Very interesting experiment with the RF-1D, Larry. I may try the same
life test with an RJ1a to see how it holds up. Incidentally, I did
test an RF –1D earlier this year and found it to be surprisingly slow,
especially for such a little tyke. I don't have my notes here at hand,
but I think the make time was around 4–5 ms with several bounces.
As I'm sure you know, some vacuum relays are specifically designed for
hot switching DC loads, but most are not. Gigavac makes some very nice
PCB-mount relays rated at 5 ADC/10 kV. I believe they have tungsten
contacts, with high melting points.
73.
Jim w8zr
Sent from my iPhone
> On Nov 10, 2013, at 8:39 AM, Larry Benko <xxw0qe@comcast.net> wrote:
>
> Jim,
>
> Relay contacts stick only if hot switching is involved in some way. There is
> no mechanism for them to stick (unless the internal contact pivot wears down
> to nothing or the spring fails) that does not involve current. All relays
> are designed to be hot switched at some current level (extremely low for many
> reed relays) and it is the job of the relay manufacturer and product designed
> to get acceptable life out of the chosen part. Yada, yada, yada.......
>
> Now back to your issue. I have looked at several transceivers with a logic
> analyzer trying to determine the RF sequencing vs the key line to the amp.
> This value usually is controlled but I have seen on several occasions where
> the microprocessor in the transceiver must be busy or something where the
> timing is quite different. This type of stuff is hard to find and can be the
> cause of apparently random failures. Of course there are ways for an amp to
> guarantee no hot switching but most do not spend the effort to do so. Will
> probably never know what caused your failures. I do have an old Jennings
> RF1D that I put 20 million cycles on it (via a tester) after I removed it
> from a piece of equipment. The operate and release times were virtually the
> same before and after my tests. The tester hot switched the contacts at level
> less than 1mA.
>
> 73,
> Larry, W0QE
>
>
>> On 11/9/2013 11:59 PM, Jim Brown wrote:
>>> On 11/9/2013 10:38 PM, Larry Benko wrote:
>>>
>>> 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?
>>
>> My symptoms have been sticky contacts, mostly RX, but also TX. Since I
>> stopped doing QSK with my Titans (about 2007) I've yet to replace a relay.
>>
>> As to operations -- an active, aggressive contester will either CQ
>> constantly and hopefully send an exchange every 20-40 seconds, or will
>> search and pounce and do the same. I typically operate 24 hours for
>> Sweepstakes, 24-30 hours for DX contests, 14-16 hours in RAC, IOTA, and WRTC
>> contests and I work at least 12 such contests in a year. As Bill has shown,
>> that's a LOT of relay operations if you're full QSK.
>>
>> As a competitive contester, it's not the cost of the relay or even the time
>> to replace it, but simply that I don't want to have to lose 90-120 minutes
>> of contest operating time while I do it. Being analytical about it, the
>> relays I've replaced have mostly been those that came with the three 20-30
>> year old Titan 425s I bought used, so perhaps it's only my contesting that
>> pushed them over the edge. :)
>>
>> 73, Jim K9YC
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