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[TowerTalk] ferrites & fires

To: <>
Subject: [TowerTalk] ferrites & fires
From: (on4kj)
Date: Sat Jun 28 12:11:39 2003
And the European " BON SENS"
Never play with a gun if you dont know from what hole the bullet is coming
Hi Hi.

Jos on4kj

--- Original Message -----
From: "Jim Lux" <>
To: "Martin Ewing" <>; <>
Cc: "Chuck Counselman" <>
Sent: Saturday, June 28, 2003 5:48 PM
Subject: Re: [TowerTalk] ferrites & fires

> > -Unless you have high confidence in the product you are buying _and_ you
> > understand the your operating conditions, you need to over-rate your
> components.
> >   That means that a $30-40 PVC thingy might not be a good idea for your
> multi-KW
> > transmmission line. [In a conservative system design, you might require
> that
> > components should survive a serious fault, like an open or shorted
> > connection - or at least fail safely.]
> It's way extreme beyond what's needed for ham gear, but, in the spacecraft
> business, the usual requirement is demonstrated capability with 4x rated
> power (actually twice voltage and twice current, so you could get it with
> open/short/transmissionline at rated power). Analysis might work if
> isn't feasible, but your analysis would need to be fairly rigorous.
> >
> > -Everybody uses PVC, but PVC is not known for its ability to dissipate
> heat, and
> > it makes pretty nasty smoke.  Is there a better design?  Open air? Water
> cooled? :-)
> PVC should work just fine, if designed appropriately.. (the IF is the
> important word)
> >
> > -Some 3rd party should be doing destructive testing on QRO items.  This
> could be
> > fun for the right person! Burning attic anecdotes are nice, but it's an
> > inefficient way to learn about products.
> Perhaps manufacturers should publish their design analysis that backs up
> their rating claims?  The initial thought is that you're going to be
> revealing trade secrets, but, I think that none of these products have any
> special magic in their design.  What you're really paying for is that
> someone else is scrounging up the parts, assembling it, keeping them in
> stock, shipping it to you (or to HRO,AES,etc) in a nice box. This is
> definitely worth something (nobody's time is really free, if nothing
> If someone really does have a magic design, then (theoretically) they can
> patent it, and keep others from manufacturing it for 17 years (I say this
> somewhat cynically... having been involved in some patent infringement
> lawsuits over the years).
> >
> > -The line isolator product is available from at least 3 vendors at about
> the
> > same price.  MFJ's product info says _nothing_ about power handling
> ability.
> > The W2DU unit ( claims 10 KW PEP at 10 MHz and 2:1 VSWR.
> What's a
> > fella to do?
> Oh yeah, theoretically, that retail price also covers some liability
> insurance to cover the mfr of the device when it doesn't perform to spec,
> burns down a house, and it's traced back to the device.  I am fairly sure
> that Chuck's insurance company would do the forensics, find that the fire
> originated where that isolator was, and attempt to recover some of their
> loss from the manufacturer.  The net result would be unhappiness all
> (Chuck would never get the full value back, the mfr probably would have
> insufficient resources anyway, and lots of people would spend lots of time
> responding to paperwork of one sort or another), but, at least the mfr
> theoretically learn to be a bit more forthcoming and responsible.
> But, to answer Martin's last question: What's a fella to do?  A fella is
> challenge the mfrs on their specs. A lot of mfrs catering to the amateur
> market seem to play a bit fast and loose with the specs , particularly
> it comes to max power ratings and antenna gains. If they can't
> it, get larger organizations to stop them from advertising (i.e. do they
> advertise in QST? what about the FTC?). Don't be complacent, don't assume
> someone else is going to take care of it.   In my mind, what separates a
> real business from someone making stuff for their friends and
> is the acceptance of the responsibility that comes with selling a product
> the general public.  That responsibility implies real analysis, real
> testing, real disclosure, etc., and, it doesn't come cheap.
> Jim, W6RMK
> _______________________________________________
> See:  for "Self Supporting Towers", "Wireless
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