Portable dipole

Discussion in 'On the Road' started by KA8MNP, Mar 11, 2014.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: Left-3
ad: Subscribe
ad: L-MFJ
ad: Left-2
  1. KA8MNP

    KA8MNP Ham Member QRZ Page

    Probably not. I found out there is a park right across the street with plenty of room. So if the kid calls the guy on the golf cart I'll just move over there. Thanks.
     
  2. KA8MNP

    KA8MNP Ham Member QRZ Page

    Well after weighing everything out. I decided to use a Shark S-F75 mobile antenna and a mag mount. I'm really just interested in working while I'm stationary. I know this won't work as good as even a bad dipole but I just can't get everything I need together in time for my trip. Also since the antenna will be attached to the vehicle and nothing will be away from the vehicle it makes it easier to find a place to operate.

    I've never used an HF mobile before. The antenna I bought is designed for 75 meters. I wonder if I use a tuner if I can work the CW portion of 80 meters as well. Is there a possibility that any other band will work. I know hams use dipoles cut for 75/80 meters all the time all over the place.

    I know mag mounts are not really efficient and can blow off when moving. As I said I'm mostly wanting to sit in the parking lot and work what I can. Is there anything I can do to get a better ground between the vehicle and the mag mount? I chose the mag mount because its a work vehicle and my employer is very supportive of my ham radio but a permanent mount isn't an option. The mag mount is the MFJ 335BT 5 inch magnet mount. The mount with three magnets wasn't available. Any help or comments appreciated.
     
  3. N2ADV

    N2ADV Ham Member QRZ Page

    I have this as a bookmark and am going to build something similar but instead of having it mounted to the car, I am going to have it welded to a plate so I can just drive the car onto the plate and hold the pole.

    [video=youtube;nusno8I_eTs]https://www.youtube.com/watch?feature=player_detailpage&v=nusno8I_eTs[/video]

    (he gets into the antenna around the 8 minute mark)

    As for a better ground between the mag mount and the car, you may want to bring along some wire and make some radials so you can get the most bang for your buck if you don't plan on going through the car with a fine tooth comb and bonding all the wire together or using sheet metal screws to get a better ground between antenna and car :)
     
  4. KB0LPM

    KB0LPM Ham Member QRZ Page

    When and where do you plan to do this? I use several portable HF antennas: A SuperAntenna vertical, an 88 foot doublet using a Jackite pole for the mast or an ENZ Fed antenna. My working rig is a QRP Yaseu FT-817. any of those solutions could work for you.
    Cheers / Don KB0LPM
     
  5. K0BG

    K0BG Ham Member QRZ Page

    I'm amused.

    I've seen several installations like this, and I'm always taken back by folks who clamp onto the cargo tie down, rather than remove it, and use the existing bolts? Should be obvious why.
     
  6. KA8MNP

    KA8MNP Ham Member QRZ Page

    Thanks for all the input. I'm back home from my little trip and want to thank all you guys and share my experiences.

    I ended up using a shark 75 meter antenna with a mag mount on top of my Jeep Grand Cherokee. I was able to work several stations a few states away during the night time hours and strangely enough the antenna was flat for SWR around 14.025 with a fairly wide band width. I worked several CW stations on 20 meters. The antenna is adjusted by sliding the metal whip in and out of the loaded portion of the antenna. The junction is about four feet above the mag mount. Add about five feet for the distance from the vehicle roof to the ground, makes a total of about nine feet. I had to take the antenna off the roof every time I wanted to make an adjustment. I know there are better choices for an antenna but I was limited on what I could spend. I had about fifty dollars in the antenna and mount and I'm pretty sure I had fifty dollars worth of fun with it. By the way I did use a tuner but I wanted to get the antenna as nearly as resonant as possible and as near the center of the band as possible.

    One problem I hadn't counted on was that every time I keyed the mic or pressed the code key the displayed voltage would drop. At idle speeds and in receive mode voltage was 13.8 to about 14 VDC. At idle speeds when keyed the voltage sometimes dropped as low as 9.5 vdc. I didn't count on that and have no idea how to change that situation. I'll need to figure it out before going out again. I'm sure this isn't good for my radio (Yaesu FT897d) and I know it hurt my transmitted signal because one guy kept telling me my signal was dropping during the transmission. I thought it was QSB until I watched the displayed voltage and saw it drop. Sometimes it would bounce up and down. I had the power cord ran directly to the positive and negative terminals of the battery. The battery is located under the passenger seat.

    Next time I plan on using a home brew dipole, maybe even a fan dipole and raising the center up about 16-20 feet on a mast. I was concerned about finding room to stretch it out like that but I found a nearby park and there was plenty of room. Another possibility is to buy a another shark and get one of those mounts that hook 'em together to make a dipole. Still need a mast but it would be more compact. Just like N2ADV (Jim) mentioned I thought of making a steel plate with a metal pipe to drop the mast in and then drive the car onto that. I've seen something like this for sale but it shouldn't be hard to get a local welding shop to rig something like that.

    Anyway I had fun. And likely will do it again.

    Thanks to all and 73.

    Randall - Ka8MNP
     
  7. AA9SD

    AA9SD Ham Member QRZ Page

    Cool, glad it worked out for you! Operating "park portable" is fun. I've got a couple antennas for that but neither is home brew. A fan dipole might be fun to try if there is sufficient room.
     
  8. KA9MOT

    KA9MOT Ham Member QRZ Page

    Assuming your power wires are of sufficient gauge for your rigs current requirements and the length of the wire and all connections were clean and tight, I'd head down to AutoZone or O'Reilly's Auto Parts and have your charging system tested.

    Your Charging System should be more than capable of carrying the current requirements of your rig. I'd be very suspicious of both the Battery as well as the Alternator.

    Just because it starts, runs and shows more then 13.8V while your engine is running does not mean it is healthy. It needs to be tested under a load.
     
  9. KA8MNP

    KA8MNP Ham Member QRZ Page

    Thanks Steve, I'll do that Monday. Hadn't thought of that.
     
  10. K0BG

    K0BG Ham Member QRZ Page

    The battery is not the issue—the issue is common mode. This is a typical scenario when using a mag mount!
     
Thread Status:
Not open for further replies.

Share This Page