[Elecraft] Re: mod to allow K2 to handle huge in-band signals--please try

[John, KI6WX]

Placing the diodes across the K2 antenna jack would decrease the dynamic
range of the K2.  Strong broadcast signals and other out of band signals
would intermodulate each other producing lots of non-wanted signals right in
the amateur bands.

Placing the diodes after the Xtal filter guarantees that only inband signals
would be strong enough to cause diode conduction.  The filter following the
IF amp removes some of the distortion caused by the diodes.

-John
 KI6WX


I had exactly the same reaction as Gary ... why would anyone transmit on the
same frequency in such close proximity to each other?  Now with Eric's
explanation, I understand the HFpackers' application and it makes sense.

However, I don't understand why the protection is applied to the IF amp
rather than the antenna jack.  Isn't it possible to fry stuff between the
antenna and the IF?

Back in May during our QRO (KW amps) multi-multi operation from 6Y, we were
very concerned about damaging our K2's by harmonics from other bands getting
into our RX Antenna jack (with RX antenna connected and in close proximity
to all the other antennas).  Eric and Wayne suggested a back-to-back diode
solution and even a series resistor to clamp the voltage and limit the
current at the jack itself.  This has always been a concern with commercial
rigs and it is common to blow up something in their front end.  Perhaps the
K2 front end is more robust?

73,
Ed - W0YK