[Lowfer] ERP?

Fri, 31 Oct 2003 20:05:34 -0600 (CST)

Hi, Bill,

John just emailed me that he made an error in the gain -- he's re-working 
his numbers but the measured uV/m will likely be much *lower*.  But, FYI, 
the noise measurement he gave was at 0.076 Hz bandwidth.

Eric

On Fri, 31 Oct 2003, Bill Ashlock wrote:

> >I know this can be calculated other ways, but this interested me, so I'd
> >like to see how it can be done.  If other info is needed please let me
> >know, but the reading was 0.39uV/m at 68 miles.
> 
> Eric, this number is too low, maybe 10X. If the S/N is 7X that would place 
> the noise at .39/7 = .0557 uv/m which is way too low. In this area, on a 
> very quiet winter day, maybe at 12:00 noon, the AT noise out in the 
> countryside is about 0.3uv/m. I'll study the following "snip" when I find a 
> moment and see if I can figure out where he goes wrong.
> 
> Bill A
> 
> 
> >Here is how he did it:
> >
> >===============snip=================
> >I've got a number for you.  It turned out to be not too difficult.  What I
> >did was first find the voltage amplification from the whip to the receiver
> >input.  I hooked a length of wire (about 1 meter) onto a high impedance
> >active probe connected to an HP 312A selective voltmeter (they called them
> >wave analyzers back in the old days), and tuned it to 1450.  That wire gave
> >a signal strength of 14 mV for KGFF carrier.  Then I hooked up the active
> >antenna with 1 meter whip to the voltmeter.  That gave a 50 mV reading for
> >the same carrier, so the voltage gain for the active antenna is 50/14 or
> >3.57.  Looks like my homebrew antenna has a gain of about 11 dB.
> >
> >Next I had to go from the antenna input on the receiver to the signal
> >analyzer display.  I tuned in your signal (still there today).  It was
> >running about 1.4 mV with the noise at 200 uV (still a 7 S/N).  Then I
> >disconnected the antenna and put a signal generator on the receiver.
> >Without changing anything on the setup I adjusted the generator to give the
> >same response on the analyzer.  This turned out to be .1 uV gave a 1 mV
> >response on the analyzer.  There's about a factor of 1000 from the receiver
> >input to analyzer display.  The overall voltage gain is 3570.  For your
> >signal on the display of 1.4 mV the antenna input must be about .39
> >uV/meter.  Hope this all makes sense.
> >===============snip=================
> >
> >73
> >Eric
> >
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