Jim,
What is failing on the relays? Is it the coil opening up, the contacts
sticking, the receive side contact appearing open, or the pivot getting
sloppy and the contacts bouncing too much? I have tested many relays
for mechanical life (low current in the contacts) in previous employment
and many exceed 20 million cycles. All the relays I have tested were
made by reputable manufacturers and were generally tested at about a
15Hz rate. In a well designed amp guaranteed to not hot switch driven
with the proper coil voltage the life should be very close to the
mechanical life.
There is a problem using a relay as a T-R device where the receive side
of the contact sees only very low current (gold plated or gold flashed
contacts are best) and the transmit side sees high current (definitely
not gold plated). The dilemma is what type of contact material to use.
Generally the high current side rules and the low current side may need
a bias current to be reliable. Often using 2 relays in parallel or
bifurcated contacts will give the desired reliability.
73,
Larry, W0QE
On 11/9/2013 9:54 PM, Jim Brown wrote:
On 11/9/2013 5:44 PM, MU 4CX250B wrote:
I have had Jennings RJ1a relays last
decades in my QSK homebrew amplifiers.
That would have a lot to do with the use they get. How many contest
QSOs do you make in a year? I do a lot, and after the second time
having to replace relays in the middle of a contest, I've switched to
semi-breakin. :) I use Ten Tec Titans, which are well sequenced.
73, Jim K9YC
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