Hello TowerTalkians,
I am getting closer to get some towers back up in the air and figured that I
should check the TowerTalk reflector archives. It took me almost two days to
browse through this wealth of wisdom and found quite a few very useful and
perhaps life saving hints, especially on crankup towers. Thank you TTs!
I can't resist to make few comments. On subject of Quad vs. Yagi and N6NB.
Wayne did some tests with portable towers, and conclusion was that quads are
not better than Yagis. Interesting thing is that he also described in HR
magazine "Quagi", which was basically Yagi antenna in which he replaced Yagi
reflector and Yagi driven elements with quad loops. He did the test, and it
worked better than Yagi alone. To me that indicates that those quad elements
had to be better than two Yagi elements. Looks like we have some contradiction
here. There are some questions how the comparisons on HF were made (Quad and
Yagi shouldn't be compared on the same height, I should re-read the articles,
I forgot what was "bad" about quads.)
Here are some experiences that I have found while experimenting with
design of my Razor Beams (Quad Yagi combination). I spent about 3 months
fiddling with the stuff on 2m scaled models on the antenna range in search for
the most gain per boom antenna (computers were not around yet). Some of my
findings were:
1. 3 el. Quad beat 4 el. Yagi or 5 el. KLM log Yagi. Better B/w and
pattern.
2. Having more than one parasitic Quad element behind and on the front
of
driven element (or log cell) does not contribute more gain than having Yagi
elements. In other words the second and rest of parasitic elements from the
driver should be Yagi elements. Appears that Quad elements by the virue of
lower Q are poor parasitic "cuplerers". They work better than Yagi element
next to the driven Quad el., but beyond that, Yagi elements work better.
Situation might be different with more phased elements, and they should
be
used if one insists on having more quad elements in the antenna.
3. On more than 5 elements, I found it beneficial to use log cell for
driven
element, improves F/B and gives smaller side lobes.
4. Adding second Yagi reflector gave me better pattern and more gain
than if
I added another director at the front at about 3x longer spacing.
5, If I changed the height of the antenna, and repositioned the
elements, I
would get better gain. Indication that antennas should be designed for their
destined height?
With this exercise my aim was develop maximum possible gain antenna for
given
boom length, in my case 62 feet (wider than my property). The configurations I
ended up with were:
1. 3 el. Quad to be used for 40m.
2. 5 el. Razor - Q refl., Q Dr., Q dir., Y dir, Y dir. - for 20 m
3. 7 el. Log Razor - Y refl., Q refl., 2 Quad log driven cell, Q dir., Y
dir., Y dir. - for 15m
4. 8 el. Log Razor, same as 3 with one more Y director at the front.
for 10 m
I also had some designs for 4, 6, 10 el., but did not try too hard to perfect
them.
They all were designed for best pattern (minimum side and back lobes), had 50
ohm feedpoint impedance and no matching crap and frying baluns.
I had them stacked on 110' Big Bertha (on 46x120' lot in Toronto), flat
ground. We have done numerous test and comparisons and this thing played, one
Italian station gave me report: "59 plus forty - bomba atomica". Having
Razors, it was like having telescope vs. field glasses. Main lobe had deep
nulls around 45 dB, when beaming Scandinavia, I could not hear 10 over 9
Italians, I had to put up another "lousy" 3 el. Yagi to fill in other
directions that might be coming through. Comparing this with 6 el. KLMs there
was clearly big difference.
Now I have 20m GP on the roof, 160m Inv Vee up in the tree and
beginning to
itch. I realized that Bertha is a wonderful 110' mast, and I am figuring the
base for it, I will lift it up 40 - 60' for some serious low band antennas and
new generation of Razor Batteries. I love the Bertha design, no guy wires,
self supporting, whole thing rotates, easy to work on antennas. I am surprised
that not more people use this thing, few were home brewed (W0SYK), "all" you
need is some pipe and a welder. Even XYL likes it (looks).
I am slowly working on getting my home page up and I will have some of
my
adventures presented there, including Flying Big Bertha, etc. Found number of
interesting things while "playing" with stacked Razors. It typically gave me
jump on competition by about one to two hours in band openings and closings.
Can't wait to get them up again.
On Beverages:
I see more often comments that 4 square beats Beverages on receive. When
operating from VE1ZZ's place, I found 95% of the time Beverages better than
4sq. His Eu beverage that is 800 ft and terminated with stainless stell hub
cap in the salt water hears even better than his WW2Y staggered beverage (has
better F/B, quieter). At the times it is "frustrating" to operate from there.
I can hear Eu coming through around 2 pm, have to wait about 5 hours before
they start answering. Not sure if his 4sq is "inferior", but seems to be
getting out and there is pattern when switched (NE, S, SW, NW). When the sun
is out, the beverages "die", signals go way down.
It is good to have that low inverted Vee (60') too. T32 and A45 could be heard
only on Inv Vee and not on any of the 10 beverages, nor 4sq. (Never enuf
ants!)
So don't throw your Quads and Inverted Vees away. BTW thank Mr. N6NB for
implementing this "RF Safety stuff" - what a bunch of unsubstantiated bull!
Thanks for giving big brother another weapon against ham radio. Add tower
restriction, RF polution from apliances and nasty neighbors, and we wonder why
ham radio is dying (but not contesting). (Yea, much easier to plug the
computer in, and "talk" to the world. Are we the only fools left enjoying the
mystery of radiowave propagation?)
Anyway, I am working on my first crankup on the trailer to be used for site
surveys, portable operation and antenna tests. I really appreciate the info on
crankups on TT and
I have learned lot and saved some potential problems that I wouldn't be aware
of if no TT.
Thanks a bunch and Merry Christmas to all antennists!
Yuri Blanarovich
K3BU, VE3BMV, VE1BY, VA1A, P40A
c/o Tesla RC - N2EE, NT1E
P.S. Congratulations to 6Y2A bunch - "the vertical contesters" - incredible
"result of the decade" - are the towers/beams out and verticals in?
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