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Re: Tuning 2M duplexer
Gary, Sig and Kadir
Thanks a lot for your replies. Already have enough information to tune up the cans, hopefully with better results than last try. Then I tuned the notch down but had no power out and never figure out the band pass measurement. Again thanks and will let you know of the results. 73 de CU3AA, Joao |
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Re: MY CMC MEASUREMENT
#measurement
You wrote: "KEY Down on CW and 175 volts p/p"
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Please behave like an adult. On Wed, 10 Feb 2021 at 08:35, Peter Ivanooff <gp2zl2gpg@...> wrote:
Halloooo.... miro - Your answers are nagging. Only bla, bla, bla. |
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Re: PROCEDURES for MEASURING DM LOSS and CM ATTENUATION of CMCs
Wind 5 turns on one side of the core and measure the inductance.
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Wind additional 5 turns on the other side, parallel them and measure again. Do you get half of the inductance? * Considering each wire of the bifilar pair contributes equal inductance by itself, so the total connected in parallel will be half that |
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Re: Tuning 2M duplexer
Greetings from cm3kma, I comment that last month I had to readjust the TPRD-1554 in the place where they are installed and the only tool I have to be able to do this readjustment was a modest VNA of the brand (Nanovna-F HW3.1 Deepelec ), which at the end is the same principle of the NANOVNA of this forum, in the attachment are the photos of the notches and the band passes corresponding to the frequency (TX: 145.210 and RX: 144.610) of this repeater that we have mounted on the hill de candela, g¨¹ines, mayabeque, cuba.
If you look at the photos, the nanovna configures the range to be measured in such a way that the jumps were from 10 to 10khz, starting at 144,500 to 145,500Mhz since it is the range assigned for the repeaters in Cuba and also to coincide with the 101 points of the vna for jumps of 10 in 10KHZ. Very important to have greater precision in measurements of this type, I recommend that you recalibrate your nanovna in the range that you are going to work with. I hope my humble contribution will help you 73.CM3KMA |
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Re: how to test s11 and s21 dynamic range?
Op 10-2-2021 om 17:15 schreef Jim Lux:
On 2/10/21 7:36 AM, mender5@... wrote:I would do it in a different way. Calibrate the analyzer. Terminate port 2 in 50 Ohm. The noise floor is the lowest level you can measure. To get the dynamic range you would need to know the maximum signal that can be applied. Therefore you would need an RF amplifier (input to port 1). Do not overload port 2, but to find the maximum usuable signal, you must find the level where it is no longer linear. You can find this level bij adding a know attenuator in series with the amplifier output. S21 should follow the attenuation.I made some small changes of my Nanovna-H.S21 - start putting attenuators in and seeing where it bottoms out (or where the displayed attenuation change doesn't match the actual attenuation change) S11 dynamic range: calibrate the VNA and do the 50 Ohm load as the last one. Leave it connected. Apply the calibration. Make sure you tell the analyzer (or the PC software) that the load is a perfect load. Now the displayed value of s11 is the dynamic range since it sees a perfect load, perfect in the sense that it is exactly the same as the reference. For noise floor, take the peak values and add a few dB for safety margin. For S11 a dynamic range of 30 to 40 dB is enough for all practical applications. All values are frequency dependent. Note that a 20 dB attenuator does *not* mean a 40 dB return loss. Most likely it is less in practice if the input is not exactly 50 Ohm (or better, exactly the same as your reference) |
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Re: [nanovnav2] PROCEDURES for MEASURING DM LOSS and CM ATTENUATION of CMCs
What you are measuring is DM loss through the balun. Ideally, this should
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be low. The Smith Chart, S21, and S11 all look about right for that measurement. If you wish to measure CM attenuation, connect just the braid between the two ports. That is the path the CM energy 'sees'. Dave - W?LEV On Wed, Feb 10, 2021 at 1:21 PM Chris Keladis <ckeladis@...> wrote:
--
*Dave - W?LEV* *Just Let Darwin Work* |
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Re: PROCEDURES for MEASURING DM LOSS and CM ATTENUATION of CMCs
Thank you for the great summary and information about measure CMC CM
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attenuation. I have a couple of follow up questions for you and/or the group, if I may. I notice the process is for bifilar chokes. And, it looks like you only connect one wire of the bifilar turns to the VNA. You also said you can connect both wires if you short both ends. I am still trying to make sense of shorting both wires and why their wouldn't be a difference in CM impedance compared to only connecting one wire. To me, it would seem that connecting both ends together would create a parallel path and would not be a true measurement of impedance (i.e. due to wires in parallel, similar to two resistors in parallel). But, I know we are dealing RF and ferrite toroids ... my intuition can't make that jump, yet. * I have actually tried one vs. both wires in parallel with the VNA in measuring CM attenuation.. There is a very minor difference. The largest practical effect is to reduce resistance (not so much the ¡ÀjX portion). * * Considering each wire of the bifilar pair contributes equal inductance by itself, so the total connected in parallel will be half that of each wire alone. This ignores mutual coupling. A 3 dB difference in 30 dB of total * * attenuation, to me, is of little concern. The total inductance of two inductors in parallel can be calculated from L(total) = [L(1) X L(2)] / [L(1) + L(2)], just like resistors in parallel.* Second question, what is the procedure for coax chokes? I *think* what I have seen and understand is that you connect the *braid* only on CH0 and CH1 (Port 1 and Port 2). This is the path that the CM would take. Is this correct for coax chokes? *You are correct. Connect the braid from one end to CH0 and the other end to CH1. * I have the NanoVNA and love it. Building and measuring CMCs is my next adventure. Thanks to you and the group for a wonderful resource. *Anything to encourage learning the NANOs and building your own "whatevers". Experience is the best teacher!* *Dave - W?LEV* On Wed, Feb 10, 2021 at 3:28 AM Adam Young <way@...> wrote:
On Sat, Feb 6, 2021 at 04:00 PM, David Eckhardt wrote:Dave, --
*Dave - W?LEV* *Just Let Darwin Work* |
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Re: COAXIALLY WOUND CHOKE
Brian, no pix. I took it apart as I had another application for the
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RG-142. In the future, I'll take pictures. Dave - W?LEV On Wed, Feb 10, 2021 at 2:16 PM Brian <k0fbs73@...> wrote:
Dave, --
*Dave - W?LEV* *Just Let Darwin Work* |
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Trouble compiling DiSlord's 1.0.46 for H
Hi DiSlord,
I just tried to compile your H code with the updates from a few days ago and got the following errors in the ChibiOS area. I installed ChibiOS from your current repo. ChibiOS/os/hal/osal/rt/osal.h:241:34: note: in expansion of macro 'chDbgAssert' #define osalDbgAssert(c, remark) chDbgAssert(c, remark) ^~~~~~~~~~~ ChibiOS/os/hal/src/hal_usb.c:932:5: note: in expansion of macro 'osalDbgAssert' osalDbgAssert(false, "EP0 state machine error"); ^~~~~~~~~~~~~ ChibiOS/os/hal/src/hal_usb.c:934:3: note: here case USB_EP0_ERROR: ^~~~ Compiling nvic.c Compiling hal_lld.c ChibiOS/os/hal/ports/STM32/STM32F0xx/hal_lld.c:54:40: error: expected identifier or '(' before 'void' static void hal_lld_backup_domain_init(void) { ^~~~ ChibiOS/os/hal/ports/STM32/STM32F0xx/hal_lld.c: In function 'hal_lld_init': ChibiOS/os/hal/ports/STM32/STM32F0xx/hal_lld.c:235:30: error: expected expression before ')' token hal_lld_backup_domain_init(); ^ make: *** [ChibiOS/os/common/startup/ARMCMx/compilers/GCC/rules.mk:216: build/obj/hal_lld.o] Error 1 Any idea where to look? The last code I compiled for the H was from Aug 2020 and it still compiles OK today, so did something change in ChibiOS? Thanks, Larry |
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Re: how to test s11 and s21 dynamic range?
On 2/10/21 7:36 AM, mender5@... wrote:
I made some small changes of my Nanovna-H.S21 - start putting attenuators in and seeing where it bottoms out (or where the displayed attenuation change doesn't match the actual attenuation change) S11 - calibrated mismatches - attenuator into an open or short. If you put a 20 dB pad on the Tx port, can you see the difference between short, open, and load?? (20dB pad is -40dB S11, 20 dB going out, 20dB coming back from the reflection). A couple decent step attenutors (one in 10dB steps, the other in 1 dB steps) makes this easy.? But a handful of fixed attenuators can also do it, just more time consuming as you swap them around. Watch out for leakage from cables etc as you get to higher isolations. 80 dB is hard. >120dB is really hard. |
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Re: Start up error.
A kluge way to see/capture the quickly disappearing screen...
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If you have a smart phone with camera capable of taking video, start a video recording of your nanoVNA screen during start up. Stop video after the screen goes blank. You should be able to scroll back through the video to a still frame of the screen display. John, wa3jrs On Feb 10, 2021, at 9:06 AM, daniebjoubert <daniebjoubert@...> wrote: |
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Re: RF Sampler
On 2/9/21 7:07 AM, Max via groups.io wrote:
I need an RF sampler of some sort for monitoring my RF signal. This might be used with a scope or TinySA or ... If you want to build your own.. A nice 20dB sampler is a voltage divider with a 450 ohm and 50 ohm resistor in series. That gives you a nice 10:1 voltage ratio, and the 500 ohms in parallel with a 50 ohm line is barely noticeable (45.5 ohms). If you have higher powers, go for 4950 ohms and 50 ohms, for a 100:1 ratio (40dB). |
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Re: Tuning 2M duplexer
Rough tuning can be done with the NanoVNA but fine tuning the notches is best done with the actual repeater receiver.
To rough tune, use the s21 measurement. Connect the source port (ch0) to the antenna of the duplexer and the detector port (ch1) to either the receiver or transmitter port of the duplexer. Tune whichever port to get the passband centered on the desired frequency. Now connect the NanoVNA between the receiver (ch1) and transmitter ports (ch0) of the duplexer and put a 50 ohm load on the antenna port of the duplexer and fine tune the receiver duplexer cans to put the notch at the transmitter frequency. Reverse the NanoVNA connections and fine tune the transmitter duplexer and to put the notch at the receiver frequency. Now you are rough tuned. Hook up the repeater receiver and input a signal generator at the transmitter port set to the receiver frequency. Tune the transmitter cans to minimize the signal at the receiver, increasing the signal generator amplitude as required. Now attach a mobile or portable radio to the transmitter port tuned to the transmitter frequency and put the signal generator on the receive port and adjust the receiver cans to minimize the signal at the receiver. And now you are done. Gary W9TD |
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Re: Tuning 2M duplexer
This youtube video shows a comparison between the NanoVna H4 and a Tektronix TTR506A "professional" VNA to show the difference in dynamic range.
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? Of course comparing something that is $100 to? something that is in the $12K price range you do see the difference.? They were tuning a mobile type duplexer I believe (not a duplexer expert here...) which I believe is the dual notch type and they showed how the NanoVna was connected.? I would guess with bandpass/band reject duplexers something similar would be set up with the "cans" (cavity filters).? I am sure better exerts will chime in on this... But the big issue was the dynamic range of the NanoVNA to allow you to see where the notches were according to this video. Sig - KB2HHU On Wednesday, February 10, 2021, 09:52:46 AM EST, Joao CU3AA <cu3aa.azores@...> wrote:
Hello I'd like to tune up a duplexer for our Club's 2M repeater but don't know how to configure the nanoVNA to do it. That's the only tool we have here. Does anyone can help me on that issue? Thanks and regards from Azores CU3AA, Joao |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
On 2/8/21 1:51 PM, Manfred Mornhinweg wrote:
Indeed - so it would be an issue in laminated steel cores, but nobody is going to be using that for RF. This is all true, but in practice, we rarely see "pure" plastics, except in applications like clear windows, or high end applications like spaceflight, where they want "traceability to sand". They're formed in various ways, with fillers and additives, as well as scrap from earlier batches or recycling.? So you can have a plastic that is normally quite low loss, in the pure form, but quite high loss in the form used. This is especially true in price sensitive applications - plumbing and wire insulation strike me as in that bucket.? I would think that coax has fairly well controlled properties, and the inner dielectric is quite pure. But hookup wire, machine tool wire, THHN (which is PVC, with a nylon coating on the outside), and plastic pipe are not so well controlled, except for manufacturing ease and price. As long as the THHN passes the voltage breakdown test, it will pass, lossy or not.? Even wire procured to MIL standards might not be particularly well controlled - they test to the spec, and if the spec doesn't call out RF properties, it might be variable. |
Joao CU3AA
Gary W9TD