I have taken the executive decision to abandon DVB-T (the US 'standard' for DATV) in our area and go with DVB-S2. This decision was made based on preference, BATC / Portsdown loyalty, proven technology, and the possibility/probability (ongoing program) for a GEO satellite over the US that will be all digital DVB-S2X/DVB-GSE based.
I don't have the time or budget to experiment, too much of both has been spent this far, so need to go straight to a known working build.
My prime focus will be on RX, control & switching, and TX with the hope that others will take on filters, antennas, etc.
My thanks in advance for any help and advice.
How much functionality do you want with the logic? I can send you some details on the logic which is used on GB3CT with the PCB board layout if this helps?
It quite simple, multiple user and has 8 inputs which can be either sync operated (for legacy analogue RX) or TTL level switched for digital RX (there is hardware for both options on the board using the single chip Sync detector as per G0ATW's article in CQTV a few issues ago which may work with NTSC – I'll need to find an NTSC video source to test & confirm) It can be easily used with a 16 channel multiplexer (which can be purchased very cheaply online such as the Robot MV96P / Pelco 4000 or similar) for switching using its alarm inputs and audio switching/mixing done by a pair of cheap audio switching units available on Ebay in kit form.
Outputs are open collector switching for 8 full screen outputs (for single active input), Quad (more than one input active on inputs 1 - 4) and 9 screen (more than one input active above #4). It also has open collector outputs for selection of K and Testcard (beacon mode) which are provided using an old Trust TV photo viewer unit (for K) & a cheap Android/Kodi TV box running a photo viewing app (for testcards).
CT has been built on a budget and uses composite video, but there is no reason why you couldn't use an HDMI cameo processor if you wanted to go fully HD which some repeater groups have done. It is based on the PIC16F877A. Provided on the PCB is RS422 data interface for future expansion (not currently used on CT) interfaced to the Pics UART.
I have the source code in written in Proton Pic Basic Compiler (free download from Crownhill Associates with PIC16F877A support) which you can easily modify to suit your requirements.
Let me know if you are interested and I'll dig out the info and send it across to you (I have your Email address).
73s, Jason G7KPM
I would be grateful for all and any information that you can share.
I have the VMAC logic from HamKits which is capable to composite and component depending on how I rewrite the python script - quite the adventure learning that - so getting at least one HD input and one HD output should be 'simples' especially as I have the 12 I/O version and another extension hat promised.
My time to complete continues to get shorter as I am noticing my abilities deteriorate faster as time passes so I am more grateful for all your advice than you know.
I have looked at your logic and it has a lot more functionality than ours as ours is quite basic in comparison. Our logic does not have any built in video routing capability but is designed to switch an external video cameo processor with up to 8 inputs. However, I'll dig out the info over the weekend and Email it to you, although I would imagine it would only be useful to you as an item of mutual interest.