10 MHz Upconverter
For Clean and Sensitive Reception of the LF and VLF Bands
...with an added bonus:
Pick one of your radios that has a particularly good front end and feed its IF Output (like 455
KHz) through this device to be received on a second radio that has a particularly good IF filter
Tune with the first radio.
Set the second radio to 10.455 MHz.
Use the first radio as a tuner.
Use the second radio as an independent IF receiver.
You now have the best of both receivers.
Enlarged view of left and right sides.
Although many general coverage receivers have VFO sections that cover
the LF and even VLF bands, many of the manufacturers will caution you
that the advertised specs do not apply below 1.5 MHz, or below 500 KHz, or
some such frequency.
Typical spec sheet quote:
"General coverage from 100 KHz to 32 MHz (specifications below 500
KHz not guaranteed."
Also, a good general rule is that many of these same radios have the best
performance specs somewhere in the mid-bands of their coverage rating.
10 MHz fits that general assumption nicely.
Of course, you may just connect an antenna to the input and use it
normally as a 10 MHz upconverter - plain and simple.
This is the basic operational connection.
I have done extensive testing, both on the bench and in
actual receiving conditions with this setup, for VLF and
LF monitoring. This arrangement proves to be very
synergistic; the combination of the two radios provides
better reception and either one separately.
I have spent many hours comparing this combination
against the individual radios while surfing NDBs and
various Government facilities; Cutler, WWVB, etc. The
results must be heard to be appreciated, and speak for
themselves ... amazing.
But it isn't limited to frequencies below the Broadcast
Band. In fact, the pastime of BCB DXing has become a
more exciting and rewarding adventure.
Here is the basic device wiring. I have found that Chuck's
(WB9KZY) basic circuit, using the SA602 mixer chip is very
clean and bug-free. I have no connection to Chuck or his
products, but his kits are nicely executed and complete with
quality PC boards and components (http://wb9kzy.com)
For the preamp, I am using the video amp LT1252. If you don't
want to "dead bug" your own circuit, there's a kit available from
AADE (Almost All Digital Electronics), which includes a nice PC
board, all parts and an on-board 8 volt regulator.
I have evaluated using MMIC (MAR6) preamps (MiniCircuits)
and discrete Darlington arrangements, but it seems to be a
"why bother" situation, since the 1252 is nice and quiet and has
NOTE that the final assembly eliminates the 3 rotary switches
for Antenna, IF Output and receiver selection. The UCM-1 will
be in a "connect and forget" application, so it won't be
necessary to accomplish all that switching ... although the
added flexibility could be really handy in some cases.
|Low Pass, Band Pass, High Pass Filters
Typical response curves of the three filter sections.
In most cases the LF filter is necessary for LF/VLF upconversion due to high-power
More to come.
Thanks for looking.
The preamp with about
20 dB of gain.