On 4/15/12 9:52 PM, K8RI wrote:
> On 4/15/2012 11:08 PM, Jim Lux wrote:
>> On 4/15/12 5:47 PM, Jim Brown wrote:
>>> On 4/15/2012 1:48 PM, Frank wrote:
>>>> Good point. Sounds like a good reason to build your own.
>>> One of the points I've tried to make in my writing is that we can build
>>> MUCH MUCH better ferrite chokes than we can buy at any price, if we
>>> understand how they work. The ordinary stuff (in the $30-50 range) I've
>>> seen is essentially useless, and while the expensive stuff ($120 and up)
>>> is far less likely to burn up. it isn't very effective either.
>> which makes me wonder, why is that..
>> There's a labor cost (which can be substantial.. something the "you can
>> build it yourself cheaper" doesn't always contemplate).
>> but it seems that I could build, for instance, chokes with decent coax
>> jumpers, some number of 2.4" mix 31 cores, and an enclosure of some sort
>> for around $20-30 in parts.
> Depending on where you get them and how many you buy the main cost is
> the cores. Currently "I think" they are running between $5 and $7 each.
> So a 6 core, all band choke that covers 160, 75, and 40 could run $30 to
> $42 for the cores and about $6 for a pair of PL-259s. IIRC it takes
> about 6 feet of Davis BuryFlex for 6 turns. It takes about 20 minutes
> to wind a choke and install the connectors.
As a made-up product for sale, though, there's other costs than the 20
minutes of assembly. The time to order the parts, inventory them, etc.
And, as you point out, you're going to need more like $30-40 in cores.
So now you're talking a MSRP of $500 for that choke, $300 discounted.
I think it's in a zone of "cost to build yourself, counting time" and
"buy retail" where it just doesn't pencil out.
There's no way someone could sell such a thing for $100, unless they're
selling out of their garage, with no staff, no "business overhead", and
doing the work themselves.
there's a lot of ham radio related things in this general area that I've
run across. Single Band filters (like the NQN, etc.). Array solutions
sells the set of 6 for $600-700, and a guess at the material cost is in
the $50-70 range.. you can buy a kit of the toroids for $44, for
instance, which I'm sure is more than the quantity purchase price for
the actual ferrites. But you also need the capacitors, some boards,
boxes, connectors, etc.
It would be tough to make money building and selling them. I'm sort of
surprised that people do..
> You can plan on these things really working. I had RF coming back into
> the shack on 75 to the point I couldn't run full power. All the LED
> were lit to full brilliance at about 1KW out. I added a choke at the
> feed point and one where the coax came back to the tower. Absolutely no
> RF coming back into the shack now.
Yep... I've used them for all kinds of things. Making measurements on
antennas on my car, for instance. Put the VNA in the trunk, run the
coax through the chokes.
Completely solved a problem with 40 meter mobile shutting down the radio.
> Roger (K8RI)
>> Based on my experience in the "low volume specialty equipment" business
>> for the entertainment industry, that would turn into a list price of
>> around $200-300, normally sold discounted at maybe 20-30% off that.
>> Maybe that's why.. hams won't pay $250 for a decent choke.
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