7###10.150MHz###1.5###Entire band
20M###14.000MHz###2.0###14.350MHz###1.7###Entire band
17M###18.068MHz###2.0###18.168MHz###2.0###Entire band
15M###21.000MHz###1.9###21.450MHz###1.4###Entire band.
12M###24.890MHz###1.3###24.990MHz###1.3###Entire band
10M###28.000MHz###1.1###29.700MHz###1.5###Entire band
* Minimum vswr 1.2 at 3.745MHz
Band###Frequency###vswr###Frequency###vswr###Bandwidth
6M###50.980MHz###2.0###51.780MHz###2.0###800kHz###**
2M###144.000MHz###1.5###146.000MHz###1.7###Entire band###**
** Antenna not specified at these frequencies.
Peter Frenning
wrote:
>Hello from 2 miles east of the GW border!
>
>Having seen some messages about the GAP Titan DX vertical
>I thought you might be interested in reading my review of that
>antenna I wrote for Practical Wireless in 1998.
>
>I hope you enjoy it.
>
>73
>David Butler G4ASR
>
I did indeed enjoy the review, and basically agree with David in his
observations, with a few comment added (I have one as well and is
mostly very happy with it)
If you don't guy it, as I omitted, the basic antenna will withstand
even gale to hurricane force winds, but in the february storms of this
year I had the following happening (at times the antenna was bent like
a fishing rod to angle of more than 45 degrees!): It tore out the
expansion bolts in the wall it was mounted to, but fortunately didn't
come down!
The connecting wires from the tuning rods were torn apart (easily
replaceable, but poor quality joints)
When it goes up again it will be guyed!
I have a version built for the US market, I had to lengthen the 21 MHz
tuning rod to make it resonate in both the 7 and 21 MHz bands (by
about 15 cm)
Can anybody tell me the value of the end cap for 3.7-3.8 MHz use (mine
is tuned for 3.950! (You dave?) I have tried mailing GAP for a new one
- no response!
73 de OZ1PIF, Peter
kingpop
This portion of *your review* seems to be a direct quote of GAP
propaganda I have seen. But in any case it is a bunch of baloney. The
"GAP" in the coax has absolutely nothing to with the radiating
components of these antennas. It merely provides a method of isolation
of the 40'+ of coax that loads up the 80mt.band. This is stuffed up
inside the antenna inside the first 8' section above the center
insulator. Please don't help to perpetuate the farce under the guise of
journalism.
Bill
multiband vertical antenna. The GAP was one of the antennas I was
researching. The manufacturer's literature included performance
quotations from the IEEE. However, I could not find any confirmation of
the quote from that organization.
I contacted the GAP manufacturer requesting a copy of the reference as
well as some information of the antenna's performance on 17M. Although
they don't advertise performance on that band, they said that users have
reported the ability to tune that band. They indicated that they would
mail me a photocopy of the IEEE report and said that they would include
tuning information on that band.
I'm still waiting for both pieces of information.
I bought the Butternut HF9V. It works as promised.
Bill Manley KB4XE