Re: Full QSK for a uBITX
Here's a manual for the Argosy, T/R switching (and SWR metering) is on page 51:toggle quoted messageShow quoted text
The full transmit RF waveform goes through C1, diode D4 ensures the bottom of that
waveform is at DC ground, diode D3 then rectifies it to create a DC voltage across C2 that
is equal to the peak-to-peak voltage of the transmitted RF. The notes then say that this
relatively high DC voltage available during transmit is used to reverse bias diodes D1 and D2
such that no transmit signal goes through them to the RCV connector (which then goes into
the receiver front end).
I'm still staring at it, almost have it figured out.
But D1,D2 look to me like they would be forward biased during transmit,
which would not work at all.
Note that the PIN diodes at D1,D2 are called out as 1n4007's.
And that this transceiver works up through 30mhz.
Another thing to note, the final remains connected to the antenna during receive,
shunting some of the receive energy to ground.
Some of the other T/R switches use additional PIN diodes to isolate the final
from the antenna during receive.
On Wed, Aug 7, 2019 at 01:37 PM, John Seboldt K0JD wrote: