Tuesday 24 August 2010

Going mobile

My mobile setup for HF appears to be working well, on receive at least. I have ordered a small auto ATU to broaden the bandwidth of my mobile whips as at the moment the TX bandwidth is very narrow. Nevertheless on 20 metres I have heard stations In Austrailia, Indonesia and the USA as well as the Carribean, all on 20 Metres, note I say heard the only transmitting I have done so far has been a local QSO in order to get an audio report!
I am happy to report that my car does not seem to generate much QRM at all on HF and what little there was (on 40metres) the noise blanker on the 706 deals with.
I am not so pleased with the boot mount I bought for the HF antennas. It looks like the one below

Mine is unbranded but I have seen these branded as Sirio mounts. The connectors to the centre pin and earth under the mount are not in any way weatherproofed. Worse than that tightening the nut (as I needed to do) around the SO239 connector can cause the coax to disconnect and break away from the mount. This happened to me and I had to remove the mount from the car and solder the coax back on. Yes the mount does work and it holds the HF whip on fine. It is however poorly designed and its a pig to fit!  Not clear in the picture  is the plastic dome on which the SO239 sits which is mounted on a smaller metal dome. The plastic dome is free to slide over the metal one below altering the angle of the antenna. All very well but there doesn't seem to be a way of stopping it moving. So the antenna will not stay at the exact angle you want.
I guess its a case of you get what you pay for as these mounts are fairly cheap. I am looking for something better now as I don't think mine will last to long!


  1. I used this mount (http://www.rfparts.com/diamond/k400s.html) for my Tarheel II antenna on my jeep. It's lasted thru many northern Michigan winters and many miles on the highway. It's not cheap, I paid around $70-80 for it but then again it's held up great.

    Good luck and 73,
    Jay aka KD8EUR

  2. Hi Kevin, I dont know what vehicle you have, but have you thought about drilling the roof ?

    I would never do that to our 'nice' car, but my current work hack, a clio van, and my previous Vitara have both been drilled in the roof centre, I have found that the swr is defintely lower on HF versus a typical hatch/boot lip mount, and dare I say an improved bandwidth as well.

    Plus it's up and out of the way of any de-tuning objects.

    73 Paul.

  3. Hello Jay,

    thanks for the comments, the Diamond mount looks pretty good, that is the kind of think I had in mind.
    Paul- I'm sure drilling the roof is the best way, I know several amateurs who have done it with good results. Although my Volvo is ten years old I am very reluctant to start drilling holes in it!!
    I have also soon a very substantial looking mount that attaches to the towing eye of the car which may be worth a look.

    Thanks for the comments guys.

    73 Kevin

  4. Good evening Kevin, I too for sometime had a similar mount like the one in your photo. The problems I found with it was the plastic dome cracked. Also up under the dome was a great spot for corrosion and thus SWR troubles. At that time the way I looked at it was like you it is a cheaply priced mount, I will replace it every couple of years. But that wore out fast. I have the same mount as Jay mentioned. They are very well built and great for HF duty antennas.
    Greetings from Canada