I just finished my EMTECH ZM-2 and wanted to know what length of wire to use portable with this ATU.
My wish is to be able to use as many HF bands as possible.
Can you give me your feedback on the subject?
Jo - F5NFB
Hi. With a similar ATU I use a LW of 16.2 m with good results in SOTA activations. I use also an UN-UN 9:1 between LW and ATU, to match better the SWR. The antenna is erected in a “L” configuration (about 3-4m on vertical pole and the remaining stretched with some meters of cord. Hope to contact you soon. 73 de Claudio
Thank you for those informations. I hope being active during the first three weeks of july from South west of France.
73 - Jo
I have one ZM-2 tuner and have used it for some time to run my rigs portable.
It’s a nice tuner.
You could use almost any length of wire but. of course, some length will radiate more efficiently (avoid a too short length for a band).
If you’d like to use your antenna multiband, say for 40-30-20 meter bands, I would choose a length close to a quarter wave for the lowest band.
I sometimes use a 9 meter long wire installed inverted L plus 4 short ground radials of about 4 meter each and it tunes nicely on all bands 40-30-20-17-15-12 and 10 meter.
The tuning is sometimes very sharp, so you have to move first the two variable capacitors to get the maximum noise and then fine tune monitoring SWR very very slowly back and forth both wheels together at low power. The built in SWR Led is perfect for this fine tuning process.
I annotate the position of the wheels for each band and then the next time it’s easier.
I would not recommend to use a half wave length with this tuner as it is too critical.
You can find on the web recommended multiband wire random lengths that avoid those tricky resonant lengths.