[TowerTalk] Re: Turnstyle Polarization???

[K7GCO@aol.com]

In a message dated 6/27/00 6:24:18 PM Pacific Daylight Time, 
k5ra@mail.pulse.net writes:<<
To: K7GCO@aol.com
    Can you give me a month/year for the QST article about the antenna with
 Turnstile polarization??  Switching between H and V at an RF rate 
 sounds like CIRCULAR polarization (or probably more likely elliptical
 polarization).  The net effect of circular polarization into a
 conventional linearly (pure horizontal, vertical, or slanted) polarized
 antenna is a three dB loss.  It is interesting that it seemed to work so
 well.
 ---Timothy L. Bratton  K5RA >>

    Yes it's Circular polarization at a 3dB loss on peaks but the average 
signal is stronger most of the time on xmit and receive.  This would be a 
great contest and net control antenna for 160-40M.  I don't remember the date 
it occurred but look in the QST yearly index in the 40's (go to a library) in 
the antenna section for the first word in the title was "Pollyphase" as I 
remember.  All my antenna articles are packed for my move to SD--if I ever 
get there.  There was also an automatic tuner circuit in the article for when 
one changes the operating frequency.  When I unpack it I will put it on TT.   
 

As a top loaded vertical it's really an upside down vertical.  This top 
loaded dipole is a great antenna when fed in all the various ways at the 
bottom.  Pumping RF into an antenna in the Hi-Z end is the most efficient way 
to do it.  The 2 radials on top which is all that it needs for loading, 
cancel each other and only the shorted feedline radiates as the currents are 
in phase in each wire with the high current section on top.  The radiation 
field is like an ice cream cone for radiation.  It's affected less by 
surrounding objects and has a pattern and performance edge on the 
conventional 1/4 wave with ground radials.  For the L network tuner at the 
bottom, it really only needs a ground rod to cool the coax shield back to the 
shack.  Try it with just the ground rod and then start adding radials.  A 
great installation is to have it hang over the top or corner of the house if 
you can get it high enough.  It should be easy for the 40M version.  I had a 
selsyn tuning the variable in the L network (inductor to ground--variable Xc 
to the coax center) to maintain low SWR over the whole band.  I first used a 
parallel tank circuit as a tuner with relays to unshort the feedline and 
connect to the tuner for horizontal polarization.  Some radials can be laid 
on the roof in a circular manner.  There is very little current in the 
radials and radial losses are very small.  I had an article on this called 
the 10-90 Degree Antenna in CQ about 35 years ago.  Radio Electronics mag had 
an article on it also in the 40's.  It will work great even over black top 
with just a ground rod also.  Most any antenna feedline can be shorted using 
the antenna whatever it is as top loading.  If you can match the Z at the 
shorted feedline, 100% transfer of energy occurs minus the tuner losses. 

Another trick for a quiet receiving antenna ONLY on 160 or 40M is to use say 
a 20M beam and using a tuner to match the Z at the end of the unshorted 
feedline whatever it is.  If coax is used only the 20M beam is the 160M 
antenna with some interesting results.  It may be hard to match in some cases 
so try all the combinations and/or add coax for more Z selections.  The SWR 
is high on the feedline but no damage occurs on receive only and a small 
tuner can be used.  You might even try a pre-amp also.  There are all kinds 
of tricks that can enhance the performance of most any antenna.  K7GCO

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com