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We have a local radio shop that started selling us Relm P150s with a high gain 9 inch antenna, and those are ok.

He also has thrown in longer 15 to 14 inch dual band antennas saying use those in rural areas for 155 MHz.

I thought the 144/430 MHz split meant it performance best and only at those tuned splits.

I'm no expert, just a public safety user. While I can tell the repeater does catch it with this antenna, it is a backup repeater in no man's land and nobody monitors it unless they have to or know there is operations going on; as being a small entity, we only have 1 console and getting dispatch to go off from the 16 channels going elsewhere is a arm break.

It sounded clear when I keyed in with truck radio volume all the way up and I was a good 20 miles in hilltop terrain from the repeater.

So while it works, is this bad for the radio since the antenna says 144/430 to transmit on 155 MHz? If not and they work well, why do most not recommend these?

I figure ham radio operators would best answer my question, as them radio shops try to sell anything to counties with clueless commissions leaving us the users at mercy.

The thought crossed my mind they are trying to cheap fix some issues with this antenna over installing a new repeater or another.

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  • $\begingroup$ I found this website where some antennas claim to cover 136-174 MHz. Do you have more information on the antenna in question? $\endgroup$
    – Mike Waters
    Mar 7, 2020 at 18:06
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    $\begingroup$ There is a few mix and match, one a relm bk type dual band, other is a retech rha-771, other type is expert power xp-77. All appear to cover 144/430 mhz primarily. All about same length 14.5 inches or there abouts give or take. $\endgroup$
    – Dean M.
    Mar 7, 2020 at 18:25
  • $\begingroup$ Only issue is any other accessories I'd have to buy for self since they contract with them for the radios l, batteries, mica, antennas etc. $\endgroup$
    – Dean M.
    Mar 7, 2020 at 18:26
  • $\begingroup$ Looked at the bk site. The initial first few had those as throw ins. We got a guy that knows the local shop who works with us so I'm wondering if there was a mistake. $\endgroup$
    – Dean M.
    Mar 7, 2020 at 18:28
  • $\begingroup$ m is milli, M is mega, that's only 9 orders of magnitudes in error you've got there ;) I'm going ahead and will fix that :) $\endgroup$
    – Marcus Müller
    Mar 7, 2020 at 23:43

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Ask the radio shop to show you the VSWR of the antennas at the frequencies you use. Have them do it in front of you. That will likely tell you whether the antennas are suitable or not.

To ensure an accurate measurement, the antenna must be plugged directly into a VHF (not CB) SWR meter with no coaxial cable jumper between the antenna and the meter.

A perfect match would be 1:1. (That is, the forward reading should be adjusted for a full-scale meter reading and the reverse reading would read zero.) If the VSWR is less than 1.5:1, it's probably not a cause for concern*. A higher SWR than that would likely cause the power output of the radio to drop. As for damaging the radio, well, it's possible, but most radios have built-in mismatch protection circuits.

* A low SWR reading could also mean that the antenna has unacceptable losses. If that's the case, you might feel the antenna grow slightly warm on an extended key-down. However, if you don't have any problems communicating, that's probably a moot point.

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    $\begingroup$ Thanks will do. While it seemed to operate fine I just wanted clarification like you gave. I will have them do what you said and watch. I know recieving that high gains can and will sometimes rx other bands but the transmit is the key as there wouldnt be a purpose to have it if I couldn't talk out on a portable. Thank you for your expertise. $\endgroup$
    – Dean M.
    Mar 7, 2020 at 20:00
  • $\begingroup$ You may get a better answer. If this answer has solved your problem, please upvote it and click the checkmark icon on the left to mark it accepted. This helps keep track of which problems are still unsolved and gives you a little bonus. $\endgroup$
    – Mike Waters
    Mar 7, 2020 at 20:18

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