Wow, if half the guys that asked questions put up a Slinky I'm going to
buy some stock in the company!
OK here goes all the answers you should need:
1. This is used as a Beverage and as such IS NOT on the ground. Run at
any height yo would normally use a beverage....typically 6-12' above
ground. Just remember to leave it high enough so as to not decapitate
someone either walking or on horseback as the case may be.
2. Supporting with a rope down the middle has been done by some, to me
its a royal pain in the butt...been there, done that back around 1986 or
so. I either support with some rope from an overhanging branch or tie a
rope between 2 trees and let it ride on that. Purists may wish to
actually insulate the Slinky from the rope. I did that on one of
mine....cant say it helps or not; I just got lazy with the others.
3. I use 5 of them here and stretch them a total of 175'. At the far end
I terminate with a 600 Ohm resistor (not critical, I've used 470 to 750
Ohms) to an 8' ground rod. I then run three 125' radials on the ground
IN FRONT of the antenna; one directly in front and the other two at about
+ and - 15 degrees either side. The radials are optional and they made a
slight improvement in directivity ( F/B ratio). There is nothing magic
about my length; it just fits my property requirements.
4. Slinkys are cad plated spring steel so they take solder easily. I just
tie the end rings together in 3 or 4 places with small buss wire and then
solder the rings together. Spray that area with aluminum paint or similar
to prevent rusting. My European Slinky has been up at this QTH here in NH
for almost 7 years and is just now showing some serious rust but it still
works fine. I think I paid $1.29 for them back then. Those near the coast
may want to spray or dip the complete antenna.
5. Feed it the same as a standard wire Beverage with a 9:1 transformer.
I use fairly large FT114-61 cores and a quadrifilar winding. STAY AWAY
from those half inch cores with Al values of 5000 or 10000 that Misek
and others recommend. They are pure high loss junk and will cost at least
10dB in signal strength. Ferrites with a mix of 61 or 43 should be used;
sizes can be from FT82 thru FT140. I carry them in stock along with
magnet wire if anyone needs them; anyone needing winding info on my
FT114-61 xfmrs, send me an SASE. Some other designs for different size or
material cores is in the ON4UN book.
6. A preamp may or may not be necessary. In no case will you need more
than 10dB of gain. I use an old Ameco Mosfet preamp that I modified with
a gain control. Most of the time it is bypassed; other times I use 3-6 dB
of gain...never more than 10dB.
7. Since I have no way of modeling this antenna I HAVE NO IDEA what is
the ideal length, terminating resistor or matching transformer. They work
fine for me 160 to 30M. Get out there and experiment and then tell the
rest of us!! I'm guessing that my 175' ones are electrically equivalent
to at least 1 wavelengthon 160 and they are fantastic on 80M; on 40M the
preamp helps a bit and is necessary on 30M. I also run a 700' feedline
of .5" CATV hardline back to the shack. Anyone who has seen the KM1H DX
Contest scores in past years knows that this station hears very well on
the lowbands.
8. I have tried small receiving loops, snakes, full size horizontal quads
and half wave dipoles 10' above ground all back in the 1984-89 era at my
old QTH. The Slinky Beverage is the only one to give me directivity and
S/N performance comparable to a full size 500 to 1200' wire Beverage. Now
that I own some sophisticated HP test equipment I may try and run some
serious tests in the spring.
I hope that I have finally provided enough info to get everyone started
and welcome any comments and feedback. The better some people can hear
the less time they will spend calling the DX out of sequence.
73.............Carl KM1H
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Sponsored by Akorn Access, Inc & KM9P
|