The RFP Signal Preconditioner / Preselector
This is the basic (and preliminary) layout of the RFP front panel. It is a 2U rack panel (3.5" x 19"). The control nomenclature should be sufficient for the experienced operator to intuitively understand, with little or
no explanation. In order to make it readable, I've split the graphic into its left and right halves
This device is basically a homogenized collection of everything I've learned about this stuff so far, and literally represents many hundred's of hours of experimentation,
testing, and practical use. Much of the original preselector work has been refined to the point where I can achieve about 24 dB of selectivity (4 S-Units) per 10 KHz
I've also satisfied (for me) most of the questions concerning the most practical ways of keeping certain modes of interference from getting from the transmission line to
the receiver's input (see noise filters). And, the Noise Blanker is an improved version of the "pre-biased" detector that I've experimented with on the PDC and DCNB
type circuits. This has now been optimized for broadband use - about 10 KHz to 32 MHz - and should be attractive to Lowfer beacon hunters, AM BCB DXers, Tropical
band DXers, SWL's, Utility Hunters, and Hams. Likewise, I've incorporated a series of fixed band filters to help manage front end overload and intermod.
The actual preselector circuit now incorporates a reciprocal "Notch" filter, which can independently be "slid" up along side the peaking filter to effectively double the
selectivity - or can be manually moved around to kill adjacent heterodynes, etc. The panel also features an antenna selector as-well-as a receiver selector, for instant
receiver switching and convenience. Instead of a Tee or Pi matching unit, I've elected to use a high-efficiency toroidal matching transformer, which is essentially
lossless across the bandwidth of the RFP.
Also added is a Diversity control for a second antenna which can be used either for "steering" the combined antenna patterns or for out-of-phase noise abatement.
There's a 100 KHz marker calibrator and a dedicated LF up-converter which will cover 10 to 300 KHz, beginning at 10 MHz on the receiver's dial. A built in preamplifier
offers about 18 dB of low noise gain ... as needed.
While all of these circuits are working quite well, i still feel the need to refine some of the specs and characteristics. Once that's done, I'll make them available here.
Please bear with me as the R&D and assembly proceeds over the next few months -- and check back often for updates.