Hi Hank:
Just another thought. Are you taking the Rx antenna feed from the T4x?
That uses the TR relay to release the Rx antenna as the relay switches.
I wasn't originally thinking of adding the RF into the muting test.
Just open and close the mute line without the transmitter. I have heard
other receivers make a thump when going in and out of mute this way.
Always thought it was just like an AGC spike.
Curt
Henry Foglesong wrote:
Thanks for the reply, Curt. No, I have not thought of a good way to
simulate the switching without the T-4XC and still have similar timing
of the RF load. The muting method in the NC-300 is simply opening the
cathode circuit (same method as used with the RX / TX switch on the
receiver. I suppose if there is enough capacitance in the cathode
circuit, there could be a very small delay in shutting down the RX. A
bad or leaky bypass cap might exaggerate that. Simply turning the RX
/ TX switch on the receiver on and off is very quiet, but, of course,
there is no simultaneous RF load. That is why I suspect that the RF
is hitting the receiver before the RX circuits are completely shut down.
If necessary, I could look into muting the RX with a bias source that
is switched within the TX (would need -22 to -50 volts) to mute the RX
using grid block. That would also facilitate QSK keying capability.
That is probably a last resort, however, as it would require a little
work on the TX, which I would like to avoid for now.
Hank
----- Original Message -----
*From:* Curt <mailto:[email protected]>
*To:* [email protected] <mailto:[email protected]>
*Sent:* Tuesday, October 18, 2011 8:09 PM
*Subject:* Re: [Drakelist] Receiver Muting
Have you tried seeing what happens when you simulate the same
muting in the Rx without the T4x? It might be something in the Rx
that does that when it switches.
Your suggestion is certainly possible if the Rx Mute response is
slow. It does not do this with a R4any.
Curt
KU8L
On 10/18/2011 2:56 PM, Henry Foglesong wrote:
I am using a T-4XC with a National NC-300 receiver and am using
the receiver mute circuit to mute the receiver. This works well
except that when I initiate a transmission with any mode, I get a
rather sharp and loud thump in the receiver. It almost sounds as
if the rf from the transmitter is hitting the receiver slightly
before the transmitter relay switches the antenna and mutes the
receiver.
Is this typical of that kind of setup, and what, if anything, can
be done to minimize the effect?
_______________________________________________
Drakelist mailing list
[email protected]
http://mailman.zerobeat.net/mailman/listinfo/drakelist
------------------------------------------------------------------------
_______________________________________________
Drakelist mailing list
[email protected]
http://mailman.zerobeat.net/mailman/listinfo/drakelist
_______________________________________________
Drakelist mailing list
[email protected]
http://mailman.zerobeat.net/mailman/listinfo/drakelist
