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Saturday, 18 September 2010

Yaesu Atas 120 issues

When I bought my second Yaesu FT857D it was to use in the car. I bought the first one because I wanted a bit more power when portable than my Yaesu 817 allowed. I had used my Icom IC706 MKIIG and found it wanting when portable. The problem is the Icom draws too much current both on receive and transmission and when used from a low battery voltage it goes loopy and starts to self oscillate. The problem is in the DSP circuit but turning DSP off does not fix the issue. In the shack the Icom is superior but in a field or on a hilltop the FT857 wins hands down as my battery lasts longer and long after the Icom has died it is still going, way down to around 9.2 volts I have still managed contacts on HF.

I bought the second 857 because I wanted an easy to tune antenna for mobile HF operations and the Yaesu is designed to work with the Atas 120 antenna. There are better screwdriver antennas than the Atas but none work on a single button push like the ATAS does with the 857.

I had trouble finding somewhere to mount the antennas on my Land Rover Discovery and settled for a home made mounting bracket inserted into the runners for the roof rail. This worked fine for my VHF/UHF antennas but I initially could not tune the ATAS at all. The addition of an earthing strap almost sorted that but I could not tune the 40 metres band.

A chance clue was picked up on air when I heard someone say they had shortened their earth strap and got an antenna they could not tune to tune up. I prepared a new shorter earth strap and swapped it over, bingo! 40m now worked. As a result I had an amazing run of great contacts with SOTA stations usually while travelling at the national speed limit on motorways (Helen was driving), which collected me plenty of chaser points I previously would have missed. However when I came to try to work a SOTA station on 20m it no longer tuned there, but every other band still worked fine.

The whole thing is a little curious and but feel sure there is an optimum length for the earth strap that will allow all the bands to be tuned, so I have a few exeperiments to do when I get time. In the meantime maybe someone will read this and explain what might be going on.


  1. ALSO if you use a hatchback mount on your tailgate be sure to check the grub screws and tighten them regularly (and keep a couple of spare alan keys in the car for good measure ...!!If you hapen to own another make of vehicle make sure there is a secondary form of earth to the tailgate (LANDROVER do this as a matter of course !!! )and do not take for granted the earth return in the wiring loom ...and lastly I know you have heard it all before, watch the coax run (very easy to get a slight nick in the coax and water in and trouble abounds )

  2. Hi Steve,

    I've The ATAS 120 on top of the roof rail of my Grand Vitara with a Diamond antenna mount. I made an earth strap and connected it directly to the chassis of the car under the roof rail mount.
    With my FT-450 I can tune the ATAS without any problem on 40m to 10m. Works great!
    If you need any info or picture, just let me know.

    73, Elmar PD3EM

  3. Elmar, I would be interetsted in the length of your earthing strap as I believe it may be quite critical in my set up (if not in a lot of cases) and I have been reading up on the Diamond MAT50 magnetic earth mat, which may give a clue...

    >A single sheet will enable HF coverage from 7MHz and two sets of sheets for coverage from 3.5MHz with a suitable HF mobile antenna.
    Note that to operate on 50MHz the connecting cable has to be cut to less than 20cm and that 50MHz can not be operated when two sets of sheets are used.

    The fact that the cable of the MAT50 needs to be cut (for 6m) seems to say that there may be an issue with the length of the earth strap on my vehicle. My first earth strap was quite long, but I then put a short one in its place and gained 40m but lost 20m.

    Mads, LA1TPA tells me he "uses the “Counterpoise Magnet Mat” from wimo.com with my ATAS-100 and FT-857" and that the lead is 27cm long. 27cm is about twice the length of my present strap and about half the length of the first one I tried. So guess what I will try next?

    Regards Steve GW7AAV

  4. hi steve i have the same setup as you but put my atas on the rear door just above the hinge using a boot mount and works great on all bands no earth straps hope this helps