[Elecraft] K3 VLF transverter?

[Edward R Cole]

I am working up a design for a 470-480 KHz transverter to have a 25w 
output.  One version would use the K3 in TEST mode on 10.470-10.480 
being mixed with a high stability 10-MHz OCXO.  But also looking at a 
version that would use 3.570-3.580 mixing with a 3.1 MHz xtal osc. 
for the usual ham radio that will not transmit outside of a ham 
band.  A built-in 20 dB 50w attenuator would lower HF transmitter 
levels.  This would lower 25w to .25w and an adjustable 0-20 dB 
attenuator would lower the level for correct input to the mixer.  A 
low-level sma connector would permit driving the adjustable atten 
directly with up to 100mw.

I already have a prototype mixer-buffer that outputs 10mw for 
transmit-only.  I chose 25w as antennas at 500-KHz exhibit very low 
efficiency (my 43x122 foot inverted-L radiates 4.15w ERP with 100w 
output from my 500-KHz transmitter).  A 25w output would result in 
about 1w ERP which is the highest permitted level expected for the 
new ham band.

I still have to chose a good preamp design and final amp design.  I 
will use pin-diode switching.

At this point its only on-paper idea, but I hope to be early in the 
market when the band is finally offered for ham use.

Ed - KL7UW
Sixty North Electronics
"Kits made by KL7UW"
www.kl7uw.com