Rockmite VXO Mod update


Date: Sat Sep 28 2002 - 13:53:08 CDT

Hi All,

I have just begun work on "Modding" a Rock-Mite 40. Results thus far are
very encouraging.

There are still a couple of things to work out, but the tuning range on this
RM40, with the components I detailed in the article posted on Rod N0RC's
website, is from 7029 to 7042 KHz.

I still need to do some work on the TX/RX offset, as it is made more
complicated by the need to switch inductances in and out in order to cover
the whole range indicated. However, progress is being made, and I hope to
have that worked out soon.

I have made some changes in how I implemented the VXO Mod and will be
updating the article in order to make that info available. I decided to use
the existing 7.5 Volt Zener diode to supply regulated tuning voltage, and
ended up leaving the oscillator supplied with 12 Volts, unregulated, as the
amount of drive to the PA was reduced too much when the oscillator was
working from 7.5 Volts.

Because of the difference in drive levels available from the oscillator,
reduced as it tunes lower in frequency, the TX power output at present ranges
from just over a Half Watt at 7029 to over One Watt at 7042. This is with a
2N3053 in the PA and R18 shorted.

A change in the values of the feedback capacitors in the oscillator might
help even out the drive level, or perhaps a change in the driver circuit will
bring the drive up enough across the tuning range that the output will be
closer to a watt at the low end as well.

11:45 AM - Just got off the air from a QSO with Kerry, N6WU, on 7032 KHz, who
gave the little rig's signal quality a very good report. Fun stuff!

Now back to the bench, hi hi.

More later.

Wayne NB6M

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