DIPOLE FOR PMR446 HELP NEDED

Licence free two-way radio services that now includes both FM and digital channels. Discuss models, modifications and other similar worldwide standards such as FRS and GMRS.
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WARLOCK
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DIPOLE FOR PMR446 HELP NEDED

Post by WARLOCK »

I Would like to use a antenna for pmr446 on my car on a magmount , If i was to buy a antenna used by taxis what length would i need to cut it for pmr446 or is there a better antenna i could use any thoughts please
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by ch25 »

160mm
You are not allowed to use external antenna with PMR.
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by 26mb04 »

The Midland GB-1 has an external antenna and is (apparently) type-approved.
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by ch25 »

Yes, but antenna is integrated. That's why it's approved.
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by WARLOCK »

HI CHRIS The radio i have is a crt spirit its a mobile for the car not a handheld so it is possable to fit any antenna you want to ???
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by ch25 »

No, because PMR regulation described precisely what you can and what you can't do. Have you ever read that?
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by Mudslinger »

Most antennas for the 70cm band will work ok. If you get one with a PL base use a PL magmount, the CB ones are fine if you use an adaptor at the radio end if needed.

There is a PMR dx group on facebook. They are very active.

https://www.facebook.com/groups/1627623600814724/
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by paulears »

As far as I know, that is NOT a PMR446 radio, but could be a commercial set programmed to PMR channels. It will almost certainly be too high powered, and the external antenna makes it illegal in Europe/UK. However, it will be perfectly fine in operation. A quarter wave is best for a vehicle - being a good compromise of length and performance, BUT remember these are NOT dipoles in any shape or form, they're just a quarter wavelength vertical ground plane.

There's legal and illegal operation, and it's a moral/ethical choice, not a technical one. I suppose it depends most on who you wish to talk to?

16cm or 17cm if you want the ham band nearby will work fine.
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by Mudslinger »

I find it funny when people on here say that running a Baofeng or other PMR antenna on PMR is illegal, yet many of those people probably run many times the legal limit on CB, as well as using illegal frequencies such as 27.555
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by paulears »

As I said, doing illegal things runs from things that might be viewed as trivial and pointless through to activity so serious you go away for a very long time, or forever. Most people decide where on that spectrum they sit - often because of their upbringing, or religious or ethical reasons. The facts are very simple - if in your jurisdiction something trivial is illegal - then doing it is wrong. Does it matter if you use too much power? Probably not - but that doesn't make it right. Does connecting to an external antenna really increase the chances of you going to prison? Of course not - so it's down to your own morals and beliefs. This does not mean that we should promote illegal activity. Clearly it goes on, but should not be promoted. That's it.
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by MrWeetabix »

If you want to build your own, there is a guy selling kits on eBay....

https://www.ebay.co.uk/itm/Make-your-ow ... SwZGNeLEvG

There is also a thread right here on the forum you may find useful. I think it states that whip should be 16cm (ish)

viewtopic.php?t=36785

Good luck :thumbup:

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Re: DIPOLE FOR PMR446 HELP NEDED

Post by MrWeetabix »

Also found these, which could be useful....
446_Dipole1.jpg
Ant001.jpg
Ant002.jpg
gp.jpg
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by Chris_M1BIK »

On paper, you only need the widely known formula, using centre of the 446 frequencies range to calculate the nominal electrical length, then modify against the velocity factor of the material used.

However, it's irreverent as you're already operating at the legally mandated max ERP for license free operation if using a legit certified Tier 1 radio with it's restricted antenna.

So going from a restricted probably negative gain vertical to a dipole will create a technical improvement, even if it's at the cost of a license breach, but the actual improvement isn't worth the grief is you become under the microscope.

Let's face it, if you get fined, it'll cost more than the equipment and if they really throw the book at you to make an example, you can find any TX license applications in future become a lot more scrutinised instead of routine and can be rejected on discretionary grounds rather than by failing to meet valid licensee requirements.

In the Ham world, there's a well worn belief you never want anything recorded against you that's more than a sign-off verifying your station management is in order on the outside chance your setup is examined formally, and even before I got my Ham license, I kept my CB and early license exempt 49mhz stuff 'by the book' bar necessary filter mods (to clean up both directions, internal xtal filter and a high grade LPF in the antenna feeder chain) as part of ensuring I followed the Ham wisdom, because it made a lot of sense. After all, getting disbarred or a prohibition to operate is a huge loss to them and a very high price to pay for stretching the licensed use interpretation to beyond the max.

If it matters to improve things, go properly legit for extended 446 operation as befitting commercial use and get Tier 2 licensed if your using it in a cab or a commercial vehicle - then you can benefit from the difference what isn't a kiddie grade UHF license.

Sure I used 446 on an LF/LE status, and whilst useful, a £50 pair of PF1 sized 49Hz synthesized handhelds I got (when £50 was a lot of money) where you programmed which n numbers of frequencies were setup by a jumpered matrix in the early 80s still leaves 446 Tier 1 equipment for dead today even. If I had the choice, 49mhz digital voice license exempt for VHF (where it was available) or Tier 2 DPMR/DMR would be where I'd go for UHF as it leaves a lot of room for extended future use vs the garden wall of license-exempt DV and analogue 446 use. And from experience, I'd probably ditch dPMR as an option, as it's disproportionately costly for not much more than basic functionality on simplex use.

Tier 2 DMR starts to make a lot more 446 sense when you look at the scope that relatively cheap TA certified equipment offers and how the added Tier of formal licensed use can give you room to move towards optimised operation.

But none of that will matter or mean much if you see your 446 equipment as UHF CB equivalence.
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by Mikel »

MrWeetabix wrote: 05 Jul 2020, 12:32 Also found these, which could be useful....

446_Dipole1.jpg

Ant001.jpg

Ant002.jpg

gp.jpg
Some good ideas there!

I made the top dipole out of some spare bicycle spokes and a Chocolate Block Connector, works remarkable well for a simple antenna. Just make sure to use the best coax you can afford, best not to use RG58 unless it's a very short run as the attenuation will be high.

You don't need to spend a fortune to get a good signal going :)
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Re: DIPOLE FOR PMR446 HELP NEDED

Post by Chris_M1BIK »

Good optimised choice of antenna siting, and respecting that you can't bypass physics costs nil. But if you can't manage those with restricted setup, you'll never really appreciate or see the full benefits of well constructed paasive unity or positive gain antenna well constructed and setup.

As paulears notes, just because we can do doesn't necessarily make it a good idea in practice and it would be pretty irresponsible to actively encourage unlicensed operation of radio systems - and the moment you stray from compliance with your license terms and restrictions you are effectively unlicensed until you revert things back to full compliance.

The only acceptable time you should consider extending past your license limitations ‘garden wall‘ is under notified agreed exception you apply for, or as we know it in the UK NOV (Notice Of Variation). But given NOV’s (translate accordingly) are few if any on license-free or license exempt LMR services and where they exist are incredibly limited and very much a subject of absolute need being justified on formally licensed LMR use, I wouldn't hold much hope on a NOV being granted on a Tier 1 PMR446 operation, in fact if I was depending on getting it to be in the clear and easy to get your need to be accepted, you've probably got better odds on getting 6 exact numbers on a state/national lottery.

I mean, in the ham world, the authorities in question generally grants NOV applications to full license holders in most cases - but that's mostly because we have a totally different grade of license and are treated as technical grade operators with technician/engineer rights/provision to bypass TA limits provided we operate within the limits of license schedule and don't interfere with other users with the scope of NOV and standard permitted non-NOV limited use of normally NOV requirement extended use.

Totally alien worlds, you could say, where coexistence goes (which we do as radio users like ever other radio user) or parallel dimensions of existence would be another valid type of analogy.
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