Hello everyone.
In keeping with my inability to leave well enough alone, I have
modified a SoftRock for use on 80m. The input filter and transformer
have been changed to allow operation at 3.5Mhz. Essentially, I just
doubled the value of all the original parts, and recalculated the
windings for T1 to maintain the proper impedance matching. I
breadboarded the revised input filter on a piece of perfboard. I
used T37-2 cores to wind the inductors and transformer. Due to the
number of windings on L2 and T1, 30 guage wire was used. If molded
inductors are used for L1 and L2, the new filter could fit in the
original position on the SoftRock board.
A local oscillator crystal at 14.318Mhz yeilds a net center
frequency of about 3.579. This nicely covers the QRP CW frequency
range. A LO crystal of 15.75 Mhz allows tuning around the upper
portion of 80m, for SSB receiving.
I have posted three pictures in the N1RX photo folder showing the
changes. It seems to be working well here. Several SSB stations are
being heard at similar levels to my Elecraft K2. I'm waiting for
dark here to give the CW portion of the band a serious listen.
How much fun can YOU have with a $23.00 radio?
-Bruce, N1RX
