Longer VHF Antenna

Mark-1

Well-known member
Joined
22 Sep 2008
Messages
4,362
Visit site
I've pondered getting a longer antenna for my handheld VHFs for years, for occasions when I don't need the shorter Antenna for portability.

I know nothing about RF engineering.

Chat GPT tells me 50cm is a good length because it's 1/4 wavelength. Correct?

I've measured the thread diameter on 2 of my radios as 5.9mm. The antennas seem interchangeable. I'd guess that's 6mm? Does that sound plausible? Is that a typical HH VHF thread?

My third radio is an Icom IC-M21, thst has a larger thread which I can't measure. (Radio on boat.) It's this one:
IC-M21 : Handheld VHF Marine Radio - Icom UK

Can some expert radio ham:

- Comfirm a longer Antenna is worthwhile for both Rx and Tx?

- Spoon feed me the Antenna I need to buy for either/any of my Radios.
 

B27

Well-known member
Joined
26 Jul 2023
Messages
2,068
Visit site
The handset is probably tuned for the aerial it's sold with.
With a short stubby antenna, I'd expect either a coil in the bottom of the screw-on aerial, or a coil inside the handset, and possibly other components to 'match' the aerial to the radio.


A handheld does not have a proper ground connection, most of them have a single stud aerial connection not a 50 ohm coax output.
Back last century, I had a Switchtech handheld which had a BNC connector, that worked well connected to a masthead aerial.

Bigger aerials with gain tend to be less omnidirectional.

What works for transmit is also the same for receive, 'passive' RF stuff is generally reversible if there's no 'magnetiics' involved.

If you need better range, then a fixed set with the antenna on a pole is good.
 

Mark-1

Well-known member
Joined
22 Sep 2008
Messages
4,362
Visit site
The handset is probably tuned for the aerial it's sold with.
With a short stubby antenna, I'd expect either a coil in the bottom of the screw-on aerial, or a coil inside the handset, and possibly other components to 'match' the aerial to the radio.

Bigger aerials with gain tend to be less omnidirectional.

What works for transmit is also the same for receive, 'passive' RF stuff is generally reversible if there's no 'magnetiics' involved.

Thanks.

That's pretty convicing, I won't bother.
 

Bilgediver

Well-known member
Joined
6 Jun 2001
Messages
8,183
Location
Scotland
Visit site
I've pondered getting a longer antenna for my handheld VHFs for years, for occasions when I don't need

- Comfirm a longer Antenna is worthwhile for both Rx and Tx?

- Spoon feed me the Antenna I need to buy for either/any of my Radios.
You are not clear about exactly what you need. Walking around with a 2meter whip Antenna might be effective but a problem for everyone else.

If for use on your boat then you can get an adaptor that screws onto the radio and this can then be connected to a fixed antenna on the boat using coax. This can work surprisingly well.
 

st599

Well-known member
Joined
9 Jan 2006
Messages
7,530
Visit site
None of the handhelds I've had over the years have had a matching unit or matching circuit built in, they've always expected that to be integral to the antenna.

You could certainly try adding a 1/4wave whip, or hoisting a slim jim antenna. However, if you have over 3dBi you'll be in to the range that requires a risk assessment by Ofcom as part of the licence conditions (depending on duty cycle).

The IC-M21 seems to have a male SMA connector
 

B27

Well-known member
Joined
26 Jul 2023
Messages
2,068
Visit site
The M21 is another last century product which was available with a proper coax socket output.
 

Dellquay13

Well-known member
Joined
19 Feb 2021
Messages
972
Location
Boat at Milford Haven, Home in Chesterfield
Visit site
You are not clear about exactly what you need. Walking around with a 2meter whip Antenna might be effective but a problem for everyone else.

If for use on your boat then you can get an adaptor that screws onto the radio and this can then be connected to a fixed antenna on the boat using coax. This can work surprisingly well.
I did this for a few years with a fibreglass high gain antenna on a small mobo and a XM2000 handheld. The HH had a TNC thread fitting, I used an adapter to connect to the pl259 plug on the antenna. Obviously I wasn’t walking around with it all.
 
Top