Andrew, a major antenna and waveguide manufacturer offers a system design guide to design antenna/waveguide systems with guaranteed return loss performance. The method, on page 228 of the catalog here includes a 30% derating based on empirical evidence from thousands of systems they have designed (warning ~36MB file) : plymouthcolony.net/starcityeng/files/AndrewCatalog38.pdf
The method generally makes sense in that the return loss, or VSWR, performance of each element in a transmission system additively degrades the system return loss. I am wondering if anyone has practical experience with this or has knowledge of any software or online tools which performs a similar function?
At some of our radio sites we are measuring a system return loss of 14dB with as few as 5 rigid waveguide sections between our radio and elliptical waveguide which terminates in a high quality antenna. At other sites we have 6 to 7 sections of rigid and the system return loss measures higher than 20dB. Per the Andrews design guide, using only 5 sections of rigid waveguide with a VSWR spec of 1.05, it could be this bad. It could be better, but the guaranteed number is 14dB. Switching to narrowband rigid waveguide with VSWR spec of 1.02 could solve this, if Andrews is correct. However, coworkers are reluctant to believe the results and I am looking for other authoritative sources to collaborate (or debunk) what we are seeing.
The method generally makes sense in that the return loss, or VSWR, performance of each element in a transmission system additively degrades the system return loss. I am wondering if anyone has practical experience with this or has knowledge of any software or online tools which performs a similar function?
At some of our radio sites we are measuring a system return loss of 14dB with as few as 5 rigid waveguide sections between our radio and elliptical waveguide which terminates in a high quality antenna. At other sites we have 6 to 7 sections of rigid and the system return loss measures higher than 20dB. Per the Andrews design guide, using only 5 sections of rigid waveguide with a VSWR spec of 1.05, it could be this bad. It could be better, but the guaranteed number is 14dB. Switching to narrowband rigid waveguide with VSWR spec of 1.02 could solve this, if Andrews is correct. However, coworkers are reluctant to believe the results and I am looking for other authoritative sources to collaborate (or debunk) what we are seeing.
