[BC] WLS dead cxr prob. this a.m. at ~6:50

[Paul Christensen]

> That's the beauty of the GSC3000.  When the signal strength on the STL 
> goes below a certain threshold, a macro is triggered to dial the back-up 
> codec and then put it on the air automatically before the STL fades.

That's an indispensable technology to have in these instances as well as 
microwave paths affected by rain fades (e.g., 23 GHz switching to 950 MHz or 
telco backups).  I suppose the only thing the GSC3000 could not protect 
against is a total failure of the unit, and hence the loss of the BER-based 
switching control.  Mike, maybe you can clarify on that point.  This type of 
sampling and path switching may be best located external and independently 
to the very equipment it's sampling for that reason.

Prior to the availability of a software solution or even BER detection, we 
had to design the path-fade hysteresis algorithm by hardware.  In once 
instance, the only triggering source available was a DC voltage that 
appeared on a 23 GHz gunnplexer.  In a nutshell more or less, here's how the 
scheme worked...

- Sample the gunnplexer at the antenna through series R and lightning 
abatement;
- Route the sample down a spare conductor of the gunnplexer control cable;
- At the mod/demod equipment below, install a simple A/D converter based on 
a 10-segment LED bar.  The gunnplexer dynamic range was approx 0-10VDC and 
produced 0 to 10 LED bars, depending on signal;
- Control switching sample at LED segments 3 and 9 (corresponds to 
gunnplexer V of 3V and 9 V, respectively);
- When the path fades to 3 segments, circuit automatically switches to 950 
MHz or telco;
- When the event is nearly complete, circuit automatically switches back to 
main STL when 9 LED segments is achieved BUT must remain at 9 segments for a 
continuous time of 2 to 5 minutes (this protects against rapid, ragged-edge 
switching as the signal goes above and below a predetermined level).

So, to take this hardware mess and do it all with software based on what 
really counts (BER), is a real salvation today.

Paul


====================================
Paul Christensen, CPBE, CBNT
LAW OFFICE OF PAUL B. CHRISTENSEN, P.A.
3749 Southern Hills,  Jacksonville, Florida 32225
Office: (904) 379-7802   Facsimile: (904) 212-0050
pchristensen at ieee.org