Gain vs takeoff angle.

I have made over 2000 contacts with it and brought it to Spain for park activations

John ve3ips

Yes heavy due to the base and spike

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Hi Tobais,
How about this solution, which I am working on:

Using:

  1. €17, 5.6m high telescopic whip from Aliexpress.
    16.26€ |Kurzwelligen Radio Positive V GP Yagi Diy Oszillator 5,6 Meter 14 Abschnitte 201 Verstärkt Edelstahl Stange Antenne|Ersatzteile & Zubehör| - AliExpress

  2. 6 x 3m radial wires made out of a PS2 mouse connection extension cable,

  3. A Hama “Mini-tripod” modified with a mag mount SO239 socket

  4. adapter to go from PL259 to 3/8-24 thread.

I could have mounted the 3/8-24 socket straight to the tripod but as I use it with other PL259-based antennas I went the adapter route.

By the way, I also had to rethread the M10 bolt on the bottom of the “Monster Whip” (as I call it) to fit the SO239 - 3/8"-24 CB antenna mount adapter. Why do they use a non-standard M10 bolt rather than the 3/8-24 bolt, don’t ask me, but they do state it correctly in their advert.

With 1.5 sections pushed in this is a 20m ground plane with no loading coils, UNUN, BALUN or ATU in sight and the SWR across the whole of 20m is less than 2:1 (1.26:1 at best).
image

I am still working on a lightweight set of non-conductive guy cords as this antenna needs them because of the stupidly small tripod at the base that I am using - a plastic or aluminium stake may be a better idea.

I have yet to try this from a summit, only on the analyser but for a “true” 1/4 ground-plane solution for 20m-6m, this is certainly a cheap small (when packed) lightweight, solution.

73 Ed DD5LP.

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This is similar to the approach I am taking.

The battle of the 3/8" 24TPI vs M10… I think part of it is the fact that the American thread can’t be measured nor understood by anyone outside the USA. I have M10 taps and dies.

One thing I am curious about is the impedance reading. I don’t have an analyser that gives me the components of the analysis (or I don’t know how to read them on my NanoVNA). I was under the impression from calculators and charts that I would be expecting an impedance of 32 ohm with my radials laying on the ground. Seeing your results I really should make the base for the antenna before I start winding transformers.

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You are probably correct with the M10 vs 3/8-24 in my case I re-threaded the M10 bolt to 3/8-24.
As you can see the impedance for this quarter-wave ground plane is 62 Ohms “close enough” to 50 Ohms not to need any impedance transformation. A 1:1 Choke balun will stop common mode currents on the cable but at low power (e.g. under 30w) this is (in my experience) not usually a big problem.

In this case, I used a super-light cable that was originally 6-core and hence the 6 radial wires. My default (laid on the ground, not raised) radial configuration is 8 runs of about 3 metres long hook-up wire.

Keep it simple, keep it light and that, as you said, will maximise the efficiency of the portable station.

73 Ed.

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A Moxon is a wonderful antenna, but… if conditions support prop to AZ, a simple end-fed inverted-L will do fine. If you want to bias it, deploy it part way down a steep slope that is in the direction you want to go. What might have been straight up, is now straight out! Be sure to check a great circle map centered on where you will be so you know what direction is AZ from there!

Note that I work EA from New Mexico, while running just five watts, nearly every time out.

GL, 73 fred kt5x / ws0ta

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Hi Tobias,

Height is always the main factor in reducing the take off angle. Being on a sharp ridge is also an excellent way to reduce takeoff angle.

I would not worry about gain for portable use. Getting the antenna higher and a low takeoff angle is the main goal. Halving the take off angle for 0 dB gain is worth more than heaps of dB of gain at a higher angle.

The band will open earlier and close later if you have a lower take off angle

I’m currently using a flowerpot half wave vertical on 10 m. The design is copied from one published by Andrew VK1AD.

It’s very easy to deploy and no radials to worry about. SWR could hardly be better. I’ve been working 8,000 - 16,000 km on SSB and ditto on CW so it’s going OK. It’s hung from a 7 m fibreglass (not carbon fibre) telescoping pole.

73
Ron
VK3AFW

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