THE POWER LOSS ADVANTAGE OF USING 3 dB COUPLERS

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glovisol
Posts: 567
Joined: Thu May 10, 2018 6:42 pm
Location: Piedmont, Italy

Re: THE POWER LOSS ADVANTAGE OF USING 3 dB COUPLERS

Postby glovisol » Tue May 07, 2019 6:35 am

sdrom33, knowledge from experience has general usefulness only if supported by theory. If you experience certain results from your practical setup, nobody can guarantee the same results will be experienced by somebody else. Therefore your experience is only valid for yourself. The more so if you state that generally accepted measurements and criteria, like VSWR or return loss, have no validity and are just a waste of time.

The calculations exposed in this thread put anyone who needs to split an antenna output among receivers on solid ground for his work and also explain in detail why certain results may be experienced under given conditions.

To conclude, while with small aperture antennas the rule is to use any single drop of incoming signal, so any loss between antenna and receiver should be minimised or eliminated, with medium and large aperture antennas in between attenuation should be beneficial in that it increases dynamic range of the receiver without damaging the signal to noise ratio (incoming noise is reduced of the same amount as useful signal). The real point is how you get this attenuation.

viewtopic.php?f=5&t=3723

In my opinion one should strive for minimum loss in any case and then add known and controlled amounts of attenuation as necessary: only in this way one proceeds in a fashion whereby he knows what he is doing and does not go blindfolded.

In this respect the HI Z 3 dB Hybrid, used with a long wire antenna has the advantage that eliminates all losses due to coaxial cables and mis-match, while providing a balanced and local noise rejecting termination. With this device the power loss advantage is exploited in full.

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