I wrote the test message.
I had made my first post, but I could not see it.
I made the second test post to see if that would go through.
When I posted the test post, I saw the note that it would be moderated.
Then I knew that's why I had not seen my first post it had not went through the
moderator yet.
I got both posts in my email at the same time.
Tell me how to remove it, and I will. Or you can continue to read it and say you didn't ;-)
Mikek
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Nor that nobody has asked to initial poster to remove his post once it has served its (secret) purpose. ;-)
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It is a good indication of the good-natured character of this forum that nobody has popped up to correct your spelling, punctuation or grammar (yet) :-)
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Re: ¡°Fixture In A Hurry¡±. And a Transformer.
So when is it 20log and when 10log?
I think 10log for power and 20 log for magnitude?
John
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Hi,
A newcomer facing the base of a steep hill probably doesn't know what words to use when asking a question. First would be "how do I turn this thing on?" They probably can look that up for themselves but other questions may not be so easy.
I am new to the nanoVNA but came to it with some foggy ideas about what it does and even how. But as with other new ventures, I read the wiki and the how-to and find new words or even old words in a new context. With Google and other search engines we can then look up those new words. that constitutes 'climbing the hill'.
I am a radio amateur. I had to learn CW. No..it's not weeping about dropping that requirement. I helped some others working for their license. The ones who actually took the time to learn the Morse code succeeded. I could not *learn* it for them. All we can really do is point to the start of the trail that leads up the hill and the newbie is then welcome to climb as far as they want to go. There may come a fork in the trail and a new pointer can be offered.
The people who *know* cannot know for you (newbie). There is a reference to "hands-on" in the thread. I have found that a balanced mix of 'book learning" and hands-on is needed. Newbies should not feel 'dissed' by 'rtfm' if given the page and paragraph number to read.
73,
Bill KU8H
bark less - wag more
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On 6/6/20 7:07 AM, gary.sewell@... wrote: First I want to thank all that responded to to my question. I remember back in my college days in the late 60¡¯s, we used very large Tektronix scopes, and on the top of the scope was a small pop-up compartment that held a small manual. On that manual it stated ¡°RTFM¡±. For those that don¡¯t know what this acronym means, it is ¡°Read The Fu#king Manual¡±. I remember how thick that actual manual was, and it may take hours of searching the manual to find out how to use a function on that scope. So instead we would ask the instructor and they would give you the answer.
Fast forward to today with Google, YouTube, Wiki, etc. These tools make life so much easier. But, the problem is sometimes even with these great tools, you still cannot find the answer you are looking for. After many hours of searching, you have two choices: give up and move on, or ask for help. I choose the later.
The NanoVNA is a great tool, and I wish I had something like this many years ago. But, like that old Tek scope, it has features and functions, that to some, are new and hard to understand. I come from ham radio where SWR was all you had to found out how an antenna performed. Now, I am an engineer with many years in RF communications, but a lot of the brain cells have reformatted and now need to be updated.
I would hate to think that this great tool we have could be construed to be so complex and hard to understand and use, that it too ends up on the unused shelf in our shack collecting dust.
Thanks again
Gary
AA5I
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I read it, but I don't think that anyone saw me read it.
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Re: New user, dove in above my head.
First, I think that you are shorting one side of your balanced input to ground.< Yes, at the very least, to the shield potential of the radio, connecting an earth ground to the radio makes no difference to the common mode signal attenuation. I did not realize the grounding. Yes. measuring the input with a 50 ohm resistor on the output gave me about 92 ohms at 500kHz rising to 109 ohms at 4MHz.. Ah, I will add a 4 to 6 turn transformer at the input and measure again, and I'll wind the second just to measure the loss of the two transformers, divide by two to find the loss of one. Good, I will measure the common mode impedance with that method. Thanks, Mikek
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First I want to thank all that responded to to my question. I remember back in my college days in the late 60¡¯s, we used very large Tektronix scopes, and on the top of the scope was a small pop-up compartment that held a small manual. On that manual it stated ¡°RTFM¡±. For those that don¡¯t know what this acronym means, it is ¡°Read The Fu#king Manual¡±. I remember how thick that actual manual was, and it may take hours of searching the manual to find out how to use a function on that scope. So instead we would ask the instructor and they would give you the answer.
Fast forward to today with Google, YouTube, Wiki, etc. These tools make life so much easier. But, the problem is sometimes even with these great tools, you still cannot find the answer you are looking for. After many hours of searching, you have two choices: give up and move on, or ask for help. I choose the later.
The NanoVNA is a great tool, and I wish I had something like this many years ago. But, like that old Tek scope, it has features and functions, that to some, are new and hard to understand. I come from ham radio where SWR was all you had to found out how an antenna performed. Now, I am an engineer with many years in RF communications, but a lot of the brain cells have reformatted and now need to be updated.
I would hate to think that this great tool we have could be construed to be so complex and hard to understand and use, that it too ends up on the unused shelf in our shack collecting dust.
Thanks again
Gary
AA5I
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One huge problem with looking up info on the wiki or elsewhere is that
of generating the correct search term. Once in a while one hits on it
quickly, but more often one wastes hours in a futile effort, and in the
process is bombarded with an almost infinite number of things to look
through.
Another problem is that much material is written so poorly that it fails
to answer the real question satisfactorily and without ambiguities.
I submit that in this day and age one should not have to invest hours
looking for information- it should be easy to find. Hence, my own
inclination is to ask people (as opposed to algorithms) for help.
Dana
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Me either 73! Mark KA6WKE Website: On Fri, Jun 5, 2020, 20:48 Jim Allyn - N7JA <jim@...> wrote: OK, I didn't.
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Re: New user, dove in above my head.
First, I think that you are shorting one side of your balanced input to ground. Starting at "Transformer center taps connected to case", then through the case to the BNC shell, then to the ground on the VNA, then to the shell of CH0, then to one of the balanced input lines. So I don't think that any of your measurements mean anything.
If you want to measure the balanced input impedance, you could connect a floating 50 ohm load at the output BNC. You should expect to read 112.5 ohms, this is the impedance because the 6 to 4 turn ratio results in the turns ratio (1.5) squared (2.25) times 50 ohms.
To measure the through loss, you could make another 4 to 6 turn transformer and connect it between the CH0 and the balanced input. Any loss you measure needs to be divided between this balancing transformer and the device under test. You could connect two identical 4 to 6 turn transformers back to back, measure the loss and divide by two, then just subtract this test fixture loss from the overall loss you measure.
You might also want to evaluate the common mode impedance by connecting the CH0 center connector to the shorted together balanced input lines and connect the BNC to CH1, to provide both a ground return and a load on the output.
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New user, dove in above my head.
I have the circuit below, I built to remove Common mode signal from a 225ft CAT6 Feed LINE.
It works extremely well. So now I want to know what loss I have put just before my radio.
(The 225ft feed line is connected to a Beverage on the ground.) Feel free to ignore the antenna.
Per the drawing, CH0 is feeding the 100 ohm input thru a short piece of CAT6 (1ft).
CH1 is connected to the 50 ohm output through a BNC connector with a short piece of coax (1ft).
I ran a scan 550 to 4MHz, I only care about the broadcast band, but it still looks good at 4MHz. (I think)
The display reads,
CH0 10db/ -8.63
CH0 1.0FS 105 ohms 4.07uh This is at 1MHz.
The ohms are pretty flat, the Reactance goes capacitive at 4.2MHz.
CH1 Logmag 10db/ -0.99db
CH1 Phase 90*/ -0.637
What line above is the pass through loss?
How do I account for the 100ohm in to 50ohm out? Or how do I back that out of the numbers.
The only line I understand is "CH0 1.0FS 105 ohms 4.07uh" If it was perfect it would say
"CH0 1.0FS 100 ohms 0.00uh"
Can you describe what the other lines mean?
Thank you Mikek
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Re: white screen and flashing
Great, tnx for the lead. With the saver sw working fine, I should be good to go, makes sense
rich
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On Fri, Jun 5, 2020 at 01:53 PM, David Eckhardt wrote:
No, it isn't "you just gotta know". Those of us who actually spend the
time and make the effort to find an engineering sound reference online
which everyone can access to answer the question(s), simply mean to help
and give you a sound answer without your invoking any number of search
engines and avoiding snake oil so prevalent on the www. Chances are we've
"been there, done that" in our training/careers. There are sources online
that put things much clearer and more succinctly than our own wording.
Chances are, we know where to look for clear and concise and engineering
sound answers which all can access and learn if they choose to pursue the
URL's.
I agree with much of what you have said. In the days before the Internet it was a real struggle to find a textbook or magazine article which covered a subject of interest. Nowadays there is a plethora of material available including videos and online courses which can answer most questions with a little effort. As a bench engineer and electronics/computer science teacher I found that one can only acquire and retain a solid technical understanding by hands-on experimentation, personal study and investigation. Just receiving the answers to a question does not result in good retention of technical material. As they say "no gain without a little pain". This does not mean that folks like me and other knowledgeable members of this group do not want to help. On the contrary most of us here to share and learn from each other. But I hope that most with a question will at least Google a bit and try and read some of the excellent material available on the Internet before asking basic questions. Roger Need
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Re: Help Testing a Low Pass Filter
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No, it isn't "you just gotta know". Those of us who actually spend the
time and make the effort to find an engineering sound reference online
which everyone can access to answer the question(s), simply mean to help
and give you a sound answer without your invoking any number of search
engines and avoiding snake oil so prevalent on the www. Chances are we've
"been there, done that" in our training/careers. There are sources online
that put things much clearer and more succinctly than our own wording.
Chances are, we know where to look for clear and concise and engineering
sound answers which all can access and learn if they choose to pursue the
URL's.
I take the effort of helping others by emailing out sound, correct, no
snake oil references to properly answer question(s) very seriously. If you
don't want to pursue those links, I can't help you. Please don't put them
in the "you just gotta know' category.....please.....
Yes, I'm just a bit offended.
*Example:* Just this week I had to put out yet another "take" on the 101
points allocated to any set frequency span. I just hope others read it and
internalized it and are willing to pass it on to other newbies of the
NANOVNA community. Nothing but VERY SIMPLE algebra, no "higher" math!!!
Distance between points for a given frequency range = (Frequency
Range) / 101.
Of course, if you use SAVER, you can set any number of bins to
greatlyincrease this frequency resolution.
EXAMPLE: Frequency Range defined as 1 through 30 MHz.
Point spacing (resolution: = (30 MHz - 1
MHz) / 101 = 29 MHz / 101 = 0.29 MHz
If I then look specifically at 75/80
meters which spans 3.5 to 4.0 MHz, a total span of 0.5 MHz, I will have
1.74 (at best, 2) points in the whole
band. This is not too terribly useful for looking at tuning a multiband
antenna.
EVERYONE: PLEASE,......P L E A S E,.............., take the above and
pass the 101 point "gotcha" on to other new members of the NANOVNA
community. PLEASE??
Dave - W?LEV
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On Fri, Jun 5, 2020 at 11:52 AM BruceN <k4tql@...> wrote: Gary,
This is something that I have issues with, too. It reminds me of the day,
way back in the day, when I asked someone where I could find documentation
regarding the Unix operating system. This was before the Internet (over 50
years ago). The answer was "you just gotta know".
When the answers to your questions are "read this wiki" or "read that
wiki", the answer is just the same as: "you just gotta know where to
look". It would be just as easy for a response to be furnishing a link to
"where" to look. And, as in your case, maybe you looked there and missed
it. Happens to me all the time. And maybe there is a better place to look
as one responder provided.
I've run into many instance of this smug attitude of "I know and you
don't. Go find it yourself". I'll bet a lot of them wouldn't know how to
solder two wires together without burning themselves for all their
"knowledge". I knew professors of electrical engineering in college who
couldn't change their car battery. That wasn't an electrical task, it was
a mechanical task.
And, no I can't answer your questions either. If you find a good place to
find them, let me know. I need the answers, too. You might also point out
where you have looked unsuccessfully.
BruceN / K4TQL
--
*"To invent, you need a good imagination and a pile of junk"* -- Thomas
Alva Edison (1847-1931)
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Yes, I think I'll order from Mouser, Newark or Digikey - they have them for around $10ea (I tried to save $$ but....)
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On Friday, June 5, 2020, 2:41:32 p.m. EDT, Gyula Molnar <gyula.ha3hz@...> wrote: On Fri, Jun? 5, 2020 at 07:26 PM, Larry Rothman wrote:
STM32F303
I¡¯m just asking in parentheses why don¡¯t you buy from a reputable seller? With us, farnell is a good name. -- *** If you are not part of the solution, then you are the problem. ( ) ***
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Re: white screen and flashing
The traces on the LCD flex circuit can crack if the flex is bent at a right angle.
Also, a few other forum members have seen this issue - they carefully removed the LCD (just release it from the metal frame around the edges) tilted it up and re-touched the soldering. Then, snap the LCD back into the frame.
Good luck!
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On Friday, June 5, 2020, 2:46:29 p.m. EDT, Rich <k0zx.co@...> wrote:
Its the activity LED that's flashing, always.
Just tried the usb path and yes that's ok, so a display issue does appear to be the issue, just ran a few sweeps and ok except for screen still white. Will check that, tnx Larry
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Re: white screen and flashing
Its the activity LED that's flashing, always.
Just tried the usb path and yes that's ok, so a display issue does appear to be the issue, just ran a few sweeps and ok except for screen still white. Will check that, tnx Larry
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John
Jim Allyn - N7JA
Roger Need