There's another Ukrainian business "60dbm" in Kyiv that's active right now. I wonder if they're related? I believe the first name on the return address of my items was "Maxim".
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). So while adding cores helps bandwidth performance greatly, there is still a slight phase imbalance due to the inductance on the shield not being present on the center conductor (i.e. the topology is no longer symmetrical). This is solved by adding the same inductance to the center conductor of the coax. That's what the other side of the core is used for and that is why only the shield was used (the center wasn't connected and isn't needed) - you just need the shield inductance. This is sometimes referred to as the 'dummy' coax. This BALUN topology is used often in wideband transmitter designs when combining multiple devices (i.e. push-pull, etc.).
To me it's just a common mode choke, so that you block common mode signals, and let the differential signal pass. (You could use a transformer; but, you probably wouldn't get as broad a band-width.)
@@willthecat3861 Thanks for your comment Will. I think the HF HAM guys (which I'm a part of) tend to call it that, but the important aspect is that it's configured as a wideband TLT (transmission line transformer) Balun. Whereas a common mode choke doesn't necessarily imply it's being used to take a balanced input (i.e. the bridge) to single-ended output (i.e. the grounded SMA connector), with the 'dummy' Balun coax being used to help get the performance closer to ideal. That's just the distinction I wanted to make in my initial post because I thought some people might have missed that important aspect. The cores help extend the lower frequency whereas the TLT length sets the upper frequency limit (usually around when the frequency is 1/8 wavelength of the coax, but picking the wrong core can limit the upper freq too). You can see that in the 1-3000MHz range the designer silk screened on the board (3000MHz might be a stretch in my opinion). If you google "A Tutorial on Transmission Line Transformers" by Chris Task, he has a nice write about the Guanella Balun (but it doesn't cover the 'dummy' balun coax). You probably know all that, just wanted to add clarification for others. I agree about your BW comment and using a transformer. Kind of hard to beat the performance of a TLT, especially at UHF and above.
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.
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.)
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.)
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.
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.
Glad you posted this!! I replied to your response on the previous video suggesting you try one of these, but RU-vid 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
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!
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?
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.
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
I built a similar unit myself, but I used a 4:1 Toroid Transformer instead of the binocular transmission line transformer. It works well, but my design only works to 200 MHz.
I have the SSA3021X Plus, and it has all the hardware, including a bridge, to be a VNA, and I think the same is true for the non-plus version as well. The instructions are on EEVBlog for the hack.
Edit: The "Plus" models do seem to have VNA features while maybe the non-Plus do not. With just the "open up everything" hack I can go to VNA mode (pressing the Mode button to select modes) and am able to do SWR, return loss, Smith Chart, etc testing. Previous comments: I was led to believe (by the EEVblog forums) my SSA3015X Plus also has all required hardware and the same firmware swap should convert it to an SVA1015. Other comments to IMSAIGuy's recent videos have cast doubt. I've done the "open up everything" hack on my unit, but so far I've refrained from the SVA firmware swap. I may have to buckle up and try that soon just so I can set that doubt to rest one way or the other.
Bah! I bought one of these on AliExpress and it's been in the box since as I could not get it to work. Before I received my 3021 I was using a noise generator (BG7TBL) and a cheapo RTL-based SDR and would get curves I could tune with, but soon found it was way off. I bet that jumper fix will help mine. I checked and have the same issue on my PCB. My only concern is yours had a different arrangement on the coax terminations. None of mine are flapping in the breeze like that.
Also, my 3021x does not have the measurement features because the demo license on them expired. So frustrating that they put all of that behind a fricken paywall. It makes me not want to recommend the product to people.
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. Unless of course they've ripped off the silkscreen as well. How well does it perform up around 2.5GHz?
Don't know if they're related at all but the "60dbm" COMpany based in Kiev is still in operation and offers a 0-3000 MHz RF bridge in a nice enclosure for 33 US. I should have got one of those last month when I ordered their 100W bandpass filter board.
I bought the same unit a number of years ago. Appears to be wired correctly. Tracks present and coax inner cut at both ends. I think it was from the original seller. Sounds as though yours might be a copy...?
The original seller of this (the ones that work) is based in Ukraine and has curtailed selling due to what's happening. The majority of the ones on ebay/Amazon are from China and I'm guessing the design was made from copying a photo, not following a diagram or properly understanding the theory, so they all appear to be faulty or of suspect quality. Thanks for bringing the 'fix' to a wider audience.
Sounds like a great explanation, but it's still black-magic wizardry to me. Anything that is not 0 or 1 is greek to me. Especially if it's in dBs :-) Anyway. Happy New Year. I hope you have a great 2023 full of cool and interesting experiments :-)
I had same issue and it turns out they the bridge you/we bought is a CN copy of the original, did read about that after I did order it from eBay years back- Also they did copy the website on the pcb-
For folks with the same issue, might this be an opportunity to upgrade the tolerance and/or wattage on the resistors? This is not my area of knowledge, so I do not know how exact things must be. But, if an improvement in tolerance is beneficial, then all sorts of component packages could be considered. Some of which might make bridging easier.
I bought one a year ago. It didn't work. It took me about a half hour to figure out what the problem was because like an idiot I ASSUMED the PCB layout was correct. How does one screw up something so simple and not catch it when they are producing a mass-produced product? They never even tested one? Anyway, once I fixed it it worked OK. I wrote a comment on the Amazon site of the supplier describing the problem and the fix - a year ago. BTW, I know you were just demonstrating the functionality of the repaired bridge, but you might want to remind your viewers that you only screwed in half of an antenna to test. The fixture needs to properly provide the other half of a halfwave dipole in order for the return loss (or VSWR) readings to be at all meaningful. These days, RU-vid is full of 'tests' of just the whip portion of HT antennas without any thought as to what they are actually measuring, so they often claim good whips are bad, and possibly bad whips are good.
I would be interested if you or IMSAI guy would say or show how to properly emulate the other pole for an HT antenna. I've been told that the user makes up the rest of the antenna when going portable. I spent some $35 on a telescoping HT antenna that claims certain gain numbers and SWR on 2m and 70cm when fully collapsed or fully extended, but my measurements (on SWR) could not be made to agree. It's their FAQs that say "you can't measure it", more or less.
I have tried several things. you can add a ground radial hanging below, you can hold a radio and touch the SMA/BNC of the radio to the ground of the antenna. Most of the time it doesn't matter much. the biggest effect is having the antenna away from any object so it can radiate. here is a fun video I did: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-wem0DoPe5O0.html
Sure, individual cores of identical ferrite mix and "ui" initial permeability would work fine. Employing the "binocular" or "pig nose" core is to assure that the very exact CMC (Common Mode Current) impedance is imposed on the "outside of the coax shield braid" and the "inner conductor". By using individual cores this may not be possible because the ferrite torroids of the same mix form the same batch lot bought on a single order from the same manufacturer would be having small but measurable differences among them. De VU2RZA
@@subramanianr7206 Nice explanation VU2RZA! Adding the 'dummy' balun to the center conductor really cleans up the slight phase shift error between the ports. I recall first seeing this in some of the old Motorola app note decades ago. Probably in the early 80's. Seemed odd at first since I didn't understand the purpose at the time. :)
@@Mark-hb5zf thanks for your comment and appreciation. I attempted one 5 years ago without much success. I wanted the bridge (in fact it's nothing but the Wheatson bridge known and familiar to many) just for the HF spectrum and used FT37-43 cores which I had bought new from the "W" land dealer. And I used RG174 Teflon coaxial cable. The resistors were 100 ohm smd type with the connectors being the BNC type. Maybe I should try it again for any obvious fault on my side! De VU2RZA
@@subramanianr7206 I definitely don't have any experience with the bridges. Only reason I commented was that the balun caught my eye since I use that topology all the time. I'm sort of retired (wideband and high power transmitter design), so I spent my life pretty much going from Point A to Point B on the Smith Chart, and the designs almost always included some sort of TLT (transmission line transformer) and a balun. Even tho I didn't use a bridge in my designs, I almost always used couplers (either microstrip for narrow band or a mix of cores and coax for wideband) for VSWR detection and sometimes for a ALC loop. It's pretty easy to get well over a decade of BW out of a coupler with great directivity. One of the biggest concerns to get the BW was to use the lowest perm possible cores for the low-end that are still well-behaved at the high end. The cores can become lossy at the high end if you don't pick the right core material carefully. So sort of a balancing act between the lower and upper freqs. Holler if you want to try one of those! - Mark
@@Mark-hb5zf that's very nice of you. I tried the EB104 kit SSPA using the MACOM kit, a 600w HF amplifier about 7 years ago; I didn't succeed. All the MRF150 MOSFET transistors went qrt for no obvious fault on my side (or as I hope) Then a year ago I assembled a similar version, this time with 4× SD2933 MOSFET transistors using TLT and got a grand success. I have been operating it to put out 1200w on a 53v power supply drawing just more than 22-25 amps. So, I have proceeded on to making two more such amplifiers with the intention of putting out 2.5kw by the use of splitter/ combiner. One board is nearing completion and the other would be over by the end of this month. The ferrite loaded TLT is the key for the wide bandwidth covering the HF spectrum and up to 50 MHz ham band. The 13 mm copper heat spreader on the Aluminium heat sink really gets very hot to touch! It's a real fun and thrilling project I have been currently working on. Thanks again for sharing. De VU2RZA
Hello. What firmware version do you have in your SSA3021X? Mine, shows nothing when I press on "Meas Setup". I have only "Cal Open Load" in Reflectiuon page. Thank you.
@@IMSAIGuy Already seen that video, but still, on my SSA3021x I have only the option for Open calibration directly in the Mode : Reflection page. Pressing on Meas Setup nothing happen.Ițm using the latest available firmware (1.3.9.10). Hardware version is 07.03.00.
@@IMSAIGuy Same here. Reflection is activated. What firmware version do you have? The latest one available for SSA3000x is 1.3.9.10 and does not have Short calibration option. Are you using the firmware from SSA3000x Plus?
Chinese clones are even getting worse now: I just received such a piece where the shield and core of the coax are just soldered together on all 4 sides. It was clearly manufactured by someone who only was able to create an optically similar product to the original but had absolutely no idea about electronics and HF...
@@IMSAIGuy yes, you did. In the Wheatson bridge all the 4 sides must be 50 ohms (or any such identical value or the resistors in the opposite arms) to get the bridge balanced so that no current can flow in the meter or any detector De VU2RZA
I speak Russian and communicated with the guy in Ukraine and he is back in business, so I ordered from him. It looks like the Chinese are already copying. Dunno if the Ukrainian guy was also copying, but I wanted to support him. Слава Украйнe! Update: Shipped. Now at the Kiev Post Office. Progress.
Interesting... is his business called "60dbm" ? They have some really good stuff, including an enclosed 0-3000 MHz RF bridge. I should have ordered it along with the bandpass filter I ordered last month.
Thank you VERY much for this video. I've found myself with a defective one of these and I'm about to see if I can get it working. My soldering skills are awful but I'm going to see if I can mangle it together. I was wondering if you would be willing to take a few minutes and look at the video/images of what I am dealing with and maybe offer any guidance/tips on what I need to do to get it working. Much appreciated if you can. The video is here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-swWjJ8iiZ3I.html (there is a longer video on my channel that shows what I'm trying to do and me discovering that something wasn't working correctly).
@@IMSAIGuy Thanks very much for responding... and so quickly. As I sit down to see your reply I just came from my workbench where I did exactly that. It was ugly but seems to have worked. I recorded some more footage of getting it working that I'll probably publish on my channel as well (don't think you'll learn anything from me here but if you are curious to see the beneficial results of your helpful video it will be out there)! Thanks again!
