Monday, May 4, 2009

Entering a New Phase

I've been out to the beach for a while and all I have is really unreliable dial-up out there so I've been incommunibloggo. Next time I go, I'm going to throw in F3K and a collapsible fiberglass 40M vertical and see what kind of trouble I can get into running "portable" from the edge of the Atlantic. I got up yesterday and went down to the water to watch the sun rise. As looked out at the horizon waiting for 6:41 to arrive, I noticed a band of dark opaque clouds maybe 100 miles off shore. As I looked I realized I was looking at probably the most common source of the static I hear every morning in the summer.

N4HY last week started a new SVN series around the F5K's diversity feature. I have a MFJ 1026 "Noise Canceller" and it works by mixing signals from 2 antennas and adjusting the phase and amplitude one against the other to get either a peak or a null.

The F5K allows for dual diversity reception when you have both receivers installed. Since the data that comes out of these are sync'd, Bob decided to do a 1026 in software, that is you can adjust the phase and amplitude of one receiver against the other. In addition you have the advantage of dual diversity and AGC polling with this kind of set up. I haven't had the chance to give this console a whirl yet but hopefully soon I will get the chance. It should be very interesting. I presume the tuning could be made to be automatic.

This morning I was listening to the V88 on 40 CW. He was weak in my summer time static (band noise in the -112dBm range) and it would have been very interesting to listen with this kind of set up and try and dig him out of the noise, either notching out some of the storm activity or peaking his signal. The storms would be exactly opposite from his desired direction, and I have 2 40M verticals that are about 100ft apart that would be ideal to give this kind of noise canceling a try. I don't know if the storms are "point source" enough to get a deep null on them. I never had that much luck with the 1026, but it was a big enough pain in the patootie to use with all the TR relays etc it had in the line to make it more trouble than it was worth. Also I never really saw deep nulls using the 1026, this implamentation should prove to be mucy more interesting

This is what I find so interesting about SDR. Dual diversity noise reduction done in software. Just plug in 2 antennas and have at it

Many people have been wondering what is the "difference" between the F5K and the F3K, and this is an example of the difference. There is probably nothing you couldn't hear with the F5K that you could't hear with the F3K when running a simple single antenna topology. Both receivers are superb. However when it comes to more exotic implamentations such as dual diversity with noise canceling, this is where the F5K simply runs away from the pack. The radio was designed with this kind of exotic implemantation in mind.