Re: Signal loss - loft v roof mounting


"Ian Jackson" <ianREMOVETHISjackson@xxxxxxxxxxxxxxxxx> wrote in message
news:+DecDfTCrybJFwBa@xxxxxxxxxxxxxxxxxxxx
Because of their mechanical construction, a lot of 75 ohm connectors are a
bit (even distinctly?) capacitive. Some are adaptations of their 50 ohm
counterparts, where the capacitance isn't a problem. It's usually the
females which are worst (isn't it always) - especially certain F and B&L
barrels. These will certainly produce a reflection, and thereby introduce
a small insertion loss (and maybe also some response ripple etc), but this
is unlikely to exceed 0.2 or 0.3dB in the worst cases at UHF TV
frequencies. However, such impairments are likely to add up, so it would
be unwise to have more additional connectors than really necessary.

It's worthwhile to subject various connectors to tests if they are a new
item. I use a noise generator and spectrum analyser. The results can be
amazing. One make of 'f' rt angle connector (as Ian mentions) somehow puts a
6dB ripple right across the UHF and satellite IF band.

One make of earth bonding 'f' adaptor for multswitch use seemed to cause
ripple at UHF but not at satellite IF. Dunno how this can be.

Don't get me wrong. 'Additional' connectors should always be used with a
certain amount of circumspection. There are times when they are definitely
'out'. But I do feel that they have an undeserved bad reputation for
causing problems with normal domestic TV signals.

There are certain rogue items that give the rest a bad name! I normally
regard two 'f' conns and and 'f' barrel as lossless, and I stand
undisappointed as yet.

Bill


.

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