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Old February 12th 18, 09:13 AM posted to uk.radio.amateur,rec.radio.amateur.homebrew
Rob[_8_] Rob[_8_] is offline
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First recorded activity by RadioBanter: Dec 2008
Posts: 352
Default Computer / radio isolation for digital (or even voice?)

Ian Jackson wrote:
In message , Lucifer
Morningstar writes
On Sat, 10 Feb 2018 11:21:17 +0000, Ian Jackson
wrote:

In message , Lucifer
Morningstar writes
On Fri, 9 Feb 2018 21:53:50 +0000, Ian Jackson
wrote:

In message , Gareth's Downstairs Computer
[email protected] com writes



https://www.ebay.co.uk/itm/10x-Audio...Ohm-Europe-1-1
-EI14-Isolation-Transformer-Newest/172824007609?epid=2184088304&hash=ite
m283d1d13b9:g:d2EAAOSwDmtZlWH2

That's a fantastic price. I'm using a 600/600 ohm audio transformer to
isolate an earth-loop problem between the rig and the PC (extracting the
audio to feed into the sound card so I can get SSTV and DRM pictures
using MMSTV and Easypal).

I intend to try transmitting DVB-T on 438 Mhz but from what I have
read doing such will result in extra bandwidth due to sidebands.

I'm not sure how wide a single 'programme' DVB-T MUX is - but I suspect
it should fit inside the top end of the band. However, be aware of the
presence of certain non-standard repeater shifts (some up to 7.6MHz, I
think). Aren't some people trying live digital in the 1MHz extension of
2m? You need to check with the BATC.
http://www.batc.org.uk


I have DVB-T encoder modulator that can do 4 programs anywhere
from 30 to 960 Mhz.


But how wide is it when it carries only one 'programme'?


In theory it could omit carriers and transmit a narrower signal at
lower bitrate, but in practice "standard DVB-T transmitters" cannot
do this. I heard some amateurs produced modulators and alternative
firmware that can do e.g. a 2 MHz wide DVB-T signal.