[Elecraft] KX1 transmit on 80 m without the 30/80 m board? Not!

[wayne burdick]

> Thanks for the info about the KX1's performance on 30m without the 30m 
> board!  I'll have to try that.  I have an uninstalled 30m kit, but am 
> waiting for the upcoming 80/30m combo kit to be available.

Chuck,

The KX1 will transmit on 30 m without the 30-m module because the 
signal doesn't go through the band-pass filter on transmit. Thanks to 
the DDS VFO, it need only go through the low-pass filter. On receive, 
signals will be highly attenuated on 30 meters without the module. But 
you'd still be able to hear very strong signals.

The new firmware also provides coverage of 80 meters. So, sooner or 
later someone is going to ask me whether they can transmit on 80-m 
without installing the KXB3080. Allow me to head this off at the pass: 
don't try it  ;)

Here's why. The KXB3080 kit actually includes *two* boards: a receive 
band-pass filter module that goes in the same place as the KXB30, and a 
low-pass filter module that replaces L1 and L2. The low-pass filter 
board includes a relay to select one of two values of inductance, and 
is absolutely necessary for 80-meter transmit. The original low-pass 
filter works well on 40/30/20 m, but presents a very poor impedance 
match on 80 m. If you did transmit through it, you'd have very high 
harmonic content, very low power output on 80 m, and might damage the 
PA transistor.

As in the 30-m case, the new firmware would allow you to listen on 80 m 
without installing a KXB3080. But signals will exhibit very high 
attenuation without the new band-pass filter arrangement, so you'd only 
hear extremely strong stations.

73,
Wayne
N6KR

---

http://www.elecraft.com