At 07:18 PM 06/19/08, you wrote:
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.
My experience has been that the Micor 1st limiter current tops out too
low, and the second limiter never really gets to zero and tops out even
faster. So there's no real zero-to-max limiter test point.
A 1 uV meter "peg" will result in users getting a pat on the back for signals
which have little margin for fade.
In the situation where the 1uv max was used it prevented the local
idiots from having games seeing how high a number the controller
would announce. I already was hearing "capture contests" and
didn't need the hassle. We had one user that had a 500w base
feeding twin 16 element beams on an el-az twin rotator mount
pointed at the repeater. Nobody but the control ops could talk
over him (and they could only because they were on another
band). He once bragged that he had melted a piece of RG58
with it.
A 1uv max made sense as it was a handy number to max out at,
we wanted to make the point about "communications quality"
versus "autopatch quality".
Your situation could be different, and you may want to adjust the
DC gain to max out at 2, 3 or even 5uv.
73,
Paul, AE4KR
----- Original Message -----
From: <mailto:[EMAIL PROTECTED]>Mike Morris WA6ILQ
To: <mailto:[email protected]>[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>http://www.repeater-builder.com/micor/micor-s-meter.html>
No, it won't cause degradation of the received signal.
Mike WA6ILQ
