Mobile unit temporary in car

Discussion in 'Mobile Radio' started by W9BXX, Jan 15, 2014.

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  1. W9BXX

    W9BXX Ham Member QRZ Page

    Hi all
    So I'd like to get like a FT7900 for use as both a base and a mobile when i need it. I like not to have to drill holes in the car, mounting holders or other permanent type work in the car (besides wife wouldn't be happy). Couple of questions, like power supply, can it run off a cig lighter or would it be better to run a permanent power line to the battery,that has easy to plug into ends on it?
    I've got a mag mount antenna that I use with my HT now that will be able to handle the FT7900, but what about not mounting it? some sort of box that sits in the passenger seat? I'd only use it when I'm alone or with passengers only in back.

    anyone do anything like this? Some sort of case that you can easily move in and out of house and car?

  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    FT-7900 draws about 11A on transmit (full power) and that might be handled by the "accessory power" port in some vehicles, but maybe not. For very temporary use I'd give it a shot; but for repeated use I'd certainly wire to the battery.

    Without using the mounting bracket supplied with the rig, and drilling holes to screw that in place, the rig becomes a bit of a missile if you hit the brakes hard or are involved in a collision. That's why it's dangerous. Also placing it a container or even laying it on the seat doesn't allow normal airflow around its heatsink, which can result in overheating the final amplifier stage and ultimately causing it to fail: These rigs are designed for "all around" air flow, so the heat sink can do its job. The mobile mounting bracket, affixed under the dash, provides for that.

    In a pinch, I've done stuff like install the rig in the bracket (to elevate it off the seat) with the bracket under the rig rather than above it, and then used strong stretch cords that wrap around the seat bottom and the rig to hold the rig securely in place. That looks goofy, but at least prevents the rig from flying out of position. I find it much easier to just drill the holes and install the mount in a professional manner. In most cases, nobody could ever possibly see those holes.
  3. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    I have a Kriket Kamel that I use in the back seat area of my car. The radio is harder to operate in that position, but it's safe, removable, and does work. If you don't have to QSY often, it's no big deal.

    You can get one here for $35 and it comes with a free CB...

    I have gotten used to operating my radio by feel. It was designed so it could be used that way, and an FT7900 is not. However, I think it could be done.

  4. N7WR

    N7WR Premium Subscriber QRZ Page

    As to your question about not mounting the mag mount on the vehicle but putting in on some sort of box on the passenger seat (if I am understanding you correctly) why? First of all it needs a ground plane which putting it on the vehicle would provide to some degree. On a box on the passenger seat, no ground plane and it would not work very well. Plus the metal of the vehicle body would shield it both tx and rx. Finally, an antenna that close to your body on VHF frequencies at the radio's full rated power would most likely not meet the RF exposure standards and would not be really good for your body.
  5. W9BXX

    W9BXX Ham Member QRZ Page

    Sorry, the mag mount is on the outside of the vehicle, that's not the issue. In rereading what I wrote, I can see how that could be interpreted.
    No, I want to figure out a temp mounting for the RADIO inside the car. I get the issue of things flying around, that's why I'd not just set the radio in the front seat.
    Of course, like most cars now a days, the front console has little to no space and the space between front seats has shifter, drink holders etc etc.

    So any ideas...
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't think there are any "good ideas," frankly. I've had VHF-FM mobile rigs in my cars since 1969 (they've gotten smaller, lighter and way more featured over that time!), in at least twenty different vehicles, and could never figure out a way to "temporarily" install one that would be safe and convenient.

    It takes me five minutes to drill four holes to install the rig's mobile mount, and then I'm done. I've done this in at least six "leased" cars, including a Z-28, and never once has the dealer even mentioned any "holes" (probably because they're so inconspicuous, he couldn't see them) when I've turned the leased vehicles back in. Never been dinged a dollar for anything.
  7. KD5FLN

    KD5FLN Ham Member QRZ Page

    Well if you already have the radio right there when you open up the users manual you will be greeted with a bunch of warnings, one of them is to Never use a cig lighter as a power source. You run the risk of fire by using the cig lighter to power your radio. The cig lighter adaptor that you would use is NOT intended to be used in high amp situations . I would suggest crimping connectors on the power wires and hook it directly to your car battery and carefully route the wires thru the firewall and into the trunk where you would mount the radio. That radio has a remote head so you can mount the body of the radio under the rear dash in the trunk and mount the face of the radio up front by you. Its really a matter of 2 minutes to detach the head, put it in your pocket, pop the trunk & disconnect the radio & carry with you inside the house...
    To use it as a base just order another replacement power cable.
    Last edited: Jan 31, 2014
  8. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    There used to be Quick disconnect sliding mounts for Chicken band rigs. You mounted 1/2 of it under the dash (in your 1970s car) and the 2nd half mounted to the top of the radio. That way, U could quickly pull it out so the ROTTEN RB VERMIN on the streets wouldn't break in to steal it.
    It also had a connection for the antenna, so it was a truly slide in/slide out affair. Those are probably still available at Chickenband shops or on Ebay. While the coax connection is probably poor for VHF/UHF, it will still work. And U just pull it out, take it in the house, to a matching mount in the radio room. The slide mount does Power, speaker and Antenna!

    Poor, but it will work!
  9. WA4OTD

    WA4OTD Ham Member QRZ Page

    I have accessory outlet plugs on all of my 2 meter rigs and find that works well. Even when I did aeronautical mobile the plane had an accessory outlet (with a 5 amp fuse so had to run 5 watts). I just sit in passenger seat or the floor when just listening.
  10. SA6CKE

    SA6CKE Premium Subscriber QRZ Page

    I have my rig (FT-857) in a modified suitcase for the purpose and then I have added some power wiring in the car to be able to pull full power. Dual ground points just to make sure, and a low-pass filter on the 12V feed to limit interference both ways.

    The antenna is on a roof rack, but I need to see if I can do some grounding mod for it since the roof rack doesn't ground into the car body. And modern cars sucks when it comes to the ability to do custom installations. Right now I can hear other stations well enough, but it seems to me that most of the power just goes up in heat somewhere on the HF band. For VHF/UHF that's not a big problem since a small magnetic antenna is doing a pretty good job - not perfect, but it works.
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