Glyph wrote:
It's for balanced lines only (ladder line, TV ribbon,
etc.) and not for any antennas designed for coax feed.
Well, yes, but it comes with directions on how to mod it to feed
coax, which takes all of 3 short pieces of wire, a chassis-mount BNC
female (or your favorite coax connex), and an SPDT switch.
It's really just a good implementation of the classic Z-match ATU
(which, IIRC, is the same as the ZM-2 everyone raves about) It uses
low-power, easily available components; I believe the variable caps
are actually designed for use as trimmers. It includes a 50-ohm
absorptive bridge to ensure that you don't fry the finals in case of
a huge impedance mismatch. Also, there is an SWR "indicator" in the
form of an LED fed with a diode pointed in the reverse direction, if
you follow. When it goes out, you're at 1:1. It is "rated" by
NorCal for 5 watts but they say on the website they think it should
be good to 10.
I don't tune for low SWR; I tune for max power out (& trust the
protection circuit in the rig), so I didn't put the LED in. I also
didn't use the case that comes with it (a "roll-your-own" out of PC
board & a clear plastic top). I put it in a ****4"x2"x1"**** Radio
Shack plastic box I got for $2. Talk about tiny!
2 transformers to wind (one big for impedance transformation & one
small for the LED. Very easy to use. Flip the impedance switch
(selects output winding on the big toroid) to High, then tune the
caps. If you're not satisfied, flip to Low impedance, and try
again. I matched an 8-1/2 foot whip on my truck on 40M (and I think
80 also). External SWR meter then showed 1:1. WOW!
$29 incl. US shipping; don't know if they ship overseas. I believe I
already posted the URL; if not, start at www.norcalqrp.org and
navigate.
