How do I wire up an external amplifier for my HT inside my car?

Discussion in 'Mobile Radio Systems' started by KC0BUS, Aug 7, 2018.

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  1. KC0BUS

    KC0BUS Ham Member QRZ Page

    I'm thinking of possibly hooking up an external, outboard amplifier to my handie talkie which I keep inside my car, boosting it from it's 1, 2.5 and 5 watt power levels to a more usual or normal mobile power level of 50 to 100 watts or so.
    What is considered to be the proper way to wire everything up inside the vehicle for this type of set up?
    Thank you
  2. W7UUU

    W7UUU QRZ Lifetime Member #133 Volunteer Moderator Life Member Platinum Subscriber QRZ Page

    Curious what amp you have in mind and what band(s).

    If you don't already own an amp, you'd be way better off IMO just buying a 60 watt dual-band mobile radio like a Yaesu FT-7900 or similar. Any amp in the 100-watt class is going to be priced about the same as a whole radio in the 60-watt class, and there is very little difference between 60 watts and 100 watts for a 2-meter mobile station

    But the wiring of amp and radio is straightforward - antenna out of radio to input of amp, antenna connects to amp. Just be sure to run heavy wire straight to the battery and fuse both sides for the amp (or higher-wattage radio) power.

  3. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

  4. KC0BUS

    KC0BUS Ham Member QRZ Page

    But what do I do if I need to take the radio with me when I get out of the car? Maybe I need to go pedestrian 'walk-about' mode with a radio, what then? You can't do this with a mobile transceiver you can only do it with an HT.
  5. KC0BUS

    KC0BUS Ham Member QRZ Page

    *I don't have any amp in mind just yet. I'm still working this all out on paper.
    *Put a fuse on both sides of what exactly?
    *What gauge of wire is typically used, for, lets say, a 50 watt amplifier, for example?
  6. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    That is what the handheld is for!

    Handhelds are a mixed bag of tricks. Their front end is typically really hot, and when you use a decent antenna with them, they overload easily. Some makes have a build in attenuator for the purpose, but it doesn't seem to help much inter-mod wise. If that wasn't enough, it really gets tiresome R&R the setup. As noted, the best solution is two units.
  7. KC0BUS

    KC0BUS Ham Member QRZ Page

    I was thinking possibly going the 'two radio's' route too.
    Would it be possible to do the following:
    -wire up heavy gauge wires directly to the cars battery and then back out to the car's interior/driver's seat area
    -to those wires ends, hook up some kind of centralized fused junction box "control center" thing upon which 2 or 3 potential radio's can be plugged into and unplugged from and be used as needed or whenever needed?
    -this mission control center box thing with fuses would prevent any potential problems such as blowing fuses or burning out wires elsewhere in the hard-to-get-to nether regions of the car, thereby isolating any possible blow outs or burnouts inside the safety junction box thing???
    Last edited: Aug 7, 2018
  8. AG6QR

    AG6QR Subscriber QRZ Page

    You could sort-of do that, but you MUST fuse the power wire as close to the battery as possible, to protect that heavy wiring between the battery and the junction box. Otherwise, if the insulation gets damaged anywhere between the battery and the first fuse, there is nothing to prevent the battery from heating up the wiring and starting a fire. And it will do that quite quickly.
  9. W7UUU

    W7UUU QRZ Lifetime Member #133 Volunteer Moderator Life Member Platinum Subscriber QRZ Page

    Probably would be best to just use the handheld for a while ;)

    You need to run pretty heavy wire - 10-gauge would be my choice - and put an appropriate fuse on not only the positive but also the negative line, and run it straight to the battery. The fuse holders need to be right at the battery!! Do not use the car chassis for power ground. Not a good idea.

    Please note: you mess this up, regarding wiring for amps and radios, and you car could catch fire while you drive down the interstate!! Maybe you can find a local ham who can help you.

    In the meantime, I really suggest you just stick with the handheld and see what repeater action you can hit. I've run a handheld in a car many many times.

    Even better, just get a magnet-mount antenna to mate to the handheld antenna jack and stick the antenna in the middle of your roof. Get a decent 5/8th wave mobile mag-mount and you'll probably be surprised how well it will work. And be SAFE at the same time.

  10. WB2LBV

    WB2LBV Ham Member QRZ Page

    I can tell you from experience that using an HT as a mobile rig has a lot of downsides. Almost guaranteed front-end overload and intermod in RF-heavy areas, not enough rx audio power for a mobile environment (speaker-mic doesn't cut it either), gets tiresome quickly setting up and breaking down every time.
    The far better solution is a 50-watt mobile rig of your choice (single-band, dual-band, +HF if you're so inclined) properly installed, plus an HT to carry with you when out of the vehicle.

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