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Harness mounted 2 meter antenna


alan_k
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Do you want greater radio range?

Or longer battery life with the same performance (radio set to low power transmit)?

Can also be used on the ground when suspended from a tree or non metallic pole.

The ‘rubber duck’ or helical antenna is notoriously inefficient. I have found a design for a half wave antenna with much better performance. http://f3wm.free.fr/radio/pocket.html

Advantages:

Easy to make

Inexpensive

Lightweight

Flexible

Disadvantages:

Something else to couple up

Small mismatch due to proximity of frame/cage (see Technical later)

Parts list:

3 meters of RG58 coax cable or equivalent 50ohm 5mm diameter cable.

Short (40mm) length of 32mm diameter plastic pipe.

Sealant or heatshrink.

BNC Plug or to suit radio.

See instructions and diagram at http://f3wm.free.fr/radio/pocket.html

2mantenna.jpg

Additional notes for harness mounting.

A. Be sure to seal the end of the cable.

B. Length = 45cm

C. Seal at this point also.

D. Length = 47cm

E. Coil can be further secured with insulating tape.

F. Length = 1.5m (see Technical later).

G. Coaxial plug to suit radio.

Finished antenna

Finishedantenna.jpg

Harness mounting

Harnessantenna.jpg

The run from A to B wants to be reasonably straight and vertical. Keep away from the frame and cage and mount on the opposite side to the ignition lead. For shorter harness construction run the lower section underneath the seat. The additional length of section F is coiled in the harness side pocket.

Technical.

This antenna will suffer from mismatching to the radio when mounted close to metallic structures and to some extent the pilot. If used on the ground when suspended in free air the matching is extremely good when the length F = 1.5 meters. VSWR is close to 1:1.

When mounted on the paramotor harness the proximity of the frame affects the matching and improvement can be had by reducing the length F. I have reduced it to 50cm, which also gives no spare cable to be secured or coiled in the pocket. On my machine this gives a good VSWR of around 1.5:1. A reading of 2:1 or below is perfectly OK and need not be improved upon.

Shortened version

P1030012.jpg

Cheers,

Alan

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You should have asked, we've been making and using these for years except we usually run them up the risers. The good alternative for cage mounting is to split the coax inner and sleeve, cover sleeve in heatshrink and then run the inner upwards and the sleeve downwards with the coil in the middle. Sort of like a capital T on its side. Cage mount on opposite side to coil pack and sheath kill switch wire to reduce RF.

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