Comments interspersed..
At 06:27 PM 5/12/2007, jeremy-ca wrote:
>$45 is obviously a rip off for that relay. Since Ameritron makes a big deal
>about selling any individual part Id start there to get a more realistic
>resale price.
I don't think $45 is the actual each price Jay sells them
for. However, it could well be a realistic cost for him to put one
relay in a box and ship it. Might be that 3 relays would also cost
$45. The realities of "spare parts sales" has been beaten to death
on the forum. It's an expensive service to provide for the seller,
although some mfrs do "subsidize" it (but eventually, you pay, in the
form of original purchase price). Also, many mfrs only sell
replacement parts if you own the original product (especially those
that are subsidizing the cost stocking, shipping, etc. onesie-twosie
parts orders).
>To find the source go to your local library and ask for the Thomas Register
>that covers the letter R. This is a reference book that cannot be removed.
>
>Make a list of the pertinent info from the relay manufacturers; then its a
>matter of detective work.
Both Ameritron and Jay use custom relays in their products. They
have enough voume to justify the order.
One can also find off-the-shelf relays that might be acceptable. A
custom relay gives you the opportunity to make it just like you want
it: e.g. Form X contacts, coils wound like you want, pinout or
terminal configuration like you want. I personally find the
Ameritron relays in the RCS-8V a bit shock sensitive, which is a
problem in a portable installation (bumping the box hard enough will
cause the armature to come off the bracket) but that would be no
problem in a fixed install.
Then, there's some testing involved. Since very few mfrs rate their
inexpensive power relays for their HF properties, you have to build a
prototype, measure the properties, revise the design, etc.
Furthermore, it's highly, highly installation dependent (are those
relays being mounted in a metal box? What about parasitic C to the
case?) What about parasitic C to the coil? RMS current
handling? Voltage ratings? None of these will match the 60 Hz
ratings in the datasheet.
If you're building a one-off for yourself, you might just build it
once, and if works good enough, you leave it. Maybe you don't care
that the port-port isolation is different on each port? Maybe you
don't care that the parasitic C and L is different on each port,
because you're running an autotuner anyway? Maybe you've got the
relay box in your shack, and if you fry a relay accidentally, you
just move the cable to an unused port and go on. Maybe you've got
the relay box at the top of a 300 ft tower in a remote control
installation, and it requires driving 5 hours just to get to the base
of the tower.
Jim, W6RMK
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