Does my mobile installation sound okay?

Discussion in 'Mobile Radio Systems' started by N2GRI, Feb 15, 2011.

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  1. N2GRI

    N2GRI Ham Member QRZ Page

    I know there is a lot of advice out there with tips about certain things that should be done when installing a mobile rig, but I was wondering if anyone could give me any specific feedback about my new (and first, if you don't count the HT) mobile installation and if anything seems glaringly wrong or could be improved.

    The radio I'm using is a new Yaesu FT-1900R (max current draw is 11A on highest power of 55W, but I plan on using the lower power modes and just listening most frequently). I used 12 gauge stranded copper wire to connect the rig directly to the battery, and about 6 inches from both battery terminals I have ATC blade fuse holders with 15A fuses installed. I soldered all connections and wrapped them in multiple (5+) layers of good quality electrical tape. The wires themselves are enclosed in that ribbed plastic flexible tubing from a few inches from the fuses into the cab, through an existing hole that was originally plugged with a rubber stopper just under the drivers side dash. Once inside, I managed to fit the wires and tubing under the plastic molding along the drivers side floor boards, where it comes out and is secured under the seat to the center console (just a removable plastic cooler with cup holders, basically), where the radio is mounted. The wires come from the tube and terminate in a power connector that connects directly to the pigtail coming from the radio. Total wire length is about 8 feet. The antenna is a 3/4 wave 2m antenna magnetically mounted to the center of the roof of the minivan (I know mag mounts aren't ideal). The antenna feed goes out through a back window (the type that only cracks open as a vent, and is rarely opened).

    My concern comes into play since the rig itself isn't actually grounded, and I read online that some people recommend fuses at the radio as well. The radio's manual says nothing of grounding the chassis or anything like that, and I'm wondering if that's okay. The wire gauge and fuses I used fall right in line with what the manual recommends. Also I know the antenna situation could be improved, and I'd take suggestions on that as well, although I'd really rather not drill any holes.
     
  2. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I think you're fine, as long as the flexible ribbed plastic tubing goes through the firewall, so that the power lead does not rub against the sharp metal of the edge of the hole. You should be able to run full power with no problem.

    And, don't sweat the antenna. A magmount in the center of the roof is not bad on 2 meters and up. If the antenna works, that is, it gets you into the repeaters you're going to use, that's all you need. A 3/4 wave antenna isn't absolutely optimal, either, but I had a homebrew one years ago that seemed to outperform everything else I had. I think the added height was a big factor.
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Why fuse the negative lead? Yaesu didn't do that.

    How is the radio mounted? Using the supplied mobile bracket with screws?

    The risks with the antenna installed that way (from my own experiences) are:
    -Vibration will eventually wear the coax where it comes through the vent window
    -The mag mount will eventually scratch the paint under the antenna base
    -The coax is visible and subject to external tampering, cutting, or possibly stealing of the antenna unless you remove the antenna every time you park and store it inside the locked vehicle
    -The "temporary" look of the antenna installation creates the appearance of a temporary radio installation as well, making it more tempting for vandals to consider breaking into the vehicle to steal the radio

    No real need for that if the cable is fused at the battery. Adding more fuses in series just adds more voltage drop under load.
     
  4. KD8NPB

    KD8NPB Ham Member QRZ Page

    Welcome to California : We don't know what the hell it is, but we'll steal it anyways.

    Ideally, I'd swap the antenna out for a 5/8 wave base loaded magnet mount. They're not very tall, and will give you at least 25 miles of solid range on high power, even in the piney woods.

    I talk simplex a lot on 2m.

    They work great for that too! Although now I'm upgrading to something even bigger. :D
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Funny thing is I've never had a car broken into or anything stolen in CA.

    However, I did have my mag mount whip (Larsen 5/8-wave NMO magnet base) stolen, my car broken into, and the rig stolen (all at the same time) while parked at a very nice restaurant in New Jersey years ago. That lot even had valet parking, and the attendants were all over the place. Possibly one of them did all this; if not, I'll bet they saw who did but wouldn't admit to anything.

    So, because there was damage to the car (broken window), I did call the police to report it. They showed up promptly and took a report. When I explained about the radio equipment and antenna, the cop said, "Oh, yeah...any time a temporary CB antenna with a magnet holding it on is on a parked car anywhere around here, they steal it and then break in looking for radios..."

    Great.

    Never used mag mounts after that.
     
  6. N3AEI

    N3AEI Ham Member QRZ Page

    When I bought my FT-2900R it came from Yaesu with fuse's on both positive and negative leads.
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yeah, I've seen some rigs do this: Lately, most don't.

    Here's an interesting reply to this question from another board (this one: http://www.mail-archive.com/elecraft@mailman.qth.net/msg101134.html)


    > Tom W8JI wrote:
    >> Positive lead fuses are a good idea.
    >>
    >> Negative lead fuses never were a good idea unless the radio has a totally
    >> floating negative buss.
    >>
    >> If the negative lead fuse to the radio opens for any reason all the
    >> negative
    >> lead current for the radio will flow through the negative lead of any
    >> accessories connected to the power supply.
    >>
    >> They are a terrible idea for any system with the negative lead common to
    >> ports in and out of the radio, or to the chassis. You certainly won't
    >> catch
    >> me using one!The negative lead needs to be connected solidly to the power
    >> supply negative for a multitude of reasons, the most prominent of which
    >> is
    >> if the negative lead fuse to the radio opens you can blow up accessories
    >> or
    >> open ground traces including traces in the radio.
    >>
    >> They are not even recommended in vehicles any longer in some countries
    >> because of the fire and damage hazard they create.
    >>
    >> 73 Tom
     
  8. N2GRI

    N2GRI Ham Member QRZ Page

    Thank you for the responses. The Yaesu cable supplied with the radio is the same guage, and has cylindrical 15A fuses on both leads close to the battery connection. I decided to wire with my own 12 gauge cable so that I was ready to go as soon as the radio was delivered. I will probably just leave it as is. The plastic tubing does protect the cable at the hole in the firewall, so it should be pretty well protected -- it is one continuous piece from the battery to the rig. And as far as the antenna situation, I would like to keep the antenna I have now for the time being. I just installed the setup last night and on the drive into work today it seemed to work well (at least for monitoring, I didn't transmit yet). I'm not too worried about vandalism or theft since, despite the 2 region call I think cows outnumber people in my area, and I'm already in the habit of taking it down if I'm ever somewhere shady. Nevertheless, I may get myself a hatch mount for the rear hatch and probably a little bit of a shorter antenna (like the 5/8 wave recommended above).
     
  9. K0RGR

    K0RGR Premium Subscriber QRZ Page

    Nobody ever messed with my Larsen mag mount in California, but my car was burgled twice in the midwest - and I had solid mounts both those times. The nice thing about a mag mount on the trunk is that it's easy to hide fast, which I always did when I had a sedan.

    As for the fuses - what Tom is saying is the flip side of the argument that you need the fuse in the negative lead. I happen to agree that it isn't needed, and I think the other general suggestion of using the car body as the negative return lead is probably a good one, too. However, the old argument was that if the car's ground return for the starter mechanism opened up, you could get the full starting current through the ground lead of the radio. Hence, the fuse... But, according to Tom and others, that theory has been disproven.

    From looking at the manual, I think the FT-7900 comes with fuse holders in both leads. The IC-2820 definitely does, and there is a special BOLD warning "Never remove the fuse holders!". My Kenwood only has one fuse, though.
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I thought he said FT-1900. That manual shows only one fuse and lists the cable as P/N T9021715 "cable with fuse."

    None of my rigs have the negative lead fused. Then, for serious mobile installations, Motorola and just about everyone else advises to attach the radio and its negative wire to the car chassis and use that as the DC return, without a separate wire to the battery...
     
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