The 'Magic' portable antenna subject

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The 'Magic' portable antenna subject

Postby G4RMT » Sat Dec 16, 2017 11:22 am

I've been seeing an increase on many forums in the questions being asked about the superior performance antennas people seem to immediately buy for their cheap hand-held radios as soon as they buy them.

I'm marooned in Belfast until mid January, but I'm going to order a variety of these antennas and when home I'm going to do some tests of these things because the number of questions about these 'magic' antennas, in terms of gain and origin have made me think a bit.

I've never seen any proper tests - and the gain figures seem a bit suspect, so I'm thinking about how to test them to get some sensible results. I really am getting the impression that people are starting folk-lore on the subject. We have tales of poor performance being explained away because the colour of the wrapper shows it's a fake/forgery/counterfeit and that brand A is better than brand B because it costs a lot more, when the actual designs that these things are based on suggest that they will perform the same, and perhaps the difference is just in physical aspects - like size, weight, bendiness (if that's even a real word).

I'm thinking how best to compare them. What I'm thinking is that I use one of the antennas here into a decent quality receiver - I've a spare Kenwood repeater that would easily pop into a rack - and then I'd calibrate the level at which the squelch opens to set a benchmark. I designate a particular spot where the handheld under test would be placed and then with a lab type attenuator in the repeater input line, gradually adjust it to the point the squelch does not open when the radio is put into transmit, At this point I'd then have a signal of known strength - XdB at the receiver input. Replace the stock antenna with one of the after market ones and then with the attenuator, restore the receiver input level and see how many dB difference there is. This would give an indication of the real gain opposed to the claimed one, but it could also be interesting to adjust the polarisation, because my experience over the years is that ¼ wave antennas can be moved a fair way away from vertical before performance significantly drops off, while gainer type do this worse. Maybe the test could be done at vertical and then 45 degrees making a mismatch with the receive antenna?

My suspicions are that many of these after market antennas may well be not as good as their claims and hype suggest.

I'll probably do this once I'm back home and the kit all re-installed. Anyone got any suggestions on other things? There are lots of reviews that are about 'quality' of reception, but are a bit subjective - so I'm also wondering about maybe recording the audio from one of the repeaters and then using lots of different radios to access it and then comparing the recordings to see if X is different to Y. Any mileage in that kind of thing? Most reviews on youtube record the receive audio on the camera mic, so so difficult to know if you are hearing camera artefacts or real radio ones?
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Re: The 'Magic' portable antenna subject

Postby m0lsx » Sat Dec 16, 2017 4:11 pm

My personal experience is that these antennas make no difference to what you can hear, just to how well you can hear what is there.
I have been using the longer whips for years & have never yet heard something on a longer antenna that I could not hear on a reasonable standard duck. However I do find that what they do well at, is, that they pull weaker stations up & out of the noise so you can hear them a little better.
Years ago, when I bothered with 2 meters FM. I was on top of Cromer Church Tower working into NB using my £200+ Yaesu VX-7R plus a £30+ Diamond antenna. Someone said they could hear me on the input at North Walsham 9 miles away & past a high inland ridge. So as a experiment I swapped to my under £30 Puxing using the standard antenna.
The difference? No CTCSS could be heard on the Puxing. Everything else was the same.
Personal & non scientific experimentation has led me to use resonant tails & a speaker mike so I have a good counterpoise & an extra foot or two in height when wanting to work handheld. They are for me what makes the difference.
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