Broadcast Band Monitor
AM/FM Commercial Radio Bands
This radio is the basic architecture of the
Here it's under beta test sitting on the Sangean
HDT-1X modified console.
The lower cabinet houses the WWV and NOAA
All of these receivers have a place in the
spouse-approved area of the family room.
I selected the UCR-900 for its performance. It
began life, years ago, as an under counter
kitchen radio. I'd sit at the dinette counter, for
long periods, just surfing the AM broadcast band.
This was especially entertaining after dinner, and
when the nighttime grayline had passed. I was
always impressed at the performance of this little
radio, but always thought that if it was that good
as a kitchen appliance, that maybe it could be
more with the right modifications.
I bought my wife a new Sony with a CD player to
occupy the same space and slinked off to the
basement workshop with the Sangean.
I milled out a 2RU (3.5 inch) rack panel for the
display and totally gutted the remainder of the
I added a 3-band, high-Q preselector that covers
400 KHz through 2 MHz.
Then a 18 dB variable gain preamp and switched
attenuator were added.
Since there was no S-meter, I tapped the AGC
circuit and added a mini volt meter. I made the
meter sense circuit switchable so it could indicate
either S-Units or RF microvolts. The two scales
are switchable and were calibrated on the bench
for 50 uV @ 50 Ohms for a reading of S9.
Other controls include the switch selection of
internal or external speaker or just headphones.
Also an antenna shunt switch was added to
ground both the AM and FM inputs, for safety.
Since AM signals vary greatly depending on
distance to the station and station power, I wired
the RF Attenuator directly after the Preselector
and before the input to the radio's front end. The
Preamp and its gain control can be bypassed,
but the attenuator is always in-circuit.
Eventually, I'll get some photos of the internal
wiring and assembly.
Thanks for looking.