Re: Measuring the output impedance of a 20m push-pull power pre-amp
#transformer
A quick question on impedance. I'm using a NanoVNA H4 for simply checking
SWR on antennas across the various amatuer HAM bands.
It seems to work great. However, I've also been curious about the
Impedance. In the menu I select "SWR" to be displayed. I do not see a
selection for Impedance.
How do I configure the H4 to display the Impedance that is being measured?
Keep in mind this is just a simple case of a HF antenna and 25' - 75' feet
of coax hooked directly into the H4. I'm just curious as to what the
impedance is and I can't puzzle out how to see that value.
Sorry for the rookie question.
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On Tue, Dec 14, 2021 at 2:27 PM W0LEV <davearea51a@...> wrote: 1) The impedance of the primary, the collectors, is highly dependent on
drive level from the previous stage. Looking into the 50-ohm port with the
VNA even with the PP output stage properly biased but with no RF on the
bases, the impedance will not be that when the PP stage is properly biased
AND RF in the circuit. The measurement you are attempting is highly
questionable for that reason. A better and more rigorous method would be
to optimize power output into a 50-ohm load. Then disconnect the
collectors and look into the "network" from what would be the collector
side with the "network" output terminated with a 50-ohm load.
2) The broad band matching transformer on the output should have its turns
ratio adjusted to transform something in the vicinity of 1 to 3 ohms (real)
to 50-ohms - "nominally" a 5:1 turns ratio. Most of the BJT RF power
transistors reside on the extreme left side of the Smith chart with some
reactance as well. The data for the Smith chart plots from the suppliers
are usually made at full rated power and not a couple of milliwatts (from
the VNA).
Dave - W?LEV
On Tue, Dec 14, 2021 at 3:52 PM picoguy via groups.io <s1ig0=
[email protected]> wrote:
Hi,
I'm in the process of building a BJT transistor based push-pull amplifier
that I hope will develop 1 watt to drive a final power amp stage.
The design is relatively common. It uses a pair of impedance matching
transformers at the base and collector of the power transistors. The input
transformer is an FT37-43 with a biflar wound centre tapped secondary fed
from an active biasing circuit and the output transformer is an FT82-43.
The output transformer primary is connected across the transistor
collectors, with the DC (12V) supplied via a biflar wound centre tapped
FT37-43. The transistors are 2SC2078's, which should have no problem
supplying the power I need at this stage: 1 watt.
I've had some issues with the output transistor, where my experiments
would suggest it isn't acting like an "ideal" impedance transformer. The
toroid is confirmed genuine and the type 43 material should be good for
14MHz.
Anyway, that prompted me to try looking for the output impedance of the
push-pull arrangement. I figured I could use the NanoVNA by having it feed
a signal through the output port with a bias applied (but no input signal
obviously!) The experiment sort-of works...let me explain. I find that
the impedance (resistance + reactance) is not quite what I expected. The
reactance is very inductive and my experiments would suggest that this is
certainly influenced by the secondary winding inductance. If I put 10
turns on the output secondary, I get xx uH. If I reduce the turns to 3 or
4, I get nH's. However, and importantly for what I'm looking to achieve,
when the real/resistance part of the impedance is near 50 ohms I can see
that the amp reaches a power peak.
So, while I may not have figured out what the output impedance of my amp
is, I can at least see a figure of merit on the VNA and I can tune my setup
to achieve a 50 ohm resistance. I'm still puzzled by the inductive
reactance and I'm not sure I'm doing any of this right!? Any advice from
an old hand who has done all this before would be greatly appreciated!!
Regards.
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: Measuring the output impedance of a 20m push-pull power pre-amp
#transformer
picoguy, I infer that you have a class B push-pull amplifier you are measuring.
S-parameters are by definition characteristics of a linear small-signal device. Any non-Class A power amplifier will exhibit different impedance characteristics depending upon the drive level at its input.
Measuring the output impedance of an un-driven, "cold" amplifier will tell you little about its behavior under drive, or "hot".
Measuring it WITH drive is risky and not for the unexperienced nor faint of heart and will almost certainly result in a destroyed nanoVNA. I have been making VNA measurements since the '70s and have always been able to avoid making such a measurement.
Google "hot S22" and you will find many references.
73, Don N2VGU.
|
Re: #general SD card function on H4
#general
Some earlier versions of FW had timing issues. Use the latest HUGEN or DiSlord FW for the H4 and you should be OK.
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On Tuesday, December 14, 2021, 02:32:10 p.m. EST, <rseverns@...> wrote:
I have a new H4 with a micro SD port.? The port polarity is not marked on the case but with a little care I was able to insert it correctly.? However, when I try to save a screen plot I get "fail write".? What have I missed?
Rudy N6LF
|
Re: #general SD card function on H4
#general
Hi Rudy!
Be sure to have the unit fully charged, and use a SD card max 32GB formatted with FAT32. Turn unit OFF, insert the card and then ON again. If you try to put it the wrong way, there is some kind of lock, you just "feel" it. If correct, you feel the spring. If you use a little force, it's possible to insert it the wrong way. Be careful!
I had the same expirience with another unit!
Karl
|
#general SD card function on H4
#general
I have a new H4 with a micro SD port. The port polarity is not marked on the case but with a little care I was able to insert it correctly. However, when I try to save a screen plot I get "fail write". What have I missed?
Rudy N6LF
|
Re: Measuring the output impedance of a 20m push-pull power pre-amp
#transformer
1) The impedance of the primary, the collectors, is highly dependent on drive level from the previous stage. Looking into the 50-ohm port with the VNA even with the PP output stage properly biased but with no RF on the bases, the impedance will not be that when the PP stage is properly biased AND RF in the circuit. The measurement you are attempting is highly questionable for that reason. A better and more rigorous method would be to optimize power output into a 50-ohm load. Then disconnect the collectors and look into the "network" from what would be the collector side with the "network" output terminated with a 50-ohm load. 2) The broad band matching transformer on the output should have its turns ratio adjusted to transform something in the vicinity of 1 to 3 ohms (real) to 50-ohms - "nominally" a 5:1 turns ratio. Most of the BJT RF power transistors reside on the extreme left side of the Smith chart with some reactance as well. The data for the Smith chart plots from the suppliers are usually made at full rated power and not a couple of milliwatts (from the VNA). Dave - W?LEV On Tue, Dec 14, 2021 at 3:52 PM picoguy via groups.io <s1ig0= [email protected]> wrote: Hi,
I'm in the process of building a BJT transistor based push-pull amplifier
that I hope will develop 1 watt to drive a final power amp stage.
The design is relatively common. It uses a pair of impedance matching
transformers at the base and collector of the power transistors. The input
transformer is an FT37-43 with a biflar wound centre tapped secondary fed
from an active biasing circuit and the output transformer is an FT82-43.
The output transformer primary is connected across the transistor
collectors, with the DC (12V) supplied via a biflar wound centre tapped
FT37-43. The transistors are 2SC2078's, which should have no problem
supplying the power I need at this stage: 1 watt.
I've had some issues with the output transistor, where my experiments
would suggest it isn't acting like an "ideal" impedance transformer. The
toroid is confirmed genuine and the type 43 material should be good for
14MHz.
Anyway, that prompted me to try looking for the output impedance of the
push-pull arrangement. I figured I could use the NanoVNA by having it feed
a signal through the output port with a bias applied (but no input signal
obviously!) The experiment sort-of works...let me explain. I find that
the impedance (resistance + reactance) is not quite what I expected. The
reactance is very inductive and my experiments would suggest that this is
certainly influenced by the secondary winding inductance. If I put 10
turns on the output secondary, I get xx uH. If I reduce the turns to 3 or
4, I get nH's. However, and importantly for what I'm looking to achieve,
when the real/resistance part of the impedance is near 50 ohms I can see
that the amp reaches a power peak.
So, while I may not have figured out what the output impedance of my amp
is, I can at least see a figure of merit on the VNA and I can tune my setup
to achieve a 50 ohm resistance. I'm still puzzled by the inductive
reactance and I'm not sure I'm doing any of this right!? Any advice from
an old hand who has done all this before would be greatly appreciated!!
Regards.
-- *Dave - W?LEV* *Just Let Darwin Work*
|
On Mon, Dec 13, 2021 at 05:51 PM, N5SE wrote:
Came back in and checked eMail one more time. I have gone to both URL's and
downloaded en.stsw-stm32102.zip and NanoVNASaver.x86.zip. Since I run Windows
7 32 bit, that looks right. will get after this Wednesday. Gone this time.
Will let you know via private eMail rain or shine. Thanks a million.
Hope it now works for you. Please post any replies to this group instead of private email. That way others that search this topic later will have the full conversation. Roger
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Re: Newer version firmware
Here is the latest firmware for the H/H4 posted on the manufacturers (Hugen) github.
DiSlord is the major developer of new firmware and his improvements/changes are verified by Hugen and then posted on his github for buyers of his products.
Roger
|
Re: Measuring the output impedance of a 20m push-pull power pre-amp
#transformer
Apologies, my original mail should have read: "I've had some issues with the output *transformer*, where..."
|
Measuring the output impedance of a 20m push-pull power pre-amp
#transformer
Hi,
I'm in the process of building a BJT transistor based push-pull amplifier that I hope will develop 1 watt to drive a final power amp stage.
The design is relatively common. It uses a pair of impedance matching transformers at the base and collector of the power transistors. The input transformer is an FT37-43 with a biflar wound centre tapped secondary fed from an active biasing circuit and the output transformer is an FT82-43. The output transformer primary is connected across the transistor collectors, with the DC (12V) supplied via a biflar wound centre tapped FT37-43. The transistors are 2SC2078's, which should have no problem supplying the power I need at this stage: 1 watt.
I've had some issues with the output transistor, where my experiments would suggest it isn't acting like an "ideal" impedance transformer. The toroid is confirmed genuine and the type 43 material should be good for 14MHz.
Anyway, that prompted me to try looking for the output impedance of the push-pull arrangement. I figured I could use the NanoVNA by having it feed a signal through the output port with a bias applied (but no input signal obviously!) The experiment sort-of works...let me explain. I find that the impedance (resistance + reactance) is not quite what I expected. The reactance is very inductive and my experiments would suggest that this is certainly influenced by the secondary winding inductance. If I put 10 turns on the output secondary, I get xx uH. If I reduce the turns to 3 or 4, I get nH's. However, and importantly for what I'm looking to achieve, when the real/resistance part of the impedance is near 50 ohms I can see that the amp reaches a power peak.
So, while I may not have figured out what the output impedance of my amp is, I can at least see a figure of merit on the VNA and I can tune my setup to achieve a 50 ohm resistance. I'm still puzzled by the inductive reactance and I'm not sure I'm doing any of this right!? Any advice from an old hand who has done all this before would be greatly appreciated!!
Regards.
|
Hi ,
Sometimes I have tis problem as well, mostly it helps when I delete the .ini file in NanoVNA-App's directory? restart the application and set my preferences again.
Just my 2 cents,
Joss.
Op 14-12-2021 om 14:11 schreef Antonio (EA7HJ) via groups.io:
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Hi
Thank you, Larry Rothman for your help.
I'm sorry, but after trying everything, I give up.
1) installed the firmware version that you indicate to me (V1.0.69), also v1.0.71 and V1.1.
2) Uninstalling all software and controllers on the PC.
3) I make a clean installation of VCP_V1.5.0_SETUP_W8_X64_64BITS.EXE and DFUSE_DEMO_V3.0.6_SETUP.EXE.
4) Terratem installation. (The nanovna is connected and disconnected from the terminal, as well as Teraterm perfectly recognizes the serial port with the installed driver STMicroelectronic).
5) Nanovna-App works in DFU mode, he installed the different firmware, but it does not recognize the Nanovna in serial port mode.
6) Back to original firmware V.0.5.0 and everything returns to normal.
So far my experience. I hope that one day you see the light. LOL
I am very grateful for your help.
Antonio - EA7HJ.
--
Dit e-mailbericht is gecontroleerd op virussen met Avast antivirussoftware.
|
Thank you, Robert. I just ordered one. Jerry ________________________________ From: [email protected] < [email protected]> on behalf of Robert Klaus <robert.w7xlr@...> Sent: Tuesday, December 14, 2021 8:21 AM To: [email protected] < [email protected]> Subject: Re: [nanovna-users] NanoVNA-H4 Case Here is one with next day shipping: ;data=04%7C01%7C%7Cfa44d38bb3854f130e5d08d9bf0d00cf%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637750884844292823%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=UhvB1MfqcHHS5lnWDBTpqf6vUuALCDRBtzImGVe0%2FZo%3D&reserved=0
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Here is one with next day shipping:
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Wow - that is really strange that your unit works with old FW but not the newer FW.
My last suggestion is to try to remove all references to the STM drivers and use USBDview to reset the USB devices associated with the STM drivers, then reboot and re-install.
It's stuff like this is why I got out of being a SysAdmin and went back into electronics ;-)
Maybe another forum member can help you with this going forward.......
Good luck!
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On Tuesday, December 14, 2021, 08:12:01 a.m. EST, Antonio (EA7HJ) via groups.io <ea7hj@...> wrote:
Hi
Thank you, Larry Rothman for your help.
I'm sorry, but after trying everything, I give up.
1) installed the firmware version that you indicate to me (V1.0.69), also v1.0.71 and V1.1.
2) Uninstalling all software and controllers on the PC.
3) I make a clean installation of VCP_V1.5.0_SETUP_W8_X64_64BITS.EXE and DFUSE_DEMO_V3.0.6_SETUP.EXE.
4) Terratem installation. (The nanovna is connected and disconnected from the terminal, as well as Teraterm perfectly recognizes the serial port with the installed driver STMicroelectronic).
5) Nanovna-App works in DFU mode, he installed the different firmware, but it does not recognize the Nanovna in serial port mode.
6) Back to original firmware V.0.5.0 and everything returns to normal.
So far my experience. I hope that one day you see the light. LOL
I am very grateful for your help.
Antonio - EA7HJ.
|
Re: Newer version firmware
The latest version is V1.1 2021121 by Huge79/DiSlord.
|
Hi
Thank you, Larry Rothman for your help.
I'm sorry, but after trying everything, I give up.
1) installed the firmware version that you indicate to me (V1.0.69), also v1.0.71 and V1.1.
2) Uninstalling all software and controllers on the PC.
3) I make a clean installation of VCP_V1.5.0_SETUP_W8_X64_64BITS.EXE and DFUSE_DEMO_V3.0.6_SETUP.EXE.
4) Terratem installation. (The nanovna is connected and disconnected from the terminal, as well as Teraterm perfectly recognizes the serial port with the installed driver STMicroelectronic).
5) Nanovna-App works in DFU mode, he installed the different firmware, but it does not recognize the Nanovna in serial port mode.
6) Back to original firmware V.0.5.0 and everything returns to normal.
So far my experience. I hope that one day you see the light. LOL
I am very grateful for your help.
Antonio - EA7HJ.
|
Re: Newer version firmware
That looks like Hugen's firmware. Actually 1.0.71 is available since last month
|
I'm sure that you can find something similar locally or on Amazon.
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On Tue, 14 Dec 2021 at 01:23, Gerald Payton <gp_ab5r@...> wrote: Thank you Dragan. I think it would be unwise to buy from a China seller
now. It would take weeks if at all, arriving. It might even ROT sitting
on a cargo ship outside California.
Regards,
Jerry
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Roger, Came back in and checked eMail one more time. I have gone to both URL's and downloaded en.stsw-stm32102.zip and NanoVNASaver.x86.zip. Since I run Windows 7 32 bit, that looks right. will get after this Wednesday. Gone this time. Will let you know via private eMail rain or shine. Thanks a million. 30, Billy ________________________________ From: [email protected] < [email protected]> on behalf of Roger Need via groups.io <sailtamarack@...> Sent: Monday, December 13, 2021 19:02 To: [email protected] < [email protected]> Subject: Re: [nanovna-users] Confused Newbie Billy, I understand your frustration so I will help get you started. The NanoVNA uses 2 drivers to communicate with the PC. One is when you want to exchange data with a terminal or application program like NanoVNA Saver. The second is when you want to update the firmware by loading a "DFU" file. In this post I will only cover the first. Windows 7 does not have the driver installed for exchanging data so you have to install it manually. The procedure to download it from ST is cumbersome and requires registration for some reason. So I have placed it on my Box clouid drive for you to easily download. Here is the link: Once you have successfully downloaded it you need to unzip it and install the driver Win 7. There are 32 bit and 64 bit depending on what type of CPU you have in your PC. Do not plug in the NanoVNA until after you have installed the driver. When you plug in the NanoVNA after installation you will hear Windows "bing" and you will set it in the Device Manager as a COM port. Next step is to install NanoVNA Saver. You will find it at this link. Download the Windows 32 or 64 bit version, unzip and install. Then run it and patiently wait - it often takes 10 seconds or so to load because it is a Python program and it unpacking the support routines. Then in the bottom left hand corner it should show the COM port of the NanoVNA (Rescan if necessary). Click "Connect to Device" and it should plot in the graphs. This will get you started. In the Wiki for this group and on Youtube there are tutorials on how to use NanoVNA Saver. Roger Roger
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Hi All,
My NanoVNA-H4 arrived from R&L today. It shows this version firmware. I
"though" 1.0.69 is the latest version?
73
Stan
KM4HQE
Board: NanoVNA-H 4
2019-2021 Copyright NanoVNA.com
based on? @DiSlord @edy555 ... source
Licensed under GPL.
Version: 1.0.70 [p:401, IF:12k, ADC:192k, Lcd:480x320]
Build Time: Oct? 9 2021 - 09:36:48
Kernel: 4.0.0
Compiler: GCC 9.3.1 20200408 (release)
Architecture: ARMv7E-M Core Variant: Cortex-M4F
Port Info: Advanced kernel mode
Platform: STM32F303xC Analog & DSP
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Donald S Brant Jr
Roger Need
Robert Klaus W7XLR
N5SE