One side of the binocular cores are configured as a BALUN (BALance-to-UNbalanced). The cores help minimize the current flowing on the outside of the coax shield. Think of an ideal coax, current flows on the center conductor and an equal but opposite current flows on the inside of shield. Current on the outside of the shield causes the design to stray away from the theoretical, and limits the bandwidth. Also causes a phase shift. So to get the coax back to more of a theoretical topology, you try to increase the impedance of the outside of the shield by adding cores to raise the impedance, forcing the current back to the inside of the shield. If I'm not mistaken, this is called the 'choking' or 'magnetizing' inductance (not sure about those terms, they seem to be loosely used).
What is this black magic you speak of :) You sir are more than "just some guy in a garage". Machining, 3D printing, C/C++ programing, PCB designer, HAM operator and more. Love the channel, always a variety, thanks for sharing your knowledge. Happy New Year and please keep the videos coming
I have the same bridge, I was scratching my head wondering why it was not working properly and I have the same problem with the 2 100R resistors not paralleled, thank you for sharing the information I will correct mine too. Also I read somewhere that the chap that was making the original is based in Ukraine and has stopped trading due to what going over there at present however; a lot of these bridges that are now for sale are knockoffs coming out of Asia and I guess whoever is making them hasn’t fully grasped of the concept.
Thank You! You saved me a bit of work and probably a few expletives. I picked one of these up a few years back to use with my Nano VNA both of which have been sitting unused so far, picked them up for portable use. I have a Rigol 815TG on the bench with a few Mini-Circuits directional couplers and Narda attenuators where I do the majority of my work. Unfortunately, I just haven't had time to play RF much over the past several years due to various life events that seem to occur much more frequently as I get older.
You don't need the center conductor of the coax connected. The other piece of coax carries the differential signal to the output, and uses the shield and the center conductor. You only need the shield, on the other piece (together the shields form a balanced line.) You can even use a solid piece of wire. (If using a solid piece of wire, you should use one the same diameter as the coax, to keep the capacitance balanced.)
Tracking generator - fancy! You don't necessarily need one. You can get a long way running this sort of device as a noise bridge, and even using the station receiver as the detector. (Yes, I'm old.)
Just checked mine, yes, it does have that exact fault. I need to start the soldering iron. I do have a NanoVNA 2, so I could do without this, but as I have it, it should be in good working order. First little project of the year.
You said maybe the operator of the site has a health condition or something -- no, it's quite clear from the site that he's been displaced by the war in Ukraine. Here's to hope that things resolve and he can return and set up shop again!
Glad you posted this!! I replied to your response on the previous video suggesting you try one of these, but TH-cam deleted it ('cos of an eBay link 🤷♂). A better schematic is online if you search VK3DIP bridge I think, although the transverters-store construction is different. Well done for finding the calibration menu, that eluded me for ages!
Great explanaintion :) I do have this bridge from the Ukranian guy in a metal case :) Also the analogy that you did helped me understand it better especially now when I am wokring with some Wheatstonebridge for electronic Scales :) Thank you
Thanks for this. Haven't tried to use my RF bridge yet but now that I inspect it closely I see that it needs a little corrective surgery. Heating up the iron now.
My understanding is that the guy who originally designed the bridge used to have a shop selling them through the address on the board. He closed it down after the chinese cloners reproduced the board, even with the web site address on, however with the fault that you have pointed out. He realised that the board was being cloned and was receiving loads of enquires about faulty ones. He tried to resolve the problem but eventually was forced to shut down the site and his shop.
I have set up a tracking generator with my TinySA and a 433.9 MHz generator as you did, and it works great. Am wondering if I can do reflected measurements with it, as you did here?
Before I bought my NanoVNA I bought this and a noise generator board connected to the SDR Play device RSP1a and I was trying to measure a small RFID loop antenna for 13,56 MHz
One side of the binocular cores are configured as a BALUN (BALance-to-UNbalanced). The cores help minimize the current flowing on the outside of the coax shield. Think of an ideal coax, current flows on the center conductor and an equal but opposite current flows on the inside of shield. Current on the outside of the shield causes the design to stray away from the theoretical, and limits the bandwidth. Also causes a phase shift. So to get the coax back to more of a theoretical topology, you try to increase the impedance of the outside of the shield by adding cores to raise the impedance, forcing the current back to the inside of the shield. If I'm not mistaken, this is called the 'choking' or 'magnetizing' inductance (not sure about those terms, they seem to be loosely used).
The guy is from kherson in Ukraine and was under occupation by the Russians so he had to leave.
What is this black magic you speak of :) You sir are more than "just some guy in a garage". Machining, 3D printing, C/C++ programing, PCB designer, HAM operator and more. Love the channel, always a variety, thanks for sharing your knowledge. Happy New Year and please keep the videos coming
I have the same bridge, I was scratching my head wondering why it was not working properly and I have the same problem with the 2 100R resistors not paralleled, thank you for sharing the information I will correct mine too. Also I read somewhere that the chap that was making the original is based in Ukraine and has stopped trading due to what going over there at present however; a lot of these bridges that are now for sale are knockoffs coming out of Asia and I guess whoever is making them hasn’t fully grasped of the concept.
Thank You! You saved me a bit of work and probably a few expletives. I picked one of these up a few years back to use with my Nano VNA both of which have been sitting unused so far, picked them up for portable use. I have a Rigol 815TG on the bench with a few Mini-Circuits directional couplers and Narda attenuators where I do the majority of my work. Unfortunately, I just haven't had time to play RF much over the past several years due to various life events that seem to occur much more frequently as I get older.
You don't need the center conductor of the coax connected. The other piece of coax carries the differential signal to the output, and uses the shield and the center conductor. You only need the shield, on the other piece (together the shields form a balanced line.) You can even use a solid piece of wire. (If using a solid piece of wire, you should use one the same diameter as the coax, to keep the capacitance balanced.)
Tracking generator - fancy! You don't necessarily need one. You can get a long way running this sort of device as a noise bridge, and even using the station receiver as the detector. (Yes, I'm old.)
Just checked mine, yes, it does have that exact fault. I need to start the soldering iron. I do have a NanoVNA 2, so I could do without this, but as I have it, it should be in good working order. First little project of the year.
You said maybe the operator of the site has a health condition or something -- no, it's quite clear from the site that he's been displaced by the war in Ukraine. Here's to hope that things resolve and he can return and set up shop again!
Glad you posted this!! I replied to your response on the previous video suggesting you try one of these, but TH-cam deleted it ('cos of an eBay link 🤷♂). A better schematic is online if you search VK3DIP bridge I think, although the transverters-store construction is different. Well done for finding the calibration menu, that eluded me for ages!
Great explanaintion :) I do have this bridge from the Ukranian guy in a metal case :) Also the analogy that you did helped me understand it better especially now when I am wokring with some Wheatstonebridge for electronic Scales :) Thank you
Thanks for this. Haven't tried to use my RF bridge yet but now that I inspect it closely I see that it needs a little corrective surgery. Heating up the iron now.
Thanks very much. I just bought one of these and it did not work. Your fix solved the problem. Andrew ZL3DW
My understanding is that the guy who originally designed the bridge used to have a shop selling them through the address on the board. He closed it down after the chinese cloners reproduced the board, even with the web site address on, however with the fault that you have pointed out. He realised that the board was being cloned and was receiving loads of enquires about faulty ones. He tried to resolve the problem but eventually was forced to shut down the site and his shop.
Thank you so much for this video.
I have set up a tracking generator with my TinySA and a 433.9 MHz generator as you did, and it works great. Am wondering if I can do reflected measurements with it, as you did here?
I'd seen a few copies of the Transverters Store board with dodgy PCBs but I thouht the genuine ones from Ukraine were all good.
Bought my 2m transverter from the same company. He is shut down until the war is over
Before I bought my NanoVNA I bought this and a noise generator board connected to the SDR Play device RSP1a and I was trying to measure a small RFID loop antenna for 13,56 MHz
Nice! Congratulations🎉🎉