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Bending coax cable decreases output power?
#1
Is it true, that bending coax cable decreases output power? My VTX has a SMA connector on a wire and after mounting it to the frame it would be like in the drawing, maybe even stronger bend. Should I care about the bend or it's just a myth?
#2
Yes you will get reflexions if you bend the cable too much.
Look at the spec sheet of the cable, there should be a minimum bend radius somewhere. There's one version that is very sensitive while the others tend not to be as bad if you curve rather then corner them.


basically this happens because bending the cable will cause slight EMF interference from the reflection at the bend. Signal quality can be marginally affected
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#3
Exceeding the maximum allowable bend in a coax cable changes the distance between the centre wire and surrounding metal sheath. It also compresses the dielectric and changes its dielectric constant.

Both of these things change the impedance of the cable and result in a mismatch between the transmitter and the cable which will cause a significant increase in how much of the transmitted signal is reflected back into the transmitter's output stage. If the mismatch is really bad, it will not only result in less radiated signal, it can damage the transmitter!

As to it being a 'myth', things are made the way they are for a reason and if anyone seriously suggested that bending a coax cable beyond the maximum allowed was problem free and that the negative effect is a myth, I'd say that you should ignore anything that person has to say on the subject as they don't know what they're talking about!
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