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Great to hear it works for you!
OTG cables, which are typically microUSB, always have pins 4 & 5 connected at the micro plug end.
Pin 5 is GND and when 4 is pulled to low on a device that supports OTG, its interface switches to USB host mode and supplies +5V at 500mA max.
As for the USB-C socket on your Nano - there have been a number of comments about the quality of the part and my unit has the same issue.
One user found it was the cable that was shipped with the unit - they bought a good cable and the problem went away.
Cheers,
Larry

UPDATE

Got it working. Looks like the usb-c socket on the nano may be a
little sloppy.

First, I used the USB Serial Console app and was able to send
commands that worked such as "help" and "pause" and resume". So OK
this is communicating.

Then I opened the NanoVNA android "webapp" app, and it indicated it
was connecting but wouldnt respond, moving the unit I noticed it
asking to connect again, and figured out that (I think) the usb-c port
on the nano, or possibly cable end, is sloppy.

Played with it and now the android app runs the nano.

INTERESTINGLY, the web site "app" approach still generates the "fail
to claim interface". But, who cares since the android app now works.'

I'll try another USB cable before exchanging the nano itself.

Lessons learned: mainly, the OTG cable must be on the phone, not the
nano. They dont work both ways. also, the console is a big help to
test communications because u know instantly if it is responding.


thanks to all who helped

I'm not sure whether this filter was specified to be linear-phase, but I believe that was probably part of its goals. It's an IF filter specified and sold for use in FM stereo tuners. In these signals, the peak FM signal deviation is 75 kHz. The baseband signal extends out to about 53 kHz (L+R audio bandwidth is nominally 15 kHz and there's a double-sideband-modulated L-R subcarrier centered at 38 kHz). So, Carson's Rule suggests that we'd want at least 128 kHZ of bandwidth on either side of the carrier. More bandwidth and more-linear phase behavior results in better demodulation of the FM signal, and thus lower distortion (particularly in the stereo L-R signal).

Yes, I plan to re-sweep these filters with a narrower bandwidth, and multiple sweep segments in order to get a more accurate look at the passband behavior.

I played around with a spreadsheet copy of one sweep's S2P data last night - wrote the formulae to plot the amplitude, and much of the math to calculate the group delay. I need to implement the phase-unwrapping step next... less easy in a spreadsheet than in something like Python. In any case I should soon have a package put together to go from an S2P file, to a nice dual-axis Gnuplot PNG file.

There is for sure a problem with this measurement. When the two GD-peaks in pass band looks like this something is wrong. That is confirmed by the pass band curve that is too un-symmetric - rolling off in pass band.

Hi David.
I understand and it is often the case when measuring with Network analyzers. In the first setup you find all the flaws and the second is much better. I have experienced it so many times, but on the same time it is where the experience really builds up. Sounds good about your new thoughts.

About plot and S2P file. You can easily import the S2P file in fx LTspice and do your plots there. I fully agree with you that this is a good way to move forward, because when you can also add additional components and immediately see the impact. In the end you can then simulate the complete circuit around the filter before building anything. And of cause if perfect, you also extract a S1P of the passives you intend to use and use that in the simulation also.

My experience is for the ceramic filters, that if Group delay or attenuation in stop-band is bad, it is often a filter impedance matching problem. Matching problems does often not affect pass-band.

My H4 arrived today. Although I didn't pay for it, it looks like it shipped by DHL on the 15th of Feb, arrived YYZ on the 20th, and spent the rest of the time clearing customs and taking the slow boat from YYZ to YOW to my QTH...

Tnx Maggie & Hugen.

N-connectors at full legal limit: I exclusively used N-connectors when
doing EME at 1.5 kW on 2-Meters. No problem. A short run of RG-8 coax to
the Bird meter got warmer than the connectors in that application on 144
MHz. N-connectors have no problem taking full legal limit on HF.

Dave - W?LEV

--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

This reader operates in the 13.56 MHz ISM band. The reading range is very
close-in, roughly to 1 cm. While the RF link is established by an
"antenna" of sorts, it is not an antenna in the usual sense of the word.
"Antennas" for these RFID applications consist more of a printed planar
inductor in a parallel resonant LC circuit. So design a spiral planar
inductor, model or measure the resulting inductance and choose an
appropriate capacitance to resonate the circuit at 13.56 MHz.

Here is a reference for calculating the inductance of printed spiral planar
inductors:



From there, you can calculate the required lumped capacitance from:
2
LC = 25330 / F

where: L in microhenries
C in picofarads
F in MHz (that's F squared in the above formula)

The combination of these will, then, form a parallel resonant circuit
"antenna".

Dave - W?LEV

--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

Pl-259 was invented in the 1930s as a form of shielded "banana plug."Sent from my Galaxy Tab? S2

It's interesting how the focus or center of discussions drifts. This started about testing filters with UHF connectors, so obviously they would have to be used in this case.. The discussion of N connectors has happened often, and in fact I'd read some time ago that, as well as 'inertia', one strong reason for using UHF connectors on ham gear was power handling. Someone in that discussion said that N connectors wouldn't handle ( or maybe just wouldn't be reliable) for high-power ham rigs. The main reason given was the small center pin of the N connector. (I suppose if that's the case, BNC's might have the same problem.)

It would be good to know how much improvement was gained by the folks who have changed their HF station connectors from UHF to the N series, both in transmitting and in reception measurements.

Somewhat related to this (but not the NanoVNA) has anyone researched the development of the UHF (SO-239/PL-259) series and what it's original purpose might have been?

Doug, K8RFT

Hi Daniel,I have no idea what you are building (HI), but I Googled "mfrc522 antenna" and got LOTS of sites, including construction pages.Good luck.Ed? KB8ESVSent from my Galaxy Tab? S2

A simple google search:
yields:
check page 20 for details.
Hopefully, this helps.

Hi Everyone,

I'm trying to develop my own rfid antenna for mfrc522. It's my first one, so... it's very difficult. Do you know the procedure to properly tune my antenna ? Or a good tutorial to help me use my NanoVNA properly ?

Any help will be very appreciated

Thanks

Less than 690ns of group delay difference is quite good. Is this filter specified to be a linear phase filter? Is there an inter symbol interference and data rate you are trying to achieve? When GD is being measured it is important to choose a frequency step which represents a proper aperture window which is usually a small percentage of the filter bandwidth. I believe Rune who wrote the saver routine took that into account. You might reduce the frequency span and see if you obtain the same GD value. All of the GD values well beyond the passband are of no consequence.

On Mon, Mar 2, 2020 at 12:21 PM, Nbridgema wrote:

David, thank you, very interesting! Did you measure phase?

I didn't display the phase, but since I had saved a couple of measurement sets in S2P format, I went back into NanoVNA Saver and loaded one and displayed the group delay (thanks for the hint about that, Alan!). With a bit of manual fiddling I was able to generate plots of both gain and group delay for the same ranges - haven't figured out if I can do both in a single graph yet. These graphs are fairly coarse - I would want to re-sweep over a narrow frequency span and perhaps do multiple segments to get a nice clean graph.

The attached plots are for one of the 180 kHz filters. Not what I would call a particularly flat (or symmetrical) group delay curve but maybe that's not very surprising for such a narrow filter.

Interest in US FM has waned with the changes for HD that take out adjacent
channels, and FCC coverage area equalization. Lack of geomagnetic or auroral
activity doesn't help.

Yeah, the HD noise is a real bother. I sought out a Sansui tuner that uses a Walsh function in its multiplex decoder, as it's pretty much immune to HD noise from the station's own signal. HD noise from adjacent/alternate channels is another matter, alas.

Would you be interested to try a North Hills NH13399 0.1 - 300 MHz 50 to 75
ohm converter followed by a 75 to 300 ohm balun? That could get within range
of a little resistive padding.

I might look into that approach after I try out a simple resistive match. The test setup requires two of whatever matching arrangement is used, of course.

I've been considering using the NanoVNA to measure a Marantz IF strip
(modified Butterworth filters), using a sequential sweep for better
resolution. I don't know the design impedance or have skills/sw to determine
by simulation. Thoughts?

Ugh... that's sort of "how long is a piece of rope" question. From what little I know of the details, transformer-based IF strips used all sorts of different transformers and impedances (tube radios probably being generally different from transistor radios). There was/is lots of variation there.

Do you know a Marantz receiver/tuner model number? Is a schematic available? or part numbers for the transformers?

I'm not even sure whether looking at the S11 return loss characteristics would be meaningful... I'm not sure there's any reason to be confident that the IF strip would necessarily be driven by a matched source.

Thanks, Soren! Yes, I can see that some shielding would probably be beneficial. This was definitely a "quickie" jig construction and I neglected a bunch of issues like that since I wasn't at all certain that this approach would work well enough to be worth the extra effort.

A "next generation" jig would probably be done a bit differently. I think I'd put the two SMA jacks along the front side (rather than opposite edges) to make it easier to hook up. It might be worthwhile to solder the whole thing up in a copper-clad box, with a strip of shielding (copper flashing or whatever) running perpendicular to the direction of the strip-line, dividing the whole box in half. The 3-pin receptacle might present itself through a small slit in the top of the box.

I'll definitely want to do some group-delay measurements and displays. I did manage to coerce NanoVNA Saver to display the group delay for one of the measurement sets I saved, but I haven't yet found a convenient way to overlay the gain and group delay in a single plot (such as I've seen in Murata's data sheets). I may have to do my own post-analysis of the data in the S2P file, and then feed it into gnuplot or something like that.

The pc saver routine that works with the vna will do group delay measure and display.

David, thank you, very interesting! Did you measure phase?

Interest in US FM has waned with the changes for HD that take out adjacent channels, and FCC coverage area equalization. Lack of geomagnetic or auroral activity doesn't help.

Would you be interested to try a North Hills NH13399 0.1 - 300 MHz 50 to 75 ohm converter followed by a 75 to 300 ohm balun? That could get within range of a little resistive padding.

I've been considering using the NanoVNA to measure a Marantz IF strip (modified Butterworth filters), using a sequential sweep for better resolution. I don't know the design impedance or have skills/sw to determine by simulation. Thoughts?
--
I_B_Nbridgema

Hi, Thanks for sharing.
I have worked with development of FM tuners for 10 years (1995-2005), so have a lot of experience in measuring these filter and characterize them mathematical.
The group delay is one of the most important parameters. So to evaluate your setup, you need to make amplitue and group delay in same plot with markers set on the right points (-3dB and -20dB -> but check with datasheet).
I would say your setup looks OK, but I have experienced that shielding may be needed between in and out of the filter to evaluate stop band performance.

Cheers
Soren.

Hello,

This email message is a notification to let you know that the following files have been updated in the Files area of the [email protected] group.

• /Crystal measurements with the nanoVNA.pdf

Uploaded By: EB4APL <eb4apl@...>

Description:
Some notes about my tests for measuring crystals. Second version

Cheers,
The Groups.io Team