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Author Topic: Ham Antenna(s) for offroading  (Read 1388 times)

K6TLR

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Ham Antenna(s) for offroading
« on: July 22, 2016, 05:51:41 PM »

Hey all, I have a couple of awesome elmers in my Ham club that help me with a lot of things, but I think I need some more offroading opinions on this one...

I am getting a FT-8900 and converting/committing my FT-5200 to an APRS setup... I am having some issues with what to do for an antenna for the 8900.

There are some solid quad band antennas from Diamond and others, but they seem a little too solid. In order to get a good SWR on 10m I need to have a good ground plane, and a modest height for the antenna. But, because the antenna is not a whip, I am thinking it is going to get smashed pretty quickly on any wheeling adventures. I would need to mount it very low in order to avoid hitting it on branches and trees... but then mounting it low compromises the SWR and gain of the antenna.

It can be very difficult to build a whip, multi band antenna due to the necessity for the traps and coils for each band at certain points of the antenna. Obviously, a securely mounted whip would be the ideal situation, but the very difficult task of building a multi band whip seems to make this idea not feasible.

My other option, is to use 3 antennas... a 2m/70cm whip, a 6m whip, and a 10m whip. I would then need to put an antenna switch inside the cab to switch between them all when I want to use them. But then I won't be able to monitor 10m simplex and repeaters during snow runs in the winter, and use a 2m repeater or simplex at the same time with the radio... So, I would need to also install a triplexer for the 3 antenna setup if I wanted to use any combination of the different antennas simultaneously.

The last option is to just use 3 different radios, and end up with 4 radios in my truck (one for the APRS, one for the 2m/70cm, one for 6m, one for 10m). I Already have the APRS radio and the 10m radio... would just need to get the 2m/70cm and 6m. I would mount the APRS antenna and the 2m/70cm antenna on top of the roof, and put the 6m and 10m on the edges of my bed.

Anyone have experience with multi band whips? Or with putting multiple radio setups in your rig? Thoughts on whip antennas vs a solid trap and coil antenna for offroading? Does mounting a solid, multi band antenna low, with no ground plain (off the side of the rig) compromise the SWR and Gain significantly enough to justify not doing it? Thoughts or other ideas in general?

Thanks for the input!
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monyman

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Re: Ham Antenna(s) for offroading
« Reply #1 on: July 22, 2016, 06:58:13 PM »

I'm a licensed Technician, but this is way over my head. This sounds like a Greg, H2O_Jeep, question.
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H2O_Jeep

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Re: Ham Antenna(s) for offroading
« Reply #2 on: August 11, 2016, 11:16:44 AM »

I think it's great to seek out more options for more communication opportunities. I'm in the process of looking to add an HF rig with a whip antenna to my Jeep. But I also want it to be simple to operate and maintain. A simple whip with a dedicated HF rig (Yeasu 891, when it comes out). The whip will just be a whip and have an antenna tuner inside the cab. No traps other than a coil if needed, haven't tried yet.

That being said, it is also good to know your limitations. Having a quad band antenna does well with vehicles that are dedicated for on road use only. The antennas won't get much abuse from debris or low flora that could catch and remove a heavy trap antenna. My philosophy in off road communications is keep it simple and least amount of moving parts. A dual band is more than enough for communication needs. But again, I'm also looking to add an HF whip. The point is don't try to do everything with a single antenna system. Off road abuse will make short work of that quad band antenna. 

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K6TLR

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Re: Ham Antenna(s) for offroading
« Reply #3 on: September 14, 2016, 08:54:26 AM »

Just giving an update, just in case anyone was interested :)

I am going with 4 antenna. (1) 1/4wave 2m whip, drilled with an nmo for APRS, (1) 1/4wave 2m/440 whip drilled nmo for 2m/440 coms, (1) 1/4wave 6m whip drilled nmo, and (1) 1/4wave 10m whip ball joint mounted near the end of my bed on the side of the vehicle. Due to Cal4Wheel rules, I will have to take down the 10m for any Cal4Wheel events I go on.

I will be setting up an Alinco 75w 2m radio with a TinyTrack TNC, spliced into my GPS receiver to run a dedicated APRS unit.

And then I will have my FT 8900 for 2m, 440, 6m, and 10m. In order to run multiple antenna, I will have a duplexor installed that will split 2m/440, from 6m and 10m. Then, since duplexors for 6m and 10m frequencies are a little more difficult to find, I will just run an antenna switch in the cab between the 2 antenna. The radio cant duel 6m and 10m anyways, so a duplexor would be slightly useless and a little overkill.

Both radios will be sitting in the back, screwed into a board, behind a seat, and thus out of the way. The control head of the 8900 will be mounted right under my cabin AC controls, with an external speaker either mounted down by my leg, or embedded into the overhead sunglasses unit that I will cut into.

In order to run the radios and never have to worry about draining the battery, I am also installing a low voltage cutoff that will control the power flow to an external fuse box that all of my aftermarket electronics will be hooked into.

Big project, but it will be worth it! I will post updates in the rig section in case people are curious about the process :)
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Improvise, Adapt, and Overcome. If you're not having fun, it's not worth doing.