[TowerTalk] RF Inquiry HI-Q Filter CF5KV?

[Jim Lux]

----- Original Message -----
From: "Michael Tope" <W4EF at dellroy.com>

> ----- Original Message -----
> From: "Jim Lux" <jimlux at earthlink.net>
> >
> > As Tom pointed out, some mfrs claim performance that defies rational
> > expectation, basing their optimistic estimates on "designed to" or the
> > results of  poor measurement technique.  While, as a RF professional,
I'd
> > love to see real, calibrated test data on ham products, I'm also a
> realist,
> > and recognize that I don't want to pay for it, so I'm willing to accept
> > whatever the actual performance is, based on a knowledge of the internal
> > design (or other factors) and ignore the manufacturer's claims.
> >
>
> This is where the ARRL could help. The have a very nice
> lab that all past and present members have helped to pay
> for. They could easily test stuff like this a publish the data
> in short product reviews on their website (I checked and didn't
> see anything from Radio Works or RF Inquiry). In fact, if you
> look in the their RFI handbook, they have, for instance, swept
> frequency response data for a whole bunch of different TVI
> filters that they tested.

I think you're right, Mike. However, they are faced by the same limited time
resources as are we all.  They're also somewhat restricted by their policy
of only testing things that they buy themselves on the open market (a good
thing, in general, because it keeps a mfr from submitting a "golden" test
article), so there's a budget limit. An interesting question would be
whether they get their investment back when the resell the test articles.  I
suspect also that ARRL (because they want to resell the item, or out of
general policy) won't test an item to destruction or damage.  You'll not
see, for instance, high power breakdown/failure tests of items.  It would be
nice to see them test things like antenna tuners (rated at typically 100-200
W) to see where they fail.

However, it all costs money.  A typical ham product mfr selling baluns or
what not is probably working on a pretty thin margin, and can't afford to
sacrifice a half dozen test articles to potentially destructive testing,
much less hire the test gear and someone with the specialized knowledge to
do the testing.

Let's take a concrete example (and, folks, shoot at this if you will...)

Say I was going to go into business selling RF choke/baluns.  I'm going to
take 40 or 50 toroids, stack them on a piece of coax, and put it inside a
piece of PVC pipe.  Lets say, for discussion, that the parts and direct mfr
cost is $40 (2 connectors ($5), the coax ($0.50), the pipe ($2), the
toroids($20), and 30 minutes of labor ($12.50) to manufacture, pack, and
ship the orders (which is very, very optimistic)). I'll sell the puppy at
$45 for a $5 margin (which is thin).  (Lest anyone think that labor is less
than $25/hr, you haven't paid for taxes, liability insurance, workmens comp,
etc.))  (and this is direct sales... If I want my product sold at HRO or a
mail order place, I'm going to have to be a LOT cheaper, because they're
going to want a minimum of 20% margin)

Now, lets say I was going to devote half a dozen test articles for testing
(assuming I send them off to ARRL, who has generously offered to test them
for free).. That's $240 in costs, which is the gross profit on almost 50
units.  Will I sell 50 more units by testing?  Nope... Heck, I'd probably be
excited to sell 50 units at all. There aren't 50 hams who would care enough
that there was test data.  However there's certainly 50 hams who will write
eham reviews whining about how expensive my unit is, and how they can build
it for $20 using toroids they found in a dumpster at a computer recycler.
Nope.. it's a race to the bottom in this market.

Now lets add in the costs of the testing.  Figure you could do all the tests
in a month, with an engineer spending maybe half time on the project to work
out the test procedure, actually run the data, and come up with meaningful
analysis. Call it 80 hours of engineer time at $50/hr (for a cheap
engineer).  That's $4k (my gross margin on 800 units!).  And, of course, the
engineer is going to need some equipment.  Maybe $2k for a month's rental?
(Sure, you could do the testing with a surplus GenRad bridge or something
else, but you'll burn a week's engineer time getting it calibrated and the
measurements will be that much slower).

I would have been ecstatic to sell 50 units, much less sacrifice the margin
for test articles. I would be insane to expect that I'm going to sell 1500
or 2000 of them.  And this is for something simple.  Imagine if I'm selling
an antenna.  There, I'd need to find an antenna range to do testing on,
along with the staff to do the testing.  Range testing is hideously
expensive, and full of traps for the unwary that can suck up $10k in the
blink of an eye.  Even if I'm selling $1000 antennas, my gross margin is
probably around $50-100, and I'm probably not going to be selling  100 of
them in the first year.

Nope... detailed testing is going to be the province of things where it's
required by regulation or where there's enough volume to justify it.  A new
HT would justify it (presumably you're going to sell thousands of them).