Thank you!

Gênio!!! Parabéns!!!​@@pauldenisowski

Lollll prolly from Keysight

3 from keysight, 2 from anritsu XD

Why did you think of that?

@Alter Kater Yeah that kind of bothers me as well. The video assumed that the source is perfectly matched to the tline

😂😂😂

We're happy you're here - and more is on the way!

Thanks Richard - really appreciate the feedback!

Thank you!

Thanks a lot for the positive feedback - that motivates us!

Thank you!

@@pauldenisowski Thanks for the great video! and I have some things to ask. The frequency of the reflected signal is the same as the frequency of the forward signal or not? And how about the relative phase between them?

​@@Tom-dn5de Generally speaking, the signals appearing at all ports of a network will have the same frequency as the input signal but different phases and amplitudes. It is possible to make S-parameter measurements on frequency-converting devices, but this is a more advanced topic that needs its own video :)

@@pauldenisowski Thanks a lot for your explanation. I am taking a VSWR measurement of an RF source, but I don't know why an auxiliary generator is used which transmits a wave with a slightly offset carrier frequency into the DUT. Could you explain it to me?

Thanks -- sometimes a picture really is worth a thousand words :)

Thanks for the support! There are always things that I could do better in these videos, so I appreciate any and all comments. 73, Paul KO4LZ

What a wonderful comment.

Good

Thanks!

😎 👍

That's great to hear Glen! Thank you for the feedback

Glad it was helpful. Foldback has saved me from destroying quite a few things in my career :)

Thanks! There is obviously a LOT more than can be said about VSWR and return loss (not to mention all the underlying theory and math), so we try to focus on the basics :)

Thanks! We just posted a series of videos on oscilloscopes today and there will be many more videos in this series, so please stay tuned!

Thanks!

Thanks - appreciate the feedback!

Thanks!

Thank you!

Thanks for the feedback!

My pleasure - thanks for the feedback!

I actually agonized over whether to pronounce it the way all of my customers and co-workers do (viz-wahr) or spell it out :)

Thank you!

Thanks and good luck!

Thank you!

Thank you!

Hi Yaroslav - Thanks for your comment. "Return loss" is the standard industry term for this measurement, but I will agree that this term can be a bit problematic. In fact, the editor-in-chief of IEEE Transactions on Antennas and Propagation published a short article in 2009 describing the origins and proper use of the term "return loss" -- it appears close to a third of the people submitting papers to this journal were using the term incorrectly. (Link below, available to IEEE members). From the article: "Turning to present-day usage, return loss is now the most common term used to describe reflection and mismatch." ieeexplore.ieee.org/document/5162049?arnumber=5162049

@@pauldenisowski Thank you Paul. I will look into it.

Thanks for the feedback!

Dear Richard, for calculating VSWR using power instead of voltage, you can use the following formula: VSWR = (1 + p) / (1 - p), where p = sqrt(reverse_power / forward_power). Best, Rohde & Schwarz Social Media Team

@@RohdeundSchwarz If above formula is to be used fo this conversion, when should we use the the formula mentioned at 6:12 relating return loss and VSWR?

Unless the load is purely resistive (and your antenna almost certainly isn't), the VSWR will be a function of frequency -- i.e. it will change depending on the frequency of the signal generated by the source. In most cases, the easiest way to minimize reflected power is to have a source, load, and line impedance that are all as similar as possible. Even though a lot of people successfully use RG6 with 50 ohm sources, you might want to consider a different cable type. There's not much you can do about the impedance of the antenna, but keep in mind that this may also change based on how and where the antenna is mounted (i.e. what's next to it). It can be very difficult to reliably and accurately determine VSWR based on the (nominal) values of components in a system. I can do the math and calculate how long a dipole *should* be to have a given VSWR over a given frequency range, but when I actually build it and hang it from a tree or (especially) in my attic, the VSWR is never precisely what I calculated (and is sometimes quite different). The math may give you a good starting point, but the actual value of the assembled system will often be at least somewhat different. This is one of the reasons why instruments like network (or antenna) analyzers exist -- measurement is the only reliable way to know for sure what your VSWR actually is. Hope that helps!

Thank you!

The complex conjugate provides the exact match. This calculator might be helpful to play around with: www.analog.com/en/design-center/interactive-design-tools/rf-impedance-matching-calculator.html

RL should have the name unloss :))

I agree completely that the term "return loss" is very problematic. As I've mentioned a few times in the comments, it's confusing even to RF engineers, so much so that the editor of an IEEE journal had to publish an article explaining the "proper" way to use the term :)

Hi, thank you for your feedback. This is correct, yes.

If the forward and reflected powers are in units of dBm, the difference between these values (X dBm - Y dBm) will be in units of dB (not dBm).

@@pauldenisowski ?? i thought dBm-dBm=dBm. could you please explain more or give me an example ?

@@43SunSon Sure :) One of the more common "rules" when it comes to decibels and logarithms is that reducing a value by 3 dB is the same as decreasing it by one half. The difference between one watt (30 dBm) and one-half watt (27 dBm) is .... 3 dB. The power value 3 dBm is approximately 2 mW, not one-half watt. Rohde and Schwarz actually has a whitepaper that explains this and quite a few other things regarding decibels: scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1ma98/1MA98_13e_dB_or_not_dB.pdf Hope that helps.

@@pauldenisowski oh my man! you did well! I am reading that pdf. How did you know that much? Are you in this area as well?

@@43SunSon Thanks. I'm an engineer at Rohde & Schwarz working in radio frequency test and measurement, so I deal with dB all day, every day :) If you're interested in learning more about RF, please check our website for additional whitepapers, application notes, etc.

If you mean S11, please see the video "Understanding S-Parameters"

@@pauldenisowski I am not referring to S11 I am trying to say that when two ports which are connected differential then the S parameter for that is called Sd11 it is not as same as S11 we will get S11,S22,S12,S21 from that we need to find Sd11 that was my doubt if you can help me.please reply.Thank you sir for your reply

​@@kavithasenthilkumar4533 Differential mode S-parameter measurement is probably a bit too complex of a topic to address in a UKposts video comment :) Rohde & Schwarz supports these measurements using our VNAs and we have numerous application notes and presentations on this topic, e.g. cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ez53/1EZ53_0E.pdf Hope that helps!

Sorry, but could you clarify what you're referring to? I don't believe I ever said anything about antenna gain in units of dB or dBi. The y-axis of the graph at 2:39 was intentionally labelled with the generic unit "impedance" for the purpose of illustrating that impedance is non-constant for most antennas, at least compared to the dummy load on the previous slide A graph of gain for a directional antenna like the yagi shown would usually be a polar plot showing gain in dBi (relative to an isotropic radiator) as a function of azimuth. You are absolutely correct in that the gain of an antenna is almost always given in dBi -- one exception would be something like front-back ratio, which would be in dB, not dBi. Again, my apologies if I'm misunderstanding you. And I can assure you that the good people at R&S are familiar with the different types of dB: in fact, we have an entire educational note on this very topic :) scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1ma98/1MA98_13e_dB_or_not_dB.pdf

For a start because decibels is based on log functions there are no units as such in the argument. One can refer to an antenna gain without referring to a theoretical antenna that has a perfect spherical radiation pattern, in practice such an antenna does not exist or you can just use decibels without the isotropic reference. Decibels is based on ratios of things like power, voltage so that the log function argument has no units.

The reflected power can damage the finals in radio transmitters. These finals then need to be replaced. Been there and have witnessed this happen.