Mike, If you go to the trouble to meter signal strength ahead of the limiter, why would you make 1 uV full scale? You could achieve almost the same resolution by reading limiter current.
A 1 uV meter "peg" will result in users getting a pat on the back for signals which have little margin for fade. 73, Paul, AE4KR ----- Original Message ----- From: Mike Morris WA6ILQ To: [email protected] Sent: Thursday, June 19, 2008 3:24 PM Subject: Re: [Repeater-Builder] Re: software repeater controller At 12:59 PM 06/19/08, you wrote: >Mike Morris WA6ILQ wrote: > > Any of the controllers with a analog input can do that.... for > > example the Scom 7K can't as it doesn't ave an analog input. > > The Arcom 210 can. > >The S-Com 7330 also has A/D inputs, but the code to read them >isn't done yet. Yes, there are three analog inputs on the DB25 connector. > > The second way to read receiver quieting - but the DC > > voltage is backwards - it's at max with no signal and minimum > > with a full quieting signal. Some controllers can't handle that > > and you end up building up an outboard analog DC voltage > > inverter. > >Which would make NOW a good time to ask for inverted A/D logic as a >feature in the code, I assume. > >:-) > >Nate WY0X Unless there's a use for a backwards meter other than a quieting measurement, it probably isn't worth it. On the other hand if an inverter checkbox is simple to implement, then it makes sense. The 7330 code is complex enough that there is no point in delaying a release due to a feature that 90% of the users will never use. I was reminded in a private email that's there's a third way to implement a signal strength meter... sample the incoming signal after the first gain stage in the high IF of the receiver (i..e before the limiters), rectify it to DC with a voltage-doubler, and buffer the DC voltage with a variable gain op-amp... then diddle the gain so the A-D is at full scale with a 1 microvolt signal at the receiver. Despite the schematic diagram below being Micor-oriented the technique will work on any receiver at any IF frequency. See <http://www.repeater-builder.com/micor/micor-s-meter.html> No, it won't cause degradation of the received signal. Mike WA6ILQ
