Success Stories

Discussion about this major DATV Project. See also https://wiki.batc.org.uk/The_Portsdown_Transmitter
VK5BI
Posts: 27
Joined: Mon Mar 30, 2015 9:32 am

Re: Success Stories

Post by VK5BI » Sat Feb 17, 2018 4:26 am

Just completed this afternoon. Uses the element 14 touchscreen. Now for the final testing tomorrow.

Wayne VK5BI
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G8PEF
Posts: 97
Joined: Mon Oct 30, 2017 6:42 pm

Re: Success Stories

Post by G8PEF » Fri Mar 23, 2018 3:22 pm

Not quite a success story (yet), but progress - and successful in the sense that I managed to get this far without b*ggering anything up (we'll brush aside a slight issue with L10 on the LO filter board... ;) )

I'm now at the point where I need to join all the bits together and devise a suitable layout inside the case - this, mainly metalwork task, might take me a while as I'm up to my eyes in extensive house DIY when I'm not at work, at the moment. With that in mind, once I have the tx working properly, I might nip up the hill and arrange some on-air testing before its boxed up. Watch this space, as they say.

EDIT: I tried to attach pics of the pcbs, but for some reason, although the post looks (or rather, looked) fine in preview, it lost all but one of the pics when posted - and therefore the caption(s) didn't make any sense. If anyone knows how to insert (inline attach) multiple pics successfully, please let me know...
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G4uvz
Posts: 121
Joined: Sat Dec 09, 2017 10:30 am

Re: Success Stories

Post by G4uvz » Fri Mar 23, 2018 5:23 pm

I too have struggled with multiple pic uploads...There seem to be two routes to doing it but neither is intuitive!

M1ASR
Posts: 19
Joined: Mon Dec 11, 2017 8:24 pm

Re: Success Stories

Post by M1ASR » Sat Mar 24, 2018 1:05 am

One of the objectives of The Portsdown Project is to use ordinary antennas across town. Tony G0AZQ and myself managed to transmit and receive a 2M signal around 10 miles this evening. We both used 2m/70cm colinears at no great height. I live at sea level and Tony isn't much higher. Tony sent a signal at 333Ks, via a 16W PA. I received a solid signal on a MKII Minitioner without a preamp inline. No great shakes, but it does demonstrate proof of concept. Test Card & Picam image rx fine. Good constellation, but MER low (not sure if Minitioune Software is a bit mean!).

Next stage is to repeat on 70cm, however we failed at first attempt. Preamp definately needed using this lash up. Will reverse the route when my PA arrives. Saving 23cm until GB3EY hopefully gets resurrected.

Graham M1ASR

gi3vaf
Posts: 11
Joined: Thu Apr 05, 2018 6:01 pm

Re: Success Stories - Portsdown to MiniTiouner across the shack 23cms..

Post by gi3vaf » Tue Apr 24, 2018 3:19 pm

Setting up was straightforward and it even knew my callsign and grid square ;)
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M0YDH
Posts: 137
Joined: Sat Dec 31, 2016 5:59 pm

Re: Success Stories

Post by M0YDH » Mon May 07, 2018 6:24 pm

Yesterday I sent DATV on 437MHz 333Ks/s to Dave G7MEG a whole mile away and, after a while / hoisting the mast up to max height, he received my test card then Pi Camera pictures on Minitioune. Well done Dave :!: :D I'm cocker-hoop. That was BATC activity day in Wolverhampton - the first one in living memory. Here's my gear in action.
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73

David M0YDH

M0YDH
Posts: 137
Joined: Sat Dec 31, 2016 5:59 pm

Re: Success Stories

Post by M0YDH » Sat Apr 13, 2019 7:34 pm

Hello All
I've made a Portsdown 2019 with a 3.5" screen so I can have composite video out for FM transmitter use.
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Front Panel
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As is traditional the bloody Waveshare screen packed up after the Amazon return period and a second had to be bought :oops: . The bezel is printed by Gareth G3XAT which provided the near net shape and needed rebates cutting in with a router plane and a 30 thou styrene packer to remove lost motion on pressing the screen. Below the screen is a circuit card from a scrap PC with USB sockets and microphone and Headphone sockets. I've replaced a USB with a HDMI socket card from Tindie RPi Camera HDMI Lead Extension Kit. a 30cm PI cam extension ribbon is used. The Portsdown was receiving BBC Radio 2 on FM during the photos [after I'd found that the audio from the RTL SDR dongle comes out of the headphone socket when the USB sound dongle is connected!].

I made the case from aluminium lids out of scrap 19" rack cases which were anodised black. It's 320 long by 220 wide by 110 high. for neat wiring runs you would need an enormous case and start with larger sheets of ally than box lids! I bought a rivnut set and extra M3 rivnuts to make the connections between sides. Folding was in my woodwork vice over a section of industrial aluminium window frame so I worked with the resultant bend radius when fitting the front and end panels.
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Lime SDR in G3XAT case and 8 way RF switch are on a bracket above the 7 port USB hub
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The arrangement of the ICZI brand 7 Port USB 3.0 Powered Hub at right angles to the RPi 3B+ with a the Lime Mini SDR on a bracket over the hub that carries the 8 way RF switch seems the best way to get all these components in the right orientation and cope with the awkward, stiff nature of USB leads.
I haven't fitted the attenuator that I have yet. The RF switch isn't amplifying at the moment so a re-do of all the soldering on this card is imminent.
8 band decode is fitted and fully wired to a bank of RCA sockets [on a plastic sub-panel]. I also have LSB, MSB, T, PTT etc on a Sub D connector for use with my Tx/Rx relay changeover controller. The EASYCap and RTLSDR are held by a bracket with a nice joggle in it to the side wall.
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Rear panel shows band decode outputs [RCA sockets], RTL SDR on the BNC
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Portsdown 2019 just uses two voltages ie 12V battery and 5.25V everything else. The single buck converter I found that works well (as far as I can tell) is described as DC-DC CC CV Buck Converter Step-Down Power Module 7-32V To 0.8-28V 12A 300W on Ebay. A small LCD voltmeter advises what it's up to. Mostly it displays blue no load light and changes to red on the Pi executing commands, going into Tx or running the audio amp. The converter is wired for -ve and not connected to chassis as its current load sensing is in the negative line.

The audio amp is described as TDA7297 AC/DC 12V 2*15W Digital Stereo Audio Amplifier Dual Channel AMP Module C on Ebay and is a bargain at £2.15. It drives a pair of 8 Ohm speakers. I originally thought that the audio from the RTL SDR comes from the composite video out on the RPi and took this to a double pole switch so I could send it to the loudspeakers or the composite video outputs. RTFM on the Wiki.

I hope that's interesting and useful to other builders. :)

Thanks to Prof Portsdown - Dave G8GKQ

73
David M0YDH
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g4hiz
Posts: 24
Joined: Thu Oct 18, 2018 6:40 am

Re: Success Stories

Post by g4hiz » Sat Apr 20, 2019 9:52 am

Hi all,

Please see below a few photos of my latest Portsdown 2019. The Pi and Lime are treat as two separate blocks with their own power supplies, with a switch-mode PSU for the Pi and Linear PSU for the Lime and they can be switched on/off independently. The Lime also has a USB socket such it can be connected to the Pi normally, or to an alternative computer if desired. For possible future use, the Lime Rx input is taken to a rear SMA terminal.

The Lime is powered via a hub and to ensure that the Pi cannot power it, the track with the series diode supplying power from the host is cut. To note that, at switch-on the Lime takes about 230mA and on transmit takes about 500mA. The Pi current can vary considerably, but typically 250mA was measured with no dongles and not taking into account any transient current demand due to intense operation.

The build has a 4-way band select board and a programmable attenuator. The display cable is taken out through the front panel so that the display is optional. The display itself fits snugly into a die-cast aluminium box and sits on spacers. For console control, the display can be detached.

A special feature is the ability to switch-off the Lime via the Pi. A series FET switches the Lime power supply off when a little-used band is selected, although this feature in itself is selectable via a link, so making the band available at other times. This provides the ability to remotely reset the Lime if it hangs-up.
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