FlightAware Discussions

Antenna Testing, Home Built super J pole or ¼ wave?

The principle and probably sole advantage of the 1/4 wave GP (or its ‘cantenna’ variants) antenna for home builders, is that it is the easiest to replicate and thus get an effective result.

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Absolutely right.

Spider and Cantenna are naturally tuned for 50 ohm / 75 ohm system, and have lot of dimensional tolerance. These two characteristics makes them ideal DIY by a novice.

This is the reason in the thread Three Easy DIY Antennas fo Beginners, I have included only Spider, Cantenna, and Quick Spider.

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Total agree the 1/4 waves can be built again and again and you will get consistent results. They are also are easy to mount and are robust.

Thanks for posting your tests. I’m curious…looking at the photos of the J-pole I see what looks like fiberglass cloth near the coax feed point. Why is that there? Tnx.

Probably just insulation or strain relief from the coax.

Doesn’t look like it has a purpose.

Good morning. tnx for reply… Yeah, I didn’t think it added to the antennas performance :slight_smile: Maybe like you say it’s for strain relief. Have a great 2019.

No i meant it is just material that emerges when you strip the coax cable. (It could have been for strain relief in the coax but not anymore :slight_smile: )

Happy New Year.

OK…I’ve never seen material like that in the coax I use, rg-8/58/174 coax…but have seen foil used along with braid. I don’t know what the other types have under the jacket…unless it’s the shield…maybe the lighting or angle of the photo makes it look like fiberglass cloth… anyway, hope his experiments continue. I enjoy seeing what others are building.

Yeah i haven’t seen it either. But it would make sense for structural stability.

Could be a coax meant for laying directly in earth?

Hello, @wiedehopf @wa4chq You are correct - the connections to the “j” are very close together and the glass fiber tape was simple insulation. (its the tape we wrap arround the conductors in super conducting magnets) Stay safe this year ATB