5/8 over 5/8 Vertical for 70Mhz
A highly efficient 2 x 5/8wl FORKER Vertical antenna for 70Mhz with excellent wind handling ability and 5KW rated.
If you are finished with toys and would like a decent, high quality vertical to last, you have come to the right place!
Justin Johnson G0KSC become well known for his LFA (Loop Fed Array) Yagi antennas with their exceptional low-noise performance. He has always been mindful of potential losses caused by matching devices and their placement within antennas. Some of the associated issues of matching devices include, power limitations on TX, noise induction on receive and alteration of the signal/antenna pattern. See a more detailed overview at the bottom of this page.
This G0KSC designed 5/8 over 5/8 does not use any 'lossy' coils or traditional forms of matching devices. It uses a double-J arrangement or 2 vertical radials that run parallel to the main radiating element in order to achieve a balanced, 50 Ohm input. Unlike the J-pole which has a slightly directional pattern, the double-J or Fork type feed arrangement (hence the FORKER name!) produces an almost perfect symmetrical radiation pattern. This too can be seen in the plots listed in the 5/8 overview at the bottom of this page. Without traditional matching coils/devices, radiating efficiency remains higher than most competitive products.
The InnovAntennas 2 x 5/8 has been designed in order the pattern angles slightly downwards (11 degrees) in free space (above ground placement will alter this but radiation angle will remain low).This ensures even when this antenna is installed very high up, it will provide excellent near and far-field coverage.
Not 'boys toys', just professional, appropriately built antennas
Our antennas are constructed with the best quality materials in order that the best mechanical construction can be achieved, not the cheapest and most profitable! Even a digital caliper is used (with an accuracy of .01mm) to measure the elements during production to ensure they are within tolerance, ensuring they work as well as our software model predicts.
- Marine grade Stainless Steel Fittings*
- Original Stauff insulator clamps
- Mill finished for highest levels of accuracy
If you are looking for the best of the best from both a performance and mechanical construction perspective then look no further, you have come to the right place!
Don't be fooled by made-up BIG gain figures, these are real and verifiable.
Gain: 5.12dBi/2.97dBd @ 70.1MHz @ -11 degrees in free space
Gain @ 10m above ground: 8.41dBi/6.26dBd @ 4.2 degrees
Gain @ 20m above ground: 9.44dBi/7.29dBd @ 2.5 degrees
Maximum Power handling: 5KW
SWR: 1.02:1 @ 70.1Mhz - 1.5:1 @ 70Mhz - 1.5:1 @ 70.5Mhz (Centre frequency can be adjusted from 69.9 to 70.5Mhz with 2Mhz1.5:1 bandwidth
longest Section Length: 5.13m (17'')
Weight: 4.52Kg / 10LB
Wind Loading: 0.1 Square Metres / 1.2 Square feet
Wind Survival: 160KPH / 100MPH
Other options available if higher wind loading/survival is required.
The 2 x 5/8wl FORKER vertical for 6m uses no coils or loading to ensure maximum radiated power. A solid rod delay-line is installed between the upper and lowers 5/8wl elements and the FORKER twin stubs at the base ensure this antenna has a 50 Ohm impedance.
The boom is 1.25 inch square (31.75mm) and a boom guy is supplied with this antenna.
If you want an antenna to last and perform in all weathers without SWR or bandwidth shifting, this is it.
Free Space Elevation Plot
Elevation plot at 10m above average ground
Elevation plot at 20m above average ground - note that even at 20m up the Forker does not lose pattern
SWR Plot - This antenna can be centered anywhere from 50 to 54Mhz and have a 1Mhz 1.5:1 bandwidth either side
Comparisons between the InnovAntennas FORKER vertical and other vertical antennas
The above plot is looking down on this vertical from above. An almost perfect symmetrical pattern is seen
J-pole comparison - this plot shows the same azimuth pattern of a J-matched vertical. Directivity can be seen and this is why the FORKER is a superior design
Why Our 5/8 wave antennas do not using coiled matching devices
In the next few lines we will take a look at a direct comparison between a coil matched 5/8wl vertical antenna (the most common) and an InnovAntennas Forker. Keep in mind, while you might see prediction plots of 5/8wl antennas with much lower angles of radiation that what is shown for the coil matched 5/8 antenna shown below, often predicted plots are shown WITHOUT matching devices attached and thus, you see an incorrect view of the antenna you could be purchasing, before the matching devices does it's worst!
First, let us take a look at the InnovAntennas single 5/8wl vertical and the traditional 5/8wl vertical with a coil and radials.
Above the element layout of the InnovAntennas 'FORKER' (black lines). The feed point is indicated by the red circle and the vertical radial/matching stubs are easily seen either side of the 5/8wl radiator.
Above is the layout of the traditional coil-loaded 5/8 ground plane antenna and below is a zoomed view of the 5/8wl
A close-up view of the coil loaded base of a traditional ground plane 5/8wl vertical
Note that the radials make no impact on the angle of radiation, they are there purely to help the antenna achieve its 50 Ohm feedimpedance
The above plot shows a single 5/8wl vertical antenna in freespace. Note the slight tilt down of the radiation angle
The above shows a base (coil) loaded single 5/8wl ground plane antenna in freespace. Notice the angle of radiation is far from being low-angle. Gain is well down too.
A Single 5/8wl FORKER vertical for 50Mhz produces this nice, clean pattern with a radiation angle of 4.7 degrees when the base of the antenna is placed 10m above ground.
The coil-loaded 5/8wl ground plane is as far way from the FORKER vertical as can be. Much of the signal is radiated at high-angle and as a result, the main lobes are at 5 degrees (when placed at 10m above ground) and gain is almost half that of theFORKER 5/8wl vertical