Re: Analysing Input Impedance Matching Circuit for the NE602
Kerr,
Here is a link with actual tests of transformers made with 73-202 binocular cores. Make sure you use insulated wire because 73 Mix material has low resistivity compare to Mix 43.
Roger
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Re: Analysing Input Impedance Matching Circuit for the NE602
Kerr,
Something is off with your results. I don't know how you are winding the binocular cores. You need full turns and one turn is a complete loop through one hole and back again. Try measuring VSWR and insertion loss by making two transformers and connecting them back to back with a 50 ohm load on the second core.
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Re: Analysing Input Impedance Matching Circuit for the NE602
Ok, understood, but a picture would help to clarify it.
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El 17/03/2020 a las 19:16, Jim Allyn - N7JA escribi¨®: The BN cores aren't actually toroids, they are "balun" cores or "binocular" cores that have two holes through them. So, if you wind through only one hole, you have a half turn.
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Re: Analysing Input Impedance Matching Circuit for the NE602
The BN cores aren't actually toroids, they are "balun" cores or "binocular" cores that have two holes through them. So, if you wind through only one hole, you have a half turn.
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Re: Dumb question: What are REAL, IMAG, and PHASE good for?
#general_vna
REAL and IMAG apply to reflection coefficient ¦£, in its complex form (a+j.b). That's why values are always in the [-1,1] interval, without any associated unit. When REAL=-1 and IMAG=0, it is the Short circuit situation. When REAL=1 and IMAG=0, it is the Open circuit situation. When REAL=0 and IMAG=0, it is the normal Loaded (50 ohms) situation. Thanks, this is what I was trying to figure out. And thanks for those files! -- KV0A - Robert
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Re: Analysing Input Impedance Matching Circuit for the NE602
hi Kerr,
I really don't understand the 0.5 to 8 ratio and the "full turn" comment. In toroidal cores, one pass through the hole counts as a full turn, there are not things as half turns, so probably your "full turn" is in fact 2 turns.
Regards,
Ignacio EB4APL
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El 17/03/2020 a las 16:55, Kerr Smith escribi¨®: I have received my new toroids (BN-73-202) and have been having a look at the difference between them and my FT37-43 ones. In this reply I have attached three images.
The first is the NE602 with an FT37-43 on the input and output - with -30dB in at 10MHz the output is -15.79dB
The second image has a BN-73-202 on the input and an FT37-43 on the output - here the output is -23.69dB
The third image has a BN-73-202 on both input and output - here the output is -33.98dB
From these tests I can see that lots of the harmonics disappear when using two BN-73-202 toroids but the gain drops quite a bit. I did try adding and removing turns on the BN-73-202 but the best ratio seems to be 0.5 to 8 (1 full turn on the primary reduces the gain and matching).
I will post the NanoVNA results in the next reply.
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Re: Analysing Input Impedance Matching Circuit for the NE602
To this reply I have attached the images from my NanoVNA, there are two VSWR plots and two smith chart plots.
When using the FT37-43 toroids on the input and output I get about a 1.58 to 1 VSWR at 7.15MHz
When using the BN-73-202 toroids I get 1.093 to 1 VSWR
(When using a full turn on the primary the VSWR is 2.6 to 1 at 7.15MHz and increases rapidly, at 15MHz it is about 6 to 1)
From these two tests I can see the match is much better when using the BN-73-202 toroids and these work well up to 30MHz (VSWR 1.45:1).
Looking at my results so far I can see I get a good match when using 2 x BN-73-202 toroids but the gain out of the NE602 is reduced quite a bit.
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Re: Analysing Input Impedance Matching Circuit for the NE602
I have received my new toroids (BN-73-202) and have been having a look at the difference between them and my FT37-43 ones. In this reply I have attached three images.
The first is the NE602 with an FT37-43 on the input and output - with -30dB in at 10MHz the output is -15.79dB
The second image has a BN-73-202 on the input and an FT37-43 on the output - here the output is -23.69dB
The third image has a BN-73-202 on both input and output - here the output is -33.98dB
From these tests I can see that lots of the harmonics disappear when using two BN-73-202 toroids but the gain drops quite a bit.
I did try adding and removing turns on the BN-73-202 but the best ratio seems to be 0.5 to 8 (1 full turn on the primary reduces the gain and matching).
I will post the NanoVNA results in the next reply.
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Re: ON7DQ_NanoVNA_Presentation_English
Well, I think that the right number is? 1000000 or 1E6
Regards,
Ignacio EB4APL
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El 17/03/2020 a las 9:52, F6EGK - Jean-Roger escribi¨®: Dear Luc,
Before, congratulations for this nice presentation.
On page 52 (TDR measurement), there is a small typo error with the example in the formula. With 1 MHz frequency step, divider must be 1.10EXP06 and not 9.10EXP06.
Just a last remark : if final result is right (198 m), the round trip of the signal on the cable allows at VNA level a maximum length measurement of (198/2) = 99 m
73 - Jean-Roger - F6EGK
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Re: NanoVNA-H4 What are the exact steps to adjust the display brightness?
Thank you Herb! I've made note of your instructions.
Rick
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Re: ON7DQ_NanoVNA_Presentation_English
Dear Luc,
Before, congratulations for this nice presentation.
On page 52 (TDR measurement), there is a small typo error with the example in the formula. With 1 MHz frequency step, divider must be 1.10EXP06 and not 9.10EXP06.
Just a last remark : if final result is right (198 m), the round trip of the signal on the cable allows at VNA level a maximum length measurement of (198/2) = 99 m
73 - Jean-Roger - F6EGK
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On Mon, Mar 16, 2020 at 06:37 PM, Hern¨¢n Freschi wrote:
Hmm that seemed to work! I wonder why?
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±á±ð°ù²Ô¨¢²Ô,
That shows that your cable is o.k., CH0 is putting out a signal, and CH1 is receiving it. Either something is amiss with your calibration procedure or you need to perform a "clearconfig 1234" from a terminal program to get rid of a corrupt configuration.
- Herb
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Hmm that seemed to work! I wonder why?
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One more thing to try. You can do a thru calibration without doing an OSL calibration if all you are interested in is the S21 loss/gain. I often do that if I am checking an attentuator or filter over a different range than I calibrated. Try doing a "THRU" and "DONE" and see if you get a zero reference across the screen.
-Herb
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Yes, I was doing that too. I also did as Roger suggested and hit RESET several times with no luck.
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±á±ð°ù²Ô¨¢²Ô,
Ensure that you do a "CAL->RESET" before you do the OPEN, SHORT, LOAD, ISOLATION, THRU calibration. Skipping that step can result in a bad calibration state even though all screen indications look normal.
- Herb
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Are you doing a RESET before Calibration. I find sometimes I have to touch RESET a few times to perform the operation.
Roger
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I had tried with another set of cables with the same result. I measured the cables not connected to anything and on DC they measure fine. Connected to the VNA both read 50 ohms (DC)
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Check your cables with an ohm meter (DMM). Your photo is fuzzy but it looks like you have a short....
Roger
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I recently tried to measure the loss in my cables for HF ham radio. I did the calibration steps, but when I do the THRU calibration, after calibrating the CH1 LOGMAG line isn't flat at 0dB. It looks like this:
What could be causing this?
Thanks.
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Roger Need
Jim Allyn - N7JA
Robert Stone
