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
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