For all you antenna guru's....

[Steve F]

I was thinking about mounting a VHF antenna (GL1800) in the same location as shown in this link: http://gl1800riders.com/forums/showt...na-trunk-mount

However, since the bodywork is plastic (or fiberglass), what are the chances of getting a working ground plane to this location and having it actually work? Would a grounding wire be enough? It'll have to be a wire since this part of the trunk lid is on hinges..... I'm only running 2 to 3 watts @ 150MHz, and the antenna will be light weight and about 18" long. What are your thoughts?
Steve F

[WingAdmin]

The link you posted doesn't work, so I can't say without not knowing exactly the position you're talking about. However, in general, a motorcycle is a miserable place to put an antenna, as you likely know.

I've heard of people lining the inside of their trunk lids with foil, grounded to the frame, to create a very small ground plane, which I suppose is better than nothing.

[Steve F]

I don't know what happened with the link I posted....hmmm.
Here it is again (maybe copy/paste into the browser heading):
http://gl1800riders.com/forums/showthre ... runk-mount

If that doesn't work, picture this. The uppermost point on the trunk lid on a GL1800, just behind the back rest on the rear seat, there's a place that I would like to mount a bracket of some kind, to which I mount a VHF antenna. I have gotten a suggestion of placing some wire loops around the perimeter of the trunk lid to simulate a ground plane, and attach it to the ground of the antenna bracket, and I might give it a try.

[ka4yqi]

Are you going to run a 1/4 wave style antenna? I would try my best to make sure that you have the ground to reach the metal of the framework for the trunk. That way it would be better than nothing. Goodluck and picture of what you do. When I get slowed down enough, I got to try toput my 2 meter/440 antenna on the 1500 here. That way I can try to play with the ham repeaters.

[virgilmobile]

There is a metalic base paint that is used for this application.No it dosen't need to conduct electric.The painted area can then be painted over with enamel to cover it up.Just get the antenna mount in contact with the paint.

[N2PPN]

Diamond NR770 antenna in NMO or UHF style mounts (http://www.diamond-ant.co.jp/pdf/nr/nr770h.pdf) . NEEDS NO GROUND AT ALL!! (that's why its NR as in No Radials) will work and even though it is a dual banded antenna (144/430Mhz)it has 3.0 Dbi gain on VHF... I use one with my dual band VHF/UHF ham radio HT on my GL1100... Made a mount that clamps to a saddle bag rail and has a hole in it for the NMO mount to fit in... works great all over the NYC metro area on 3 watts into any repeater I can here...

As an aside, I used one of these NR770's on my boat, mounted to the top of an eight foot tall fiberglass extension and it performed perfectly even all the way up on the marine VHF portion of the VHF band with good VSWR and good radiation patterns (when using higher gained antennas on a moving vessel like a boat the omni directional pattern gets "squished" into a kind of "donut" shape as the gain is increased so if the angle of the radiator or antenna goes off vertical the radiated signal pattern will "tilt" on it's axis and can sometimes cause fade out on your signal. This should not be as much of an issue on a motorcycle as it would be on a boat that is rocking from side to side in the waves) and since the antenna had no coils and is made from stainless steel, it held up to the weather and salt spray.

73 de N2PPN

Rich

[Steve F]

Diamond NR770 antenna in NMO or UHF style mounts (http://www.diamond-ant.co.jp/pdf/nr/nr770h.pdf) . NEEDS NO GROUND AT ALL!! (that's why its NR as in No Radials) will work and even though it is a dual banded antenna (144/430Mhz)it has 3.0 Dbi gain on VHF... I use one with my dual band VHF/UHF ham radio HT on my GL1100... Made a mount that clamps to a saddle bag rail and has a hole in it for the NMO mount to fit in... works great all over the NYC metro area on 3 watts into any repeater I can here...

As an aside, I used one of these NR770's on my boat, mounted to the top of an eight foot tall fiberglass extension and it performed perfectly even all the way up on the marine VHF portion of the VHF band with good VSWR and good radiation patterns (when using higher gained antennas on a moving vessel like a boat the omni directional pattern gets "squished" into a kind of "donut" shape as the gain is increased so if the angle of the radiator or antenna goes off vertical the radiated signal pattern will "tilt" on it's axis and can sometimes cause fade out on your signal. This should not be as much of an issue on a motorcycle as it would be on a boat that is rocking from side to side in the waves) and since the antenna had no coils and is made from stainless steel, it held up to the weather and salt spray.

73 de N2PPN

Rich

Thanks for that info on the antenna. However, I'm operating in the 150+MHz range, and according to the chart, I'd be too high in the SWR at that point. Is it tunable to above 144MHz?
Also, can you post a pic of your mount?

[thrasherg]

You can always shorten an antenna to make it work at a higher frequency, just remove small amounts at a time and check the SWR as you can never stick a bit back on!!

Gary

[WingAdmin]

You can always shorten an antenna to make it work at a higher frequency, just remove small amounts at a time and check the SWR as you can never stick a bit back on!!

Gary

I have a really nice mobile CB antenna sitting in my garage that would work great for oh, say a 28 MHz 10m radio for exactly that reason.

[Steve F]

You can always shorten an antenna to make it work at a higher frequency, just remove small amounts at a time and check the SWR as you can never stick a bit back on!!

Gary

Sorry, I had a brain fart...of course, higher freq., shorter antenna

[thrasherg]

You can always shorten an antenna to make it work at a higher frequency, just remove small amounts at a time and check the SWR as you can never stick a bit back on!!

Gary

Sorry, I had a brain fart...of course, higher freq., shorter antenna

Unless the laws of physics cease to apply in Chicago.. Had to pull your leg...

Gary

[N2PPN]

Be careful when using the "Shorter the antenna the higher the operating frequency" rule.... it only works for 1/4 wave end fed and 1/2 wave center fed DIPOLES!!

The NR770 is a phased collinear type of antenna and just by trimming a little off the bottom of the radiator, you might adversely change the antenna's characteristics.

The VSWR for 160 MHz on this antenna is well within acceptable limits for an average modern day transceiver (below 2.0 :1) and it performs well on the marine portion of the VHF spectrum (156 MHz) as mentioned in my previous post.

It is a no-brainer antenna for an easy install and plug-n-play use.

I will look around for a pic of my mount, but any style mount for a truck mirror or luggage rack mount can be used... as well as just drilling a hole in a trunk or other piece of plastic and using either style (UHF or NMO) mount in the hole...


Rich
N2PPN

[N2PPN]

This is a picture of my mount. It may be "down and dirty" but it works. It is 1/2 copper buss bar (1/4" thick bent into a 90 degree angle) and 1/2 of a C.B. mirror mount bracket. It is drilled out for an NMO through-hole mount and the cable runs back up to the fairing where the radio is. The copper buss bar was rounded off on a bench grinder to get the same radius as the antenna's base.

Only drawback is that since the antenna is mounted to the saddlebag rail, the top of it is within "eye-poking" height when the bike is on it's sidestand. (a great deterrent to those who would like to "look" at your bike)

So a higher mounting point for a 27" tall antenna might have been a better choice.


Rich

[Steve F]

Well, I have this antenna and will be removing it from the trunk lip mount and making something else for a mount, that "something" is still to be determined. But it's a MAXRAD VHF antenna, simple, no load coils, and the whip is about 15". For right now, let's say that the whip length isn't important (I know it is) since I can get a whip any length I need to tune it.......will this thing work? I'm on a really tight budget, and right now $50 for an antenna isn't doable right now.
I want to mount it to a bracket behind the passenger back rest (again on a GL1800).

[N2PPN]

Ok, I'm posting from my itouch so hopefully there won't be too many typos. The maxrad antenna and mount are perfect for what you want to do. As shown earlier in this thread someone made a bracket for their 1800's trunk. You could do the same thing to provide a place to mount the antenna. Just make sure that the metal bracket BEHIND the trunk cushion is as wide as the entire back of the trunk as to provide a proper ground plane for your transmitted signal. Without a proper ground plane for the antenna the radiated signal can't "push off" of the antenna and radiate into space. Kind of like floating in a pool and trying to move without pushing off the side. Fun but not very effective. If you have trouble finding a piece of aluminium or sheet metal large enough to make the bracket/ground plane, a trick is to go to Lowes or Home Depot and find aluminium tape used for ductwork. It is sufficient enough to become a ground plane when electrically connected (or mechanically connected) for your antenna. Just make sure you have at least 17" of linear length for your operating frequency as the antenna you have is a 1/4 wave whip and it will most definitely need a ground plane for correct VSWR.



Rich

[Steve F]

Q: Does the groundplane surface have to be at a right angle or horizontal to the antenna radiator (whip)?
What you described, sounds like it doesn't matter much.
What about running a grounding wire from the antenna mount to the bike frame? Is that necessary?

[thrasherg]

The emitted radio wave typically bisects the angle between the antenna and the ground plane, hence a dipole where you have a vertical antenna and a vertical ground plane causes the radio wave to be emitted horizontally.. For what you are doing and the range that you will get on a bike, the actual angle between the antenna and ground plane is really not important, the antenna was probably designed to work with a ground plane at 90 degrees to the antenna, but you are never going to get a great result on a bike so just make the ground plane as large as possible but don't worry about the angle to the antenna.

Gary

[N2PPN]

Gary is correct. if you can try to keep the ground plane as close as possible (within reason and your mounting location and bracket fabrication) it will perform as well as you would expect from a mobile antenna mounted on a motorcycle... As far as grounding the bracket and the shielded side of the antenna mount, most definitely do. Not only for safety reasons, but it will make sure your coax doesn't pick up any extraneous electrical noises on it's route back to your transceiver. (and in a small way it will also allow the frame of the bike to be included to a small extent in the ground plane of the antenna system....


Rich

P.S. post some pics of your finished installation and let us know how it performs....

[Steve F]

Ok, will do, when I get to that point. But for now, I am wondering about what's under the "hump" on the GL1800's trunk lid. I thought it was the stuff for the remote keyless system. If it IS, are there any concerns about mounting a TX/RX antenna in such close proximity, and will making a groundplane panel so close to this system have any effect on it?

[N2PPN]

Since I don't have one of those models I can't tell you... but I would assume if it was placed there, it was designed to be shielded from extraneous RF interference..... and if it is the key-less entry system, then it should be deactivated when the bike is running, no??

Try it and see if the 3 watts of RF affect any of the bike's systems... that's the only thing I can think of...

Rich

OH and JUST WHAT frequency will you be operating this equipment on and for what purpose??? Just curious...

[Steve F]

The radios are operating on the MURS frequencies 151.82 to 154. MHz.
Here's a link to the specifics:
http://home.provide.net/~prsg/murs_faq.htm

The reason I'm going with these radios is first they were free to me, MOTOROLA Spirit MV21CV portables. I got 3 of them with the charger bases, wall warts, and speaker mics. My family and myself and the S.O. are driving out west this summer, they in the cages, and I on the 'wing. I'm going to be using these radios with external antennas, the cars get mag-mounts and I have the permanent mount VHF like in the photos. I really like these, they're really quiet, have PL, and operate at 2 watts, compared with FRS at only 500mw (plus you don't need a license). Even with the rubber-duckies, we were still getting almost a mile car-to-car!
Thanks guys for all your help so far, I really appreciate your knowledge and expertise, and as soon as I get the mount made and installed, I'll be posting some pics.

Steve F

[N2PPN]

Just a "plug" for Ham Radio.... Steve, ever thought about getting your ham license?? It would open up a whole lotta new two way stuff to you and the MURS radios would all be available to you with your new spiffy ham radio working "out of band".. so to speak.... and there really is nothing like chatting with a guy in Australia from your GoldWing as you cruise down the highway telling him about the stuff you see while he "puts another shrimp on the barbie"...


The mount and all the work you do for the MURS stuff would easily be converted to Ham use with very little $$$$$...

G'day to ya mate,

Rich

[thrasherg]

I have to agree with Rich, I passed my ham license some 25+ years ago and love playing with radios.. I don't transmit that much but love to see what I can pick up, and you meet some really great people.. Definitely worth considering.

Gary

[Steve F]

Yeah, you know, I've been thinking about doing just that, but haven't found a real desire for this. I have several friends that have had their licenses for decades, and some a little more recent. Personally, I'm really not interested.

[thrasherg]

Yeah, you know, I've been thinking about doing just that, but haven't found a real desire for this. I have several friends that have had their licenses for decades, and some a little more recent. Personally, I'm really not interested.

Oh well, each to his own.. Hopefully the wing will keep you occupied and happy!!

Gary