Hello Andy.
Thanks for your mail. I will try to isolate the relay coil as much as
possible. If that doesn't work, I will try a high-voltage/RF open frame
relay. Some people from the list have reported identical problem and
solution with such relays.
Regards,
Paris 5B4XF
-----Original Message-----
From: antennaware-bounces@contesting.com
[mailto:antennaware-bounces@contesting.com] On Behalf Of Andy
Sent: Monday, December 29, 2008 5:36 PM
To: antennaware@contesting.com
Subject: Re: [Antennaware] RF relay switching problem
> I have added a diode and 0.01 uF capacitor across the relay coil, but this
> has not solved the problem.
One little thought came to mind. Is it possible that the diode actually
makes the problem worse, by rectifying the RF that is picked up by the relay
and giving the coil a DC current? Maybe the capacitor alone (or perhaps an
R+C combo to lower the Q) would be better. The diode doesn't serve any
purpose for the RF; it only protects the driving circuit from the back-EMF
when it de-energizes the relay.
The electronics that drive the relay might also be contributing to this, if
the RF is getting back into it and being rectified by the transistor that is
driving it.
How do you know there is arcing, unless you see evidence of it? Maybe there
isn't any arcing but you are getting a lot of relay chattering that sounds
like arcing (which then might cause arcing between the hot contacts that are
opening/closing).
I would guess a healthy amount of RF bypassing might be one approach. On
the other hand, it might be better to go the other way and isolate the coil
at RF using chokes, to block the path to RF. Or get a different relay with
a lot less coupling capacitance between contacts and coil.
Andy
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