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[TowerTalk] Sigma 280-S

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Subject: [TowerTalk] Sigma 280-S
From: "Jim Thomson" <>
Date: Wed, 13 Oct 2010 05:43:17 -0700
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I'm considering the 180S or 280S also, likely the shorter (not Magnum) 
versions.  The Tornado variable pair of inductors at the feed point 
(squeeze/expand the coils) appears to be a good idea at least for the 
dipole, and should be easy to set, using SWR.

It would also seem to be possible to make a pair of Tornados work for 
the 2L beam, but with two sets of variable inductors the tuning might be 
a nightmare to figure out.  Moving around the 70Khz bandwidth would be a 
real plus.  With enough L range, it might tune to some other band, but I 
won't even go there, other than to suggest it might provide some 
detuning/decoupling from adjacent yagis.

So, are there any Tower-Talkians with experiences or models with either 
of these setups?

Grant  KZ1W

## The control box  for EACH Tornado drive comes with 10 x pre-sets. Each 
box also has a 4 x digit, digital turns counter.  The digital turns counter 
counts the turns
of the big threaded  delrin lead screw, that goes down the middle of both 
coils. It also has a 
'park' mode, where it compress's  both coils fully, and re-sets the counter to 
ZERO. [ max inductance]
OK, then it's easy to  tweak the DE..1st  for resonance.   Then, the REF will 
always be tweaked slightly lower in 
freq than the DE.  The turns counter for the REF  will always be a lower number 
on it's digital counter
VS the  DE.  Once the REF  is tweaked for max F/B... for say 3800... then the 
REF turns counter readout
is entered into say memory #1.   The turns counter for the DE is  entered into 
it's own  control box,
also memory #1.     Then re-tweak  both the DE  +REF  for a new freq... then 
enter both of em into memory #2, etc. 

## You only have 10 x memories[pre-sets]  per controller.   For the in between 
freqs, you can  take note of the turns
counter readings..and  log em.    Then bring up the closest pre-set.... then 
manually tune  to the logged readings. 
On paper, one should be able to tweak the 280-S  for max gain, max F/B  and 
flat swr  across the entire band. 
The big advantage here is.... both els can be adjusted  from the shack...and 
with the 2-el yagi  at full operational
height... VS  crank up tower at min height.   I have been  talking to both Mike 
at Seco systems  who makes the Tornado
drives  and also Mark  @ F-12.    All  3 of us think it's  doable.  If a 
SPST-NC vac relay is added to each ele, and a 2nd
coax+balun run to the REF  [ and routed to spare port on remote ant switch 
box], then the DE  can be  opened off, and 
REF  tuned up dead on any freq u want.  The REF  can also be opened off,  and 
DE  tuned up on any freq.  You can then
do  cool stuff,  like open off the REF, and make it instantly BI-directional  
[and also do an instant F/B check]. 
You can also tune the REF  higher in freq than the DE... and reverse the 
pattern , without rotating the array !  [ it's
now a DE-DIR].  

## The Ameritron / MFJ  screwdriver controller is what Mike uses to control the 
Tornado drive.  The Tornado drive
not only has +/- inputs for the reversable motor, it also has a 2nd pair  for 
the digital turns counter.   So to pull this off
requires a 280-S... with a tornado drive on both els, and 2 x controllers.   
The hairpin still needs to be manually tweaked,
but that's a minor issue.  I'm hell  bent to try this config next spring.  I'm 
convinced it would kick butt..with it up 100'
My concern was if the 80m array will screw up a 20m array below it.  Even if it 
did, both vac relay's  on the 280-S
could be operated, and then both REF and DE  could be opened off, when 
operating on 20m...end of problem. 

Jim  VE7RF

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