Antenna on a Fiberglass Airboat - Grounding Question

[firefighter331]

Even with no coax attached to the radio it should pick up a handheld easily.

So I brought a dual band HAM antenna that I happened to have laying around. I know that works. I connected it to the radio and got the same results as with the Motorola antenna that I thought was the issue. My handheld picks up our repeater clearly with no antenna at all. This APX, even with the antenna, doesn't. To me it seems like there's an issue with the radio's antenna connector. Maybe a loose wire internally or whatever.
The radio should still be covered by Motorola's 5 year warranty, since it was installed last year. I'm going to get in touch with one of the department officers and let them know my findings, and the radio can be replaced under warranty.

Until it gets replaced, we have cell phones. We can call dispatch by phone if we have to. Plus a couple members have handheld radios, but they only work on repeaters due to how far away we are from the dispatch towers.

 

[KevinC]

So I brought a dual band HAM antenna that I happened to have laying around. I know that works. I connected it to the radio and got the same results as with the Motorola antenna that I thought was the issue. My handheld picks up our repeater clearly with no antenna at all. This APX, even with the antenna, doesn't. To me it seems like there's an issue with the radio's antenna connector. Maybe a loose wire internally or whatever.
The radio should still be covered by Motorola's 5 year warranty, since it was installed last year. I'm going to get in touch with one of the department officers and let them know my findings, and the radio can be replaced under warranty.

Until it gets replaced, we have cell phones. We can call dispatch by phone if we have to. Plus a couple members have handheld radios, but they only work on repeaters due to how far away we are from the dispatch towers.

How are you connecting the coax to the QMA connector on the radio? Via an adapter or are you putting QMA connectors on the coax?

 

[KevinC]

Maybe it's as simple as the QMA isn't pushed on all the way or it's attached to the wrong port (WiFI or GPS)??

 

[davidgcet]

again, TRY A SIMPLEX CHANNEL. not the repeater, but a direct channel. the radio could be programmed incorrectly for the repeater. but yes, the best thing to do is let someone with both experience and the proper tools to diagnose the problem handle it, a radio tech could likely have had this fixed in a few minutes(barring having to send the radio for warranty repair).

 

[KevinC]

again, TRY A SIMPLEX CHANNEL. not the repeater, but a direct channel. the radio could be programmed incorrectly for the repeater. but yes, the best thing to do is let someone with both experience and the proper tools to diagnose the problem handle it, a radio tech could likely have had this fixed in a few minutes(barring having to send the radio for warranty repair).

He stated he tried simplex in this post...

Antenna on a Fiberglass Airboat - Grounding Question

May be, but I don't recall an issue with having the VHF whips on the arch above the outboards. But then again, that was stuff used on the ocean where it was simplex and we needed range. My bigger concern would be mooring lines with the antenna mounted right down on the deck like that. Or...

forums.radioreference.com

That's one of the reasons I suspect the radio has no antenna attached to it (either the the QMA isn't snapped in or it's in the wrong port).

 

[paulears]

Is 156-163 or so within the realm of your operating channel? If so, stop messing a bout with antennas that need a ground plane and just use a fibreglass marine antenna, designed to work on a fibreglass boat, with decent performance! The ones we install will actually do pretty well on the ham band, and there is a resonant frequency at UHF, at 3 times the operating frequency with a not dreadful VSWR (just under 2:1)

Let's face it, a handheld on low power can do 100ft, so if this one cannot, it is either broken or the cable is broken, or the thing driving it is broken. Those Wideband antennas need a physically large ground plane to get good performance, and even then, are only approaching unity gain at a few frequencies, and just a bit of wire in the sky at everything else.

If the vehicle is fibreglass, all this silliness with ground wires may well trick a few meters, but the feeder cable will start to be part of the antenna system and any readings severely compromised. Just put a proper suitable antenna on it and move on.

 

[Cameron314]

Is 156-163 or so within the realm of your operating channel? If so, stop messing a bout with antennas that need a ground plane and just use a fibreglass marine antenna, designed to work on a fibreglass boat, with decent performance! The ones we install will actually do pretty well on the ham band, and there is a resonant frequency at UHF, at 3 times the operating frequency with a not dreadful VSWR (just under 2:1)

Let's face it, a handheld on low power can do 100ft, so if this one cannot, it is either broken or the cable is broken, or the thing driving it is broken. Those Wideband antennas need a physically large ground plane to get good performance, and even then, are only approaching unity gain at a few frequencies, and just a bit of wire in the sky at everything else.

If the vehicle is fibreglass, all this silliness with ground wires may well trick a few meters, but the feeder cable will start to be part of the antenna system and any readings severely compromised. Just put a proper suitable antenna on it and move on.

A VHF marine antenna isn't going to work that well on UHF.

 

[tvengr]

If you have problems hitting a repeater 93 feet away, either your antenna cable is open or shorted or your radio has a RF output problem.

 

[paulears]

Sorry - people were talking about VHF frequencies so I thought that was what we were talking about - apologies.

 

[mmckenna]

A VHF marine antenna isn't going to work that well on UHF.

Depends on the antenna design. A 1/4 wave VHF antenna will be 3/4 wave on UHF and work pretty well. I ran a 1/4 wave VHF antenna on a dual band Kenwood radio for years. SWR was lower on UHF than it was on VHF. The radiation pattern is a bit wonky, but for me and my limited use of UHF it worked fine.

 

[paulears]

My van has VHF quarter wave verticals, that perform quite well as ¾ waves on UHF. My marine, groundplaneless antennas are not quite so good at UHF, but they certainly get across a few miles!

 

[wwhitby]

epatchen, if you have access to another radio, one that you know works, try swapping out the radios and see if you get the same result.

Also, what kind of mount is being used? If its an NMO hole mount, is the location where it is mounted thicker than vehicle sheet metal? That would keep the center pin of the antenna from making contact with the mount.

 

[n7lrg]

I once saw a marine radio setup that the coax actually had the "ground plane" in the coax. It was sheathed in along the outside braid and about 6 feet long.

 

[paulears]

6ft seems a bit on the long side, but sleeve dipoles are quite common - quarter wave goes up, and the coax braid is folded back down over the top of the cable coming up. With a Biot of careful tuning, you've got something that works pretty well.

 

[mmckenna]

I once saw a marine radio setup that the coax actually had the "ground plane" in the coax. It was sheathed in along the outside braid and about 6 feet long.

Yep, also the old marine CB antennas that Radio Shack sold did the same thing.

Some cheap marine VHF antennas are simple coax cable sleeve dipoles shoved in a fiberglass tube and sold for a lot of money. Good VHF marine antennas have actual solid/rigid elements.

 

[n7lrg]

Ahhh, now thinking about it paulears you are right. That does seem long. Mmckenna you as well. I bet it was a radio shack setup.