Re: Joining co-axial cable outdoors

In which case. your, my and others conclusion that 'you won't notice any difference' is justified. Way under the sort of passband ripple you would get from the antenna anyway.

Reply to
The Natural Philosopher
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Unlikly given

(a the small refelction that has been demonstrated = 20dB (b teh fact that teh distances involved are small. you need a fair few meters to give a discernile ghost.

a line is 60Us long, roughly, so for 600 dots per line rough image quality, 100ns or less is indiscernible.

That equates to 3meters of cable. Quite a bit

Reply to
The Natural Philosopher

In message , Edwin Spector writes

Except that he's mentioned several times that it's not for TV

Reply to
geoff

Good points. However, just to clarify, the 20dB return loss was for the reasonably good joint. The bad joint had a return loss of about 11.6 dB. That's about 7% of the power being reflected. (20dB reflection corresponds to 1%). I'm not sure how noticable that ghost would be.

Also, don't forget that signals travel more slowly down cable than in air, by a factor of (say) 0.5 to 0.7 (.) So, it would only take 2m of cable to give a discernable ghost (by your test).

I added the note about reflections after a colleague's account of a bad ghost which was traced to a cable joint made using a 30A mains junction box. Who ya' gonna call?

Edwin.

Reply to
Edwin Spector

In article , Edwin Spector writes

In fact there a very well written article on a subject called pre echo where there is a possibility of direct pick up off poor cables directly from the transmitter and the delayed signal via a distribution system. Very good site this is if you're into TV etc...

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Reply to
tony sayer

3db is about 50% reflection, so probably less than 1db

I don't think its that much reduction.

I never advocated a bad joint in a 30A mains junction box :-)

Its been a long time, but certainly one TV installation I saw, had lost the entire connection to the aerial earth lead...it worked, but certain stations were vastly better than others - big drop - 10 meters plus.

No ghosts tho - or very few. Possibly because the discontinutity was at the antenna.

Reply to
The Natural Philosopher

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