ATV on 6cms - It's Cheap and Easy on 5665MHz

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Trident
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Joined: Thu Mar 08, 2018 10:28 pm

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by Trident » Sat May 02, 2020 10:20 pm

Hi,

I note there seem to be comments about the 2.5 Watt PA's being rather fragile and my experience has unfortunately borne this out despite being careful. Has anyone been able to shed any light on why they expire so easily?

GM0ICF
Posts: 4
Joined: Sun May 10, 2020 7:10 pm

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by GM0ICF » Tue May 12, 2020 1:24 pm

Hi All,
A quick hello....
I came across the BATC info on 5.6GHz entirely by accident! I already had some gear from some other activities and with a quick bit of soldering I am essentially QRV!

Have one 45cm dish for TX, that's ready to go, and an 65cm dish for RX (feed needs some attention on that one) I have access to a couple of decent sites for /p ops that give me a excellent path to GI (I can see the Antrim coast!) and good-ish to north west G. Once the Covid restrictions have fully been lifted I'd be interested in trying some video QSO's with anyone in GI or northern G (over the summer).

Cheers,
Bill GM0ICF

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

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by gi7ugv » Wed May 13, 2020 4:35 pm

Hi Bill,

Happy to have a go any time either North Down at sea level or along the Antrim coast higher up, have managed over to Arran from north of Larne so it's certainly worth trying!

73,
John

GM0ICF
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Joined: Sun May 10, 2020 7:10 pm

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by GM0ICF » Sun May 17, 2020 10:01 pm

Hi John,
Thanks for the reply. I've still got to knock together a second feed but hopefully that won't take to long. I'll let you know as soon as I'm ready.
I'm in IO75PP and have access to a couple of elevated spots or, likewise, can work at sea level but much closer to you from south Ayrshire.
If you can get to Arran you'll probably be able to make it to me.
I take the o/p from an action cam via it's TV Out mode but I seem to have an audio problem, however, one step at a time, HI!
cheers,
Bill.
PS. Who did you work in Arran?, that'd be another possible contact I could try.

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

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by gi7ugv » Tue May 19, 2020 5:58 pm

That was Nick G0HIK on holiday there, viewtopic.php?f=75&t=5551, depending where you can go to the south the guys in Cumbria might be a possibility too.

Give me a shout when you're ready, there's a couple of us over here that might want to give it a go!

John

GM0ICF
Posts: 4
Joined: Sun May 10, 2020 7:10 pm

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by GM0ICF » Sun Jun 07, 2020 2:19 am

Hi,
To keep things moving along I made two new feed horns out of 42mm copper pipe, so I'd have the same set up on each dish. However as I was messing around with an old CCTV camera I noticed the signal had gone... :shock:
The tiny TX seems to have self destructed. Took it inside and checked it over and it is a dead tx :(

Using an Agilent micro-watt meter and a directional coupler the swr of the feeds was less than 2:1, can't say much better as my measuring head is only calibrated to 4GHz. I wouldn't have thought this would have been too much of an issue given losses to AND from the antenna via the length of coax at 5.6GHz, but as it is now dead maybe it is!

One question, I only discovered this when I had to handle the thing when setting up for some terrestrial tests with the antenna supplied, do they all run that hot?!

Alarmingly toasty...!

A replacement has been ordered.

Cheers,
Bill.

g8vpg
Posts: 333
Joined: Fri Oct 11, 2013 9:35 am

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by g8vpg » Sun Jun 07, 2020 9:40 am

Bill,
I think a number of us have found that the transmitters do not last very long if you run them at full output power. The early ones had fixed output, but now most have a range of output settings. My solution has been to run it at low power and use an external amplifier. Initially I thought one solution might be to run them at reduced input voltage. However, this does not work because they have a switch mode power supply and reducing voltage makes them take more current.
73 Shaun.

GM0ICF
Posts: 4
Joined: Sun May 10, 2020 7:10 pm

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by GM0ICF » Sun Jun 07, 2020 3:24 pm

Hi Shaun,
Thanks, reducing the voltage was my very first course of action too, but I reckoned there was an internal issue as, as you say, the current went up and it made no difference. So let it run whilst I was messing around and pop, it ceased to function.
The one I've ordered is also a very cheap one but forewarned is forearmed...
I'll try some additional fan cooling with the next one. I've also been reading some stuff, mostly negative, about these so called 2000mW amps from China.
Any comments/advice on what to go for?
cheers,
Bill.

G8GKQ
Site Admin
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Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by G8GKQ » Sun Jun 07, 2020 4:53 pm

Bill

I've had 2 fail on me. One was due to a loose SMA connector, and the other simply died for no apparent reason. I've given up on them now and use either the barefoot 600 mW or my external (ex-Sat Ground Station) PA.

Dave

g8vpg
Posts: 333
Joined: Fri Oct 11, 2013 9:35 am

Re: ATV on 6cms - It's Cheap and Easy on 5665MHz

Post by g8vpg » Sun Jun 07, 2020 4:56 pm

Bill,
I was lucky enough to find a used professional amplifier at a rally. This has delivered 1W or so very reliably so far. I think many of the Chinese amplifier ratings need to be taken with a pinch of salt; you may get 50% of the claimed rating, at least for ATV. Running the transmitter module at 25mW has not caused any overheating issues.
73 Shaun.

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