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Good day,
I believe what you are saying is the noise floor of the instrument is 70 dB below the 0 dB reference line. The 0 dB reference line would represent 0 dB return loss or complete reflection of the incident voltage; a reflection coefficient of unity. Hence, the noise floor of the instrument would prevail and limit the minute reflected voltage that could be detected if the load were a perfect termination to the instrument. Hence a reflection coefficient of zero. This noise floor is 70 dB below the 0 dB reference line... Sure, I agree. I think if you drop the notion that the noise floor is the return loss value you are measuring will be on the same page. Have a great day, Alan ________________________________ From: [email protected] <[email protected]> on behalf of tuckvk3cca <tuckvk3cca@...> Sent: Monday, August 5, 2019 8:07 AM To: [email protected] <[email protected]> Subject: Re: [nanovna-users] NanoVNA Under The Covers Here is the RLB that I have got. I have checked with manual measurements that at the HF end I can get 60dB return loss. I do not expect the nano vna can out perform this unit, but I want to make sense of its 70dB return loss. Is that so difficult for people to understand?Sent from my Samsung Galaxy smartphone. -------- Original message --------From: Peter Gottlieb <hpnpilot@...> Date: 05/08/2019 03:52 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] NanoVNA Under The Covers How would you measure that kind of return loss accurately?PeterOn 8/4/2019 9:50 PM, Dr. David Kirkby from Kirkby Microwave Ltd wrote:> On Mon, 5 Aug 2019 at 00:32, tuckvk3cca <tuckvk3cca@...> wrote:>>> That 1.005 swr is up at the 5GHz end I presume. At 500MHz you can get>> 70dB. I have seen some people complain that some such loads have a bump>> at 1GHz, origin unknown.Sent from my Samsung Galaxy smartphone.>> Why do you assume that you can get 70 dB at 500 MHz? I think you can be> pretty sure if Keysight believed they could get a 70 dB return loss up to> 500 MHz, it would be in the data sheet.>> I very much doubt NPL, NIST, METAS or any other national standards> laboratory could measure 70 dB return loss.>> Dave.>> |
