[TowerTalk] Cage Antennas
Paul McInnish - K4BET
pmcinnish@worldnet.att.net
Wed, 26 Aug 1998 14:02:52 -0400
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Lee... used a cage! As soon as I get my new tower up, its going back up,
again! Experimented with many configurations... the biggest advantage of using
a cage is the extreme broad bandwidth and - why I don't yet fully understand -
a most dramatic reduction in noise! Depending on the angle of the legs, you can
adjust to get a virtual 52 ohm match @ apex. This confirmed with a rather
sophisticated impedance bridge and TDR (Time Domain Reflectrometer).
Yep, mine is in Inv V config. with apex @ 72'
3 conductors would be virtually useless and would only help slightly and would
not be enough improvement to justify the expense & effort. You need a minimum
of 8 conductors and assuming operating on 75 mtrs.... evenly spaced & a minimum
diameter of 15"!!! I know, you'll probably get some messages that I am all wet
with these figures but this was come about by a lot of hard work, expermenting,
wasted money, etc., etc.
I have mine actually cut for 160 mtrs. & with the antenna tuner... works ALL
bands... up to & including 10 mtrs. You'll notice one of the most dramatic
increases in signal strength on receive that you have ever had! The reports you
get on xmit. will be exciting. I had a regular inv. V & switching between the
two... I get several "S" units increase reports. I am accused of runing an amp
when switching antenna to the cage!
Word to the wise... takes a lot (several thousand feet) of copper wire (use
small 18 to 22 gauge, stranded) and find some 15" PVC pipe & find a machine
shop that has one heck-uv-a-big band saw and have him cut you some rings to
separate and hold the conductors.
I can assure you, once you use a well constructed cage, you'll swear off other
wire antennas!
Keep me posted!
Paul - K4BET
Lee Buller wrote:
> I have been looking for a project to work on this fall (when it cools off)
> and have been looking at a "cage" antenna for 80 meters. I think that is
> the appropriate name. If my understanding is correct, a cage antenna is
> more that one wire on each side of the dipole. I've read that in the
> golden years of radio, the cage was used quite extensively with up to six
> wires per side.
>
> My plan is to use three wires using Lexan spacers. I plan to do some
> experiementation here, but my first plan is to make all three wires the
> same length and cut the antenna for the middle of the bands. AS I
> understand this type of antenna, the construction of the antenna makes the
> wire to "appear" thicker...which increases bandwidth.
>
> A variation would be to cut one wire for 3.5...aother for 3.8 and still
> another for 4.0.
>
> Can you use these in Inverted Vee configuration or do they need to be
> flat-top?
>
> Has anyone out there fooled with this type of antenna and if so....what are
> the pitfalls?
>
> Lee Buller
> k0wa@southwind.net
>
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