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Re: [TowerTalk] SteppIR problem-update from the front lines

Subject: Re: [TowerTalk] SteppIR problem-update from the front lines
From: VR2BrettGraham <>
Date: Tue, 19 Jun 2007 03:07:23 +0000
List-post: <>
This thread has been interesting to watch, though a bit
frustrating waiting for everyone to catch up.

K4SAV said:

>My best guess as to the cause of this is that you are right up to the
>limit of what the system can do. The long cable length combined with the
>excessive current pulse presented to the power supply by the controller
>is causing the supply to drop too low.  Remember the power supply
>voltage transient is present whether the cable is connected to the
>antenna or not, so a large part of this transient problem is not due to
>load, but due to some "feature" in the controller.

I see about a 6 volt drop (without or without a motor
connected) from the power supply when power cycling the
controller for my SteppIR dipole.  This drop is the same
with or without the motor connected.

I also see 1.2 volt peak-to-peak spikes with the controller
off & 1.3 volt peak-to-peak spikes with the controller on
top of the 25.whatever volts coming from the supply at
156 kc.  The power supply by itself is very clean.

The power supply is a Franmar F19603N, rated for 24 volts
at 2.7 amps.  Franmar's web site looks to have not been
updated for four years & apparently no longer offers the
F19603N, as could not find it listed in product section.
There is a paper sticker on the case that reads "CODE
#25.2V" so presumably the output voltage is higher than
the permanent marking on the product.

You can find a spec sheet for the F19603N at:

Where one can read that it has short circuit protection,
but is rated to supply only 2.7 amps max, with dymanic
load voltage regulation of +/- 5% going from half to full
load or vice versa.

5% of 25.2 volts is 23.94 volts, so the power supply is
acting like it has a load on it well in excess of its rating
(at least momentarily).

Presumably, the only difference between the two power
supplies SteppIR offers is output voltage, so if there is
a moment where the supply is asked to source current
in excess of that, the output almost certainly is going
to wilt.

Perhaps AH6FC can share with us the markings on the
supply(s) he's received, as perhaps there has been a
change since 2003 (when I bought my dipole).

There is a presumption that the supply included with
the product would be suited for the task, but it appears
that the incoming voltage is being pulled below what
the LM2596 inside likes (that is where the 156 kc crud
is coming from - the controller design has _no_ regard for
EMC at all) & this then causes the CPU to go on
walkabout & not come back.

But having been told so many times I do not know
anything about anything, I'm obviously wrong about
this one, too.

73, VR2BrettGraham


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