[Elecraft] No XMIT on 6 meters

[Augie Hansen]

John wrote:
> There has been some chatter here lately about 6 meters not working. I 
> thought I would try and duplicate some of the problems. Well I 
> couldn't. However, I did find a problem with my  K3 #501 on 6 meters.
>
> I don't have power pwr output on 6M. Perhaps  I didn't check before, 
> or maybe I didn't run the 5 watt cal on 6M. So, I ran the cal, all 
> bands are fine, 5 watts, except 6M, where I get 1W and a ERR TXG msg. 
> I don't hear much background noise on receive, with an antenna 
> connected.  May be a BP filter issue? The Ops manual says to hit the 
> service manual, not encouraging. I really don't want to ship the rig 
> back to Aptos, it's already been sent back once. When it was returned 
> to me, I was told it met all spec's now.  BTW, I haven't had the cover 
> off the radio since it was returned.
>
> Any ideas out there?

When I attempted to do the power output calibration there was a problem 
on 6m. All other bands were OK.

My setup has an external tuner with a dummy load connected to the BYPASS 
output connector on the tuner. Checking the cabling reminded me that 
there is low-pass filter in line between the K3 and the tuner. It has a 
cut-off frequency of 42 MHz and is 80 dB  down at 50 MHz.

I had forgotten about the filter because it is bolted onto the back of 
my console - out of sight, out of mind. Hooking the dummy load directly 
to the K3 solved the problem. (I normally have 160-10m on ANT1 to the 
external tuner, with 6m on ANT2 to its own separate 4-position remote 
antenna switch, so the LP filter isn't a problem.)

Gus Hansen
KB0YH