Jim -
When I was building an outboard QSK box for my Drake L-4B to interface with my
Omni VI, I found that looking at the timing with a 'scope was essential! I just
had to be able to see when things were happening to make sure that no hot
switching was possible. I set the trigger on key down and then looked at when
the other switching events occurred. I think that is the only safe way to do
things.
Good luck!
73 - John, W4AU
At 14:28 10/31/01 -1000, you wrote:
>Hi,
>
>Have had to replace the input T/R relay on my amp (Henry).
>Relay is a small Guardian electromechanical unit, probably
>takes 10 or so milliseconds to switch.
>
>Suspect the replacement was because of burned contacts
>from "hot switching". The Omni was deaf at key up; the input
>relay had not returned to the receive side. Couple of key
>taps, or PTT pushes would return "hearing" on rcv.
>
>The Omni VI+, uses a mechanical relay
>to signal the amp's T/R switching relays. Figure at least 10 ms
>for this relay to operate. Then RF output appears less than
>5 ms after the contact closure since per the ARRL lab tests,
>my Omni keying has about a 15msec delay between key down
>and RF output, and 17 msec delay between key up and the
>RF stopping.
>
>5 to 7 milliseconds is less time than the amp Guardian input relay
>needs to operate. Therefore when the input relay contact opens, it
>is carrying RF current, and so it will arc as it opens. Every time.
>
>Prowling about in the Omni manual, I just discovered the news that
>the OSK Slow relay delay is adjustable over a range given as
>01 to 15 (what, milliseconds?). Anyway, following the manual
>instructions, have checked and found my rig, at the moment
>is at "position" 07. If I increase this to 15, will both of the amp
>relays not open for at least 15 milliseconds after key up? Even
>then that might not be long enough if the Omni requires some
>17 mS for RF to shut down after key up. And, would RF not
>"leave" the Omni until 15 mS after key down in this setting;
>probably faster as this is called "relay delay".
>
>Maybe I just don't understand what is going on here. Anyone
>use the Ameritron QSK-5 unit along with some other non-
>Ten Tec linear with their Omnis? Maybe that unit would solve
>my problem.
>
>Any ideas?
>
>73, Jim KH7M
>
>
>_______________________________________________
>TenTec mailing list
>TenTec@contesting.com
>http://lists.contesting.com/mailman/listinfo/tentec
|