GAP HF verticals

GAP - The somewhat different short wave antenna...

GAP Verticals are something else...
the perfect antennas??

A short excursion into the theory off vertical antennas:
A common vertical antenna consists of a vertically mounted metal rod with a base loaded feed and a certain number of concentric radials. In order to enable multi-band operation traps are inserted at appropriate locations that effectively adjust (=shorten) the antenna's electrical dimension to a quarter wavelength

So far so good; but where is the radio's power going?

Lets assume we use an antenna elevated by 8 m. For 80m this antenna should be elevated by 20m above ground in order to fulfill the 1/4 λ resonance case. The "missing" 12m are substituted by using traps. Now the antenna is electrically 'too short' resulting in an antenna resistance of approx. 4 Ω. The 4 Ω represent the virtual resistance that effectively radiates the RF energy.
The antenna resistance, unfortunately, is not the only one resistance in our antenna system. The most important resistance is the so called earth loss. The earth loss depends on the soil characteristics as well as on the radials.
If, for instance, three radials are used for the antenna the resulting ground resistance is in the order of 30 Ω. Our antennas system now consists of a radiating antenna with 4 Ω and 30 Ω ground resistance in series. The ground loss will very much heat up the surrounding soil! In total the system has 34 Ω. However, only 4 Ω contribute to the antenna's radiation! So if the radio feeds 100 watt into the antenna system only 12 watt will be radiated. If one adds up the radiation losses of the traps required for multiband operation with 2 Ω only 11 watt will be the effective radiated power.The earth loss contributes the most significant portion besides the traps.

Solution to this problem: Easy, just use many more radials!!
Okay.... take 1000m of wire and create 60 ground radials: This will reduce the earth resistance from 30 Ω to 4 Ω; not bad, but still the radiated power is only 50 watt and the action taken was massive!
Still one half of the RF energy warms the ground!

In order to significantly improve this situation a new antenna technology must be used.

• Radiation resistance increases as the feed point is elevated. If the proper elevation is selected, the radiation resistance will be 50 Ω - a perfect match to the feedline.
• Elevating the feed point also virtually eliminated the earth loss. The GAP antenna has an antenna resistance of 50 Ω and an earth loss of 5 Ω. This efficiency of approximately 90% creates an antenna with very little loss; if we take the above example 90 watts from 100 watts input will be radiated. The hot spot marking the maximum antenna current is now located close to the antenna center section instead of being close to the earth. Result: The RF is radiated rather than used to warming the ground.
• The resulting antenna gain for low take-off angles increases.

• no earth loss
• no loss in traps or transformers
• the entire length of the antenna contributes to RF radiation. Trapped antennas contribute only with a part of their mechanical length to radiating on the higher bands.

There are no traps in a GAP antenna, no coils nor transformer.

Here are five reasons to avoid traps:

• when not installed properly traps may be prone to take on water
• the coil portion of the trap changes its value as of function of temperature shifting the operating frequency of the antenna.
• a trap is a coil capacitor that operates at high voltage; high voltage in a moist environment is prone to arc and self destruction.
• a trap must have a high 'Q' to perform efficiently; a high 'Q' will result in a narrow band width and restrict the antennas band width.
• finally, as everyone knows, traps are lossey; they steel transmitter power.

GAP antennas don't require tuning.

There is absolutely nothing for you to tune.... In fact, as trip after trip to readjust the antenna on the roof or on the mast raises your frustration level and you may loose your "cool"... All GAP antennas come completely electronically pretuned from the factory.

GAP antennas have a high band width.
With only a few exceptions the GAP antennas cover all ham bands featuring a SWR of <2:1.

Quiet - please.

Noise is an unwanted companion of verticals - particularly on the low bands. All GAP verticals are"quiet" antennas primarily due to a sleeved feedline and the use of a counterpoise. GAP antennas eliminate the deployment of thousands of feet of radial wires "parallel to" the AC power lines which transfer power line noise.

GAP antennas are easily installed.

Just screw the nuts and bolt into the pre-drilled holes with the provided tool!

GAP antennas are built to last

All weather performance should be important to you. Simplicity and a minimal parts count are the key elements to reliability. Consider the elements of the GAP antenna - aluminum tubes and coax. Nothing else! Compare that to other antennas with a multitude of connections, coils, variable capacitors, transformers, etc. and you'll see that for everyday operation in rain, sun, ice or snow - GAP works. GAP antennas use double-drawn aluminum tubing. Each section telescopes perfectly into the adjacent and is secured with screws. The hardware is stainless steel. The coax used is a special non-contaminating high temperature type to provide added safety for high power operation.

The GAP antennas

TITAN DX

The most often bought antenna of the GAP family. All 8 Bands from 10m to 80m incl. WARC Length 7,5m No radial required! One of the primary virtues of the TITAN is the GAP center feed. The Titan is the only vertical antenna marketed with total continuous coverage under VSWR 2:1 on 10m to 40m and 100KHz bandwidth on 80m. By elevating the feed the earth loss is dramatically decreased, which means the antenna operates independent from the earth conditions and may be installed either on a roof or close to the ground. As is the case with all the other GAP antennas no further tuning is required. The operating center frequency on 80m is set by means of an integrated fixed capacity. Please specify the desired center frequency upon ordering. The standard setting is 3.65 MHz, available are 3.55 or 3.7 MHz. The TITAN requires no radials! Order No. 11330 479.00 € Buy now Download: GAP Titan Manual (PDF, EN, 120KB)

Further information:

Artikel von DL1FK aus CQ/DL 2/98.

Montageanleitung GAP TITAN (englisch, etwa 115 KB) The TITAN in our photo album Review about the GAP Titan by TM0IMD

EAGLE DX

6-Band 40/20/17/15/12/10m Length 6,5 m

The EAGLE is the smallest antenna in the GAP product line. The Eagle weights less than 9 Kg and can be installed almost anywhere - at ground level, on a pole, on your roof or atop a tower. It is essentially a set of vertical dipoles - the optimum singular DX antenna! No traps, coils or transformers are used to achieve multiband operation in this antenna either. The EAGLE provides full coverage with VSWR < 2:1 on 40/20/17/15 and 12m; and approximately 500KHz on 10m without readjusting. If the band is wide open, you might work a VK with a coat hanger, but when conditions are less than perfect you want the highest efficiency the antenna can provide. The efficiency of the GAP Eagle is without equal. It has no traps, transformers or matching coils to rob transmitted or received power. For the highest S meter reading, choose a GAP Eagle. Three rigid counterpoises are required for operation (see picture) but no radials. Order No. 11333 GAP Eagle 478.00 € Buy now

CHALLENGER DX

#8-Band 80/40/20/15/12/10/6/2m Length 9,5 m

The Challenger is designed to be mounted directly on the ground or elevated on the roof. As is the case with the other GAP antennas since it does not require earth loss to obtain a 50 Ω match.! Roof mount does not gain any specific advantage due to the 'elevated ground' structure, but is possible if there's no garden etc. available. The CHALLENGER covers the bands 6/10/12/15/20 and 40m. Over 130KHz of bandwidth is provided on 80m! The antenna requires a counterpoise of three 7.5m wires. They may be buried or just scattered on the ground. Symmetrical deployment is not critical. Adding additional wire will not significantly improve performance. As described with the TITAN The operating center frequency on 80m is set by means of an integrated fixed capacity. Please specify the desired center frequency upon ordering. The standard setting is 3.65 MHz, other frequencies are available on request. Order No. 11331 GAP Challenger 440.00 € Buy now Download: French Instructions GAP Challenger (PDF, FR, 530KB) Many thanks to the kind OM who provided us with this translation!

VOYAGER DX

4-Band 160/80/40/20m Length 13,5m

This is the first antenna manufactured specifically to provide efficient low band operation. Emphasis was given to 160m and 80m when designing the VOYAGER. Unlike the Challenger, the VOYAGER employs a capacity hat with circular ring to reduce the physical height to 13.5m while maintaining an electrical height of 20 m. A capacity hat is the most efficient way to reduce height, maintain bandwidth and eliminate corona. The entire band on 80m (!!), 40m and 20m, 90 KHz bandwidth on 160m. As is the case with the CHALLENGER three insulated counterpoises of 17m are required, the deployment pattern is very flexible - also possible around corners. Four guy anchor points 7.5m from the base mount are required. The guy brackets and aluminum pivot are supplied but not the guy rope itself. Order No. 11332 Voyager DX 580.00 € Buy now

Accessories for GAP antennas

Steel tube

Drawn steel tube made of ST 52, 32x3 mm, galvanized, fits the antenna joint. Cut to order, 1m to 2.5 m length and shipping together with the antenna through UPS.

Ground mount

23120

Tiltable ground mount for digging in or fix in concrete. Enables quick tilt of the antenna (not required for model Voyager which contains a similiar base). For use with EAGLE and TITAN please specify the desired length of the steel tube. Order No.: No.: 23110 !
Ideal for the field day etc.

Guy wire kit

11341

Consisting of a guy bracket and 30m respectively 60m guy rope made of black, ultra-violet resistant DACRON (Polyester) material;, only 3mm thick, rupture force 150 kg.

Guy rope

Only 3mm thick therefore very unabtrusive. But rupture force still 400 kg! Stranded material, only minimal lengthening when getting wet.

Spareparts for GAP Titan

Spareparts for various GAP Antennas