RB-DATV from GI-G

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gi7ugv
Posts: 8
Joined: Tue Oct 31, 2017 2:47 pm

RB-DATV from GI-G

Post by gi7ugv » Fri Apr 20, 2018 12:00 pm

I'm pleased to report my first RB-DATV two way contact on 146MHz yesterday morning with Tony G4CBW at 283km, which is also my first ATV contact.

For this test we were to try DATV on 2m and 3cm if workable along with the 6cm FPV setup. My location was /p at the car park for Scrabo Hill IO74DN38 with Tony IO83UB93.

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3cm wasn't as good as a previous site I've spoken to Tony from so we didn't progress beyond a quick SSB contact. The 6cm TX test didn't work out either not unsurprisingly.

We had an easy contact on 2m FM with me using down to 2.5w from an FT-290 with a portable Elk log periodic.

With that result I tried a 333KS/s TX test from my Portsdown on 146.5 with 8w, and some additional loss from a little too low LPF, and to my surprise Tony copied fine! Of course it worked right at the start of a conversation with an interested passer by so I didn't noticed his message for a good while. I switched from the Portsdown test card to the Pi camera for a while which also worked fine. A few captures from his .TS recording:

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Tony them moved on to transmit but despite the good signals I wasn't expecting it to work at all given I was using a compromise antenna, no BPF or preamp but the car park site itself is somewhat protected from the local nasty transmitters by the rest of the hill. To make things worse the laptop didn't hold much of a charge and the inverter I'd taken along that hadn't seen daylight for 10 years didn't work...

I did however take a Windows tablet and USB OTG connector I had tried MiniTioune on previously but had decided it wasn't usable due to the screen size. But on this occasion it saved the day and I received Tony, the cutoff edge is down to the tablet issues but it's whole on the .ts file I captured while messing things up with the tiny touch screen over and over. Happy days :D

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Next tests will be using a better antenna, a not so lossy at 2m LPF and I will have a BPF/preamp setup sorted out for the receive side. Looking forward to more contacts with others this year.

Thanks Tony for the guidance and doing most of the antenna work on this one!

John - GI7UGV

g8gtz
Posts: 958
Joined: Wed Apr 07, 2010 6:26 pm

Re: RB-DATV from GI-G

Post by g8gtz » Fri Apr 20, 2018 5:42 pm

Excellent!

That is very close to UK (world?) record for 146MHz DATV which was previously held by G0MJW (Winter Hill) and Mike G8LES in Hampshire at 294 Kms made under lift conditions - viewtopic.php?f=75&t=4775&start=10#p11492 .

73

Noel - G8GTZ

gi7ugv
Posts: 8
Joined: Tue Oct 31, 2017 2:47 pm

Re: RB-DATV from GI-G

Post by gi7ugv » Sat Jul 14, 2018 10:35 pm

Had another outing today a bit further away near Larne, IO74AU to try 2m & 3cm DATV with Tony again at 313km. I had some assistance this time from Neil MI6XZZ and was trying out a new antenna from antennas-amplifiers for the first time.

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The path was as linked here, http://k7fry.com/grid/?qth=IO83UB93&from=IO74AU98XP, and glad to report it worked on 146.5. The initial FM contact on 144.750 was s9 using 2.5w so it looked good to go on 2m, 3cm SSB worked okay peaking s8/s5 with QSB so we focused on 2m.

My 2m 333kS TX was received by Tony okay but with occasional QSB making the signal drop entirely before returning, test animation from the Portsdown and video from the Pi camera were sent.

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We did have some bother receiving Tony so he dropped to 125kS which still didn't work. After some head scratching and cable switching while packing up thinking a two way QSO wasn't happening, we noticed a drop in background noise when the laptop psu was disconnected. On removing the PSU Tony was copied at 125kS, then 333kS with the same occasional complete drop outs as observed before. Then the laptop battery died stopping play..

The screen was hard to see due to the sun, colour image from the TS file:

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We followed this contact up with a slightly delayed trip around the other side of the hill to work Nick on Arran on 6cm just after Geoff GDP had finished up.

A good day, thanks Tony, Neil and Nick!

73,
John

KenW6HHC
Posts: 273
Joined: Mon Jun 01, 2009 4:20 pm

Re: RB-DATV from GI-G

Post by KenW6HHC » Wed Aug 08, 2018 4:16 pm

Hi John GI7UGV and Tony G4CBW,

A big congratulations to both of you. Your 2M RB-DATV QSO on 2018-07-14 between N. Ireland and Staffordshire is the longest DATV QSO that I am aware of for 2M at 313 KM.

I have updated the Known-DATV-DX-Records file on the BATC wiki at https://wiki.batc.org.uk/ under OPERATING topics.

73...de Ken W6HHC

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