Losses in Coax Fittings?

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rwilsond

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Does anyone have an idea of how signal power losses in coaxial fittings vary with signal frequency?

I know coaxial cable attenuation is frequency-dependent, but what about their end fittings, and connectors? Are the losses fairly constant (regardless of signal frequency), or are they as sensitive to signal frequency as the coaxial cable? Fyi, this is for composite video signal, in the 0-20 MHz range.
 

K9WG

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0-20Mhz range won't see much of an loss with good quality connectors. Where you would start to see losses is in the VHF/UHF frequencies and even then the connectors don't contribute that much.
 

prcguy

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Most any properly installed connector will be fine for composite video, BNC, F, RCA, etc. BNC is good to over 2GHz depending on the brand and construction. For SDI or other wide band digital video modes you would not want too use RCA.

Even at 1GHz there is only a fraction of a dB loss and usually well under .1dB in BNC, N, TNC and similar connectors and adapters.
prcguy
 

Thayne

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Just adding to all that said above, it is always wise to minimize any connectors or splices as much as you can in any RF or any other electrical conductors of any kind. (Saves $$ too)

But as always, Ya gotta do what ya gotta do.
 

SCPD

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dB

Generally, every fitting is about a 0.1 dB loss. Some connectors are better, UHF is worse.
But you get a little loss at every fitting, no matter what.
 

mpddigital

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The exception to all the above is the old PL-259 connector. Loss on PL259's go up Significantly the higher you go up in freqs. For anything above 300MHz your loss will be really recognizable. Any connector increases in loss as frequencies rise but the PL-259's are pretty bad.

On another note, some of the chinese makers are using very poor quality alloys or just plain badly made connectors that "leak" much worse than average. Stick with a decent brand and be careful of bargain connectors. If price is most important there are some nice ones made in Taiwan that are not expensive.
 

prcguy

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Not really, good quality Silver Teflon PL-259s and mating SO-239s can have very low loss to at least 500MHz and even though you can measure maybe several tenths of a dB loss at 1GHz, nobody would ever notice on a police scanner antenna.

If you look at some Motorola UHF duplexers and cavaties they have PL-259s. On a 4 cavity 500MHz duplexer that's 5 PL-259 connectors in series with the RX and 5 in the TX path plus an SO-239 Tee adapter and the loss is nothing to worry about.
prcguy


The exception to all the above is the old PL-259 connector. Loss on PL259's go up Significantly the higher you go up in freqs. For anything above 300MHz your loss will be really recognizable. Any connector increases in loss as frequencies rise but the PL-259's are pretty bad.

On another note, some of the chinese makers are using very poor quality alloys or just plain badly made connectors that "leak" much worse than average. Stick with a decent brand and be careful of bargain connectors. If price is most important there are some nice ones made in Taiwan that are not expensive.
 

K9WG

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While all the above is true, let us not forget the OPs original requirement was for "composite video signal, in the 0-20 MHz range". You are not going to see much signal degradation unless you use really crappy quality connectors or an inordinate number of them.
 
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