[Elecraft] Mobile with the K2: whips, feedlines, etc.

[Wayne Burdick]

WA5PB wrote:

> You brought up something that I have been wondering about.  As to using the
> K2 mobile with its ATU for 10-20 coverage, what monoband antenna should give
> best reception and transmit, theoretically.  Since the ATU is tuning for
> received and transmit, would the ideal setup be something like a Hamstick
> designed for 20m since it has the longest electrical length?

Hi Bill,

I've never tried the 20 meter resonator on the bands above 20 meters,
but this should work, and certainly would work better on the lower bands
than the 10 meter resonator. Another approach would be to try to get a
whip that's longer than 8 feet on your vehicle (flexible at the top, and
avoid parking garages). Perhaps a few feet of the radiator could be
oriented horizontally.

The feedline you use might also be an issue. Typically you'll have 10-20
feet of coax between the radio and the base of the whip, and an
extremely poor SWR on most bands prior to tuning. You could minimize
feedline losses by:

(a) putting the whip closer to the front of the vehicle 
    and shortening the feedline;
(b) putting the KAT2 at the base of the whip and
    routing control and RF cables back to the K2;
(c) using balanced feedline between the KAT2 and the antenna and
    low-loss baluns at both ends. Simple baluns would be quite 
    efficient if optimized for one part of the HF spectrum, say 14-30 MHz.

(b) is a very common solution for high-efficiency mobile operation. 

I haven't seen much discussion of balanced feedline in mobile
installations. It would be interesting to A/B test configuration (c) vs.
straight coax on each of several bands with a given resonator.

73, 
Wayne
N6KR