MFJ HI-Q Loop 1788 Will not stay on frequency.

[Kenneth A. Christiansen]

I do a lot of camping and have used several portable antennas over the
years. Two weeks ago I bought a MFJ-1788 Super HI-Q Loop. I have been on two
camping trips with it and it does seem to get out and receive well. I used
my K2/100 and made 46 contacts for a total of almost 15 hours of operating
time. My problem is the antenna will not stay on frequency. It will tune on
any frequency easily but the only time it will stay on frequency is in the
middle of the night with no wind. I talked to MFJ and Tom recommended I
tighten the spring on the capacitor. I did and it improved  but again this
week end I saw it jump and drift. I had it tuned up on 14.058 and it dropped
down to 14.007. Another time it jumped from 14.058 to 14.076. I know others
are using this antenna so if you are using it do you have a problem with it
jumping or drifting around in the band. I have noticed this problem on every
band except during a cold, clear, calm night. If anyone has been able to fix
this problem or if my problem is not normal please let me know.

73 and thank you.
Ken
W0CA
[hidden email]
K2/100 sn 1031

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Stuart Rohre]

Hi Ken,
The problem is typically of high current small loops and tuned matching
circuits.  Also, sunlight can heat up the coil and the variable capacitor
and cause dimensions to shift and therefore the resonant frequency.

Tightening the spring is good.   Putting a shaft lock on the shaft "might"
help, but then you would forget to unlock and engage the motor leading to
major problem.

Keep the Loop cool and in the shade for less variation in tuning. Same for
the capacitor housing.

The wind might be an insurmountable problem unless you camp in lee of the
wind areas, at least for the antenna, like set up with rock cliff protecting
antenna from direct wind.
72,
Stuart
K5KVH



_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com