> I'd like to hear from the guys who have used the Stackmatch to phase their
> SteppIRs.
Bill,
I have been using a three stack of SteppIR's for one year in configuration
close to what you plan on planning. Mine are stacked at 33, 66 and 100 feet
on a 100 foot R55 rotating tower. The top MonstIR antenna is on a AlphaSpid
rotor and can be turned separately. Pic at:
http://www.ab5k.net/images/Monstir2.jpg
The antennas are feed with equal lengths of coax into a StackMatch as
recommended by the SteppIR folks. The StackMatch is the one that goes
thru six meters. There are some SWR issues that I do see in that the
antennas have low SWR individually but the SWR rises when in the stack. My
current approach is to tune each antenna up or down in frequency until I get
a reasonable SWR on the stack. That seems to work well. A better approach
would be to adjust only the driven elements for a better SWR match. I have
not had time to do that.
Also there are times when the top MonstIR does not seem to offer as much
contribution as it should while the bottom two play as expected. This may
be due to the fact that the top antenna is on a 2 foot longer boom and its
driven element is in a different place so there may not be an exact phase
match between it and the lower two antennas. If there is a phase
difference in the MonstIR and the other SteppIR, it would be easy to add a
short piece of coax to adjust this out.
Despite the observations noted, the array works well and it was used in a
North America first place win in the CQWW RTTY contest last year.
73 Terry - AB5K
----- Original Message -----
From: <Cqtestk4xs@aol.com>
To: <TOWERTALK@contesting.com>
Sent: Monday, July 31, 2006 6:04 AM
Subject: Re: [TowerTalk] Stacking tribanders (SteppIRs)
>
> In a message dated 7/31/2006 4:19:30 A.M. Greenwich Standard Time,
> w7ce@curtiss.net writes:
>
> In my models, I've also noticed that the F/R suffers when the antennas
> are
> stacked. However, I've been able to re-optimize the element lengths
> based
> on the stacking distance and height above ground and can get F/R numbers
> that meet or exceed those of a single antenna. In some cases, the change
> in
>
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This is not only the case with SteppIRs, I had the same thing with my KLM
> monobanders. However, living in FL, giving up some F/B to get the
> benefits of
> stacking was worth it.
>
> Most of the stacks I had used around .75 for spacing....pretty much what
> the
> master W2PV recommended.
>
> Plans for KH6 include three SteppIRs...the MonstIR at 90, a 4 el at 60,
> and
> another at 30, all phasable with a Stackmatch on Rohn 65.
>
> Over the last 20 years I used Ameritron boxes for switching the
> stacks...BIP/BOP/TOP/BOT, and will miss the second one, BOP, since I will
> be using the
> Stackmatch which has no provision for BOP. Yes, I know I can use the
> lower
> single antennas to achieve that, but I have always been a fan of using
> all
> antennas to get the maximum gain for the higher angle radiation.
>
> Spacing on the antennas for 90/60/30 should be a bit close on 20, but with
> the middle one switched out it should be close to the killer stack W2PV
> spoke
> of for 20. The three high should scream on 15 and 10, since I have used
> stacks
> at this height before for those bands.
>
> I'd like to hear from the guys who have used the Stackmatch to phase their
> SteppIRs.
>
> Bill K4XS
> _______________________________________________
>
>
>
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> TowerTalk@contesting.com
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>
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