On Mon, 11 Mar 2013 18:10:23 -0400, rickman wrote:

So, let's do the math and
guesswork.
http://vk1od.net/calc/FS2RPCalc.htm
I plugged in some guesses and recollections as to what the antenna
(Q=30) and amp (+20dB gain) were doing and got:
http://802.11junk.com/jeffl/crud/WWVH-rx-signal-estimate.jpg
-15.8dBm or about 36mv into 50 ohms. I amplified this about 20dB with
two or three U310 JFET's (I forgot what I did) to about 3V rms on the
scope. I didn't bother with the 50 ohm to scope input Z conversion.
Most of what I saw was noise, noise, and more noise. However, if I
was patient, I could see the data fade in an out. As I vaguely
recall, it was less than 1 division or about 0.1v change.

I'm not sure why you used 1900 meters for the distance. I also don't
get why you used 5 ohms for the receiver input impedance.

(Quick reply... still working on my expanding plumbing problem).

The 1900 meters is because I screwed up. It should be about 1900Km
from San Francisco to Denver. However, any distance greater than zero
will suffice for this calculation. The controlling numbers are the
100uV/m field strength, the -3dB antenna gain, and the receiver
bandwidth (5Hz). All of the other numbers can change without having
any effect on the recovered power. The 5 ohms rx input Z was because
the original antenna that I used, was a base loaded 100ft "whip"
antenna with a rather impedance. I couldn't decide if the field
strength to receive power form wanted the antenna impedance before the
50 ohm matching network, or if it treated the matching as part of the
antenna. I flipped a coin and chose 5 ohms. I guess for a loop,
100-200 ohms would be more appropriate. Again, the value makes no
difference in the calculations.

(Back to plumbing and fixing the 48" farm jack that my neighbor
borrowed and returned looking like a pretzel).




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558