Topband
[Top] [All Lists]

Topband: Vertical array

To: <topband@contesting.com>
Subject: Topband: Vertical array
From: "Lee K7TJR" <k7tjr@msn.com>
Date: Thu, 13 Dec 2007 14:30:08 -0800
List-post: <mailto:topband@contesting.com>
w5uc>  Looking at the effect of varying the 
phase by a small amount my simple mind said: I don't know the angle 
at which local interference arrives. The only thing I can guestimate 
is the arrival angle of stateside & DX signals, therefore I can 
possibly reduce the overall amount of signal in the receiver front 
end  by increasing the high angle F/B.<

   I think we all would like to know the arrival angles of signals however it 
will likely be a long time before we do. Enter the often heard comment that one 
can never have enough antennas. What I see here on Beverages and vertical 
arrays is that signals within about 500 miles show 'Generally' no directivity 
on any of my arrays and a slight bit further out on the Beverages. My vertical 
arrays do not show limited directivity in their plots until about 80 degrees 
elevation if we can believe the computers. Beverages slightly lower with many 
lobes. I also do see the early morning high angle signals from JA/UA0 at this 
Qth. I am working on a high angle array to the West. If it is local man made 
noise you are talking about you might benefit from a noise canceller.
    Personal observation is that if we could educate the lids to stop 
transmitting right on top of the DX a lot of these interfering signals would go 
away. Also using the maximum attenuation you can get away with in your radio 
may increase its signal handling ability. Roofing filters rule! they really 
help on handling loud signals amongst small ones. I have added an animated 
graphic to my web page that shows what happens with varying the phase in steps 
on a 2 element array.  "http://www.k7tjr.com/rx1comparison.htm"; . As per my 
previous comment some of the parameters are rather insensitive to a few degrees 
of shift. 
    Tod  K0TO recently mentioned using the DXE variable phase unit with active 
two verticals. I hope he continues to post his results here so we can all see. 
    Three active or passive  antennas in a triangular array make a really nice 
array as W4TV mentions. I have the data but it will be a bit before I can put 
it on the comparison page. Good RDF, F/B,  and 6 directions.
     I have steered away from loop type antennas as in my models I see wildly 
varying front to back with elevation angle. In my models at very low elevation 
angle the pattern always widens out and the RDF suffers. I have programmed 
loops as high as 80 feet elevation and see no improvement. If you optimize the 
front to back by setting the phase delay for a low angle, there is very little 
front to back at a high angle. This makes a variable phase network or cable 
length switching necessary with loops for all different conditions. This is 
much less prevalent in vertical arrays. Verticals show a much cleaner low angle 
response in my models than any others I have modeled. 
    For general DXing I suppose having a variable phase is OK but in contesting 
is seems to me out of the question. 

  Lee K7TJR Oregon
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband

<Prev in Thread] Current Thread [Next in Thread>