Annapolis thoughts (fwd)

Frank Gentges
Wed, 17 Feb 1999 14:23:41 +0000 (GMT)

Hi all,
I made it back in good order Tuesday night.  On my trip I found a Harbor 
Freight store and had a good look around.

I also thought about the use of Annapolis antennas.  One experiment would 
check signal to noise on the European LF broadcast stations using a 
variety of our own efield probes, loops and the Annapolis antennas as 
large aperture receiving antennas.  We could have several receivers 
connected to the various antennas measuring signal levels and noise 
levels on quiet adjacent channels.  

We can use this information to help determine if large aperture antennas can
help receive weak signals and also help to quantify system parameters needed
to establish a transatlantic circuit between amateur stations. 

1.  Rycom or other selective voltmeter meter readings could be used as 
well as variable step attenuators and more conventional receivers.  Two 
keys are the dB difference between the signal and the noise and the 
"equivalent" noise bandwidth of each receiver used to measure noise.

2.  We need quiet background so noise is non-sferic and non-powerline and 
reasonably strong broadcast signals so we are getting a true measure of 
the signal.  With occasional sferics we can just take a reading in 
between bursts.

3.  We need sky-wave signals to have confidence in the experiment truly 
demonstrating the value of receiving antenna aperture.  Aperture may not 
act the same on ground wave signals.

4.  At Annapolis we ought to have the most dramatic differences between 
small and large aperture receiving antennas we can get.  I am not sure 
the antenna needs to be tuned to acheive its best or optimum "aperture".  
I do have some sutiable fixed and variometer inductors to try out.  Any 

5.  For our site survey we need to determine how we can unground and 
connect to each antenna.  Coax may go underground and emerge in strange 
unexpected places so some buzzing out of connections may be needed.  We 
need to find where to connect to the massive ground planes buried under 
the ground for these antennas.   We need to see what the local noise 
environment is at survey time.  Hopefully we can get access to AC power 
but should check out wall outlets to see they are powered.

6.  We need to check and measure the noise bandwidth of our receivers so 
we can get all signal to noise measurements corrected to the same 
values.  A small oscillator and noise source that is calibrated and can 
be carried from receiver to receiver would be useful.

Thoughts and ideas?

Frank K0BRA