That sounds a lot like RF getting back into the controller in the ATU. Handling RF around a tuner is tricky. A whole lot depends upon the impedance presented by the antenna. The higher the impedance (which depends upon the electrical length of the wire) the more RF voltage and the more easily RF voltage can be capacitively coupled into the wrong circuits. It doesn't take a whole lot of RF to cause the controller to misbehave.
Suggest you take a close look at the RF filtering provided in the design first, to make sure none of it has been bypassed accidentally by a solder bridge or unsoldered connection. That would include the 6V line filter C4, RFC1 and C5. If either C4 or C5 isn't grounded, it would greatly reduce the effectiveness of the filter without interfering with the operation of the tuner otherwise. A solder bridge across RFC1 would have the same effect. The other critical item is C11 which bypasses one side of the relay coils to ground for RF. Unwanted RF feedback usually goes away when the power is reduced simply because lower power levels reduce the RF voltages present. Ron AC7AC -----Original Message----- Just a follow-up to my previous post... It does not always reset from TUN to CAL. I have seen it reset from TUN to other ATU settings like G03 or some other random fixed ATU state. When I use only the internal AA's, I don't see this problem happening. Only on external 12V from 10 NiMH's. But I don't want to have to give up those nice 3dB I get from the 12V and 4W vs. 2W! Thanks, Mike N9OHW _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
