Transmitter Software Capabilities and Issues

Discussion about this major DATV Project. See also https://wiki.batc.tv/The_Portsdown_Transmitter
M0YDH
Posts: 67
Joined: Sat Dec 31, 2016 5:59 pm
Location: Wolverhampton IO82WO

Re: Transmitter Software Capabilities and Issues

Postby M0YDH » Wed Dec 06, 2017 8:12 pm

Hello Dave
Signal generator question.
I shall re-read the Wiki entry but, in case it doesn't do so already, can the signal generator be switched through to the 4m signal port? It might be the least used and therefore best suited to test instrument applications.

Are you considering relay sequencing in software? It's a question that I've asked in my sequencer circuit build thread.

Great job chief. Chapeau.
David M0YDH

G8GKQ
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Re: Transmitter Software Capabilities and Issues

Postby G8GKQ » Wed Dec 06, 2017 11:36 pm

Hi David

The signal generator needs the VCO filter to be out of circuit to cover above 100 MHz (approx limit on 4m), 200 MHz (approx limit on 2m) or 600 MHz (approx limit on 70cm), and the VCO filter is switched by the same lines as the RF output switch. So that is why it uses the 1255 MHz output, so that there is no VCO filtering. Also the 1255 MHz output has the lowest loss of the 4 outputs. So, it Is not really possible to use any other output.

I do not plan to put TX/RX sequencing in the software. Primarily because I mistrust complex systems such as the RPi for controlling destruction-critical functions. Secondly, there are not really enough GPIO pins. Thirdly, everyone has different requirements, and some of my systems have different requirements for each band. Fourthly, it is very easy to do this sequencing reliably in a PIC.

Perhaps I should publish the circuit and code that I use for sequencing my 70 cm setup. I'll need to trawl through my archives to find it, so it may be a day or 2.

Dave


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