I don't have a NanoVNA, but I do occasionally tune up 75 ohm notch filters for difficult FM reception situations. Up until now I've always just used an unmatched N-male to F-female adapters on my Array Solutions VNA, figuring that it was "good enough." Thanks for demonstrating how inaccurate that can be, and for sharing your expertise here on RUclips.
@@Volpefirm Out of curiosity, would 2 of these work instead of the 50 to 75 ohm pads u posted in the description?? storefront.brackemfg.com/storefrontCommerce/itemDetail.do?item-id=10759&order-quantity=1&item-index=0&customer-item=BM10319&order-uom=EA&warehouse-id=1&item-number=BM10319&customLen=&gclid=EAIaIQobChMIjMi82di08AIVOsqUCR23UQT-EAQYBiABEgKJEPD_BwE. I just wondered because it would eliminate the 2 sma female barrel connectors and the 2 N to F connectors ....thanks
Great video, but deep-6 the background music. It’s very annoying. I don’t know why so many youtubers think adding background music enhances their productions. This is an information video, and an extremely well done one at that. The music detracts from its quality IMHO. But thanks for this video, as I had no idea how to do this.
I suspect you'd find the results are improved with the SMA to F adapters (without the 50-75 pads) if you place the SMA-F adapters directly on the VNA instead of on the end of the 50 ohm cables. You'd want to minimize the length of 50 ohm cable in the system so there will be much less less length for the reflections to get out of phase
@@Volpefirm I don't have the 50 to75 pads to test with unfortunately. I just had a thought it would improve the situation because as the reflection length tends to zero, the reflection phase would tend to zero, so maybe the error would approach zero also. My guess is this is why you observed less error at lower frequencies. At 600mhz your 50 ohm segments are long and would support a big phase offset
Yes, without the pads, the dynamic range won't be degraded as with the pads. Full explanation and demonstration : ruclips.net/video/iF_PQm5TuK8/видео.html
Thanks a lot for the video 🙂 I have some 75 ohms F-terminators lying around and I want to make a cheap calibration kit from this. No problem making the load (leave as is) and the open (pull out resistor after heating the plastic mold). But the short is not so easy. I tried to solder a very thin circle-shaped self-adhesive copper pad with a tiny center hole into the bottom of the connector. Heating is done with the heat gun only. Honestly, the result looks aweful and far from perfect. Any suggestions on alternate approaches ;-) ?
I'm not going to lie. It took a number of tries to get a good job on the short. I used copper tape and cut a circle with hole. The hole slipped over the resistor lead and fit nicely inside the connector. I did heat everything up with soldering iron and then carefully melted the solder to the sides and copper tape. It takes a lot to kill a resistor and even if you do, so what. You just need a good short between the center conductor and copper tape. The hard part is not getting solder on the threads. Best of luck.
Thanks for the nice presentation, you mentioned either in this video or perhaps part 1, and Part 2 with the Cisco engineer that in a week you would put up a video on the making of DIY pads 50/75. I am interested in how you may have gone about your approach to construction. I am aware of the 43.x and 86.x resistors I looked thru your video's and may have overlooked it. Do you have a link you could post? Thanks again.
Have you created the VIDEO on how to create the Calibration Open and Short's yet video or can you share here how to do so. I can purchase the terminators rather easily but unsure how to do the OPEN and SHORT for 75 Ohm on the cheap.
Have you tried this with BNC? I was looking and found a 75 ohm BNC load as well as a 50 to 75 ohm matching pad SMA to BNC Female. I feel you could use a male to male adapter for the through and the open you could remove the pin inside a 75 ohm load, but what about the short, could you still solder the pin inside or no?
You need a transformer 75:50 Ohm, it is better than just a pad. you can built your own 75:50 Ohm transformer for buy it cheap from mini-ciurcuit. search youtube for "75 ohm to 50 ohm impedance matching transformer" . For short I was going make small hole in a penny, to sand it to get all the rust out of it, then hammer it to make flat, then sand it again, then send the side until I can fit it in a 75 terminator, then do a little bit of soldering. copper is much better short than led. To solder it, I would use solder past behind your penny and heat it with hot air. It would melt and connect the penny to 75 termination, and short the center connector. This way you have better short. For open after you removed the center conductor, then drill and remove center conductor a bit more. This reduces the parasitic capacitor between center pin and the terminator pin.
Great video! It appears you are jumping back and forth beween pro and amateur mindset. As yo umentio the NanoVNA is $50 and your calibration kit is $2. However, you seem to be stressing that one definitiely needs the precision 50-75 ohm pads and adapters. If my calculations are correct these are upwards of $300. I do understand the need for extreme vigilance as we rove into UHF, but I really dont have the budget for more than "rough and ready. From what I see from your results I will get a good idea of the profile of a filter with the cheap setup, it is just the resturn loss that will be somewhat less than accurate. (I have to say, way better than nothing)
Have you tried calibrating the NanoVNA to 75 ohms? What are your thoughts on my calibration setup?
I don't have a NanoVNA, but I do occasionally tune up 75 ohm notch filters for difficult FM reception situations. Up until now I've always just used an unmatched N-male to F-female adapters on my Array Solutions VNA, figuring that it was "good enough." Thanks for demonstrating how inaccurate that can be, and for sharing your expertise here on RUclips.
Hi @@joelepley thanks for watching and the feedback. I'm glad it was helpful and maybe I'll add some more info in this area in the future.
@@Volpefirm Out of curiosity, would 2 of these work instead of the 50 to 75 ohm pads u posted in the description?? storefront.brackemfg.com/storefrontCommerce/itemDetail.do?item-id=10759&order-quantity=1&item-index=0&customer-item=BM10319&order-uom=EA&warehouse-id=1&item-number=BM10319&customLen=&gclid=EAIaIQobChMIjMi82di08AIVOsqUCR23UQT-EAQYBiABEgKJEPD_BwE. I just wondered because it would eliminate the 2 sma female barrel connectors and the 2 N to F connectors ....thanks
I need the instructions to make the poor mans LOAD, Short, and Open do you have any instructions written or video?
Great video, but deep-6 the background music. It’s very annoying. I don’t know why so many youtubers think adding background music enhances their productions. This is an information video, and an extremely well done one at that. The music detracts from its quality IMHO.
But thanks for this video, as I had no idea how to do this.
Thanks for the feedback on the background music. Its a pain to add, so one less thing to worry about now. :)
I suspect you'd find the results are improved with the SMA to F adapters (without the 50-75 pads) if you place the SMA-F adapters directly on the VNA instead of on the end of the 50 ohm cables. You'd want to minimize the length of 50 ohm cable in the system so there will be much less less length for the reflections to get out of phase
Hi Matthew have you tested this? Just curious if you have results.
@@Volpefirm I don't have the 50 to75 pads to test with unfortunately. I just had a thought it would improve the situation because as the reflection length tends to zero, the reflection phase would tend to zero, so maybe the error would approach zero also.
My guess is this is why you observed less error at lower frequencies. At 600mhz your 50 ohm segments are long and would support a big phase offset
Yes, without the pads, the dynamic range won't be degraded as with the pads.
Full explanation and demonstration : ruclips.net/video/iF_PQm5TuK8/видео.html
Thanks a lot for the video 🙂
I have some 75 ohms F-terminators lying around and I want to make a cheap calibration kit from this.
No problem making the load (leave as is) and the open (pull out resistor after heating the plastic mold).
But the short is not so easy. I tried to solder a very thin circle-shaped self-adhesive copper pad with a tiny center hole into the bottom of the connector. Heating is done with the heat gun only. Honestly, the result looks aweful and far from perfect.
Any suggestions on alternate approaches ;-) ?
I'm not going to lie. It took a number of tries to get a good job on the short. I used copper tape and cut a circle with hole. The hole slipped over the resistor lead and fit nicely inside the connector. I did heat everything up with soldering iron and then carefully melted the solder to the sides and copper tape. It takes a lot to kill a resistor and even if you do, so what. You just need a good short between the center conductor and copper tape. The hard part is not getting solder on the threads. Best of luck.
Thanks a lot, this is more or less what I did. I will not get a price for good looks, but it works :-) @@Volpefirm
Thanks for the nice presentation, you mentioned either in this video or perhaps part 1, and Part 2 with the Cisco engineer that in a week you would put
up a video on the making of DIY pads 50/75. I am interested in how you may have gone about your approach to construction. I am aware of the 43.x and 86.x resistors I looked thru your video's and may have overlooked it. Do you have a link you could post? Thanks again.
Thanks Bob. I'm back logged, but plan on getting back to this soon.
Have you created the VIDEO on how to create the Calibration Open and Short's yet video or can you share here how to do so. I can purchase the terminators rather easily but unsure how to do the OPEN and SHORT for 75 Ohm on the cheap.
@Volpefirm - Need some advice on making the short for 75ohm. Any videos on how you did would be wonderful.
Does the Smith chart indicate 75 ohms in the center after calibration? Are Z and X values correctly shown for a 75ohm DUT?
No. Since this a 50 ohm device the Smith chart will still be 50 ohm in the center b
Have you tried this with BNC? I was looking and found a 75 ohm BNC load as well as a 50 to 75 ohm matching pad SMA to BNC Female. I feel you could use a male to male adapter for the through and the open you could remove the pin inside a 75 ohm load, but what about the short, could you still solder the pin inside or no?
I have not. Let me know if you try it.
@@Volpefirm have the parts ordered, should be here tomorrow
You need a transformer 75:50 Ohm, it is better than just a pad. you can built your own 75:50 Ohm transformer for buy it cheap from mini-ciurcuit. search youtube for "75 ohm to 50 ohm impedance matching transformer" . For short I was going make small hole in a penny, to sand it to get all the rust out of it, then hammer it to make flat, then sand it again, then send the side until I can fit it in a 75 terminator, then do a little bit of soldering. copper is much better short than led. To solder it, I would use solder past behind your penny and heat it with hot air. It would melt and connect the penny to 75 termination, and short the center connector. This way you have better short. For open after you removed the center conductor, then drill and remove center conductor a bit more. This reduces the parasitic capacitor between center pin and the terminator pin.
Hi Aduedc, great advice, thank you.
Great video! It appears you are jumping back and forth beween pro and amateur mindset. As yo umentio the NanoVNA is $50 and your calibration kit is $2. However, you seem to be stressing that one definitiely needs the precision 50-75 ohm pads and adapters. If my calculations are correct these are upwards of $300. I do understand the need for extreme vigilance as we rove into UHF, but I really dont have the budget for more than "rough and ready. From what I see from your results I will get a good idea of the profile of a filter with the cheap setup, it is just the resturn loss that will be somewhat less than accurate. (I have to say, way better than nothing)
Thanks for the feedback
oof, price of the 50 to 75 Ohm minimum loss pads, has gone up from 56$ to 72$
Whoa. Seems like nothing is getting cheaper.
Wish someone would just make a 75ohm VNA with standard F connectors. I'd rather spend 50 bucks on that then impedance adaptors.
Hi Paul I agree with you.