On 5/2/2014 7:45 PM, Tony wrote:
All:
Need some advise on getting the best performance out of a multi-band
(80 through 20) wire antenna and tuner. My first option is the
in-shack auto-tuner feeding a doublet with a short run of coax and
remote balun. The alternative option was to go with a remote
auto-tuner mounted near the antenna feeding an 80 meter dipole with
ladder line. There would be an 80 foot run of coax from the rig to the
remote tuner. I can add dipoles to the remote setup if need be.
I have a 500 watt amplifier so I was considering the 500 watt Elecraft
in-shack auto-tuner. The MFJ remote tuner (600 watt version) is
reasnably priced, but unfortunately, didn't get good reviews.
If you run 500 watts to a 500 watt tuner, remember that tuners are
derated for lower impedances. The loss in good coax (LMR400 or
9913-7)even with high SWR is quite low. The loss goes up with frequency.
I would get a better tuner rated for at least a KW in the shack.
I use a tuner in the shack for half sloper on 160 and a fan dipole on 75
and center fed half wave sloper on 40.
The fan dipole takes two current/choke baluns
http://www.rogerhalstead.com/ham_files/AntennaFeed1.htm and another at
the tower. The imbalance of the sloping fan is substantial and take two
of these baluns to keep RF out of the shack.
I use an AT5K HP in the den and and an AT5K in the shop for legal limit
amps. I tune them using a VNA with a pair of A/B switches so I can't
accidentally feed power into the VNA. The input to the amp goes to the
exciter, or the VNA. Output goes to the tuner or dummy load.
73
Roger (K8RI)
Regarding doublets: I plan on using one for portable operation cut for
30 meters with an Elecraft KX3 QRP rig and internal tuner. Any tips on
the best ladder line and dipole lengths would be appreciated.
Thanks...
Tony
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