[TowerTalk] Fwd: Stacking question - another reality data point

[Jim Thomson]

Date: Fri, 12 Aug 2016 11:46:17 -0400
From: Hans Hammarquist <hanslg at aol.com>
To: towertalk at contesting.com
Subject: [TowerTalk] Fwd: Fwd: Stacking question - another reality
data point
Message-ID: <1567f6eb796-2629-fd8 at webprd-m103.mail.aol.com>
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I realize that the idea probably has been discussed before. I don't have the possibility to test it (yet) but was wondering if it would enhance the communication better than elevating a single beam at different heights. Switching with relays etc is faster than mechanically running a bean up and down. Two (3, 4, 5) beams will also give better signal than one (I hope).

Hans - N2JFS


 

 

-----Original Message-----
From: StellarCAT <rxdesign at ssvecnet.com>
To: Hans Hammarquist <hanslg at aol.com>; towertalk <towertalk at contesting.com>
Sent: Thu, Aug 11, 2016 2:07 pm
Subject: Re: [TowerTalk] Fwd: Stacking question - another reality data point

Seymour, W6CCP does this ... or at least did at one time. He had 2 I believe 
6 element 20's spaced horizontally on two different towers and played with 
phasing (line length) to get them to work together. He said it was a real 
barnstormer.

Gary
K9RX

-----Original Message----- 
From: Hans Hammarquist
Sent: Thursday, August 11, 2016 11:48 AM
To: towertalk at contesting.com
Subject: [TowerTalk] Fwd: Stacking question - another reality data point


I have had an idea for some time: When you feed all these stacked antennas 
in phase you will have optimum radiation to the horizon (or just above). My 
idea is to add switchable delay lines to the higher located antennas. (You 
could rather easily replace the damping networks in an attenuator with some 
coax do make this.) Thereby you will be able to get optimum angle for 
"higher up" propagation. You should select the steps to be small enough not 
to get "gaps".

###  With antennas stacked side by side, and FIXED in direction, NON rotatable, the
beamwidth can be steered or slewed  + / -  by a fair amount.  If you look at the SW HF
broadcast,  curtain arrays,  where they put the low freq portion on one side of the screen reflector,
and the high freq portion on the opposite side of the screen reflector,  The high freq portion
can be slewed  + /-  30 degrees.   The low freq portion can be slewed  + / -  15 degs.   Thats
coming right from the makers of such arrays.   They dont mention being able to slew in the
vertical plane.   The low freq portion typ consisted of ants, stacked 3 high..and 4-8 wide.  Typ
height of the 2 x supporting towers was  330 ft. Lowest freq used was the 49m band, or 5.9 – 6.3 mhz. 

##  In Bob heils book, which I cant find in my library, misplaced or lost some where,  Bob described
an interesting 40m array, where he stacked 2 x 40m dipoles, and both fed to a LC  network.  The take 
off angle could be adjusted up / down  by adjusting the phase between the antennas.   Dunno if bob used
coax..or open wire line in his phasing scheme. 

##  For typ BOP use on 2 x stacked yagis, a simple  electrical half  wave of coax is inserted into EITHER
leg.  If a half wave =  180 degs, then using a mess of relays, the extra line being inserted, could be switched,
using several different length lines, so phasing could be varied from 0-180 degs  in several increments, say
every 30 degs, so 6 x different coax lengths.  Im sure it could also be done via caps + coils.   Now whether
it buys you anything or not is another issue. 

## BOP results in a take off angle that is always higher than the lowest ant.   A buddy tried BOP on his 2 x 40m
yagis, with top yagi at 180 ft..and bottom yagi at 90 feet.  It was a total failure.   Only once did he find a single instance
where BOP actually worked...and that was a station on 40m, that was less than 500 miles away, during the daytime.  Loads 
of other stations that were 300-800 miles away  were louder when in BIP mode...go figure. 
At the time, the pair of 40m yagis was stuck in BIP mode, fed with a L network.  IE: individual yagis  could not be selected.
So all he had was BIP...or  BOP.   Since the array was stuck in BIP mode, the thought was to add  BOP capability, as a cheap
and easy way to obtain a higher take off angle.  

##  two each lengths of coax used to each yagi.  The extra electrical hale wave of coax that gets inserted into either leg
just consists of one piece of coax, and one spst relay.  The relay just shorts the center conductors of the BOP line, since the 
line is just a loop, with the ends brought close together inside the box.  Simple to implement. 
Thinking about it, a 40m yagi @ 90 ft is like a 20m yagi @ 45 ft.    And  45 ft on 20m is 
pretty low to begin with.  I cant see any case where a 20m yagi @ 45 ft would be too high..at least not on the west coast. 

Jim   VE7RF