Measuring antenna return loss with RSPduo

[@de_w8tam]

Great video. I've been meaning to try using a noise generator and an SDR... The idea of using the RF bridge is the missing bit to my plan! Thanks so much! 73 de w8tam

[@AE5X]

Thanks Thomas - it's inexpensive enough and (at least on 10-80m) agrees with my antenna analyzer, so I trust the accuracy.

[@bussi7859]

Vector Net Work Analyser is the proper tool. Cost from 47€ to 259€ in a span from 100kHz at the low end and 900MHz for the cheap to over 4GHz for the more costly one. The measure bridge is built in and the dynamic range is up to 90dB. You can also do a lot more stuff with a VNWA

[@AE5X]

"Toy factor" and other specs are all relative

[@bussi7859]

My best VNWA ranges extrem frequency from 10 Hz to 300 MHz and is limited only by 1/f noise in the lF range and by 120dB dynamic range in HF and up range

[@bussi7859]

@__logan__duvalier__ you are ignorant

[@DrenImeraj]

Thank you for the great explanation! Should I be concerned about radiating the noise by connecting the noise source to the antenna? I cannot find any references on how much power is the noise source pushing out.

[@JohnTarbox]

Nice video. Will you be showing a video with other uses for the noise bridge such as evaluating torroid cores?

[@AE5X]

Maybe eventually, but before anymore videos showing what can be done with this stuff I want to make a comparison of the items shown with more expensive test equipment. I hope to do this within the next 2 weeks or so.

[@JohnTarbox]

That would be excellent! Will you be posting links to where you purchased the noise generator and bridge?

[@cathrynm]

Nice video! I ordered RSP receiver too.

[@catalinalb1722]

Super Video. I have the same setup only difference is the enclosed rf bridge from Ukraine and the enclosed version of RSP1A. My question is what about the power source for the rf noise sorce? It's better using a 12v battery instead of a switching power supply? And what voltage is recommended? Another topic will be the attenuator in front of the RSP? Do I really need one or I risk burning the RSP? Thank you

[@RateMyRadio]

Fantastic video! We've shared your video on our Facebook Page; I hope it drives more viewers to this great demonstration! 73, Jarrad VK3BL

[@AE5X]

Thank you Jarrad!

[@Sanwizard1]

Great tips! You may have saved me a lot of money if this works on my SDRduo. If I may ask, where did you fond the reference chart you are using? Is there a link?

[@AE5X]

www.ducommun.com/engineeredsolutions/millimeterwave/convcharts.aspx

[@tdb0ne1]

how much power is the "DUT" transmitting from the noise source? i dont see any attenuators. thanks for the video

[@frankhughes7135]

Nice work 👍

[@IDcircuits]

I think your reference load is not a good reference above several tens of MHz. I had some similars loads, they contain a through hole resistor and that one has a large series inductance. Better get one (or make one) with 2 x 100 Ohm SMD resistors in parallel. Of course you could measure the performance of the load with this setup. A load with 0603 or 0805 resistors will be excellent up to at least 1 GHz if you make sure the connections are as sort as possible. Just google for some examples of diy loads or VNA calibration kits.

[@robertallen3133]

Which is better the RSPduo or the RSPdx ? And which is the newest one. Thank you to everyone. 06 March 2023

[@miguelpolillarny7258]

Hello friend, I hope you are well, I want your advice, I am trying to amplify the small signal of a satlink ws6990 modulator, to transmit digital tv at 509 mhz, could you recommend any amplifier to achieve about 8 watts of power. Thank you

[@WheezyE]

Is there are special setting you're using in SDRPlay? I can't seem to get my setup to work. I'm using the the RF bridge (0.1-3000MHz / www.60dBm.com) to connect my trusty RSP-1A (OUT) , NOISE SOURCE BG7TBL 2016-03-06 (Input), dummy load (REF), and antenna (DUT). I've checked all connections, tried feeding different voltages in (5V 6A walwart, 12V 20A powersupply), and tested four HT antennas and one J-pole and don't seem to be able to see the dip. I tried this about a year ago and didn't get results, then noticed the noise source was getting really hot, turned it off, then never came back. Your video inspired me to try again (your setup looks identical to mine except that I'm using a 10 inch SMA cable to connect noise source to RF bridge), but still no luck.

[@AE5X]

No special settings really - just make sure can can receive properly on the desired frequency normally, ie with an antenna connected, no RF bridge and no noise generator. That'll prove that SDRPlay is set up correctly and will rule it out. Then connect the other items and you should see a dip where resonance occurs. Yes, the noise generator does get hot.

[@stevec5000]

I wonder how you were able to use the RF Bridge when the ones from China have at least 2 different problems that will keep them from working? A while back I bought one of the original ones made in the Ukraine from Transverters-store.com and was never able to get it to work until recently when I found the labels for the DUT and REF ports are reversed. They were correct on the original design but seem to have got switched when a PC board version of it started being made for sale so they won't work unless turned over or the port labels are reversed. On the Chinese made copies they forget part of the copper PC board trace that connects both ends of the two 100 ohm resistors closest to the Input port (on the ends facing the ferrite beads) which causes the resistors to be connected in series instead of parallel. It's very difficult to see because of the green or blue solder resist and silk screen, which is probably why they missed it, but if you blow up the photos as much as possible and look closely you can see there is no copper trace connecting the ends of the resistors. Mine didn't have that problem and works now that I re-labeled the ports but all the ones I've seen look identical and can't work with the DUT and REF ports used as labeled. So how did you get yours to work?

[@AE5X]

They are probably made in batches and maybe even by different manufacturers. I lucked out and got a good one? That's the problem with Chinese products - poor quality control and (maybe worse) inconsistent quality.

[@stevec5000]

@@AE5X I guess they could have accidentally made some that work properly but mine is identical to yours and if I connect mine the same way you have yours it seems to work sometimes but is inconsistent and I get all sort of odd readings! Have you tried reversing the DUT and REF connections to see if it works better that way?

[@afleak]

Where can I obtain the chart you are using to read swr?

[@AE5X]

Here's one of many return loss charts: www.ducommun.com/engineeredsolutions/millimeterwave/convcharts.aspx

[@AE5X]

Here are the parts I used: www.ebay.com/itm/2017-Noise-Source-Simple-Spectrum-External-Generator-Tracking-Source-SMA-case-/201785913062?hash=item2efb60aee6 and www.ebay.com/itm/RF-bridge-0-5-3000-MHz-VNA-Return-Loss-VSWR-SWR-reflection-bridge-antenna-/332052527822?hash=item4d4fdf7ace

[@jafinch78]

Great crystal clear video. Thanks for sharing. Interesting timing as the SDRplay site just announced a few days back and about a year after this video... an update to the Spectrum Analyzer app: www.rtl-sdr.com/sdrplay-spectrum-analyzer-software-updated-to-v1-0a/ The dummy load got me thinking since I was recently reading about pass through terminators and wondering how to make since I knew the regular terminators are fairly easy to make and here is an example for an SMA build: www.qsl.net/in3otd/electronics/VNA_calkit/SMA_female.html Background and other info (maybe can use on end of a cable for TDR, etc.): www.qsl.net/in3otd/electronics/VNA_calkit/cheap_SMA_male.html www.qsl.net/in3otd/electronics/VNA_calkit/calkit.html

[@jafinch78]

Better update on the terminations design if being more critical: www.instructables.com/id/23GHz-SMA-Calibration-Kit/

[@JOHN3GTK]

Great video !!!! Clear and detailed explanation of this sdr application. mni tnx ... John PA3GTK

[@AE5X]

Thank you John

[@bussi7859]

This bridge is useful up to 1500MHz, above that it is crap. The alternative is to use a VNWA, that 50€ up to 1000MHz, for 250€ up to 4GHz. With the VNWA you can do a ton more type of measurements and a lot more accurate.this is a toy

[@AE5X]

With a Rhode and Schwatrz network analyzer you can make these measurements well into the double digit GHz range. To the R&S, your VNWA is a toy.