Re: characteristic impedance
substitute Andy's message # 10256 for mine OK, since you ask, but I find yours much simpler to follow
|
Re: Wireless control of NanoVNA
Sure it does. You just need to polarize, filter and modulate the beam.?Hmmm, starting to sound like a laser link ;-)
On Sun, 26 Jan 2020 at 2:47 PM, David Eckhardt<davearea51a@...> wrote: IR doesn't work too well in sunlight.? How about a neutrino beam from the
LHC?
Dave - W?LEV
toggle quoted message
Show quoted text
On Sun, Jan 26, 2020 at 6:43 PM Larry Rothman <nlroth@...> wrote: So, the solution is an IR link?
Let's get designing folks!
? On Sun, 26 Jan 2020 at 12:16 PM, David Eckhardt<davearea51a@...>
wrote:? With an RF instrument such as a VNA that measures down into the
"noise", an
RF source in immediate proximity to low-level electronics is NOT a good
idea!!? Compression of linear devices in the instrument are a real
possibility.? IM with instrument-produced RF is also a distinct reality.
The input of the VNA is "wide open" with no 'filtering' to eliminate stray
RF energy.? 2.4 or 5 GHz WiFi at +10 dBm in close proximity to the
electronics will completely spoil the operation of the VNA.? NO!? Bad
idea!!
Calibrate the VNA, attach it to the feedpoint of the antenna, raise the
antenna, and, well......? Better yet, as has been previously suggested,
read the impedance at the shack end of the feedline and propagate that
reading back to the antenna using SimSmith.
Dave - W?LEV
On Sun, Jan 26, 2020 at 3:39 AM gmendenh1947 <W8GNM@...> wrote:
Here is a feature idea for the next? update of the NanoVNA design.? If the
NanoVNA had a WiFi transceiver on board in addition to the USB port, so it
could be controlled remotely by NanoVNA Sharp, NanoVNA Saver, or similar
applications.
This would allow the NanoVNA to be attached directly to the feedpoint of a
multiband antenna and hoisted with the antenna into the operating position,
thereby eliminating the complication of transmission line normalizations
over multiple frequency bands.? The unit could be programmed remotely and
the data could be captured remotely.
I would be willing to pay a significant premium for this capability.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
|
Re: OT: But I hope someone from this group can provide some info on this
Merci Beaucoup Jose,
Te souviens tu si il y avait aussi un moyen de contr?l¨¦ le g¨¦n¨¦rateur par
le port USB?
Pierre
VE2PF
toggle quoted message
Show quoted text
Le dim. 26 janv. 2020 ¨¤ 16:07, Jose Luu <jose.luu@...> a ¨¦crit : A few years ago I and another OM (F1VL) we remade a firmware for this, the
code is here:
The code (Inc/board_config.h) indicates that the display is driven by an
ILI9320 and an ADS7843 for the touch controller.
The code can run on an alternate hardare configuration using a 2.4"
display controlled by an ILI9341
Hope this helps
Jose
F1FGV
|
Re: Band pass and stop measurement
On Sun, Jan 26, 2020 at 12:46 PM, <sidebores@...> wrote:
The settings I used which also now seems to show correct trace is frequency 70Mhz to 147 Mhz and format real?
==========================================================================
Try connecting the filter between CH0 and CH1, and sweeping between 50kHz and 900 MHz to see the 118-500 MHz band pass response. Your photo shows you are currently just looking at the CH0 reflection.
- Herb
|
Re: characteristic impedance
On Sun, Jan 26, 2020 at 12:34 PM, Oristo wrote:
Sorry. I should have said "worse clone reported about -72 Ohms reactive and 1 Ohm resistive"
See attached image for repeat of Herb's steps with slightly different results, but still no "j".
My point was, those steps work fine for roughly sorting characteristic impedances,
which firmware in my nanoVNA does not directly report
==============================================================
Oristo,
Would you substitute Andy's message # 10256 for mine in the wiki applications notes? His general procedure is the same but Andy does a much better job than I did of explaining the steps and not confusing the issue by using incorrect terminology.
Much appreciated.
- Herb
|
Re: OT: But I hope someone from this group can provide some info on this
A few years ago I and another OM (F1VL) we remade a firmware for this, the code is here:
The code (Inc/board_config.h) indicates that the display is driven by an ILI9320 and an ADS7843 for the touch controller.
The code can run on an alternate hardare configuration using a 2.4" display controlled by an ILI9341
Hope this helps
Jose
F1FGV
|
Re: Band pass and stop measurement
Dave,
This effect, of nearby AM broadcast stations, makes it nearly impossible for me
to do vna measurements on my 160M antenna :-(? I built a 1.7 Mhz HPF for the analyzer
but it did not help much.
73
Glen K4KV
toggle quoted message
Show quoted text
On 1/26/2020 13:10, David Eckhardt wrote: Could you please give us a picture of your filter response as you measure
it? Is your BC band filter a passband, stop band, low pass, or high-pass
filter? Typical use would be a stop band or high-pass filter to block the
strong AM broadcasters. But we don't know with the information you've
given us. Please fill in the blanks.
Dave - W?LEV
On Sun, Jan 26, 2020 at 5:59 PM sidebores via Groups.Io <sidebores=
[email protected]> wrote:
Hi all,
Could some give a rough guide in how to measure a filter. I have broadcast
band filter and when I measure it the signal looks upside down for the
bandblock. The only way I can make it look ok is by using the real seting?.
So when looking at a band pass/stop filter should the block be in the
trough and the pass in the peak.
Cheers Kev
|
Re: Wireless control of NanoVNA
The best way to measure the impedance at the antenna is to use a multiple 1/2 wave coaxial
cable at an appropriate frequency.? Stay on the ground.? When I am designing and building new
antennas, I cut a cable of 1/2 wave multiple to do my testing.
73
Glen K4KV
toggle quoted message
Show quoted text
On 1/26/2020 12:16, David Eckhardt wrote: With an RF instrument such as a VNA that measures down into the "noise", an
RF source in immediate proximity to low-level electronics is NOT a good
idea!! Compression of linear devices in the instrument are a real
possibility. IM with instrument-produced RF is also a distinct reality.
The input of the VNA is "wide open" with no 'filtering' to eliminate stray
RF energy. 2.4 or 5 GHz WiFi at +10 dBm in close proximity to the
electronics will completely spoil the operation of the VNA. NO! Bad
idea!!
Calibrate the VNA, attach it to the feedpoint of the antenna, raise the
antenna, and, well...... Better yet, as has been previously suggested,
read the impedance at the shack end of the feedline and propagate that
reading back to the antenna using SimSmith.
Dave - W?LEV
On Sun, Jan 26, 2020 at 3:39 AM gmendenh1947 <W8GNM@...> wrote:
Here is a feature idea for the next update of the NanoVNA design. If the
NanoVNA had a WiFi transceiver on board in addition to the USB port, so it
could be controlled remotely by NanoVNA Sharp, NanoVNA Saver, or similar
applications.
This would allow the NanoVNA to be attached directly to the feedpoint of a
multiband antenna and hoisted with the antenna into the operating position,
thereby eliminating the complication of transmission line normalizations
over multiple frequency bands. The unit could be programmed remotely and
the data could be captured remotely.
I would be willing to pay a significant premium for this capability.
|
Re: Is my off brand a Brick?
|
Re: Is my off brand a Brick?
The Manage screen in saver shows Status: Connected to NanoVNA Calibration: (Sweep running) Features: box
NanoVNA v0.0.0 Original sweep method.
John
|
Re: Band pass and stop measurement
The settings I used which also now seems to show correct trace is frequency 70Mhz to 147 Mhz and format real?
Cheers 73s Kev MM0KJG
|
Re: Band pass and stop measurement
Hello Dave,
Here is 2 pictures for you to view.
|
Re: Is my off brand a Brick?
I went directly to attached to the USB.
|
Re: characteristic impedance
Hi Dave - That should be -j72 ohms. Sorry. I should have said "worse clone reported about -72 Ohms reactive and 1 Ohm resistive" See attached image for repeat of Herb's steps with slightly different results, but still no "j". My point was, those steps work fine for roughly sorting characteristic impedances, which firmware in my nanoVNA does not directly report Using 1-900MHz device calibration from weeks ago,
I followed Herb's steps /g/nanovna-users/message/10210
for three generic CATV jumpers with F-connector barrels via RCA to BNC to
SMA adapters on my worse clone
which reported about 72 Ohms reactive and 1 Ohm resistive.
|
Re: characteristic impedance
That should be -j72 ohms. Proper and good use of a VNA involves respecting
the sign of the complex portion of the impedance measurement. -j implies
capacitive and the below the central horizontal line on the Smith Chart.
+j implies inductive and above the central horizontal line on the Smith
Chart. Only the central horizontal line is purely resistive, no complex
portion and, therefore, no +/- j. Without the sign, a pure resistance
would be understood.
The 'device' or concept I used long, long ago to keep which part of the
Smith Chart is capacitive or inductive follows.
INDUCTIVE: Think of a coil spring. When compressed, it pushes
upward. The coil spring 'looks like' an inductor.
Therefore, it belongs to the top of the Smith
Chart. This is +j.
CAPACITIVE: Many times we use a bypass capacitor to shunt high
frequency to a return. It pulls the HF energy
'downward' or to the reference plane.
Therefore, the lower half of the Smith Chart is capacitive. This
is -j.
Maybe this helps? I used it some 40+ years ago to keep things straight.
Of course, I no longer need this 'tickler'. Your mileage may vary.
Dave - W?LEV
toggle quoted message
Show quoted text
On Sun, Jan 26, 2020 at 6:16 PM Oristo <ormpoa@...> wrote: Well there seems to be no consensus about this Using 1-900MHz device calibration from weeks ago,
I followed Herb's steps /g/nanovna-users/message/10210
for three generic CATV jumpers with F-connector barrels via RCA to BNC to
SMA adapters on my worse clone
which reported about 72 Ohms reactive and 1 Ohm resistive.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
|
Re: Wireless control of NanoVNA
IR doesn't work too well in sunlight. How about a neutrino beam from the
LHC?
Dave - W?LEV
toggle quoted message
Show quoted text
On Sun, Jan 26, 2020 at 6:43 PM Larry Rothman <nlroth@...> wrote: So, the solution is an IR link?
Let's get designing folks!
On Sun, 26 Jan 2020 at 12:16 PM, David Eckhardt<davearea51a@...>
wrote: With an RF instrument such as a VNA that measures down into the
"noise", an
RF source in immediate proximity to low-level electronics is NOT a good
idea!! Compression of linear devices in the instrument are a real
possibility. IM with instrument-produced RF is also a distinct reality.
The input of the VNA is "wide open" with no 'filtering' to eliminate stray
RF energy. 2.4 or 5 GHz WiFi at +10 dBm in close proximity to the
electronics will completely spoil the operation of the VNA. NO! Bad
idea!!
Calibrate the VNA, attach it to the feedpoint of the antenna, raise the
antenna, and, well...... Better yet, as has been previously suggested,
read the impedance at the shack end of the feedline and propagate that
reading back to the antenna using SimSmith.
Dave - W?LEV
On Sun, Jan 26, 2020 at 3:39 AM gmendenh1947 <W8GNM@...> wrote:
Here is a feature idea for the next update of the NanoVNA design. If the
NanoVNA had a WiFi transceiver on board in addition to the USB port, so it
could be controlled remotely by NanoVNA Sharp, NanoVNA Saver, or similar
applications.
This would allow the NanoVNA to be attached directly to the feedpoint of a
multiband antenna and hoisted with the antenna into the operating position,
thereby eliminating the complication of transmission line normalizations
over multiple frequency bands. The unit could be programmed remotely and
the data could be captured remotely.
I would be willing to pay a significant premium for this capability.
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
--
*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*
|
Re: Wireless control of NanoVNA
I test older version wifi only instrument. Extreme useful. Wifi works on long distance. Easy measure antenne feedpoint without long coax cable. No any interfetence up to 70cm.
I think wifi/bluetooth or fiber optic (toslink for example) useful. You can measure without feeder line. Many times feed line radiate. Very useful for test with or without cable.
|
Re: characteristic impedance
On Sun, Jan 26, 2020 at 08:05 PM, Bob Albert wrote:
Well there seems to be no concensus about this.? I have a couple of things
Did you read the original message #8655? Let's try to do it step by step. ))) Switch on NanoVNA and connect a piece of open ended cable to CH0. No matter what is the length and Vf. In my example, NanoVNA was calibrated from 50 kHz to 900MHz. You need to switch one of the CH0 traces to REACTANCE measurements in DISPLAY>FORMAT>MORE>REACTANCE menu. You will see something like on the first screenshot. Move the marker to the first (lowest) resonance frequency approximately where the REACTANCE trace cross the zero axiss for the first time. Read the frequency value. Then, in order to rise accuracy, set START and STOP frequency a little bit lower and higher this frequency. See next two screenshots. In my example the lowest resonance frequency is somewhere near 20MHz. That's why I set START=10MHz and STOP=30MHz in STIMULUS menu. The result is on the next screenshot. Now you can move the marker to a resonance frequency, where impedance is about 0 Ohm, more accurately. Read the value of this frequency. In my example it is 21.2 MHz. Divide it by two. This is the frequency on which the cable length is 1/8 of wave length. Remember it. The final step is to switch NanoVNA into CW FREQ mode in the STIMULUS menu and set the calculated frequency. In my example it is 10.6 MHz. See last screenshot. Read the REACTANCE value. It is the cable's wave impedance. Thanks! I hope, that it helps somebody. :-)
|
Re: characteristic impedance
On Sun, Jan 26, 2020 at 10:37 AM, Bob Albert wrote:
Halfway around the Smith chart isn't 1/8 wave; it's 1/4 wave.
=======================================================
Bob,
Read message #10234 in this topic. We cleared that up.
- Herb
|
Re: Setting the vbat_offset
I don't know what the firmware does to calculate the battery level but I suspect that setting vbat_offset to 150 (as suggested by Hugen) is because the difference in voltage drop between the Schottky diode used prior to v1.34 and the 1n4148 used now is 150 mVolts.
Just a guess...
Roger
|
Oristo
Jose Luu
Andy UA3RAW
Roger Need