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Author Topic: Rig suggestion....a different kind of mobile  (Read 490 times)
N2TMC
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Posts: 15




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« on: February 17, 2008, 07:50:31 PM »

I am looking for a suggestion. I want to mount a small 2 meter rig on my power wheelchair. Something that does tones but only about 10 to 15 watts. I use a handheld now but it's hard for me to manage it and wheel at the same time. An older radio would be best but it has to do tones so I can bring up the repeaters around here.


TNX
73
George
N2TMC
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K0BG
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Posts: 9865


WWW

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« Reply #1 on: February 18, 2008, 06:13:59 AM »

What you need is a better way to hold the handheld.

I've not investigated the site, but I do know Handihams has all sorts of suggestions and help for just such matters. Here's their URL: http://www.handiham.org/

Alan, KØBG
www.k0bg.com
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N2TMC
Member

Posts: 15




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« Reply #2 on: February 20, 2008, 05:39:46 AM »

They don't really get into this. I might put my own website up when I get this figured out. Right now it's figuring out the best rig to use.
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W3LK
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Posts: 5639




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« Reply #3 on: February 20, 2008, 06:55:21 AM »

Of more concern is the antenna.

You will have virtually no ground plane for the antenna to work against and, more importantly, you need to get the antenna above your head to give you the least RF exposure.

Probably your best bet will be a sleve monopole in which the bottom of the antenna is a 1/4 wave tube with the antenna mounted on top and the coax running down inside. This was a common antenna on trucks in the 60's.

Good luck with the project.

73,

Lon - W3LK
Naugatuck, Connecticut
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NA0AA
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Posts: 1042




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« Reply #4 on: February 21, 2008, 10:20:23 AM »

There are a number of decent mobile antenna that are ground-independent for your application, although ideally you would want its base above your head.

Given the radio might get wet, how about an FT-10 by Yaesu - it's not cheap but it also does UHF and FM broadcast receive.

They make a smaller, lower power version that is water resistant and might be just to your liking.

Otherwise, almost any two meter rig with tones should do you fine, there are too many to try and list them.  Try Craigs List?  Make sure they still have the mounting bracket if that's part of your mounting scheme.

Do you have a power chair to tap for power or do you need to consider a battery pack as well?
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N6AJR
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Posts: 9908




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« Reply #5 on: February 23, 2008, 01:56:01 PM »

You can probably mount something like a radioshack 212 or a ft 1500 from yaesu.  they are physically small.  build a bracket to fit behind and on the arm of the chair to hold the antenna. use the mount to put it in clear view, but out of the way.  also remember 2 things. you may need a battery just for the radio and if this is an electric mobility type chair, some say do not use around a radio as it could cause a lack of control.  I have had no problem with my 3 wheel mobility scooter.
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N2TMC
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Posts: 15




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« Reply #6 on: February 23, 2008, 09:07:41 PM »

I have a place on the back of my seat where I can attach a "L" shaped piece of steel for a mag mount. The coil would be about head height. I can tie that into the frame of the chair to create a counterpoise. I can run the radio off of one of the 2 12 volt batteries. This chair runs a long way between charges so I don't think using a small wattage radio is going to kill the battery. I want to put a switch in to transfer the radio from one battery to the other so that I can keep the draw somewhat equal. I am doing this because I going to be doing things with the CERT team here.
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K2YO
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Posts: 436




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« Reply #7 on: February 26, 2008, 06:34:49 PM »

For your Cert work, you may want to have a special antenna that you don't use day to day. I thinking it might be interesting to use PVC pipe or the like as a mast to get the antenna over your head and then use metal measuring tape for the full wave vertical. When you are in limited quarters, you can fold over the antenna but then release it when you need full range. If you've ever seen the old military HF packpack radios, they used a tape antenna like this.  

Just an idea.

Bernie
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W3LK
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Posts: 5639




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« Reply #8 on: February 26, 2008, 07:43:10 PM »

<< I have a place on the back of my seat where I can attach a "L" shaped piece of steel for a mag mount. The coil would be about head height. I can tie that into the frame of the chair to create a counterpoise.>>

With all due respect, you are going to have an antenna with essentially no counterpoise - the feed line is going to do a lot of radiating. Just connecting the bracket to the frame of the wheelchair does not turn the wheel chair into a ground plane. You need at least a 3' diameter circle of metal under the mag mount.

You are taking probably the poorest performing antenna and giving it an equally poor mounting. Will you hit repeaters? Probably, but the SWR on your installation is going to be out of sight and change with every movement of your body and it may well be high enough to shut down the radio completely.

With the coil at head height, you are putting the majority of the radiation right at your head and that is a BAD thing! I just did a quick RF exposure evaluation and, even at 10W you are putting yourself in RF exposure danger.

As I previously suggested, a sleeve Dipole with the feed point _above_ your head is your best bet. Any mag mount solution is avery poor one, at best.

73,

Lon - W3LK
Naugatuck, Connecticut
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