#334

[@cpopte]

Alan is back !!! You know is a great day.

[@buildstoys]

Another great use of a NanoVNA, thanks Alan!

[@ricki7187]

I use a $30k Freedom 8000C service monitor and Eagle RL Bridge for my day job. It surprises me how well these little VNA's do when calibrated properly. It is nice to have an instrument that does not need constant calibration but for $29,750 I think I can put up with it :-)

[@MacintoshWizard]

Freedom 8100 here!

[@N9IWJ]

I just picked up the NanoVNA 4-in Amazing little tool, thank you so much for your video I would have never dreamed you could tune duplexes with it, absolutely incredible Putting your video in my saved files , appreciate it very much

[@mikealsop8248]

Great, I just did a TRX VHF unit for a 2M repeater with 600 KHz spacing. They are awful at the best of times. This procedure and the VNA 2 made the job very simple and it has breathed life back into a discarded duplexer. Thanks heaps. Mike VK8MA

[@Orvulum]

My favorite RF electronics video channel! 😃 Really great stuff!

[@sasines]

Alan, great presentation as always. Very practical use of the nano VNA. Next hamfest I’m going to look for a cheap used duplexer just to play with using my nano VNA. THANK YOU.

[@TallTexasGMan]

Thank you for such an informative video. I've used an Anritsu SiteMaster for field programming duplexers during disasters and it is always I just do the best I can. But, now I have one of the NanoVNA H4 units and want to play around with this myself. Since I don't have constant access to the Anritsu, this hopefully will give me the ability to hone my skill so I can do better under pressure. Thank you!

[@davideisenberger6197]

Thank you Alan! Excellent presentation! 73

[@no-ee]

NanoVNA does a great job tuning Motorola cavities with notch filters. I love this little thing.

[@weirdsciencetv4999]

I ordered the Plus4 pro, the claim it can be used to tune duplexers, seeing your video gives me confidence it can be done along with my SDR and a low power transmitter.

[@davideisenberger6197]

Excellent Alan!!

[@eduardojacome9783]

Buena calibración. Como siempre señor con buenos videos. Muchas Gracias.

[@alf699]

Interesting. At work I used to use the Agilent FieldFox VNA for RF Filter tuning. Just as a side note: For a cavity Filter (any kind), the rule is trying to get a Return Loss of at least -30dBm with the Notch at a minimum of -80dBm. This would be good for 50W Base Transceivers and of course would cover your Link and Multipoint radios anyway as they use lower TX powers of 1W + 5W.

[@thuff3207]

I love my nano VNA cheap and useful. Thank you for sharing!

[@joopterwijn]

Nice to see the comparison, and prove you don’t need a Ferrari (although it would be nice) to get to your destination!

[@w2aew]

I prefer Porsche ;-)

[@MrHotrod73]

@@w2aew yeah, Stuttgard over Maranello :)

[@SuburbanDon]

I was never good at, and hated tuning filters. But I watched this out of respect.

[@radiotek4023]

Thanks Alan i’m impressed how well that nano works 73s VK4CDB

[@bigmotter001]

Alan, another nice educational video. Thanks for your time and effort and take care!

[@ruhnet]

Excellent!

[@PowderMill]

Another excellent video. Thank you for sharing! I really like the Vari-Notch duplexers. TX+RX/Comprod makes very nice filters and duplexers. For some reason, the Fingu (OEM mfg for Motorola), CelWave and old Phelps-Dodge are popular but I rarely come across these. Of. course, I will continue to wonder why I didn’t buy a NanoVNA earlier. Great little gadget! I do have the Mini-1300 “antenna analyzer”, but am unsure about the full functionality of this device.

[@Anupkulkarni23]

This is pretty cool to see the massive duplexers from what i use at work. Maybe an whats inside episode, if you find a broken duplexer. 😊

[@w2aew]

You should see the ones used for 6m (50-54MHz) repeaters, the cans can be as tall as a small person.

[@Anupkulkarni23]

@@w2aew thanks for the recommendation will check them out.

[@kfho9783]

Thank you for your knowledge 🙂

[@derrick_builds]

Nice work man. Need to get me some cans to tune. Thanks for the video.

[@DonDegidio]

Hi Alan, Once again you provided a fine visual aide. Very easy to follow as you tuned the duplexer. Stay safe. 73 WJ3U

[@howardhiggins9641]

I knew I couldn't afford a new Agilent VNA, and hoped to someday find a used one at a prices I could afford. With the Mini-VNA,, and a little extra time spent tuning, I no longer need to wait. I expect that third-hand VNA prices will take a downward jump because of these units, if they haven't already.

[@wolfmonk9d]

Wow, NanoVNA now can scan over more than 101 points! That's a piece of good news.

[@w2aew]

Some firmware versions for the H and H4 can do 401 points, but those don't have a low enough noise floor to see the notch filters.

[@KA9DSL]

The two return peaks are caused because of over coupling of the two cavities. Cavities needs a adjustable coupling. had same problem, got solved with coupling adjustments.

[@mikepansini4904]

Thanks for the video!

[@felipefigueroa9449]

My compliment

[@Fantazier1]

Thank You, I was wondering how that was done.

[@rielhairudin]

thank you.. for your presentation.

[@TheNoCodeTech]

This is amazingly awesome helpful. thanks

[@robertmeyer4744]

That great. I got about the same duplexer TX/RX systems used and UHF. re tuning for GMRS. UHF is bigger cans . VHF hi is bigger yet and VHf LOW is quite big. I did a 6 meter some years back. and 10 meter FM duplexer is very large. only seen pic. I have nano vna ver 2 and regal spectrum analyzer. used both . another trick. nano vna as sweep gen. I did 1 can at a time. was easier for me. now VHF has more cans because of less split . 5 MHZ on UHF. I also have the MFJ antenna analyzer used that for final test. they can be tricky to tune and temperature can effect them . finished GMRS 50 watt repeater. we took a used UHF commercial one and re programmed and re tune for GMRS. a way to save some money. 73's

[@UndernetSystems]

Great video.

[@bblod4896]

Magic!

[@stanholmes4293]

Another great video Alan! Thanks. It is great to see how well the VNA-V2plus4 performs against to your TTR506 VNA. In a previous video on your earlier NanoVNA you used DisLord's firmware. Have you tried his release on the NanoVNA-2plus4? It would great if you share your thoughts on his firmware on the V2plus4.

[@w2aew]

I"m sure that DisLord's firmwre for the V2plus4 is very good, I will have to try it at some point...

[@9h1gb]

Nice video. The only thing, if I may comment, is that I think you would be best to include the cables whilst doing the calibration. I am no expert but that is how I was always told to do. Again well done and keep io the good work

[@w2aew]

Yes, including the cables in the calibration is important when you want to remove the attenuation and phase (delay) of the cables. In our case where we are only looking at the relative depth of the return loss and insertion loss (no phase measurements, no absolute parameter measurements), you can get away without including the cables.

[@9h1gb]

@@w2aew Thank you for the clarification. As I said I am no expert but always with a hunger to learn. 73's a d take care

[@tomsmith3045]

Very cool! I have a vna2, but didn't think it had the dynamic range to tune a duplexer. Do you think it would work with the narrow spacing of a 2m duplexer as well? I've only worked with them once, but seem to remember they are a PITA.

[@w2aew]

You can set a narrow span, so the frequency resolution should be adequate for a 600kHz spacing. The dynamic range is another story - really depends on the generation of the NanoVNA - the -F and V2 units have better dynamic range than the original and -H -H4 units.

[@jimaspinwall7814]

Nice. 'direction' does matter as the length of the inter-bottle cables is part of the RF circuit.

[@w2aew]

True, but the actual length differences are typically 1% or less given the typical splits for a given band, which is likely within the cut tolerance of the interconnect cables.

[@jimaspinwall7814]

@@w2aew First - good presentation... the "Nano-VNA" products are a decent 'clue' but not sufficient for really accurate, in-depth work as-is-prudent in many cases. I just did a commercial 'bottle' retune with proper commercial equipment, then checked with my Nano-VNA... nice 'hint' but I wouldn't use a Nano-VNA as final proof for a repeater I cared about before taking the set of bottles to a commercial radio site. The '1%' works if the filter package is more or less within as-designed/as-built band-segment. 220 is 'easy.' I bring this up as hams are want and often acquire to re-purpose surplus commercial products that are in significantly different band-segments. Can you use a 450-460, 470-490+ set of 'bottles' at 440-450, or 420-430? 155-159 MHz bottles at 146? Yes... sort-of... but the results are not good/best. 10-20 dB of not-quite-best pass- and/or reject- performance difference is not insignificant. It is prudent/recommended to consider and re-configure coupling if you're taking a used product 10, 20, 40 MHz out of as-built band. Some filter manufacturer's filter-prep bench have an array of various length coupling lines to dial-in each product sent out. There can also be internal coupling loop differences which is also a factor. Two 'identical' products can leave the factory with different length coupling cables. This becomes more critical as hams are want to try to re-purpose less-stringent mobile products to repeater service. MORE critical as we have and continue to see some vendors re-packaging "off-shore" mobile products with 'generic' reject-only flat-packs - all of which wholly inadequate for commercial site installations. Many commercial and government sites do not allow... re-purposed mobiles as repeater or remote-control installations, reject-only filters, lack of isolator on the TX, 'ham' antennas, LMR-type feedlines, etc. Some of our site owners call at least one of us to pre-qualify potential new tenants, and we ask about the equipment, etc. Some vendor/brand names and products trigger an immediate NO! Even if what's stated is good enough to yield a Yes, post-install inspection and spectral analysis gets interesting. If your ham radio presence at a great site is 'essential', the equipment and engineering should be equal to the objective.

[@w2aew]

@@jimaspinwall7814 Jim - thank you for all of this great insight. You've clearly done this more than I have, and this real-world practical info is very valuable.

[@AllanteLexus]

Great video my friend - thanks for posting this

[@TheRadioShop]

Very nice little tool Alan. I was just checking after the video and most are out of stock or no longer available. I do see some Asian units. Thanks for sharing.

[@davewright3088]

Nice job..! Would be interested to see a treatment on tuning a coupled resonator type. I got nowhere fast until I started tinkering with time-domain mode on an 8753D. I'm still on a steep learning curve and although I have succeeded in moving the bandpass in the desired direction, I still have far to go...

[@stargazer30721]

As always - a great video! Could you explain the cable connections for transmit side vs receive side and where exactly the terminator goes in each scenario? It wasn’t completely clear. We just had some cans tweaked for our 2 meter repeater - I want to see if I can come close to their results with my plus 4!

[@herbertsusmann986]

Seems like those plungers should have threaded rods so you can make very find adjustments and not rely on just sliding them in and out. Is there a reason why they are not threaded?

[@w2aew]

I think it might be generally more difficult to get a good, solid RF connection on the threaded rod - but I'm not the designer of these things so I can't say for sure.

[@ydonl]

Hm. The plunger and a threaded... gizmo... whatever it is... could be separate pieces. Even temporarily installed. I suppose if you did this sort of thing on a regular basis... either you develop ninja skills, or if you're incapable of such (like me), make more tools!

[@Robinzano]

I use a small-ish wrench. To move the plunger down, i slightly tap the top of the rod with the wrench. To move the plunger up, I put the open ended side underneath the knob and tap upwards. Works like a charm every time.

[@daves5765]

Great video. Dumb question, if you're calibrating the "open" then why do you need to put an open calibration connector on there? Isn't leaving the connection open still "open"? LoL sure. I'm sure there is a good reason.

[@w2aew]

At low frequencies, it doesn't matter. As you to very high frequencies, the physical location of the open needs to be the same as for the short and load, so that the phase (propagation delay) to each of these "standards" are matched. A small dimensional difference in the location of the open with respect to the other standards can throw an error into the calibration with respect to phase. This effect is proportional to frequency (because wavelength is inversely proportional to freq)

[@markmorin5587]

Is there any how to videos for dummies using the 4401A VNA ? I mean a true step by step of tuning a 50watt duplexer as used is a vertex standard 7000u repeater? All I see are nano-vna videos..

[@w2aew]

Well, if someone wanted to load me their 4401A VNA, I'd be happy to do a video with it!

[@diverbob8]

It would have been nice to see the connections that were being used. My V2 Plus 5 (Plus 4 Pro ??) Does not even have the ports labeled.

[@w2aew]

Easy enough to label them yourself.

[@JustinPriami]

I have a lite vna. Seems very similar. You seem to skip over some steps of setup in the vna. I haven't had luck following along. Or is there soke huge difference between nanotechnology vna & lite vna versions?

[@w2aew]

The intent of the video wasn't to show the complete setup of the nanoVNA (so some steps may have been not shown), but rather to check if the performance of the NanoVNA was sufficient to get an effective result.

[@WYCO_Alpha_Bravo]

I'm trying to use a vna to tune uhf repeater.

[@peteranoia4570]

Utilized this method for tuning a mobile duplexer for a desktop ham repeater at local scout camp to let scout hams experience using a repeater. I tried to diagnose suddenly weak reports from the repeater several weeks later. The S21 trace is showing a roughly -10dB S21 at the pass frequencies and a corresponding increase in the notch. Does this correspond to insertion loss? I compared it to a mini Celwave, which is showing approx. -3dB.

[@w2aew]

Yes, S21 is insertion loss.

[@TheWyleECoyote]

Just curious if the clone you once used is as good as the official nanovna v2 plus4? I am on the fence about paying ~$200 for the official one, or paying less than half price for the clone.

[@w2aew]

Dynamic range is nearly the same, but it’s about 2-4x slower.

[@stefanhummelink3662]

Hi Alan, it seems you're doing a UOSM calibration? I can't see your standard definitions so it may well be you're doing a TOSM calibration but with a non-zero length thru(don't even know if this little device is capable of doing multiple cal types). It may be wise to mention that using a non-zero length thru for a defined zero length thru TOSM calibration, the insertion paths yield inaccurate "absolute" results. 😀 Sorry if I'm so critical, but at 1.2GHz these kind of "errors", if unintentional will already become an headache for young players. 😀 Offcourse for this relative tuning of the Duplexer, the absolute calibration error is not important st all, but it must be mentioned for clarity imho.😀

[@tommihommi1]

the nanovna can't do UOSM from what I understand. but if you're calibrating at the port instead of at the measurement plane, it all is rule of thumb anyways.

[@stefanhummelink3662]

@@tommihommi1 Yep, but in the case of a true TOSM or UOSM at least one can de-embed the characteristics of the cables from the DUT if interested. 😀

[@w2aew]

@@stefanhummelink3662 Yes, but in this case of course, there wasn't a need to establish a measurement plane at the filter ports. I have another video that talks about the importance of VNA calibration and the establishment of a proper measurement plane (and another video on port extensions).

[@whateg01]

Why not do the calibration with the cables that will be used to connect to the duplexer?

[@w2aew]

Sure, if you have them, use them.

[@n1kkri]

Where can I find the duplexer tuning procedure for a Kenwood TKR-851 repeater?

[@w2aew]

As far as I know, the duplexer is not contained in the TKR-851 - it is external, so the tuning process would be similar to shwa is shown here.

[@JeffCacioppo]

as a "brute force" measurement I connected the approx 78 watt (+48.9bDm) repeater transmitter to the transmit side 449.325mHz and tinysa ultra to the receiver port and measured -42 dBm at 444.325mHz without external attenuators...no, I'm not that crazy, I had 70db of attenuators in line in case I was wrong lol, then I removed them. My question is it a safe assumption that the notch...and insertion loss is about 90db. It was interesting to note that when I tuned the cavities individually I was getting close to 45 dB each.

[@w2aew]

It is a close assumption. At that frequency, and with this level of attenuation, it is possible that you could be getting leakage through the shield of the coax - which means it could actually be a little better than 90dB.

[@wdm213]

Nice job. You're a natural instructor. How would you contrast this vs using a spectrum analyzer to tune this setup? Anyone?

[@w2aew]

To use a spectrum analyzer, you'd need a signal source (usually a tracking generator), and a directional coupler or return-loss bridge. With these, you can tune the passband. You won't need the coupler or bridge to tune the notches, but you will need to have sufficient measurement dynamic range to see the depth of the notch (90dB down or more).

[@JeffCacioppo]

Can you tune the 4 filters individually, would then the notch be only half as deep, possibly above the noise floor

[@w2aew]

Yes, but there will be some interaction when they're connected together, so the notch will move.

[@rasputinputin8103]

Should the calibration not be done using the leads you are going to use for the notch filters?

[@w2aew]

If I needed to accurately know the phase at the filter ports, yes. In my case, the loss at these frequencies and the impedance rotation due to these cables, will have no effect on the filter tuning - so it wasn't necessary to calibrate at the end of the cables.

[@leopoldoalvarez6787]

Dear Sr.., suppose to use nano-VNA as service monitor for Radio Services or diagnosis .., is possible to use it as well..?, any attach network to see high RF power...?, best regard...!! YV6ENB venezuela

[@RetroShare2]

Hello and thanks for the informative video. Could you please compare a spectrum analyzer with nano vna and a professional vna?

[@earlyadapter643]

Comparing this to your previous video #318, i was worried that the return loss S11 alos has a dip at the frequency position of the notch. I guess that in this video, you connected the port 1 (channel 0) to the antenna and the port 2 (channel 1) to the Tx or Rx ports, while in the previous video, you measured in the other direction. Therefore, while S21 shows the notch in one path, S11 has a dip at the same frequency that corresponds in reality to the passband of the other path. In the previous video, the return loss at a notch frequency was unity as expected. At the antenna point, the path that is at notch frequency should present infinite and real impedance so as not to perturb the other pass which is then in the passband and this corresponds to a unity return loss, but it has to be measured the other way around to not measure the parallel impedance of the other path.

[@w2aew]

Point of detail: S11 is not Return Loss, it is the Reflection Coefficient. The difference between the two though, is just the sign.

[@earlyadapter643]

@@w2aew Thanks Alan. Your videos inspire me to a lot of VNA uses beyond antenna analyzing. 73, F4HYZ

[@researchandbuild1751]

I have a hard rime understanding return loss. What exactly does it mean? Does it being negative mean that there is less loss ?

[@w2aew]

Return Loss in dB should always be a positive number. It is simply the magnitude of the reflection coefficient, with the negative sign removed. It is common (but incorrect) to see the Return Loss expressed as a negative dB value. Return Loss is equal to -10*LOG(PR/PI). Since the reflected power PR is always less than the input power (PI), the result of that equation will always be a positive number. Larger values mean higher return loss - which is a GOOD thing - you want the reflected power to be very low - thus you want the return loss to be very high.

[@researchandbuild1751]

@@w2aew well I was thinking, the key would "switch" to a dummy load , so, back and forth, essentially

[@R2AUK]

👍❤️

[@dariocetrari7785]

Comparacion con vna Sv4001a? Gracias desde Argentina.

[@alanwolke6253]

I don't have access to an SV4401A - so I can't perform a comparison.

[@dariocetrari7785]

@@alanwolke6253 Thank you.

[@ThinKkBIGG]

Would having used it with the software on the computer with 1001 points have brought you even closer to your reference VNA?

[@w2aew]

Not really - the software wouldn't help with the measurement dynamic range.

[@bsw9339]

i am interested in such duplexer. Where can i find its schematic? Thanks.

[@w2aew]

This type of filter can't really be accurately conveyed in a schematic. There are very few traditional electronic parts - it is mainly built of mechanical structures to create resonant cavities, etc.

[@bsw9339]

@@w2aew Thanks. Do you have simplified schematic? I want to see how the simultaneous transmit and receive work.

[@alanmainwaring1830]

Duplexers, Diplexers can be modeled with lumped circuit elements but this would be very difficult. In the Feynmann lectures they show as the RF frequency increases a metallic can acts like an LC system. I can recall for example a coke can, becomes a resonant circuit at about 455Mhz. What you really need is a mechanical diagram not a electrical schematic. I have always thought of Duplexer design as a bit like black magic. very specialized area.

[@IZ4HDM_Chris]

Always very good content, Alan! 73 de IZ4HDM Cristiano

[@daves5765]

I don't know why you would think people would be searching for and watching this video wouldn't know what a repeater is.

[@w2aew]

Some people stumble onto the video because they search on NanoVNA...

[@4150CHF]

I posted some comments and questions but they are not showing in comments section.

[@4150CHF]

Would you be willing to give me some assistance? My email address (scroll over email) is on my QRZ page.

[@4150CHF]

I am trying to tune two Comprod duplexers, one UHF (66-40-46) and one VHF (66-13-46). I am trying to learn the process on a NanoVNA V2 and I will purchase a NanoVNA V2plus4 if I can figure it out but I am beating my head against the wall. My traces look very different than what you have shown in your video.

[@w2aew]

@@4150CHF I will reply to the email that you sent to me as well. But I also wanted to share this video from Sinclair (another duplexer manufacturer) that goes through the tuning process in detail for their type of duplexer. kzbin.info/www/bejne/i2i0i62wd5d_kLc

[@4150CHF]

I am new at this. How is it possible to have 2 different LOGMAG traces that are not the same?

[@w2aew]

LOGMAG is just the display format - it is plotting the MAGNITUDE of the measured parameter in dB - that is what LOGMAG means. There are two traces that I configured - one of them is measuring S11 which is the reflection coefficient, the measure of how much of the injected signal gets reflected back off of the input, back towards the source (VNA CH0). The other is the S21, which is the transmission coefficient, the measure of how much of the injected signal makes it through the duplexer. Each of these two measurements are being displayed in the LOGMAG format.

[@4150CHF]

@@w2aew Is S11 (CH0) connected to input of one side of duplexer (Lo/Hi) and S21 (CH1) connected to duplexer output (antenna port)?

[@w2aew]

@@4150CHF yes

[@4150CHF]

@@w2aew What do I need to select in the menu to ensure that the second trace will be associated to S21 (CH1) and not a duplicate of S11 (CH0) or is it automatic ? Please forgive my ignorance.

[@w2aew]

@@4150CHF Under the Display menu, you'll see a Channel button that allows you to select which channel is being used for the selected Trace. Use the Display>Traces menu to first select the active/selected trace, then go back to Display>Channel to select the channel for that trace.

[@waynegram8907]

Can you show how to tune a Diplexer because I don't know what the differences are between a Diplexer and Duplexer they are different. So I hear that the NanoVNA can't tune filters, Diplexers, Duplexers because of the bandwidth from Odbm to (-)160dbm. To really tune out below -80db the NanoVNA gets distorted and can't do below -80db to -160dbm you need an expensive VNA that can tune filters, diplexers, duplexers because of the bandwidth of the VNA

[@ruhnet]

A diplexer is generally for separating frequency bands not as closely related as a duplexer, which needs fine notch filters to notch out very close in-band signals. Tuning method would be identical or similar, but how you actually do it would closely depend on the design of the unit itself.

[@waynegram8907]

@@ruhnet Diplexers/Duplexers are sometimes used from Receiving and Transmitting on the SAME frequency or Different frequencies using only ONE antenna and ONE receiver.

[@ruhnet]

@@waynegram8907 That is correct (as are quite a few other uses of them in different forms).

[@waynegram8907]

@@ruhnet like what other different forms? The isolation from port#1 and port#2 has to be -80db to -100dB to prevent crosstalk of the transmitting and receiving

[@ruhnet]

@@waynegram8907 One example: a simple diplexer in a receiver is used to separate low (audio) frequencies from RF in a mixer/detector output. This is one of the "different forms" I was referring to. A NanoVNA (the original design) can accurately tune just about anything as long as the required dynamic range is within 60dB or so. (But note that the dynamic range of the NanoVNA differs with the various frequency bands it covers.)

[@tamaseduard5145]

👍👍👍💖👍👍👍

[@Eduar-d-o]

Sub'd - thank you for your videos

[@michaelrockinger]

where does one learn all this? great video but I feel totally ignorant watching it 😩

[@w2aew]

Mainly by learning from more experienced mentors, reading application notes from manufacturers, we well as studying various source of information (websites, books, videos, datasheets, etc.).

[@stephenhughey8460]

Very informative…thanks! AK4R

[@byronwatkins2565]

Whomever you are talking to must have his transmit and receive channels reversed. In an amateur radio setting, I would not expect a preference for which would have his transmit channel above the center vs. below the center. You seem to indicate that there is a preference and I don't understand why there might be.

[@w2aew]

Most (but certainly not all) of the amateur radio repeaters in the US are coordinated with their output (transmit) frequencies between 1282-1288MHz and 1290-1294MHz, and the repeater inputs are between 1270-1276MHz.

[@pyrokinetikrlz]

Those bandpass cans are veeeery sensitive

[@frankthetank3342]

[@krisraps]

How Does It Feel To Buy A 30K Device When Now It Costs 40 Dolars? :)

[@thed8229]

That was AWESOME, exactly what I was looking for. K0ATV

[@nam20r]

Nice Work.

[@dimmoos757]

Excellent!