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>>>>>> The relays which we use in the Top Ten Devices boxes are 10
>>>>>> amp,
>>>>>> sealed power relays. They are very small and have very low
>>>>>> inductance. The contacts are connected to the base pins with
>>>>>> wide conductors. I have run many power tests on these relays
>>>>>> and the pc boards they are mounted on with temperature monitors
>>>>>> and they will take full amateur power (+) to over 30 MHz. We
>>>>>> rate our boxes conservatively at 1.5 KW. The part number is
>>>>>> JW1FSN-DC12V. They come with several different brand names on
>>>>>> them. Similar relays are being used by other manufactures of
>>>>>> amateur boxes and they rate them variously at 3 KW and 5 KW.
>>>>>>
>>>>>> George, W2VJN
As Paul W9AC commented earlier I've run some comparison tests of inexpensive
PCB-mount power relays in connection with my StationPro controller. The two
main contenders were the Tyco/Schrack (also labeled Potter and Brumfield)
RTB14012F (rated at 12A DC, and available in a variety of coil voltages), and
the JW1FSN-DC12V mentioned by George, above, rated at 10ADC. They are both
excellent relays and an amazing value, and each easily handled 2500W at HF, but
in the end for HF use I settled on the RTB14012F, based on its internal
construction. (Oh, almost forgot. I also tested the relays with a 100%
modulated Johnson Desk KW, which produces about 3500W on modulation peaks.)
After sawing the covers off both relays, it became evident the RTB14012F has
significantly heavier contacts and shorter strap-like leads to the relays pins
than does the JW1FSN-12V. You can see a cutaway photo of RTB14012F relay on my
StationPro website (www.w8zr.net/stationpro/), and if anybody is interested I
can post a cutaway photo of the JW1FSN-12V. Both relays have no measurable (by
me, anyway) VSWR bump in the StationPro up through 30Mz, and only a 1.2 VSWR at
54MHz. Interestingly, despite its longer internal leads, the JW1FSN-12V shows
less VSWR at 146MHz (1.7 vs. 2.0). I attribute its better VHF performance to
the coil orientation. It uses a vertically mounted coil, with the contacts
beside the coil, whereas the RTB14012F uses a horizontally mounted coil whose
magnetic flux lines loop into the contact area. Thus, I suspect the lower
mutual inductance between the contacts and the coil are responsible for the
slightly better VHF performance of the JW1FSN-12V. Inciden
tally, both relays are pin-for-pin compatible with each other and may be
freely interchanged. In the StationPro, I recommend the JW1FSN-12V for builders
who want to use the unit on 2m, and the RTB14012F for everybody else.
As mentioned in an earlier post, the RTB14012F is also available in a 16 Amp
version, and I also investigated that relay. Internally it is exactly the same
construction as the 12Amp relay, but it has two pins connected to each contact
strap, rather than just one pin. Despite this seeming advantage, I can't really
recommend the 16 Amp version. Its PCB pin configuration is much more crowded
than for the 12 Amp relay, which means one can't use wide PCB traces with it.
Also, because of the more closely spaced pins, the 16 Amp version would likely
have lower voltage insulation than the 12 Amp relay, which could potentially
cause arcing problems when using it with mismatched loads.
73,
Jim W8ZR
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