Is there a way to build an external box with something like opto-isolators
to better isolate the driver chips from getting nailed so easily? Maybe add
MOV's to the opto-isolators? The breakdown voltage of the opto-isolators
would seem to give some protection to the controller.
Presently I use a 25 pin LPT switch box to ground the controller line to the
antenna during the summer months when I am not operating.
N2TK, Tony
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Dick Green WC1M
Sent: Sunday, July 12, 2009 1:08 PM
To: 'Bob Gibson'; TowerTalk@contesting.com
Subject: Re: [TowerTalk] STEPPIR QUESTION
I have a 3-stack of 4-el SteppIRs and lost all three controllers in a
lightning hit two years ago. All the driver chips were fried. The RS-232
interfaces mounted on the control boards were destroyed as well.
Unfortunately, the RS-232 provided a path to my computer, which was killed,
along with damage to every device connected to the computer via RS-232.
Total cost was around $10,000 (including some stereo equipment not connected
to the shack), mostly covered by insurance.
The driver chips are surface-mount, so not very easy to remove and replace
unless you're familiar with SMD. I got three refurbished controller boards
from SteppIR instead. This fixed the problem, or so I thought. The antennas
worked OK for about eight months, then the CPUs started acting up and I had
to replace them. Evidently, there was subtle damage that caused the CPUs to
slowly deteriorate. The symptom was occasional high SWR, which got more and
more frequent. Believe me, that was a difficult problem to troubleshoot!
Fortunately, the CPU chips are inexpensive and easy to replace. I've had no
problems with the controllers since.
After much thought, I've concluded that lightning suppressors do not provide
adequate protection for the SteppIR control box. First, the typical ICE or
Polyphaser unit has MOVs that trigger at 65V-80V. The SteppIR driver chips
are attached directly to the control wires, which means the voltage on the
pins can get as high as 65V-80V before the MOVs shunt the surge. That's way
too high for these delicate chips. Many a SteppIR owner has discovered that
the chips are highly vulnerable to shorts, and I think they're just as
sensitive to over voltage. MOV-based suppressors for the ham market are
designed for much less delicate equipment, such as the output from a rotor
controller, antenna switches, etc., which can take considerable voltage. In
the strike described above, I also lost FET driver transistors in two Green
Heron rotor controllers, further evidence that MOVs don't do a very good job
protecting certain semiconductors. Fortunately, the FETs were cheap and easy
to replace.
K7IR, SteppIR's owner-designer, told me that a 45V MOV would be just about
right for the driver chips. That's because there's a bit of a spike on the
33V signal. I assumed the ICE protectors provided by SteppIR have had their
MOVs reduced to that value, but another owner told me they were stock. Not
sure if that's still true. I use K5FD suppressor boards and had Jim replace
the stock MOVs with 45V units. But there's something like a 10% overshoot in
the MOV rating, so I think the voltage can get higher than 45V. I don't
recall the specs on the driver chips, but suspect even a 45V MOV will let
the voltage rise too much.
For that reason, I don't rely on the suppressors to protect the controllers.
When not in use during the summer, or whenever we leave the house overnight,
I disconnect the SteppIR control cables and power supplies.
I wouldn't be so quick to sell your SteppIR. Depending on your needs, it's a
fine antenna and a great compromise if you can't put up monobanders for the
high bands. My 3-stack really rocks. You just have to take some precautions.
73, Dick WC1M
> -----Original Message-----
> From: Bob Gibson [mailto:w5rg@yahoo.com]
> Sent: Sunday, July 12, 2009 9:44 AM
> To: TowerTalk@contesting.com
> Subject: [TowerTalk] STEPPIR QUESTION
>
>
>
>
>
> Hi group...We had a bad Storm move in the area a few days ago and I may
have
> been hit by lightning..we lost a TV..also now my 4 ele Steppir is not
> working..I think it is in the box itself..I have the antenna ran into a
> protection box from Steppir and the control box was grounded...When I turn
on
> the unit all looks fine..when I change bands..the box goes out and the
light
> blink red and turns off!..Any ideas? This antenna will be for sale when I
get
> it working again..pick up in North Fl...$1400...Thanks Bob
>
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