HF Mobile Antenna

Discussion in 'Mobile Radio' started by K4TFL, Jan 11, 2022.

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  1. K4TFL

    K4TFL Ham Member QRZ Page

    So in November I traded in my 2020 Ranger for a new 2021 F-150. Didn't have the space to put an HF rig in the Ranger. The F-150 I have a mount 90% done for an IC-7300. It is a piece of 1/2" plywood about 10"x 11" with two 2 1/2" PVC caps that fit in the cup holders on the center console and a "buck" shaped to fit the cubby on the driver's side opposite the cup holders. A piece of 1/8" aluminum bent into a U-shape (starting piece was about 8"x 22") that attaches to the plywood and the radio bolts into. My wife wanted me to be able to easily remove and stow the radio to prevent the unscrupulous from breaking into my truck and taking this expensive looking black box. I do have a more permanent solution for mounting in the center console, but only if I can solve the antenna problem.

    I'm a student and my thursday class schedule gives me three 1 1/2 hour gaps between my 3 hour classes. For now I purchased a Diamond K400 lip mount and an MFJ-2640T (if I can make things work well, eventually radio will be more permanent mounted and I'll swap to a Tarhell if I find I use the rig in my breaks).

    On to the issue. I mounted the K400 on the hood trailing edge, drivers side. So as far left (from driver position) as possible, between the hood and the plastic trim the wipers sit in. With the 6.5 ft lead, gives plenty of coax to get down in the engine bay, through an existing grommet and to the center console where the radio is. Power is going to be dual 10AWG wire direct to battery, to the factory Icom plug (dual fused). With the K400 and 2640T in that position, I get about a 2.2:1 at center frequency on 40m. It tapers steeply up to about 10:1 at band edges. If I open the hood, I get about 2.5:1 across the band, which isn't ideal.

    So my question is, what is a better mounting option? Should I have just sprung for the Tarheel right away? What would be a better mounting location? I have a Diamondback Truck Covers tonneau cover on the bed (all aluminum), so bed stake holes probably won't happen. And I know I'll likely need to bond everything together, so other than that, any other advice/suggestions?
  2. N7WR

    N7WR Premium Subscriber QRZ Page

    The little Tarheel II is a better antenna choice and, of course, gets you more than just 40 meters. However given the size and weight of the Tarheel I would not be confident that the K400 mounted as you describe would securely hold it. I suspect the aluminum hood trailing edge would warp due to flexing. The truck bed cover eliminates a lot of possibilities for antenna mounting. Unless you are willing to side mount the antenna on one side of the truck bed just rear of the cab (with the mounting location backed up with metal to avoid the aluminum warping) your only other realistic choice--assuming the truck has a receiver for towing--is a mount on the rear affixed to the tow hitch.

    I wonder if your SWR readings have been without using the 7300's built in tuner. If not see if using the tuner helps. Hamstick type antennas like yours can be difficult to tune and they tend to be pretty narrow in band width. However, if you can get the hamstick to work well enough (I have on my F-150) you can buy them for other bands as well. Good luck. My son, also a ham, has a new aluminum F 150 and while he only operates V/UHF mobile mounting an antenna was a challenge.
  3. K4TFL

    K4TFL Ham Member QRZ Page

    The SWR readings were done with an AA-35 Zoom. I wanted to find a good mounting location for antenna before doing anything else, otherwise the extra work would have been a waste. I'm going to try the K400 on the top of the rear passenger door (I've seen similar mounting on the forum) and see how that does. It'll mean spending more money for the extension coax for the K400, but if it works, it'll be worth it. I've also thought of an over hang plate off the bed rail and I've seen the 3rd brake light mounts for trucks as well. If I go Tarheel route, it'll probably be the baby tarheel. I don't use 80m much, other than weekends to QSO with my uncle. But I've got a good base setup for that.
  4. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    That'll be a nice HF mobile setup, see my call on QRZ for photos/ I run a 7300 also and a screwdriver antenna. (It was one of the first 7300s in the US) I put it in and drove to Dayton for a demo when they released the radio.

    73 from,
    The K0UO "Rhombic Antenna Farm" 2 miles of wire, I'm In the Air or On the Air daily
  5. K4TFL

    K4TFL Ham Member QRZ Page

    I'll have to check it out. I'm really leaning towards just going for a more permanent install of the radio. I'll have to post some pictures of the spot. But in the 2021 F-150 there is a little cubby on the left side of the center console that's the perfect shape, just need to do some cutting under the console to make it fit, make some brackets. I do eventually want to get a screwdriver antenna and almost just got one right away. But I figured I should spend the minimum (7300 was my first radio, have a 7610 for my base and FT-101ZD as a back up) to get something set up, see how I like it, how often I use it, etc. before spending too much.
    K0UO likes this.
  6. K4TFL

    K4TFL Ham Member QRZ Page

    I'm assuming for the 7300 you did power direct from the battery? I'm about ready to start installing stuff but knowing it's solid state and alternators putting out 14+ vdc, didn't want to fry anything.
  7. WD5GWY

    WD5GWY Premium Subscriber QRZ Page

    Your alternator shouldn't be a problem. The 7300 is rated 13.8 volts DC + or - 15%.
    Connect the red wire to the positive post on the battery and the black wire to the nearest vehicle ground like a seat mounting bolt. ( it's a good idea to shorten the negative lead but, may or may not be necessary)
    KA0HCP likes this.
  8. K4TFL

    K4TFL Ham Member QRZ Page

    I figured it would be ok, but ask those more experienced right? I'm going to try to get it setup to test it before the snow sunday before i start mounting it. Have to wait on ground strap material and the longer cable for the k400
    WD5GWY likes this.
  9. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Positive Power direct to the batteries/I had dual batteries on the Duramax. Grounding you want to drown 2 your nearest frame or Central grounding point on the vehicle. Do not run a negative ground directly to the battery/ it will mess up the sensing. See http://k0bg.com/ground.html
  10. K4TFL

    K4TFL Ham Member QRZ Page

    Sounds good. Slowly getting one or two small things done a day to get it set up. I have the K400 extension coax on the way and some 0.040"x 3/4" ground strap material on the way. I attached images of permanent mount location I want to go for, but included my rough temporary solution. radio1.jpg radio2.jpg radio3.jpg radio4.jpg tempsolution.jpg
    K0UO likes this.

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