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:
>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
>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?