Transmission range

Help and support for the BATC DTX1 ATV digital encoder and modulator system
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g6rvs
Posts: 3
Joined: Tue Feb 04, 2014 1:38 pm

Transmission range

Post by g6rvs » Tue Feb 04, 2014 1:52 pm

Hi
I have been using a standard 2.4GHz video sender for a while for a 'roving camera' but I'm now finding it getting less reliable due to the plethera of 2.4GHz devices that are now around.
One of my applications I tend to have a maximum required distance of around 10 metres, has any one tried a simple aerial (dipole?) on the output of the DTX1, or should I use a tiny PA?

g4wvu
Posts: 51
Joined: Sat Jun 22, 2013 10:42 am

Re: Transmission range

Post by g4wvu » Wed Feb 05, 2014 8:32 am

10m ; you should only need a 1/4 wave stuck in the back of the receiver & likewise DTX1. Output is approx -5dBm & a half decent receiver should work down to -90dBm, so this would give a range somewhere about 500m @ 500mHz in line of sight conditions with no aerial gain (not sure what frequency you're using - path loss at 500m @ 500mhz is about 80dB). No amp. needed at 10m ! ;)

g6rvs
Posts: 3
Joined: Tue Feb 04, 2014 1:38 pm

Re: Transmission range

Post by g6rvs » Sat Feb 08, 2014 12:17 pm

Thanks for this info, it confirms my thoughts (I was guessing 200m) but casual chats with others reckoned it would not work.
I have not thought too much about frequency yet but it may be 50/50 amateur/jfmg, which is why I'm looking at the DTX.

Many thanks

Ray

2E0DTX
Posts: 44
Joined: Thu Oct 03, 2013 6:32 pm

Re: Transmission range

Post by 2E0DTX » Sat Feb 08, 2014 2:59 pm

This may seem a strange question but does the use of one's call sign as the channel name on a digital transmission alone satisfy the licence conditions for identification every 15 minutes and at the start of a transmission? :)

g6rvs
Posts: 3
Joined: Tue Feb 04, 2014 1:38 pm

Re: Transmission range

Post by g6rvs » Sat Feb 08, 2014 7:49 pm

Thats a good point.

I kinda think the ident should be in the same format as the rest of the transmission... or morse.

But I don't know!

g4wvu
Posts: 51
Joined: Sat Jun 22, 2013 10:42 am

Re: Transmission range

Post by g4wvu » Sun Feb 09, 2014 12:41 pm

Hi Ray, thought occurred to me actually. The receiver sensitivity / threshold is quite dependent on the bandwidth being used. i.e. although 2MS/s & 1/2 FEC signal might work down to nearly -100 dBm , at wider bandwidths (higher bitrates which I rather suspect you will be using for high quality / good motion MPEG performance) and higher FEC this will drop by up to 20dB (depending on parameters) I guess suck it & see :D

BTW Good Q on callsign laurence... :? ?

regards Mark.

M0DTS
Posts: 392
Joined: Sun Feb 24, 2008 9:03 pm

Re: Transmission range

Post by M0DTS » Mon Feb 10, 2014 2:36 pm

As far as i'm aware you only need to identify your callsign by the mode you are using.

but...

On D-Star voice in theory you dont need to give your callsigns as the rig is already showing it... even via a repeater.
On TV you could identify in Voice,Video and Digital channel name etc but via a repeater the channel name does not work.

Grey area as usual ;-)

Rob
M0DTS

g8gtz
Posts: 1165
Joined: Wed Apr 07, 2010 6:26 pm

Re: Transmission range

Post by g8gtz » Mon Feb 10, 2014 5:38 pm

Rob is correct - as long as we run standard DVB modes putting the call sign in the SI is more than adequate - when going via repeater, as far as Ofcom is concerned, it's the repeater that then needs to be identified in the SI.

73

Noel - G8GTz

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