[Elecraft] Upgrading K3 s/n 11xx to operate on the 472KHz

[Edward R Cole]

I used my K3 on 495-502 KHz as an experimental station.  I got 1mw 
output at the XVT Tx output jack running the TEST mode.

For amplifier, I bought a surplus Southern Avionics NDB (aircraft Non 
Directional Beacon) transmitter.  It is a xtal controlled oscillator 
amplified to 100w into 50-ohm load.  25w and 50w NDB's were also 
made.  Check surplus electronic sales for them.  I suspect the supply 
will be small and quickly disappear once discovered by new 630m hams.

Using with the K3, I removed the oscillator ckts and used a 0.1 mfd 
disc ceramic cap to couple from coax to the bandpass filter (single 
slug-tuned coil which feeds a 2N2222 pre-driver (about 10mw 
output).  I disconnected the internal antenna loading coil and 
switched the multi-tapped output coupling coil to 50-ohms.

You will need to build a base loading coil for using a very-short 
vertical antenna (if you have one for 160m, just substitute the loading coil).

630m is brand new ham radio country so prepared to design, modify, 
and build some of your equipment and antennas.  Or wait a year or so 
as small mfr's will likely show up or start up providing gear.

I should have approval by Oct. 15 to start on 472-479 KHz.  I plan to 
use CW/psk31/FT8 as ham modes and run an APRS beacon on 471-KHz as 
WD2XSH/45 under the old ARRL Experimental License.  Many of us are 
looking to run beacons around 471-KHz just outside the new 630m Ham 
Band (only legal if you hold an experimental license).

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
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