CB antenna/ PMR antenna compatibility question.

I have purchased a large magmount with my Sirio 4000 antenna which I hope to set up soon with a CRT SS 9900.

I also have a small PMR magmount antenna fitted to the roof of my car that is probably useless.
I'm wondering if the Sirio would work on PMR ?
If not, is there an aerial I could buy to screw onto the magmount ?
I'm thinking of getting a CRT space U so it would be handy to use the existing twig or if not just swop over on the same mount.

Hello, no unfortunately you need the right antenna for the frequency in use. C.B is a HF frequency 27Mhz and PMR is UHF 446MHZ you need another antenna for PMR there's loads out there on the market.

73's Gary.

Thanks Gary, I thought so unfortunately.
Is there an antenna I could buy to fit the magmount ?

Hi Sharpshooter

What mag mount have you got?
Is it a SO239 or a 3/8 tread connection?

Will you be using it while driving or parked up?

Because I can't see a problem with buying an adaptor so you could swap antenna's over but use the same mag mount.

73
Ray

Hi Ray, I've got the Sirio Mag 145 PL.
RG58 coax and PL 259 plug to SO239 .

It's the connection for the antenna to the magmount I'm wondering about . (Or is that the same? )
So I could change from the Sirio 4000 whip to a PMR one on the same magmount.
Cheers.

Sirio do an adapter for the mag mount as Ray pointed out.

Search Google for "Sirio PL Mag to 3/8" and you'll get a ton of hits.

Then you can unplug the Sirio antenna from the mag mount base and screw in a 3/8ths PMR antenna via the adapter. antenna - CB antenna/ PMR antenna compatibility question. 1f44d

antenna - CB antenna/ PMR antenna compatibility question. 1f44d

73
Victor

.
I've been beaten by Victor

I was going to offer this up

Up until I got my £1 mag mount from a radio rally, I was going to get a Sirio SO239 to 3/8" adaptor and then fit a 3/8" whip adaptor with bike wheel spoke cut to about 17cm.
I can then use my Sirio mag mount for both CB & PMR.

Yes there will be some coaxial loss but you will see an improvement on TX & RX, on a UV5R (or any hand held) over a rubber duck antenna.

Ray

Ok thanks all.
Sorry, it's not really for the UV5R.
I'm thinking of buying a CTR space U from Knights.
They do a Sirio PMR antenna for £14 and a Nagoya for £18 with magmount.
Also the Nagoya is £15 if bought with the radio.

https://www.kcb.co.uk/contents/en-uk/p2037_Sirio_SU_375-480PL__(375-480mHz).html

https://www.kcb.co.uk/contents/en-uk/p2038_Nagoya_UT-72_U_V_Mag_Mount__(2m_70cm).html

make your self a pmr antenna there not hard to make you need a 3/8 mag and a 3/8 fitting and a steel whip and cut it and measure from the base of 3/8 whip holder 16cm and thats if the whip is to thick drill out the whip holder,and fit it to the 3/8 mag mount check the transmission one they have whip lenths and i got a crt space and it works great 20 miles from my bro he was shouting for me, i was mobile and i heard him so stopped at a little car park at 900 ft asl. and had a great contact such a small antenna, and it works this is what we used to do years ago with the cb, and now we are using pmr, and lots of time we can not hear the cb, but hear the pmr i like my cb but i love the pmr harder contact but a satisfaction with the pmr, am i mad no not never but just feel great getting the great pmr contacts,.

Thanks very much for all the replies.
I see knights do the adaptor for £8.45.

So are most CB antenna connections SO239 and PMR 3/8" ?

Razz229 wrote:: .
I've been beaten by Victor

I was going to offer this up

Up until I got my £1 mag mount from a radio rally, I was going to get a Sirio SO239 to 3/8" adaptor and then fit a 3/8" whip adaptor with bike wheel spoke cut to about 17cm.
I can then use my Sirio mag mount for both CB & PMR.

Yes there will be some coaxial loss but you will see an improvement on TX & RX, on a UV5R (or any hand held) over a rubber duck antenna.

Ray

Why 17cm Ray ?
Is that for swr ?
I take it CB swr meters don't work on the PMR frequency ?

Sharpshooter wrote:

Razz229 wrote:: .
I've been beaten by Victor

I was going to offer this up

Up until I got my £1 mag mount from a radio rally, I was going to get a Sirio SO239 to 3/8" adaptor and then fit a 3/8" whip adaptor with bike wheel spoke cut to about 17cm.
I can then use my Sirio mag mount for both CB & PMR.

Yes there will be some coaxial loss but you will see an improvement on TX & RX, on a UV5R (or any hand held) over a rubber duck antenna.

Ray

Why 17cm Ray ?
Is that for swr ?
I take it CB swr meters don't work on the PMR frequency ?

I use a home made antenna for most of my PMR contacts and the whip is cut to about 16.7cm. This is about the length for a 1/4 wave antenna tuned to channel 8 PMR, which gives me a SWR of 1:1 & a reading of 52 ohms on a Nano VNA Analyzer
Yes you would need a UHF/VHF SWR meter.

73
Ray

Hi all

So putting money were my mouth is.

I thought I would make a PMR antenna that would work on a CB mag mount.

This is more a proof of concept and before anybody points it out, yes I know the coax is not ideal.

The 1st picture shows what I'm going to be working with.
A metal coat hanger, a 3/8" whip adaptor, and a 7" mag mount of dubious quality.

antenna - CB antenna/ PMR antenna compatibility question. 20220610

The 2nd picture shows the approximate length of the whip once cut down.

antenna - CB antenna/ PMR antenna compatibility question. 20220611

3rd picture shows the mount assembled and on an old biscuit tin

antenna - CB antenna/ PMR antenna compatibility question. 20220612

4th picture show the sacrificial radio if it all goes wrong.

antenna - CB antenna/ PMR antenna compatibility question. 20220617

And the last picture shows the SWR reading while transmitting

antenna - CB antenna/ PMR antenna compatibility question. 20220618

So it seems to work as it's showing no reflective power.

Now I invite those with more knowledge to improve, my proof of concept

Cheers for reading

Ray

Last edited by Wireless on Sat Jun 11, 2022 1:59 pm; edited 1 time in total

I did similar with wire, and also cut a mobile whip for 4m for use with an Ascom SE550, but I did invest in an Antenna Analyser to check the SWR before connecting up a transceiver, good idea, not sure it meets type approval for PMR446, but whose to know? Next would be a 70cms Linear Amplifier...

Update: The 25 Watt Icom IC-F210 here is programmed with 16x PMR446 Channels, obviously TX is inhibited for those worried about type approval...

Great stuff there Ray and a really good 'show and tell' mate. antenna - CB antenna/ PMR antenna compatibility question. 1f44d

Good little 1/4 wave that does the job and often better than the standard 'rubber duck' as well as some dubious Chinese teeny mag mount affairs.

As metal wire type coat hangers are thin on the ground nowadays I suggest everyone looks out for a missing wheel spoke the next time they are out on their bicycle - some PMR nut may have nicked it!! Very Happy

Worthy of a 'Thanks'. Wink

Razz229 wrote:: Hi all

So putting money were my mouth is.

I thought I would make a PMR antenna that would work on a CB mag mount.

This is more a proof of concept and before anybody points it out, yes I know the coax is not ideal.

The 1st picture shows what I'm going to be working with.
A metal coat hanger, a 3/8" whip adaptor, and a 7" mag mount of dubious quality.

The 2nd picture shows the approximate length of the whip once cut down.

3rd picture shows the mount assembled and on an old biscuit tin

4th picture show the sacrificial radio if it all goes wrong.

And the last picture shows the SWR reading while transmitting

So it seems to work as it's showing no reflective power.

Now I invite those with more knowledge to improve, my proof of concept

Cheers for reading

Ray

Interesting Ray as I was considering this old antenna I have.

A cheaper option but then I don't want two magmounts on the roof.
(I see yours has seen better days, do you live by the sea ? Very Happy

)

Question, does the PMR not need a base loading coil like a CB ?

Cheers Nige.

antenna - CB antenna/ PMR antenna compatibility question. Img_2021

Victor wrote:: Great stuff there Ray and a really good 'show and tell' mate.

Good little 1/4 wave that does the job and often better than the standard 'rubber duck' as well as some dubious Chinese teeny mag mount affairs.

As metal wire type coat hangers are thin on the ground nowadays I suggest everyone looks out for a missing wheel spoke the next time they are out on their bicycle - some PMR nut may have nicked it!!

Worthy of a 'Thanks'.

I'll just nip to the local bike shop. I'm sure he'll give me an old spoke

Or I could just cut down the existing twig as it seems short anyway

Victor wrote:: Great stuff there Ray and a really good 'show and tell' mate.

Good little 1/4 wave that does the job and often better than the standard 'rubber duck' as well as some dubious Chinese teeny mag mount affairs.

As metal wire type coat hangers are thin on the ground nowadays I suggest everyone looks out for a missing wheel spoke the next time they are out on their bicycle - some PMR nut may have nicked it!!

Worthy of a 'Thanks'.

Cheers Victor

The next step I guess, is to 'prove' if there is any improvement in the real world, over the whip antenna on my UV5R. So watch this space for a comparison video.

You can't go wrong with a meatal coat hanger. They have, over the years, proven to be a great receive antenna when bent into a diamond

and used to replace a broken car aerial

When you look around, there must be that old rusty bike

sitting in the front/back garden of the family where the children have out grown it.
Now look at the spokes and think elements for a PMR beam (but that is for another time)

73

Linda got me wire coat hangers from B&M I think it was 5 for £1 and not long ago.

Sharpshooter wrote:

Razz229 wrote:: Hi all

So putting money were my mouth is.

I thought I would make a PMR antenna that would work on a CB mag mount.

This is more a proof of concept and before anybody points it out, yes I know the coax is not ideal.

The 1st picture shows what I'm going to be working with.
A metal coat hanger, a 3/8" whip adaptor, and a 7" mag mount of dubious quality.

The 2nd picture shows the approximate length of the whip once cut down.

3rd picture shows the mount assembled and on an old biscuit tin

4th picture show the sacrificial radio if it all goes wrong.

And the last picture shows the SWR reading while transmitting

So it seems to work as it's showing no reflective power.

Now I invite those with more knowledge to improve, my proof of concept

Cheers for reading

Ray

Interesting Ray as I was considering this old antenna I have.

A cheaper option but then I don't want two magmounts on the roof.
(I see yours has seen better days, do you live by the sea ? Very Happy

)

Question, does the PMR not need a base loading coil like a CB ?

Cheers Nige.

Hi Nige

Glad you liked the "show & tell" and found it interesting.

Does your Sirio mag mount have this style of connection?

antenna - CB antenna/ PMR antenna compatibility question. 20220619

Then I would go with the earlier suggestion of a SO259 to a 3/8" adaptor and 3/8" to whip adaptor with the cut down coat hanger, bike spoke, metal rod.

2 antennas and 1 mount

The mag mount I show is over 10 years old and I have had to re-solder the coax to the mount due to corrosion

Short answer, no the antenna I show is a 1/4 wave and doesn't need any loading coil, which keeps it simple and cheap to make.

Cheers

Ray

Hi Ray.
Yes the Sirio Magmount is the SO259 .

I'll get a Sirio SO259 to 3/8th, and a 3/8th to 2.5mm whip, and also the PL259 to SMA female for into a Baofeng

I can test the waters on PMR with the UV5R then first before buying a CRT space U,

Simple and cheap to make ? It'll work out more expensive than buying a PMR antenna with magmount

Thanks for all the advice etc all. Much appreciated.

Get a Sirio SU375-480 PL antenna.

Cut it down for PMR, Sirio supply the instructions, then you can use the same mount.

I think this fulfils all of your requirements.

Razz229 wrote:: Get a Sirio SU375-480 PL antenna.

Cut it down for PMR, Sirio supply the instructions, then you can use the same mount.

I think this fulfils all of your requirements.

Thanks Razz.
I was just trying to order this from Knights along with a PL to SMA adaptor .
But I can't work out how to add a second hand swr/pwr meter so I'm going to ring them Monday to order everything.
Cheers

For PMR the magmount will be perfect.
You could use a 2m/70cms amateur radio aerial.
Or roll your own. A PL259 and a a length of brazing rod.
Solder the rod to the centre of the PL259, pack the gap between the rod and the body of the PL259 with epoxy.
Trim the rod to best swr (about 6")

Sharpshooter wrote:

Razz229 wrote:: Get a Sirio SU375-480 PL antenna.

Cut it down for PMR, Sirio supply the instructions, then you can use the same mount.

I think this fulfils all of your requirements.

Thanks Razz.
I was just trying to order this from Knights along with a PL to SMA adaptor .
But I can't work out how to add a second hand swr/pwr meter so I'm going to ring them Monday to order everything.
Cheers

Just Get a Diamond MC-200 or MC-201 Kit, both come complete with a Cutting Chart that cover PMR446.

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