Thanks allot Jon_k. You actually helped me out quite a bit but also opened up an entire new set of questions.
Glad to help.
I have been considering the possibility of punching a SINGLE hole in my roof. Problem is that I have 2 scanners and the 2 meter so I would still need an extra couple of mounting locations. If I did do a hole in the roof, it wouldn't be in the center however. It would be maybe a foot from the rear of the cab. Mainly because I have some form of access to the rear of the panel there by removing the 3rd brake light.
Understandable for one hole. I am considering 1 hole in my roof as well. I'd put it in the center horizontal, but vertically it would be further near my brake light as well.
I have also decided to be OK with an antenna on my hood lip. I have seen a couple of nice adjustable mounts with rubber in the clamps so I think I could live with that. Having a hard time finding one however.
I have also seen hood mounts that are made for specific trucks. You may see if you can find one made for your truck specifically.
Now given those 2 mounting locations and knowing that I am needing to mount a 2 meter and a scanner antenna primarily to receive 800MHZ stuff, which would you put where and why.
We may have differing priorities and interest in the radio hobby which may conflict with each other.All I can share is what I would do with your truck, and why:
ROOF: The hood is the #1 best spot, and in my mind thats for the transmitter. Mainly because transmitted signals go out further with a proper ground plane. After all, don't you want to be able to reach those distant repeaters on the other side of town? (
My biggest pet peeve is to be able to hear a repeater, but not be able to Tx to it. I try to do anything (height/groundplane) to increase my chances.) I also like to at least listen to repeaters as distant as possible.
To add to my reasoning, amateur radio repeaters (and your transmitter) run on very low power output when you compare it to the hundreds of watts your commercial Police/Fire repeaters are pushing. So you earn more with a ground plane here in my opinion. You might pick up Police with a twist-tie made into antenna buried 6 feet under concrete with rebar. Unfortunately the amateur systems aren't as powerful with their output, and your 2 meter rig probably does 50watts max. Give it the height and ground plane advantage.
HOOD / BED
The next best option with the best ground plane area will be your hood. The antenna will be likely in the top left corner of your hood by the drivers area. Not the best ground plane, but OK.
I can't tell you what to put here.
- Do you value performance on 150/440mhz?
- Do you value performance on 800mhz?
Pick one that has higher value and put it on the hood. It will gain the benefit of the ground plane. It just depends on which priority you want for which antenna.
Pro TIP: For all your antenna mounts, purchase the same type of antenna mount types. That way you can move antennas among the mounts. The antennas and each mount will be interchangeable this way. If your priorities change, you can just unscrew an antenna and move it to another mount. I've made this decision on my vehicle and have standardized in NMO. I'm happy with the standardization.
Pro TIP 2: Use the same coax connector on the end for your radios. Standardize on all BNC end connectors, or all PL-259. That way any antenna wire can be used with any radios. (I'd do all BNC since it's a small connector. For the HAM radio you can get BNC to PL-259 to connect to your radio. Your preference. This is so you can interchangeably change antennas on your radios.) This will just simplify interchangeability and makes things simple for new equipment addition in the future.
And antenna recommendations for those locations are welcome as well.
I use an Austin Spectra for my scanning needs. I use an Comet SBB-7 2 meter/70cm antenna for amateur use. I'm happy with both.
These are my first mobile antennas. I've not been around long enough to start making recommendation's for other peoples rigs. However, 3 of my HAM friends purchased the Comet SBB-7 the same day after I purchased mine at the Hamcom here (and one of the operators who purchased has been an operator for 7 years, general.)
Now on to the 3rd antenna. [SNIP] I would like to use the antenna I have there in the bed for this but I still have to address the lack of ground plane. Ground planes in the wild and particularly Mama's cookie sheet got me to thinking. What if I were to somehow attach a ground plane to the antenna mount? Something like a half circle of sheet metal with say a 12" radius. Would something like that be considered an acceptable ground plane? I also tried to research ground planes but most of what I found related to building base style ground plane antennas rather than addressing ground planes in a mobile environment...but it did give me an idea.
Building a ground plane with sheet metal is acceptable. Aluminum is an excellent conductor. When you get /really/ specific the ground plane will need to be a specific length out from the center of the antenna base. You will need to find a site with a list or the equations to calculate proper length of your ground plane for the frequency your running. (In the perfect world they say an infinite ground plane is the best. This is never possible though unless you have property rights to a place like Earth made out of pure copper. I'm also sure you appreciate some space in the bed.
What about attaching a pair elements at a 45* to the base of the antenna. It would be down in the bed where it wouldn't be visible but that would also limit to being able to only use a pair rather than four like most I have seen. Does that even make sense?
Well an proper ground plane would be a
solid circular sheet of metal with a length calculated base on the center frequency of the antenna tuning (90 degress from the whip). Of course, those guys with a huge HF antenna towers usually bury steel rods of the calculated length (as many as they can muster) under the ground in their back yard. You can do the same thing with metal rods. You would add as many as you can (or ideally a flat circular peice of sheet metal) around the base of the antenna. Again you will need to calculate how far out the metal reaches for the center frequency your antenna is tuned for.
Again, for the bed you may not even bother adding a ground plane. It's just something to do for added performance if you happen to have one in a suitable location for antenna placement. Myself, I don't think I'd fabricate a ground plane if I didn't have one readily available.
Or would a better option be to stick with just the 2 antennas and run both scanners off the same one? What effect would that have?
Having a dedicated 800mhz isn't a bad thing. But running two scanners off one antenna is fine.
Running both scanners off the same antenna has been done before plenty of times. Some people just get a T connector and do it that way. Other people get isolator devices to isolate the two scanners.
The scanners shouldn't interfere with each other in my opinion. You may get a birdie or two from internal interference from the VFO's but this should be rare and there's only about 4-5 birdie frequencies in the whole scanner. The birdies won't damage anything.
As long as you aren't transmitting no interference should be caused. (If you do transmit, the scanner connected will be destroyed from the power obviously.) I'm not an expert at running multiple devices off one antenna. This should be fine though.