Longer VHF Antenna

[Mark-1]

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]

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.

 

[Chiara’s slave]

Before taking any notice of Chat GPT, say it to yourself in French.

 

[Mark-1]

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]

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]

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]

The M21 is another last century product which was available with a proper coax socket output.

 

[Dellquay13]

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.