REVOLUTIONARY NEW TECHNOLOGY

One look at a GAP antenna and you know its radically different. The GAP design elevates the feed point. Why? Radiation resistance increases as the feed point is elevated. If the proper elevation is selected, the radiation resistance will be 50 ohms -- a perfect match to the feedline. If the design stopped here, the improvement would be dramatic -- but it didn't! Elevating the feed point also virtually eliminated the earth loss. You don't find loss with dipoles, because they are elevated. Technically, earth loss results from the capacitance of the antenna to ground, from above the feed point. That is the key. Contrast the conventional vertical's ground level feed point to the GAP feed at 16 feet (Challenger). GAP technology reduces the loss from more than 30 ohms to approximately 5 ohms.

The GAP antenna has an antenna resistance of 50 ohms and an earth loss of 5 ohms.  This efficiency of approximately 90% creates an antenna with very little loss. When compared to the 12% efficiency of other antennas the improvement is dramatic -- 600%!

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 an antenna more reliable, increases its band width, stabilizes its frequency and most important, you don't have to tune and retune over and over.

We at GAP are pleased you have taken the time to consider our product line. We provided this technical explanation, because GAP technology is totally new. You will not find it in conventional texts.

GAP is dedicated to performance, quality and prompt service. Our commitment is simple and comprehensive. If you purchase a GAP antenna, we will assist you to achieve maximum performance.

George Henf
President, GAP Antenna Products


 

ANTENNA SELECTION CRITERIA

Radiation performance should be the prime consideration in selecting an antenna. However, secondary considerations should not be ignored. Reliability, structural integrity and the ease of proper assembly are also important. An antenna that works well for a month and fails can be extremely frustrating. GAP antenna reliability exceeds the competition because it is ultra simple. Minimum parts produce maximum reliability. GAP antennas are composed of aluminum tubing and coaxial cables. NO traps to keep sealed, no transformers to protect from weather. What could be simpler?

 


TUNING

Tuning can be a nasty task particularly if you mounted the antenna on your roof. In fact, it can become dangerous as trip after trip to readjust the antenna raises your frustration level and you lose your "cool". A GAP Eagle, like all GAP antennas, comes completely electronically pretuned from the factory. There is absolutely nothing for you to tune. If you're looking for a reliable, efficient, broad band low profile antenna that will serve you well and dig out the DX, the GAP Eagle is for you.


 

THE ELEVATED GAP

GAP antennas launch RF at an "elevated" point. Elevating antenna resistance, diminishes earth loss and therefore improves efficiency significantly. The feed point is placed high, generally above the height of most verticals. An insulated gap is placed in the mast at this point, which allows the RF to flow out on the antenna. Propagating RF in this manner obsoletes the trap design and the need for matching networks.

The elevated feed also eliminates the requirement to have maximum current at ground level where you can't fully utilize it. Maximum current can now be moved up the mast. Raising the current point improves the DX angle -- and increases low angle gain. A GAP antenna does not employ traps, coils, transformers, baluns or resistors. No GAP antenna requires earth loss to achieve a match.


 

RELIABILITY

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. Like any antenna, GAP antennas are not immune to lightning, however. Disconnect and shut down when it's around.

 

  • All GAP antennas use double-drawn 6063-T832 aluminum tubing. Each section telescopes perfectly into the adjacent and is secured with screws. GAP does not use less expensive extruded tubing and "slit" the tubes to telescope and then secure with hose clamps.
  • Hardware is stainless steel.
  • The coax used is a special non-contaminating high temperature type to provide added safety for high power operation.

 


UNIQUE FEATURES STANDARD TO ALL GAP ANTENNAS

  • Unique "Elevated" Feed
  • No Tuning Required
  • No Traps
  • Automatic Band Switching
  • Input Power : Legal Limit*
  • Input Impedance : 52 ohms Nominal

FOUR REASONS TO AVOID TRAPS

  • A trap is a coil capacitor device that operates a high voltage. High voltage in a moist environment is prone to arc and destroys itself
  • The coil portion of the trap changes its value as a function of temperature shifting the operating frequency of the antenna.
  • A trap must have a high Q to perform efficiently. A high Q trap will have a narrow band width and restrict antenna band width.
  • Finally, as everyone knows, traps are lossey. They rob transmitter power.

HORIZONTAL OR VERTICAL?

Why is a dipole ineffective on the low bands for many amateurs? A dipole's performance is a direct function of its height, measured not in feet by in wavelengths. A 10m dipole at 32 ft is 1 wavelength high, but a 160m dipole at 32 ft is only 0.06 wavelengths high! To appreciate the degraded performance, lower the 10m dipole to 2 ft off the ground. Now it is .06 wavelength high. Bottom line : dipoles on 160m are not very practical; vertical antennas are the obvious alternative, but rarely are they "big signals". Ordinary verticals have their own set of problems -- excessive height requirements and vast ground areas for radials. A quarter wave on 160m is a 130ft high, on 80m it is 66ft. On 160m, one needs almost an acre of ground just to accommodate the radials. Using a vertical less than full height lowers the antenna's radiation resistance dramatically. This is the resistance that accounts for signal radiation.

The chart tabulates the VSWR and efficiency versus antenna height for a typical base fed 160m vertical.

 

IDEAL FULL SIZE HALF SIZE 26 FT KIT
Radial 200 3 3 3
Antenna Resistance 36 ohm 36 ohm 7 ohm 1 ohm
Earth Loss 0 ohm 29 ohm 29 ohm 29 ohm
VSWR 1:44:1 1:25:1 1:20:1 1:7:1
ERP 100% 50% 19% 3.3%
Input Power 100w 100w 100w 100w
Radiated Power 100w 50w 19w 3w

Check the VSWR. In all cases it is acceptable. VSWR does not measure how efficient an antenna is!

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