John & Chris
I just took a good look at the schematic, and it seems that the Mike
amp's 50 MFD decoupling capacitor (the one connected to 12 V via a 220
ohm resistor) may be storing enough voltage to allow mike-to-RX-audio
feedback when we switch from TX to RX (i.e both the mike amp and the
RX audio section are on at the same time). You might try lowering
it's value (maybe something like 22 MFD or even 10 MFD) to see if this
makes the changeover squeek shorter, or eliminates it completely.
Maybe we will have to ground the TX 12 Volt line when we are in RX
mode. This will require an additional switch or relay contact pair,
but right now I don't see any other simple way to solve this.
Arv
_._
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--- In BITX20@..., Arv Evans <arvevans@e...> wrote:
I too have the same problem, maybe worse because I'm using a VOX driving
my switchover relays and it affects the VOX setting. My fix for the
symptom was to add a relay and switch the speaker lead back ON after
the Tx voltage has totally died. However, this is not a fix for the
problem. Instead it is just treating the symptom. We may have to
resort to adding a few milliseconds delay between TX-OFF and RX-ON.
Arv
_._
On Wed, 2004-08-25 at 11:34, vdberghak wrote:
Incidentally, checking the R/T switch there is a loud squeak on
turning back from tx to rx. Has anyone else found this?
John G0UCP
Hi,
I have the same experience.
I thought it has someting to do with the way I switch over, three
wires with clamps between the circuit and a switch, but it seems
that it is a timing problem?
So now you know you are not the only one who has it, does not mean
we have a solution.
Any comments from others?
Chris.
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