Compact Quad
Bill Macpherson
I am thinking of building a two element 40 mtr quad.
I have a space limitation though and am wondering if I can reduce the height
to about 20 feet by wrapping the full wave loops twice around the frame,
instead of just once. ie two turns @ 19 ft per side for the reflector and
two turns of the driven element @ 17 - 18 ft per side for the totals of
152ft for reflector and 140 ft for driven element. How would this affect
the F/B and Gain figures?
--
Bill VE3NJW Advanced Amateur
Packet Address : VE3NJW@VE3KYT.#EON.ON.CAN
Freenet Address: aj...@Freenet.Carleton.ca
Dr Joseph M Zawodny
>
>I am thinking of building a two element 40 mtr quad.
>I have a space limitation though and am wondering if I can reduce the height
>to about 20 feet by wrapping the full wave loops twice around the frame,
>instead of just once. ie two turns @ 19 ft per side for the reflector and
>two turns of the driven element @ 17 - 18 ft per side for the totals of
>152ft for reflector and 140 ft for driven element. How would this affect
>the F/B and Gain figures?
>
A quick drawing showing the current and voltage maximuma and minimuma
tell me that if you are going to reduce the size by having multiple turn loops
then you will have to go with an odd number of turns. With an even number of
turns it looks to me as though the currents and volatges basically cancel and
all you are left with is a magnetic loop. This is not what you are looking for
in your quad. There will be other things that you may want to consider before
you reduce the size of your quad. First off the "capture area" will be reduced
and secondly you will have increased inductive reactance to deal with.
--
Joseph M. Zawodny (KO4LW) NASA Langley Research Center
Internet: zaw...@arbd0.larc.nasa.gov MS-475, Hampton VA, 23681-0001
Packet: ko...@n4hog.va.usa
Paul Zander
of wire around the loop, and put loading coils in the middle of each side.
(The loop was in the so-called diamond orientation). Feeding at the bottom
corner gave an impedance in the order of 12 ohms. I used a 4:1 balun to
match to 50 ohms. The bandwidth with reasonable SWR was 100 kHz. The low
impedance and narrow bandwidth are consistent with an efficient compact
antenna.
I was disappointed that the antenna did not have much directivity. Further
experimentation showed that the radiation pattern was mostly straight-up!
That is what happens with a horizontally polarized antenna close to the
ground. Once I understood this, my results were just like the ARRL
Antenna Book.
73, and happy experimenting,
Paul AA6PZ
Arlan R Levitan
bad performer) with a 2m/220/440 tribander. After some investigation,
I've narrowed things down to either the Diamond X3200A or Comet CX-333,
which seem to be quite similar in size (about 10ft) and claimed gain.
Any advice on which of the two is preferferable? At $165, the Comet is
about $25 cheaper than the Diamond. Am willing to listen to suggestions
for alternatives. Would like to be able to reliably hit repeaters that
are 50-60 miles away. 25 miles or so seems to be my current limit.
The discone is mounted about 35 feet above groundright now, and that's
where I plan to place the vertical. Are my expectations reasonable?
My rig is a Kenwood TM-742A with the 220 module installed (no, I haven't
experienced the dreaded S-meter squelch lockup problem). Feed line is
45 feet of 9913.
Would also appreciate advice about triplexers. Any real difference between
brands? Looking at both the Comet 324B and Diamond 324 right now.
73s, and thanks in advance.
Arlan
KB8QLV
Cecil Moore
: Are my expectations reasonable?
: Arlan KB8QLV
Arlan, The ARRL Antenna Handbook says that a discone has a similar radiation
pattern to a 1/4 wavelength vertical ground plane antenna. Therefore the
gains advertised by Diamond and Comet are referenced closely to what you
experienced with the discone. The gain of the Diamond and Comet comes from
focusing more energy in the horizontal and less in the vertical. Each 3db
of additional gain doubles your effective power so you should radiate a
signal four times more powerful in the horizontal with the new antenna.
(These antennas will not work as well as your discone for satellite
communications.) If you can hit those distant repeaters with four times the
power on your discone, then you should be able to hit them with your new
Comet or Diamond. 9913 is good. RG-58 is bad for vhf/uhf except for very
short runs. I have a MAX2x4 and the improvement over a 1/4 wavelength
ground plane antenna is almost unbelievable. I hit repeaters 100 miles away.
73, Cecil, kg...@indirect.com
howard n lester
Cecil Moore <kg...@indirect.com> wrote:
>short runs. I have a MAX2x4 and the improvement over a 1/4 wavelength
>ground plane antenna is almost unbelievable. I hit repeaters 100 miles away.
>
>73, Cecil, kg...@indirect.com
>
I'm impressed! But I can work repeaters 100 miles away with 5 watts and a 1/4
wave ground plane 13' up..... :) I wonder what I'll be able to do when I
put up a REAL antenna!
Howard