Re: RETURN LOSS thoughts de k3eui
Well, since you are being pedantic (don't get me wrong, I like pedantic, it helps add clarity and reduce confusion): On Jun 28, 2021, at 8:13 AM, Barry K3EUI <k3euibarry@...> wrote: RL is positive - You "lose" 20 dB or whatever. Exactly So now the RETURN signal is attenuated by -X dB.
Now that feels right. Now you've got it backwards again. Return signal is attenuated by some number of dB, but that number (the amount that it's attenuated) is a positive number. You should say "So now the RETURN signal is attenuated by X dB." You wouldn't say "I drove 20 miles, now my gas tank has been emptied by MINUS one gallon", would you? You would say "I'm down one gallon" or, (if you really wanted to be confusing) "I'm up by MINUS one gallon". So why is it called RETURN "loss" ? Because I sent a signal into the device, and some amount of it returned. And (usually) the amount that returned is LESS than the amount I sent, so: GAIN of the device (how much MORE I got back compared to how much I sent) is less than one (a negative number). LOSS of the device (how much LESS I got back compared to how much I sent) is a positive number. Think of measuring through a passive network, your gain is negative, but your loss is positive. Does that help? 73, Willie N1JBJ [Yes, I have the T-shirt: "Does Anal-Retentive have a hyphen?"]
|
RETURN LOSS thoughts de k3eui
I have been wondering for months why I object to RETURN LOSS being a "positive value".
Yes, we are talking about a LOSS.
And of course the formula shows RL = -20 log (rho)
Since rho is a number between zero and one, the log (rho) is itself a negative number.
And -20 times a negative number is positive.
OK OK.... I get the math.
RL is positive - You "lose" 20 dB or whatever.
Now, what if we just rename the term to RETURN voltage (drop the "loss" in the label).
The return voltage is less than the forward voltage. I hope that is true.
So now the RETURN signal is attenuated by -X dB.
Now that feels right.
It's the word "loss" in RETURN LOSS that makes it confusing (I'm not an engineer).
So the FORWARD voltage is always positive and the RETURN signal is attenuated.....
Now I can say correctly that the reflected signal is - 10 dB compared to the forward signal.
In fact, that's the way I think of it, even if I don't say those words.
When I plot SWR of an antenna, the low numbers (close to 1) are "good".
Bad numbers for SWR are 3 and above.
When I plot the RETURN voltage on the same antenna, it feels that a DIP (negative number) is also good, in the sense that the graphs have the same overall shape. Why is that pleasing?
Or is this just a play on words?
It's not a big deal, as long as we realize what the graph means.
I want a low SWR. I want a big return loss (I want no return signal at all if possible).
If my antenna-feed line match is good, there is very little power returning to the source.
So why is it called RETURN "loss" ?
de k3eui Barry
|
Re: I/O RF Matching net-works measuring with NANO-VNA
#applications
Hi Peter,
every amplifier (Transistor or Tube) will change its input (and output) impedance due to bias. So input (and output) impedance of impeadance matching network as shown in your picture will also change when bias to the amplifier is supplied.
73, Guenter, DK5DN
Am 28.06.2021 um 10:02 schrieb Peter:
toggle quoted message
Show quoted text
Hi there ...
Appreciating several features of this incredible instrument, I'm attempting to check the real Impedance of the Matching network INPUT (and/or out-put) value associated to a VHF RF Amplifier (medium-power abt 200W) ... I connected the VNA as shown on the picture and then, after related calibration, I perfomed the measure (sweep)....
Of course I didn't apply any RF source at input ... Nano-Vna only !
I found a strange Resonant Frequency ... quite far from the proper one (I expected to be around 140MHz...150MHz) .... But then , if I apply the related Power-Supply (including BIAS) , the situation changed ... the resonant frequency was really close to the expected one !
Is it normal ?? Really the Power-Supply/Bias could affect impedance values of Input matching net-work ?? This situation can be applied at Out-Put line as well ??
|
Re: I/O RF Matching net-works measuring with NANO-VNA
#applications
Sure, a couple of possibilities:
1) When your power supply is off it's a high impedance, and when it's on it's a low impedance, so you are at the very least switching in another inductor.
2) Semiconductor junction capacitance depends on applied voltage, and there are semiconductors in the amplifier block.
3) Your amplifier block is accepting input power (to amplify it) or not. You could think of this as an additonal load.
Without more details we can only speculate, but I'm not surprised at your results. I would certainly expect the input of the amplifier to change when it's powered up.
73, Willie N1JBJ
toggle quoted message
Show quoted text
On Jun 28, 2021, at 4:02 AM, Peter <yliroma@...> wrote:
Hi there ...
Appreciating several features of this incredible instrument, I'm attempting to check the real Impedance of the Matching network INPUT (and/or out-put) value associated to a VHF RF Amplifier (medium-power abt 200W) ... I connected the VNA as shown on the picture and then, after related calibration, I perfomed the measure (sweep)....
Of course I didn't apply any RF source at input ... Nano-Vna only !
I found a strange Resonant Frequency ... quite far from the proper one (I expected to be around 140MHz...150MHz) .... But then , if I apply the related Power-Supply (including BIAS) , the situation changed ... the resonant frequency was really close to the expected one !
Is it normal ?? Really the Power-Supply/Bias could affect impedance values of Input matching net-work ?? This situation can be applied at Out-Put line as well ??
<Match_Meas.JPG>
|
Hi there ...
Appreciating several features of this incredible instrument, I'm attempting to check the real Impedance of the Matching network INPUT (and/or out-put) value associated to a VHF RF Amplifier (medium-power abt 200W) ... I connected the VNA as shown on the picture and then, after related calibration, I perfomed the measure (sweep)....
Of course I didn't apply any RF source at input ... Nano-Vna only !
I found a strange Resonant Frequency ... quite far from the proper one (I expected to be around 140MHz...150MHz) .... But then , if I apply the related Power-Supply (including BIAS) , the situation changed ... the resonant frequency was really close to the expected one !
Is it normal ?? Really the Power-Supply/Bias could affect impedance values of Input matching net-work ?? This situation can be applied at Out-Put line as well ??
|
Re: last iteration of Nano VNA PPT de k3eui
Barry,
Many Thanks, I will distribute this to our Club since many have shown interest in the Nano VNA but have avoided purchasing since so many "fake" units are marketed and we are assisting in providing reliable "Real" sources.
This Fields Day antenna setup was a fantastic "proving" ground and my Nano was a busy beaver.
Best Regards.
Steve
AB2ET/4
|
Re: last iteration of Nano VNA PPT de k3eui
Thanks. I liked you ppt files.
Gustavo
Em Dom, 27 de jun de 2021 14:01, Barry K3EUI <k3euibarry@...>
escreveu:
toggle quoted message
Show quoted text
I have had my Nano VNA now for about 10 months and I think I have now
exhausted everything I can do with it.
A year ago I could not tell you what the letters "VNA" even mean (I did
know what nano means).
But ideas pop up and I have to pull the Nano VNA out again and try
something new.
I've done so much that I now have way too many slides for a one our talk,
or even a two hour talk.
But I have divided this PPT into two parts:
Part I The Basics - I try not to get too deep into the weeds
Part II Advanced - much more in depth stuff, and stuff on antenna
impedance and matching
I've given "live" Zoom talks now to over a dozen clubs, throughout the USA
and two in Europe.
This has been a learning experience for me in many ways.
So I want to thank those kind enough to offer suggestions (and point out
errors).
You know who you are.
So perhaps this is not a complete story yet, but I hope this contains some
slides for useful discussions.
If you do spot an error please let me know (off list at
k3euibarry@...)
Please use this resource any way you feel appropriate.
I hope I did not violate any image copyright laws as I put these slides
together.
73
de k3eui Barry
West Chester PA
|
Re: last iteration of Nano VNA PPT de k3eui
And here is last weekend's ZOOM talk on Nano VNA Part II (Under the Hood Advanced stuff)
This is about as far as I can understand - right at my envelope of understanding.
Watch this video if you have time on Nano VNA "advanced"
This was recorded by a ham radio club in Portugal.
I've played with this Nano VNA "tool" now for about 10 months. What a journey.
Last Friday evening I gave a talk on the Part II Nano VNA to a Portugese Amateur Radio Club (in English).
This was way beyond the 6th or even 9th grade approach.
I was stretching my envelope of understanding as I prepared this talk, and then gave it in a bit over one hour.
I think this is as far as I can take this topic.
The learning for me took place over months of "playing" with this Nano VNA tool.
TU for this way-cool gift.
Enjoy if you care to watch this video, with lots of questions and discussions by the participants, some in Portugese.
73
de k3eui Barry
|
Re: anti-stati foam sheets for lining case
I added a strap of anti static foam between the bottom and top after the I took the attached pic.
|
Re: Simple Latest Firmware list available and links to download?
|
Re: Simple Latest Firmware list available and links to download?
Very Helpful.
If it's only the font issue and no major functional improvements, I might just not update it.
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Vladimir Lebedev Sent: Sunday, June 27, 2021 1:53 PM To: [email protected]Subject: Re: [nanovna-users] Simple Latest Firmware list available and links to download? please compare two screenshots of Hugens 1.0.45 and DiSlord's 1.0.64
|
Re: anti-stati foam sheets for lining case
On Sun, Jun 27, 2021 at 12:27 PM, Jim Lux wrote: What we do at JPL is use conventional foam, and cover it with antistatic
film (like the stuff they use for ESD bags - the silvery stuff, not the
pink stuff. The pink stuff sheds particles), taping it with ESD safe
tape.? This has the added benefit that if the foam gets gunky, or sheds
particles, they're "inside" the plastic wrapper.
Clever idea... Roger
|
Re: Simple Latest Firmware list available and links to download?
Version 1.0.45 is the latest firmware released by Hugen for his NanoVNA-H. It has a lot of features and I suggest you get used to using it before you even consider updating your firmware.
The Absolute Beginners Guide that Vladimir Lebedev posted a link to is very good reading and will get you started.
I own a RigExpert Analyzer and an MFJ-259B. They are simpler to operate but do not have all the features and capability of the NanoVNA which is also less money. If all you want to do is measure SWR of antennas the RigExpert has more features for that and has a minimal learning curve. I have an AA-55 Zoom and it works well except for the Bluetooth which has a well-known design defect that RigExpert will not fix.
Roger
|
Re: Simple Latest Firmware list available and links to download?
please compare two screenshots of Hugens 1.0.45 and DiSlord's 1.0.64
|
Re: Simple Latest Firmware list available and links to download?
|
Re: Simple Latest Firmware list available and links to download?
Hello Brumey! In the files section ---> /g/nanovna-users/files/Dislord%27s%20Nanovna%20-H%20FirmwareLast version for both - NanoVNA-H and NanoVNA-H4 from DiSlord. Or here with change log You have FW Version 1.0.45 from Hugen with big fonts. All FW versionen from DiSlord for NanoVNA-H have small fonts. Best regards Vladimir
|
Simple Latest Firmware list available and links to download?
Hello:
I just purchased a NanoVNA-H and a sticker on the back saying its Hardware Version 3.5. I was expecting to see a quick link to a Firmware version list, Change log and link to the firmware and download utility. Does this exist?
Which is the firmware version, what is the latest and should I bother updating?
Looking at the current firmware screen I see:
V 1.045 [p:101,IF: 12k, ADC: 192K, lcd 320x240, Built time Jan 30 2021.
Kernel 4.0.0
It has Platform STM32F072xb
Any help much appreciated. I am beginning to think I should have gotten a RigExpert analyzer.
|
Re: FM5324B and FM5401 - NanoVNA-H4 Battery Charger and 5 Volt Converter Circuit
Jim - I am also using the Kill-A-Watt meter. In the case of the 7.8 watt reading, the Power Factor was 0.60 along with the higher Volt-Amp reading. The three AC to USB power adapters all get quite warm during charging.
My Moto G7 phone which has a 5000 mAh battery showed 14 watts during charge.
The Kill-A-Watt meter does appear to show the end of charge on my NanoVNA-H4. Last night after about an hour the wattage reading dropped about three watts. That was good to see as the LED on my NanoVNA-H4 gives no indication of end of charge.
The specification on the FM5324B integrated circuit appears to show a typical charge current of 300 mA. That would represent 1.26 watts at 4.2 volts.
73, Kent
AA6P
|
Re: anti-stati foam sheets for lining case
On 6/27/21 12:13 PM, Bill Higdon via groups.io wrote: I'm considering using anti-static polyethylene foam sheets cut to fit in a case I have for my RF test gear. My thinking is that polyethylene is more stable than the other foams out there.
2 sources I have are Granger & McMaster-Carr Anyone have any thoughts? What we do at JPL is use conventional foam, and cover it with antistatic film (like the stuff they use for ESD bags - the silvery stuff, not the pink stuff. The pink stuff sheds particles), taping it with ESD safe tape.? This has the added benefit that if the foam gets gunky, or sheds particles, they're "inside" the plastic wrapper.
|
Jim: The optimal way would be to measure several standard articles on each
test analyzer and compare the S2P files from each instrument.
The classical verification/transfer standards are a Beatty mismatch
standard which is a section of 25¦¸ air line between 50¦¸ air line sections,
a 50¦¸ air line and one or more attenuators with different values, typically
one with a relatively low value and one with a higher attenuation. The
air line standards are expensive and easily damaged:
Please note that measuring one or more of the same standards used for
calibration will tell you little about the calibration quality, only the
connection repeatability.
I have found that measuring a filter with passband and stopband within the
calibrated frequency range as a quick check gives pretty useful information
about the instruments in terms of directivity and transmission dynamic
range.
But instrument verification is an entire specialty within the science of
metrology.
73, Don N2VGU.
toggle quoted message
Show quoted text
On Sun, Jun 27, 2021 at 1:46 PM n8qoh@... <n8qoh@...> wrote: I paid more for a good used HP 85032B N calibration kit for my 8702B than
for the LibreVNA.
The LibreVNA has a spectacular price performance ratio and decent
specifications to 3GHz, 3-6 GHz is a bonus and it certainly works well
enough to be useful.
The software V1.1.2 with firmware 5 is usable if not full featured.
What tests would one choose to compare VNA'S? Sweep a filter, impedance
match a device, measure cable length, ...?
I suspect the majority of NanoVNA users use them at HF unless testing
antennas...
Jim
n8qoh
Sent from Yahoo Mail on Android
<>
On Sun, Jun 27, 2021 at 10:15 AM, Donald S Brant Jr
<dsbrantjr@...> wrote:
John: I ordered and received a LibreVNA from R&L Electronics, was pleased
at the price ($429 vs $599 at Amazon), ordering and delivery, and quality
of the unit. The software is a work in progress but the version I am using
(1.1.2) seems stable and reasonably intuitive.
I believe that the weakness of the unit is the provided calibration
standards and their definitions; I am using the values on the attached
document and they seem to work well up to 4GHz, but quickly fall apart
above that. I am considering purchasing calibration standards from SDR-Kits
which I understand are made by Rosenberger. I also plan to measure the
provided standards on a commercial VNA and use the S1P/S2P files as
standards definitions; the LibreVNA software will accept measured data for
the cal standards in lieu of L/C/Z/delay coefficients.
I also noticed that the LibreVNA runs hot, with the internal temperatures
reporting as ~53-56¡ãC; I have obtained a fan-cooled heatsink and some
thermal interface material and plan to install then and see the results.
However I do not see any temperature-related drift or other issues, coming
from a semiconductor reliability background I just prefer to have things
run cooler.
I am currently using the LibreVNA to evaluate components for a project at
work (L-band beacon receiver with VHF IF) and the measurements I am getting
compare favorably with the measurements from a Keysight Field Fox analyzer.
I suspect that when I get adequate calibration standards and definitions I
will be quite pleased with the performance of the unit; it is already
proving useful in my work.
73, Don N2VGU
|
Barry K3EUI
schweppe
Peter
Lou W7HV
Vladimir Lebedev
Roger Need
Donald S Brant Jr