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 » Wed Nov 07, 2018 9:51 am

Hi Gareth

You might want to consider a hardware shutdown button: https://wiki.batc.org.uk/Portsdown_hard ... e_shutdown

Dave

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Wed Nov 07, 2018 10:10 am

In touch-screens I trust ;-) But yes, I have that fitted direct to the socket on the expansion board so could shift that and make a nice little shielded feature of it too with LED combined.

Gareth

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Re: Portsdown boxing/build thread

Post by radiogareth » Thu Nov 08, 2018 8:08 am

That's filled the gap :-)
2018-11-07 11.28.48.jpg
2018-11-07 11.28.48.jpg (48.54 KiB) Viewed 362 times
Gareth

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Re: Portsdown boxing/build thread

Post by radiogareth » Sat Nov 10, 2018 2:12 pm

Front panel done :-) Just got to wire it all up now.....
2018-11-10 13.55.34.jpg
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Gareth

G1BVI
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Re: Portsdown boxing/build thread

Post by G1BVI » Sat Nov 10, 2018 7:32 pm

Hi Gareth
Looks like your printer has been working overtime :-)
You could add audio out, which I use when I stream to Portsdown

73
Nick

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Re: Portsdown boxing/build thread

Post by radiogareth » Sat Nov 10, 2018 8:10 pm

Sorting out a linear power supply today and work on the back panel. Using a LM338 with 13.8 as Vin (less 0.4 via a 10 amp schottky diode for reverse polarity protection). Test run with a load of 1.07 amps gives a steady state heatsink temperature of 52 Degrees C in a warm room, still air. Testing my RPi3B+ and it draws a max of 0.7 amps. The various peripherals are not going to add up to another 300 mA so I thinks its good to go. Bigger heatsink can easily be subbed-in if advice is to keep it cooler.
In pursuit of 'electrical silence' as far as possible. Case is plastic except front and rear panels, so not much screening as-is.

Gareth.

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Sat Nov 10, 2018 8:12 pm

Thanks for reminding me Nick, I'll be putting a small audio amp and speaker in there somewhere to save too many external leads :-) Probably on the lid if I can find my mylar cone units I bought about 20+ years ago ;-)

Gareth

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Re: Portsdown boxing/build thread

Post by G1BVI » Sun Nov 11, 2018 8:42 pm

I use PC speakers powered from one of the USB port of Pi.
There is plenty of volume.

73

N

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Mon Nov 12, 2018 7:14 pm

Just tested this: https://www.ebay.co.uk/itm/PAM8302-2-5W ... 2749.l2649 very adequate when fed with line level. Runs well on 3.3 or 5 volts.
Less than a £1 each delivered. With a mute function. Progress :-)

radiogareth
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Re: Portsdown boxing/build thread

Post by radiogareth » Tue Nov 13, 2018 12:41 pm

And onwards to including the attenuator (PE4302) which is directly connected to the output board input with a male/male SMA.
The data sheet says its rated for +30dBm which = 1 watt. So is anyone running one of the many 50 ohm in/out amps that are around on eBay before their attenuator? It would seem the best place to put in a bit more...

Thoughts and suggestions welcome.....

Gareth

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