SWR meter for PMR 446?

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.
Post Reply
Powermax
Regular
Regular
Posts: 64
Joined: 14 May 2012, 08:58

SWR meter for PMR 446?

Post by Powermax »

I want to check the SWR of my antennas and was wondering if there is a cheap way of doing this?

Is there such a meter on the market?

Also does an SWR of 1:1 mean that the antenna is resonant at 446MHz?


Thanks!
User avatar
ch25
Top Poster
Top Poster
Posts: 1180
Joined: 03 Dec 2016, 11:07
Call Sign: Lemmy
Location: Poland

Re: SWR meter for PMR 446?

Post by ch25 »

Cheapest, best way is NanoVNA
WE ARE MOTÖRHEAD, AND WE PLAY ROCK N' ROLL
You can't have too many antennas...
User avatar
Mikel
Radio Addict
Radio Addict
Posts: 676
Joined: 18 May 2009, 08:40
Location: South East Wales IO81jo

Re: SWR meter for PMR 446?

Post by Mikel »

Powermax wrote: 30 May 2021, 15:11 I want to check the SWR of my antennas and was wondering if there is a cheap way of doing this?

Is there such a meter on the market?

Also does an SWR of 1:1 mean that the antenna is resonant at 446MHz?


Thanks!
There are plenty of SWR meters that will work fine on 446Mhz most of the 70cm meters sold for the amateur market will work fine, 446Mhz is part of the amateur band in the US.

An SWR of 1:1 will usually be good sign of resonance, but SWR is only a starting point and one of many factors that should be taken into account when installing, building and considering antennas for any band.

Just remember a 50 ohm dummy load will show an SWR of 1:1 but you will not transmit very far with it.

As ch25 has suggested an antenna analyser will be a good investment if you are experimenting with antennas on regular basis and will allow you to take many factors into consideration.
................................................................................................2W0NBF.........................................................
Powermax
Regular
Regular
Posts: 64
Joined: 14 May 2012, 08:58

Re: SWR meter for PMR 446?

Post by Powermax »

Thanks for your replies both.

I would like to just start off with an SWR meter I think as an antenna analyser would be overkill for what I need. I was hoping to pick one up for £20-30?

I'm not intending to build my own antennas, merely to just see how bad my current ones are. They being a TTI-1446 stock spring antenna, Nagoya 701 and 771.
wa10
Top Poster
Top Poster
Posts: 1343
Joined: 19 Feb 2008, 00:37

Re: SWR meter for PMR 446?

Post by wa10 »

You can't check them mounted on a handheld, adding any kind of meter between handie & rubber duck like you see some folk do changes the whole system making the test flawed,
If you are using them on a magmount or fixed mount you can test them.
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
User avatar
ch25
Top Poster
Top Poster
Posts: 1180
Joined: 03 Dec 2016, 11:07
Call Sign: Lemmy
Location: Poland

Re: SWR meter for PMR 446?

Post by ch25 »

Powermax wrote: 30 May 2021, 19:46I would like to just start off with an SWR meter I think as an antenna analyser would be overkill for what I need. I was hoping to pick one up for £20-30?
You can't get trustworthy SWR meter for 70cm in that price range.
That's why I suggested NanoVNA. It's cheap and accurate.
WE ARE MOTÖRHEAD, AND WE PLAY ROCK N' ROLL
You can't have too many antennas...
paulears
Radio Addict
Radio Addict
Posts: 862
Joined: 10 Jun 2007, 22:41
Call Sign: G4RMT
Location: North East Suffolk
Contact:

Re: SWR meter for PMR 446?

Post by paulears »

Watch the video and see how awful some of these antennas are.
https://youtu.be/LVzlFTIMV5A
The other issue with portable antennas is what exactly are you testing? If you add a meter between radio and antenna, any reading will not be accurate. Portable antennas never get 1:1 because the ground plane is rubbish and the antennas are resonant in strange places. An antenna can be resonant in multiple places but have acceptable VSWR in others. Handheld radios transmit into terrible loads as normal!
Powermax
Regular
Regular
Posts: 64
Joined: 14 May 2012, 08:58

Re: SWR meter for PMR 446?

Post by Powermax »

Thanks, that's really helpful. I've already seen a video with someone testing a handheld antenna with no groundplane!

It's a pity that nobody seems to manufacture a 'proper' 446 handheld antenna. I don't see the point in making a set that kicks out x milliwatts only to put a trashy spring coil antenna which degrades the performance.

I know PMR isn't meant for distance but surely it's cheaper/easier to manufacture a proper antenna with a lower powered transmitter (to conform with ERP 500mW)?
paulears
Radio Addict
Radio Addict
Posts: 862
Joined: 10 Jun 2007, 22:41
Call Sign: G4RMT
Location: North East Suffolk
Contact:

Re: SWR meter for PMR 446?

Post by paulears »

tried putting a decent antenna in your pocket? The difference between a simple quarter wave for 446 - which isn't huge and a longer one with magical claimed properties is usually totally pointless. Sure - if you do the tests like I did, you can detect small differences, but keep in mind that a test with the antenna vertical might be totally pointless if you have to tilt the radio to speak into it. 1.4 waves can be moved quite a few degrees away from vertical with little detectable signal drop, but the base loaded ones get their gain by narrowing the vertical beam width, concentrating it, but this means just a few degrees off vertical and the signal just vanishes at the far end.

For years, before we went to clever radios, the police used UHF transmitting on their portable radios on 466MHz - using less than a Watt on a helical quarter wave - about an inch long. The antenna the other end was up in the air, and the handhelds could get the signal out in virtually any orientation in pocket, upside down, on their side. If there had been better antennas available, they'd have used them - the quite inefficient ¼ waves were deemed the best all round antennas - even though by ham/enthusiast standards, they were pretty poor. Marine band does the same thing. 1 helical ¼ wave or a ¼ wave over a foot long? We're talking safety radios - life saving devices. Nobody puts long antennas on them.

I firmly believe all these longer antennas are really pointless things that need the user to hold them high and straight. The you throw them on the car seat and never receive a call.
User avatar
Werthers
Radio Addict
Radio Addict
Posts: 650
Joined: 01 Sep 2019, 20:19
Location: Essex

Re: SWR meter for PMR 446?

Post by Werthers »

The best cheap SWR meter in my opinion is one of these which covers VHF and UHF. I paid about 35 pounds for mine years ago but it looks like they have gone up in price since.

You only have to buy it once. Its worth it.

For your antenna system a simple half wave dipole will be good for PMR446 you can build one easily from a bit of old copper pipe or a bit of aluminum rod or something. Just have a look in your local hardware store and make the center from a 3 way PVC pipe connector.

For cheap coax use RG58 but keep the coax length short if you can.

If you don't want to build an antenna then ebay sellers often have PMR446 dipole antennas or other 446 antennas for sale.

You don't want to much gain on your 446 station and keep your power at a sensible level to avoid any knocks on the door from Ofcom.

Your not suppose to be using external antennas on PMR446 or running high powered radios on PMR446. The legal limit is a fixed antenna and 500mW.

Having a simple half wave dipole and 5 watts of power is normally the sensible limit.
You do not have the required permissions to view the files attached to this post.
Powermax
Regular
Regular
Posts: 64
Joined: 14 May 2012, 08:58

Re: SWR meter for PMR 446?

Post by Powermax »

Thanks, I can probably stretch to £50. I used to be a CB'er back in the 1980s and did make my own 1/4 wave ground plane antenna (which outperformed a shop-bought one). It SWR'd better as well.

I have never tried to tune a handheld antenna though. My current radios are TTI-1446 (if you know them). They are supposed to have fixed antennas but someone must have forgotten about that because there is a tiny screw which allows you to remove them. So I bought a 701 and 771 which both give a noticeably better signal at about 1 mile distance, to my handheld scanner. I don't understand the slight deafness on Rx though.

The stock antenna is a crappy coil, (which I understand from my CB days) is a good recipe for poor performance and difficult SWR.

I don't want an external ground plane antenna, I just want a handheld that outperforms the stock antenna AND isn't running a crazy SWR that will damage the set.
Post Reply