ATX walkabout

counterpoise

**** THIS ANTENNA DOES NOT SEEM WORK BY SIMPLY ATTACHING A QUARTER WAVE PIECE OF WIRE AT THE LOWEST FREQUENCY AS A COUNTERPOISE TO THE RIG **** I found that the counterpoise length plays a very important part in tuning this antenna . I have heard of people putting these on magmounts and simply plugging the wander lead in and adjusting the whip to tune. I tried this using a magmount on the car with the only bands being tuned 2,6 and 10m.,after this the earth provided by the car was getting less effective for the lower bands and the swr started to rise quickly.I would expect different results depending on the type of car and whether any bonding had been done so there is going to be many people getting many results when using this on a car. When the antenna is used connected to the back of the rig or on a tripod or stand it seems the counterpoise length is just as important as the whip length. I tried two ways to tune this antenna both of which i will explain. The way i settled on seems a good comprimise against ease of tuning and keeping component numbers( counterpoise lengths ) down as this antenna seems to need a seperate counterpoise for each band and not just one long one.This would mean having 9 or 10 seperate counterpoise wires to take out /p. Below you can see my modified camera tripod which is used for all manner of portable and mobile whips.This was just under 10 pounds and the feet extend to just short of 4 foot.

tuning

This antenna is supposed to be designed for the ssb portions of the band. As i use mainly cw i wanted the best of both worlds if i could. I didn't have any instructions as this antenna wasn't new so i had a quick look through the net and decided to simply tune from scratch. Tuning for the cw portions of the band meant to work the ssb portions was a simple case of lowering the whip slightly as i went up the band.My first attempt at tuning was aborted half way through as it was apparent i was going to end up with a bunch of counterpoise wires to carry around. I also found each band change required me to take the old counterpoise off and use one specifically for the band i was on. Having the counterpoises all attached at the rig at once didn't seem to work as they interacted with each other even when fanned out. 6,10 M seemed ok but after that problems started so this way was aborted.

My final attempt before scrapping this antenna as too much trouble to tune with repeatable results seemed to work well.I started of at 6m with the whip fully extended.With the radio in ssb i tried each tap point for maximum noise. This is easy to hear and obveously was near the top of the coil and as you move down the bands so the taps move down also .I read on a few reviews that the counterpoises did not need to be a full quarter wave but for ease of a starting point this is what i used.I then checked swr and trimmed the counterpoise for lowest obtainable reading before adjusting the whip. I ended up at around 3 foot of wire then i dropped the whip till i got a flat swr on the radio. The next band (10m) was done the same way using a quarter wave counterpoise. The 6m counterpoise was left attached to the radio and the 10m counterpoise was attached using male/female connectors making a larger single counterpoise. I then started trimming again with the whip fully extended till i reached a low point on the swr meter at which point shortening the whip dropped the swr to a flat reading.This final 10m counterpoise covered 10,15 and 17m with no extra length needed and only the tapping points and whip length needing changing. If your having a go at this antenna it may be worth just checking to see if your last counterpoise will do for the next band down .40M was done the same way by adding a full quarter wave to the existing counterpoise and then trimming before adjusting the whip. This does waste a bit of wire but it was much less hassle especially with a helper to cut the counterpoise for you.The 40m counterpoise also did the ssb portion of 80m but needed an extra bit to ease the swr for the cw portion. ** i had to use a 6 inch piece of wire with a clip on stuck to the top of the whip to bring 15m in on the cw portion and i used this same extension for the cw portion of 80m). I think a slightly longer whip for this would make tuning much easier having to rely on counterpoise tuning less.

I now have the antenna tuned for most bands both ssb and cw with a single counterpoise wire adding or subtracting sections as needed. The tuning results were repeatable with minor adjustment to counterpoise placement on the ground but the whip section measurements seemed repeatable . RX using this antenna was quite suprising with many signals heard as far as Brazil from my back garden.I will have to see what the TX performs like next time im playing out. ** IT IS WORTH TAKING NOTE THAT THIS ANTENNA ISN'T SIMPLY A PLUG AND PLAY AS ADVERTISED BUT REQUIRES TUNING . MAYBE THEN IT WILL BE A PLUG AND PLAY. My first impression of this little antenna especially for rx is very good and would be a handy and very portable little addition to the 817. The performance of this antenna on 2m was quite suprising .With the antenna at ground level on my drive using a magmount simply as a heavy base and a run of coax to the radio it was only around 2db down on my roof mounted colinier .I would imagine the tx on 6m to be at the very least adequate and 10m should be more than workable,as for the lower bands time will tell and this little antenna may well come into its own as the sun spot cycle rises but it does need a little time spending on it initially to tune.