Dave,G8GKQ wrote: ↑Sun Jun 05, 2022 1:46 pmHi Ken
I really do not know what the problem is with your Portsdown and Pluto PTT. I'm sure we'll solve the mystery eventually. Does it do the same when you have no connector on the Pluto output - I am thinking a high current ground loop could be upsetting things?
Please could I suggest a different way of operating your QO-100 station? I use a separate physical switch for the QO-100 PA; I never turn this on until I know that the Portsdown is up and running. During QO-100 QSOs (such as the Thursday evening QO-100 Net) I leave the Portsdown set to transmit all the time (for over 2 hours) and just switch the PA on when I want to transmit. This means that there is no delay when it is your turn to transmit, and you can turn the PA off instantly if there is anything that you are worried about.
Also, I monitor 2409.75 MHz (or whatever uplink frequency is in use) locally in the shack on another receiver to make sure that all is well before switching the PA on.
Lastly, as a luxury, a switched RF attenuator with a hardware control in the transmit line between the Portsdown and the PA would enable you to adjust the power correctly without needing to stop transmission.
Hope that helps.
Dave
Excellent suggestions. Earlier today I fitted one of the small Chinese amplifiers between my pluto & final Amplifier. This allowed me to reduce Pluto output. (intended) as I was suspecting I might be reaching saturation on the main output Amplifier. Fortunately that small amp is 5v & I had included 5v & 12v outputs on side of my Portsdown by way of 2 DC sockets via switches and LEDs. This allows me to turn the Chinese amplifier on & off. So at least I can halt the drive to final Amplifier at will. ( This then gives me more time to find a way off shutting of the output ).
The pluto output now set at -20
This gives me enough output to still get in on 333 SR &
⅓rd fec. 30w out to helical on 1.1m dish
I thought this lower output might improve the issue. Unfortunately not.
Later I will do the other check you suggested. Only the Pluto & attempt to receive it as-is.
I'll report back what happens
Once again. Many thanks . Ken