Portsdown boxing/build thread

Discussion about this major DATV Project. See also https://wiki.batc.tv/The_Portsdown_Transmitter
G8GKQ
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Re: Portsdown boxing/build thread

Post by G8GKQ » Tue Nov 13, 2018 2:38 pm

Hi Gareth

You will get a much cleaner signal with the attenuator before the amplifier. Not sure where your 4-way output switch is, but the max sensible power handling for that is only about 40 mW, and it starts distorting above 20 mW.

Dave

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Tue Nov 13, 2018 2:48 pm

Thanks Dave, I'll alter the 'plumbing' accordingly and by the sounds of it, any additional amp stages before the final PA should be after the 4 way switch based on its 20mW power handling.
No holes drilled so far ;-)

Gareth

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Tue Nov 13, 2018 3:42 pm

Just checking out my RJ45 socket extension, it works :-)
Watching the streams available - amazing what's been done (by repeater keepers) and how well it works on the RPi Portsdown.

Question: How to reset the RPI password - I've done my usual and dreamed up something amateur related, but not written it down. I'd guess its a card rebuild required.....note to self etc...if I could remember where I put the note....

Gareth

G8GKQ
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Re: Portsdown boxing/build thread

Post by G8GKQ » Tue Nov 13, 2018 5:02 pm

Gareth

Password change: https://howtoraspberrypi.com/recover-pa ... pberry-pi/

Unless you have potential threats on your local network (as you might if you are running an unattended repeater streamer), or your RPi is powered up 24/7, and as long as you are behind a router, I do not recommend changing the password from the default.

Dave

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Tue Nov 13, 2018 7:46 pm

Thanks :-)

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Wed Nov 14, 2018 5:00 pm

I've got my 4 band decode board fitted but all its doing at the moment is controlling 5 LEDs on the front panel. As I'm using some panel mount LEDs in neat housings that already have a resistor in them I'm planning on powering just this board from 5 volts (Chip is rated for 7 V max). Only issue I can forsee is that the RPi control logic will only just make the logic switching threshold....

What sort of external connectivity have people chosen to interface with external amps? Something plug-in and multi-pined or perhaps a bank of screw down terminals. Maybe a D-Type plug/socket arrangement, cheap and reliable at the likely current? I'm planning/assuming that it will (a) operate the (chosen) amplifier power-on relay and (b) turn on e.g. amp bias when TX is also selected?

Also found a nice compact tripod for the Picam. https://www.thingiverse.com/thing:1460181 which would also do good service with a conventional camera. There is room inside the RPiCam 3D housing to accommodate a 3mm screw head which I've retained with a short hex standoff on the outside. This will allow easy attachment to anything upwards of a lolly stick.....

Gareth

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Re: Portsdown boxing/build thread

Post by G4uvz » Wed Nov 14, 2018 9:32 pm

I see that most seem to mount the RF switch LEDs on the front panel???

Personally I find them really useful on the rear panel adjacent to the relevant SMA connector ...so there is never any doubt which port is energised.

Adrian

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Thu Nov 15, 2018 8:36 am

Not impossible to run a pair of same colour LEDs from the same point. I've made a plate to help me.
Capture.PNG
Capture.PNG (101.48 KiB) Viewed 269 times
Gareth

G4uvz
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Re: Portsdown boxing/build thread

Post by G4uvz » Thu Nov 15, 2018 10:15 am

Very impressive 3D printing!
I have on loan at the moment a 23cm Tonna yagi ...and I was considering a copy if it were possible to replicate the 'stand off' mounts for the elements which are mounted on a standard square section aluminium mast.
The only difficult bit would be guessing what is in the folded dipole mount without resorting to an Xray!

A

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Thu Nov 15, 2018 11:59 am

Thanks, I'm thoroughly enjoying making it work for its living, having to learn CAD to drive it but 'needs must' is a good motivator :-) I think I have the same such aerial in my storage, and a spare. To make the clips would be relatively easy and with availability of PETG filament which is both flexible and UV resistant would make for perfect spares. Must have a look at the dipole driver, can't be too mysterious.
Gareth

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