Quick antenna question

[GreggInFL]

How close to 462/467 must an antenna be to function? I have access to the antenna shown nearby. A friend ran into it and says, "Worthless label. 154/430Mhz. Made in China. About 6 feet tall. 58 cable with a BNC connector. Free to a good home."

I'd use it (if it can work with GMRS) on a 15-20' mast with a DB25-G (25W) in a flat, wooded area. I'm not talking 5 x 9 perfection, just adequate to be heard and understood over a short distance, say < three miles. I know, I know, "Try it and find out."

I hesitate to try it because 1) it might not work for GMRS and 2) as an apparent dual-band it might lure me into becoming a ham. 

What say the crowd?

[mb523]

You want your antenna to match the frequencies you're transmitting on as closely as possible. 154/430Mhz is the common VHF/UHF split for a dual band HAM antenna. It won't have good SWR on GMRS since it isn't tuned for the 462/467 range needed for GMRS. It may work, but it won't work well. 

You want to look for a GMRS specific antenna like this one:

 

 

[OffRoaderX]

43 minutes ago, GreggInFL said:

How close to 462/467 must an antenna be to function? I have access to the antenna shown nearby. A friend ran into it and says, "Worthless label. 154/430Mhz.

The only way to know for sure is to put a meter or portable antenna analyzer on it and test it.. 
But, like the @mb523 said, its not going to work very well.

[Lscott]

1 hour ago, GreggInFL said:

How close to 462/467 must an antenna be to function? I have access to the antenna shown nearby. A friend ran into it and says, "Worthless label. 154/430Mhz. Made in China. About 6 feet tall. 58 cable with a BNC connector. Free to a good home."

I'd use it (if it can work with GMRS) on a 15-20' mast with a DB25-G (25W) in a flat, wooded area. I'm not talking 5 x 9 perfection, just adequate to be heard and understood over a short distance, say < three miles. I know, I know, "Try it and find out."

I hesitate to try it because 1) it might not work for GMRS and 2) as an apparent dual-band it might lure me into becoming a ham. 

What say the crowd?

Only quick way to find out is test it with an SWR meter. Some of these multi band antennas show oscillation in the SWR across a range of frequencies. You might get lucky where the GMRS frequencies falls into one of the low SWR valley.

The link below is a test I did of a favorite wide band mobile antenna. Usable.

https://forums.mygmrs.com/gallery/image/268-ca-2x4sr/?context=new

And this link is for a test on a Ham dual band mobile antenna to see if it was usable. Doesn't look good.

https://forums.mygmrs.com/gallery/image/283-sg7500a-swr-scans-2jpg/

 

[WRTC928]

If the SWR is acceptable, it may work well enough for what you want. It won't be ideal, but hams use all kinds of weird crap for antennas and get a signal out. I saw a guy on YouTube use a bridge railing -- still on the bridge. If you put it on a 20' mast, you'd probably get 3 miles. It will never work as well as an antenna tuned for the GMRS band, but it may do what you want. "Good enough" is a valid concept.

[Bogieboy01]

2 hours ago, WRTC928 said:

If the SWR is acceptable, it may work well enough for what you want. It won't be ideal, but hams use all kinds of weird crap for antennas and get a signal out. I saw a guy on YouTube use a bridge railing -- still on the bridge. If you put it on a 20' mast, you'd probably get 3 miles. It will never work as well as an antenna tuned for the GMRS band, but it may do what you want. "Good enough" is a valid concept.

If swr is halfway decent it will work just fine... i have been operating a 25w anytone 778uv base setup(just upgraded to 50w anytone 5888uv, which seems to output about 42w on gmrs) off a "bingfu" 30" mobile dual band antenna literally electrical taped to a piece of conduit  with a radial ground plane, and can operate a repeater 22 miles away on a daily basis, on a $30 antenna showing approximately a 1.9-2.2swr on gmrs frequencies.... and i can hit the repeater better than someone right up the road from me also running 50w, thru a commercial 6' comet for gmrs, with a 1.4 swr across the repeater band.... 

 

All that said, TLDR..... get the free antenna and see what it can do.... worst that can happen is the FREE amtenna doesnt work well, and you end up padsing it along to someone else who can use it....