Dale Martin wrote:
>On Saturday, August 30, 1997 15:37 PM, Steve
>Daniel[SMTP:daniels@bellsouth.net]
>wrote:
> does splicing together 2 pieces of coaxial
>>cable result in any significant increase in the loss characteristics of
>>the cable? For the purpose of discussion (and to make it real, to me) I
>>am talking about 30 mhz and below, RG-213 or 9913 type coax and properly
>>soldered PL-259 connectors and a good quality double female connector,
>>all nicely tightened and properly weatherproofed. Any thoughts on the
>>db/splice loss would be appreciated. 73, Steve, NN4T.
>>
>Somewhere, in the deep, dark recesses of an old NCJ magazine
>there is an article by K2TNO, Bill Schrader, in which he describes
>the results of a demonstration he did using multiple double female,
>double male, straight and right angle connectors, connected in
>series, fed with a signal generator, swr meters, and a dummy load.
>The bottom line was that, even with more than a dozen of these
>connectors in line, the swr and loss was minimal, even at UHF
>frequencies.
>
NA1L made some similar measurements on straight 239/259 junctions,
confirming that there's absolutely no practical problem up to way beyond
30MHz. Any sign of a VSWR problem indicates that the connectors are
either sub-standard or improperly installed.
At VHF/UHF there are small insertion losses, caused almost entirely by
reflection at the small impedance mismatches, rather than dissipative
(heating) losses. These can lead to minor problems at 144MHz and above
if you have several connectors in the cable run, and the electrical
lengths of the intervening sections of line are such that the
reflections all add together. In such cases you might see a worse VSWR
in the shack than at the antenna (say 1.5 for an antenna VSWR of 1.2).
On the other hand, with favorable cable lengths, the reflections could
be completely canceled at the transmitter end, so YMMV.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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