|On the previous page, you can see how I addressed the improvement of two of the more apparent areas of the received signal stream; the input, which is fed from a preconditioned
RF signal (RFP-1), and the output, which is tailored with recovered audio management (APC-1). That should cover everything pretty well -- the input and the output. Right? ... Nope,
All this equipment runs on electricity. We assume, or presume, or have faith, or (at least) hope, that the power fed to our equipment is just plain old sinusoidal-wave current flow from
a constant voltage source. Okay, generally it is. But more often than you may like there is some free electricity that comes along with the deal. Sometimes free stuff might be an
undesirable gift. This extra electricity comes to us as transient spikes, high-current surges, triangular, square and saw tooth-shaped buzzes, hums, whines, burps, and whistles. In
terms of overall power, there ain't much of that bad stuff. Actually, it's usually just a very tiny, small percentage of the overall power consumption. But guess where it resides. Yup,
right on top of the power company's sine wave ... just like a good old AM signal. Nice, huh? Radios vary greatly in power supply design, but even some of the best kilobuck radios
can fall victim to power line noise intrusion.
Enter the PCU-1 and PLC-1. These are the "Power Control Unit" and "Power Line Conditioner" respectively. Below is a sneak preview of the nine-device switched controller. The
actual "conditioner" (blue meters) incorporates several types of transient, pulse, and impulse clamps, along with noise or "hash" filters, and a magnetic/induction sine wave
smoother. Also incorporated is a 12 Volt DC to 120 Volt AC inverter with all the attendant filters and clamps required for that RFI-frightful mode of conversion. But it's all worth it. The
result is nice, steady, clean, pure sine wave AC power. And it tastes so delicious ... to the receivers, that is.
The AC power conditioning and 12 Volt inverter unit will supply about 1,800 Watts of continuous line power, with peak-demands of 2,400 Watts. That should more-than suffice for a
So that was the third, and final area of all possible peripheral receiver connections; RF input, AF output, and AC power supply. That should about do
it. Well, I was content playing with all my new creations, and taking a well-deserved break from all the schematic/circuit design, prototype PC board
building and testing, chassis fabrication, mechanical and electronic assembly, front panel decal printing, and final validation testing. It was a long road
in a life that includes a full-time day job, a home with its usual maintenance requirements, four demanding pets, a similarly demanding family, and a
radio club that constantly needs volunteers. Yup, that was me...fat, dumb, and happy...just tooling around the bands with all my new toys, and
appreciating all the new-found sensitivity, selectivity, low noise figures, and beautiful recovered audio.
Then, one night, I was surfing the I-net when I came across a fancy AM demodulator (detector) circuit that was designed by a guy I used to work with;
Rob, K2CU. That kind of piqued my interest, so I continued to surf around. Humm, what's this? A linear detector design by no other that Dr. Ulrich
Rohde. But wait, here's one by Ron, KK4PK, but in a Synchronous format. Ha! another one that boasted High-Dynamics by Frank KA1GFZ. I thought,
what the heck, maybe i can come up with a nifty envelope detector using a high-speed diode circuit.
Okay, I'm hooked. I had to get all five of them working and evaluated against the Watkins-Johnson AM detector. As good a radio that the W-J is, the
results were amazing...actually, quite stunning. I'm not ready to give a full report here, yet, but suffice it to say that it looks like simple diode AM
demodulation is the weak (very weak) link in the way a receiver recovers broadcast audio.
I will be posting a definitive test report soon, but for now, just take a look at how this project is shaping up. Hopefully, before the snow flies in
Southern, Connecticut, I'll have this monster up and running ... along with some test results that we can get our teeth into.
W-J has an excellent Demodulator, the DMS-105A. You can see that here.
Be sure to see the other MilSpec and Listening Post technology by browsing the SWL site map here.