On Nov 23, 2007, at 3:31 PM, Don Wilhelm wrote:
Sarah,
Congratulations on getting your license and venturing to build your
K2.
Thanks!
The AGC Threshold high limit is directly proportional to the 8 volt
regulator actual output - if you follow the circuit you will
discover that that voltage is really the result of a 3 legged
resistive voltage divider. With a full 8 volts out of the
regulator, the typical highest voltage is about 3.85 to 3.9 volts
depending on the exact values of the 5% tolerance resistors. Since
your 8 volt regulator is near the lower edge of its tolerance range
(actually a bit lower than it should be), you can set R1 to its
full limit and things should work fine.
I would recommend that you replace the regulator since a 5%
tolerance would produce an output between 7.60 and 8.40 volts.
Thanks! I'll email [EMAIL PROTECTED] and see if they'd like to
send me another one next week; I don't have one of those laying around.
In the meantime, I'm proceeding with the RF board, since it sounds
like it will work ok for the time being.
73,
Don W3FPR
Thanks again!
Sarah AF6FH
Sarah K. wrote:
Hi,
I'm Sarah, AF6FH! I just got my license a couple weeks ago, and I'm
now assembling K2# 0622, which will be my first HF radio. I started
assembly on Wednesday night, and so far, everything's been going just
fine.
But...
I'm having a little issue with setting the AGC Threshold.
The instructions (pg. 48) say to set the RF GAIN control fully
clockwise, measure the voltage on pin 5 of U2 on the control board,
and adjust trimmer R1 for a reading of 3.80 volts.
I did my voltage measurements with my own (cheap) DMM, not the
internal voltmeter.
My concern is that, by adjusting R1, the highest I could get the
voltage to go was 3.59v, so for the moment, that's where it's set.
I measured the voltage on the LM29307-8, and it has 12.23V at the
input, but only 7.53V at the output. The 78M05 has 4.93V at its
output.
_______________________________________________
Elecraft mailing list
Post to: [email protected]
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
