Ed:
I will share my experience with a 1/4w 80m sloper hanging from my tower with
3el SteppIR on top.
The sloper is homemade, about 72 ft long, hanging from the tower at about
the 72 ft level, and making close to a 50 degree angle.
I modified the SteppIR to ground the elements to the boom, which makes it a
capacity hat.
The resonant frequency was about 3.8MHz, with the SteppIR set for 15m with a
2:1 bandwidth of about 100kHz.
With the SteppIR set to 20m, the resonance was moved to 3.6MHz, also with a
100 kHz bandwidth. I also found a <2:1 VSWR at 30m.
After I added the 40/30m dipole to the SteppIR, I could get a better match
at 3.5MHz.
With the help of a AIM4170 antenna analyzer, I found that I could match it
on 160m with a simple series loading coil I could switch in or out using a
relay. The SteppIR could move the match around on 160m also.
The bottom line is I now have reasonably matched antennas for all bands with
just the SteppIR and the sloper.
With this configuration I have added substantially to my 80m & 160m country
counts.
As a side note: Before adding the loading coil, I used a SGC remote tuner to
tune it to 160m.
Adjusting a sloper can be problematic; I tried lengthening it to move the
resonance lower, but while resonance moved lower, the resistance value
increased, for a net no improvement.
I agree with you that the sloper is mainly a matching device to the tower,
as ON4UN notes in his book.
Your mileage may vary, I have the good fortune that the tower and antennas
are in a pasture that has experienced over 100yrs of bovine fertilization
(:^).
73s, GL, es Happy New Year.
Bob, W5LT
-----Original Message-----
From: Edward Sylvester [mailto:navydude1962@yahoo.com]
Sent: Sunday, December 28, 2008 1:54 AM
To: TowerTalk@contesting.com
Subject: [TowerTalk] Quarter Wave Sloper (half sloper)
Been trying to get up to speed on these...Learned that height is not
important, as it's the tower that will radiate, primarily. My tower is 70'
with a Steppir 3 ele and other assorted antennas for VHF, all on a 10' mast.
Looking at the Alpha Delta DX-B, which would give me 30/40/80/160m. Has
anybody installed one of these on a 70' tower? If so, what height was
ideal? Would like to do this right the first time....Thanks.
Ed NI6S
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