On the subject of interaction, brings back memories:
On my 15m installation back in Toronto, I had two stacked Razors (log
Quad/Yagi on 60 ft booms) at 105 and 45 feet on rotating Bertha. I also
wanted to cover the "other" directions that propagation was open to, I
put 3 el. Yagi between the Razors on a separate rotator, mounted off the
back end of Yagi boom.
It worked well, I was either feeding both systems or switching to either
one to maximize signal or to minimize the interference.
At my location I was plagued by the power line noise from huge HV
5 power line corridor, 90% of the time S9 noise. I was about 900 feet
South of the wires. They also seem to enhance my signals from NE to
SE/S. While VE3FFA, being on the other side of the lines had similar
enhancement to NW, W, SW. At a times either one we could work stuff that
other one could not hear, we were about 2 miles apart, flat terrain,
just separated by Scarborough "HV highway".
One day I was measuring pattern on stacks with WA2MNM, pointed at his
QTH, I was bringing 3 el. to be "nice" in line with stacks, pointing
back. He said you came up good one S unit when aligned towards back, not
connected. Hmmm! It came handy when band was dying, making sure
"useless" 3 el was pointing back, I was able to "extend" the
propagation. (Model that one :-)
By accident I found that while receiving on Razors and turning 3 el.
around I was able to minimize the power line noise while 3 el was not
connected or phased with the stack.
Further I found that this effect was frequency sensitive and I was able
to find the spot on the band where I was able to suppress the noise down
to 0, I would park on that frequency and was able to run.
By fine tuning the positioning of Razors, 3 el. and frequency selection
it was a life saver.
It appears that not connected 3 el. was able to interact with stack and
work as a directional notch.
Pictures of the antenna are at http://www.k3bu.us/razor_beams.htm
instead of pictured TH6, I had 3 el. Yagi on separate rotator.
That was one tower, as Frank points out more towers require careful
consideration, but there could be some positive effects too.
Yuri, VE3BMV, K3BU.us
www.MVmanor.com
DXcontestvention and Ham weddings venue
On Mon, Aug 25, 2014 at 11:27 AM, donovanf@starpower.net wrote:
> Hello Timon,
Pete's email reminds me of K3NA's excellent eight part series in NCJ
from 2003-2005 describing Yagi performance degradations caused by
multiple Yagis installed on the same tower and on multiple towers.
While many contesters are aware of performance degradations caused by
close spaced Yagis on the same tower, we often forget about
performance degradations caused by Yagis on nearby towers.
Among other things, Eric made us aware of performance degradations
when: - a Yagi points through a Yagi for the same band on a nearby
tower , - a 10 meter Yagi points through 15 meter Yagi on a nearby
tower, - a 15 meter Yagi points through a full sized 40 meter Yagi on
a nearby tower.
Eric showed that performance degradations among Yagis installed on
nearby towers is significant when the towers are spaced less than
about five wavelengths apart (350 feet at 14 MHz). According to Eric's
performance modelling, degradation doesn't become insignificant until
tower spacings are greater than about ten wavelengths (700 feet at 14
MHz).
Multi-band Yagis are much worse, because they cause performance
degradations to Yagis on nearby towers on many bands. I usually
discourage hams from installing them unless thay can be installed far
away from higher performance monoband Yagis.
Some of you have heard me say that a contester can never have too many
antennas... unless (and this is important) they are too close to each
other.
Timon's towers are only one wavelength apart on 40 meters, two
wavelengths apart at 14 MHz and four wavelengths apart on 10 meters.
His Yagis on multiple towers will be much more closely spaced
(especially on 40 and 20 meters) than 40 meters because of their boom
lengths.
My recommendation for his four towers is that he analyze all of the
interactions when each Yagi points through another Yagi on another
tower. His plan to install multi-band Yagis on three of his towers
will surely cause significant degradation of the performance of his
high performance stacked monoband Yagis and he should seriously
reconsider that plan.
The most serious degradation in his proposed antenna system will be
caused by his two 40 meter Yagis that will be spaced much less than
one wavelength apart when boom lengths are taken into consideration. A
better plan is to stack his 40 meter Yagis on the same tower with each
Yagi independently rotatable.
My recommendation is that Timon start with each each of his four
towers dedicated to a single band, this produces the least degradation
among Yagis on multiple towers. After this initial installation is
completed, additional antennas can be added and the resulting
performance degradations can then be evaluated.
73 Frank W3LPL
----- Original Message -----
From: "Pete Smith N4ZR" To: cq-contest@contesting.com Sent: Monday,
August 25, 2014 11:47:27 AM Subject: Re: [CQ-Contest] antenna setup
question
K3NA did some sophisticated studies a decade or so agoof the K4JA
multi-tower station, for NCJ. You might be able to find those, Timon,
or get in touch with him.
73, Pete N4ZR Check out the Reverse Beacon Network at
http://reversebeacon.net, blog at reversebeacon.blogspot.com. For
spots, please go to your favorite ARC V6 or VE7CC DX cluster node.
On 8/24/2014 9:40 PM, David Siddall wrote:
Hi Timon,
With multiple towers available, I would keep my 40 meter antennas off
any tower with 15 meter antennas -- whether monobander 15's or
tribanders. Too often 40's disrupt the pattern of the 15's. It seems
to be very antenna- and spacing- specific, and I am not 100%
confidant in modeling for this issue.
GL es 73,
Dave K3ZJ
On Sun, Aug 24, 2014 at 5:25 PM, Timon Kruijer
wrote:
Hello fellow contesters.
I have an antenna setup question.
This year (and the next) I am building a new HF station. Next to the
house I will have four rotary towers standing in a square which are
40 meters apart. The towers are rotatable and are 25m (83 feet) high
from the ground. Every tower will also have a rotor in the top with
a 2 meter mast so in total 27 meters (90 feet). The towers have
rings on 24 meters and on 11 meters (not fixed yet) as they are
still lying on the ground.
To rotate and calculate the directions for each tower and the top
antenna I use Microham Station Master de Luxe.
My goal is to have a competitive contest station for SO2R, Multi
Singe and Multi-2 use.
What would be a good suggestion for the antennas in the four towers?
The terrain is flat.
The antennas I have available at the moment are:
- 2 el Force 12 40 meters
- 4 el Steppir 10-15-20 meters
- Optibeam 10 15 20 meters
- Force 12 c31xr 10 15 20 meters
My idea so far is to use these 4 antennas for multipliers etc.
I would like to have additional 2 antenna stacks for 20, 15, and 10
meters (which I have to build).
A possible setup could be:
Rotatable Tower 1
top rotatable, Steppir
bolted at the tower 20 meter yagi
bolted at the tower 20 meter yagi
Rotatable Tower 2
top rotatable, c31xr
bolted at the tower 15 meter yagi
bolted at the tower 15 meter yagi
Rotatable Tower 3
top rotatable, 2el 40m
bolted at the tower 10 meter yagi
bolted at the tower 10 meter yagi
Rotatable Tower 4
top rotatable, 3 el 40m
bolted at the tower optibeam 10 15 20M
bolted at the tower 3 el 40m
Or setup 1 multiplier tower and use the others for 10 to 40 meters.
Which band to have a double set antennas when this would be a
solution?
For 40 and 80 meters I will have additional 4 squares behind these
towers. Also possible would be to have wire 4 squares hanging on
ropes between the towers (between the top rings on 24 meters).
For 160 meters the towers can be a 4 square by itself (they are
isolated). Also the ropes could be again for a 160 meter antenna.
Suggestions and comments are very welcome. Please your ideas.
'73 Timon
PA1T
Home page www.pa1t.com
Tel 31 (0)598416308
Cell phone 31 (0)657545506
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