Connecting my handheld vhf to mast antenna

[TreblePlink]

Sure. Works fine. Virtually all marine radios have a standard 50 ohm output port. Please see my above explanation.

[Paul Elliott]

Originally Posted by Perna

Can you just do that? Connect a handheld to a better aerial and expect better reception etc.?

I am not an expert but I thought the device would be "pre-tuned" to its standard aerial, small as it is.

Any experts?....

Thanks.

Yes, you will get better performance with a better antenna / coax. The handheld radios are designed for a 50 Ohm load at the antenna connector.

The rubber ducky antenna that comes with the radio is designed to provide something approaching a 50 Ohm load, with your hand/arm/body providing part of that impedance. It's pretty approximate, and lossy, but it works.

There are some radios with non-removable antennas, and these may not be designed for a 50 Ohm load. But you can't plug in a different antenna anyway.

[AlanR]

I am a Radio Amateur, and very concerned with these things.

You are absolutely correct, the radio has to,be matched to the co-ax cable, and the cable matched to the antenna. However, there is a standard, and the output impedance of the transmitter (and the input of the receiver) will be 50 Ohms, as will the SMA and PL259 connectors, the co-ax, both between the SMA and PL connectors and up the mast, and the two antennas.

If they are not propely matched, power is reflected back from the mismatch to the transmitter. Not only is this power not transmitted, but in a bad case, it can destroy the output stage of the transmitter. Never try to transmit without a proper antenna connected.

A gadget called a Standing Wave Ratio (SWR) Bridge can measure the reflected power, and give you a figure of merit for the aerial system. Lots more to this story.

Did you get all that?

73s
(Amateur talk for Best regards)

[TreblePlink]

Originally Posted by AlanR

If they are not propely matched, power is reflected back from the mismatch to the transmitter. Not only is this power not transmitted, but in a bad case, it can destroy the output stage of the transmitter. Never try to transmit without a proper antenna connected.

A gadget called a Standing Wave Ratio (SWR) Bridge can measure the reflected power, and give you a figure of merit for the aerial system. Lots more to this story.

This is the primary reason "rubber duck" antennas are so inefficient.

[buzzstar]

Originally Posted by Paul Elliott

Here is a link to a pre-made adaptor: https://www.amazon.com/DHT-Electroni.../dp/B00COW5E3A

I loved the hype from ad in the link (which has noting to do with the value of the posted response itself). Where does one find "pure brass... (not alloy)?" Copper, could be; brass, not so much. Sorry for the thread drift.

[Wotname]

A cautionary note for the non RF technical folk who might be reading this thread, not all coax or coax connectors are "50" ohm. While radio systems use 50 ohm cable/connectors, video systems usually use 75 ohm cable/connectors; they look similar to the untrained eye but if interchanged, losses will be introduced.

[wannacat]

I bought a direct adapter [no cable required] at Radio Shack years ago and it works great! Don't they sell them anymore?

[Paul Elliott]

Originally Posted by wannacat

I bought a direct adapter [no cable required] at Radio Shack years ago and it works great! Don't they sell them anymore?

Sure, they still make the direct SMA/UHF adaptors. Here's one on Amazon:

https://www.amazon.com/DHT-Electroni.../dp/B00CVQOOAI

We are suggesting a jumper cable approach because with a handheld radio there's a good chance that a heavy RG8X or similar coax attached to the radio via a direct adaptor will snap off the radio's SMA jack. That direct adaptor creates a pretty good lever-arm. Handled delicately it's not a problem, but with any significant side-force there could be trouble.

[Dockhead]

Originally Posted by Perna

Can you just do that? Connect a handheld to a better aerial and expect better reception etc.?

I am not an expert but I thought the device would be "pre-tuned" to its standard aerial, small as it is.

Any experts?....

Thanks.

Yes, you can "just do that". There is no "pre-tuning" -- just a 50 ohm feedline and an antenna tuned for marine VHF frequencies -- they are interchangeable between any marine VHF radio.

The antenna is the most important part of any radio system, by far.

The OP's idea is an excellent one; I keep such an adapter on board myself. My 6 watt handheld connected to my good masthead antenna with RG-214 feedline gets out better than most fixed installed 25 watt vhf sets. The OP's handheld connected to his masthead antenna will have similar performance to his regular VHF set, if the antenna and feedline are good and well installed.

I normally use my regular vhf set on 1 watt. With a good antenna that is normally plenty of power for any communications up to 10 miles or so.

[TreblePlink]

Please don't use the one-piece adapter unless you always use a plug-in external microphone with the handheld stationary.

The SMA connectors are fine but mechanically weak, and they will not stand up to the lateral pressure imposed by supporting weight of heavy cables and connectors. They will get loose and intermittent, like laptop power jacks.

Best is to use a 6 foot cable with correct connectors on each end. This should be thin, flexible cable that will allow unencumbered movement when using it, and very little stress on the connectors.

With RF connectors, 50 ohm impedance is standard, 75 ohm is rare except for video stuff.

[waterman46]

Originally Posted by Perna

Can you just do that? Connect a handheld to a better aerial and expect better reception etc.?

I am not an expert but I thought the device would be "pre-tuned" to its standard aerial, small as it is.

Any experts?....

Thanks.

Good point, anyone know if the rubber ducky whip is 75 or 50 ohms? I think 50 ohms if it's "SMA". Havnt bought a handheld in years but both of mine use "TNC" connectors not "SMA"

[Wotname]

^^ it is 50 ohm; 75 ohm is really only used in video / TV applications