Annapolis thoughts (fwd)

Elton & Nancy Sanders
Wed, 17 Feb 1999 22:07:06 -0500

 Frank, I thing that to get good readings compairing our smaller antennas to
the big guys they will need to be set up well away from the large ones (
mile or more?)

 Bob, That is what I was trying to say in the other message. There may be a
problem disconnecting the tower lights at night so we may have to forgo the
800 ft ant.

At 02:23 PM 2/17/99 +0000, Frank Gentges wrote:
>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