LF: Proposal for phased array (by Jake Brodsky)

[DL4YHF@aol.com]

Hi group, 

I found this interesting mail  on from Amrad's  LF mailing list (lf@amrad.org).

A bit 'hi-tech' but definitely not 'off topic' ..
   73 Wolf  DL4YHF.


<-------- beginning of original mail by Jake Brodsky --------->

Subject: [Lf] Greetings! I have a modest proposal...    


I haven't seen any activity in a couple weeks since I signed up, so I
figure I'll introduce myself and hopefully you guys won't laugh too
hard...

Some of you may remember me.  My call is AB3A.  

Tony McConnell (N3JLI) and I were intrigued by K0BRA's antenna
article.  We're building four of these things.  Bear with me for a
minute, I have an idea and I'm wondering if anyone has considered
anything of this sort.

I'm curious if any of you have discussed the possibility of large
scale synchronous reception on LF.  

The plan would be to use a set I and Q inputs from a quadrature
receiver, such as described by KK7B.  We would use two or more
receivers, spaced at least several wavelengths apart.  Suppose for a
minute that we manage to build an LO which we discipline to some
common reference, such as WWVB or GPS.

Knowing the precise position of each active antenna (using DGPS), one
might be able to construct a long base-line array if all the receivers
were tuned to the same frequency.  

My initial thought was to have a local station (which both receivers
could hear) transmit an in-band signal with some sort of time mark on
it so that we could integrate the recordings from each site.  

A carrier with a +/-90 degree phase shift each second would do nicely.
Using this time mark, one could take the recordings from each of the
two stations and sum them together making a long baseline phased
array.  

I was thinking that if the station we were trying to receive were
maybe 1 kHz or so away from our reference transmitter, we ought to be
able to record the I and Q channels. Then, using a packages such as
Cool-Edit Pro, we ought to be able to sum them together with the
appropriate phases and time delays.  

Has anyone considered this?  Is anyone interested in trying it?

73,

Jake Brodsky, mailto:frussle@erols.com
PP ASEL IA, Cessna Cardinal N30946, Based @ FME
Amateur Radio Station AB3A