Introduction to Waveguides using the LiteVNA, Part2, The Frequency Extender
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- Опубліковано 14 січ 2023
- This video shows my homemade slotted line and using it to validate the frequency extender shown in Part 1. The extender is also used to compare various fixed attenuators.
EEVBLOG thread, Experimenting with waveguides using the LiteVNA
www.eevblog.com/forum/rf-micr...
It was mentioned that The Signal Path channel made a video on 3D printed waveguides. The attached link takes you to what I believe they were referring to. He made a few horns and a filter. He's experimenting at much higher frequencies than I am and surface finish.
• TSP #145 - Sindoh 3DWO...
During this video, I show a couple of printed horns from the following link. Maybe we can test them out in the future.
antennatestlab.com/3dprinting - Наука та технологія
I really love this waveguide series. When I grew up and went to University in 1977 the waveguides we had in School my engineering program we're all basically silver-lined and the better ones had gold but we didn't get those from industry. All the wave guys we had were donations from basically the garbage left over from Raytheon and other companies. We had a lot of old test equipment to and finally the school had to upgrade their equipment so they were going to lose their accreditation. That was the University of Lowell back then in Massachusetts. That school is now UMass at Lowell. Prior to attending the University of Lowell it was Lowell technological Institute which merged with Lowes State College at the time. Anyway this is a great series. It never occurred to me that brass would be good enough because I was always thinking of the exceptionally High conductivity of silver and gold.
For these experiments, I've been trying to use materials that were easy to come by. We don't need anything high performance. If we did, we wouldn't be bending sheet stock and pounding it out with a hammer. LOL.
One of the best videos you have made so far, instead the digital meter it is better to use a good old analog meter, the peaks and minimums are far easier to see,
Glad you enjoyed it.
Great series of experiments! Yet another thing to put on my list of future projects... for the brass waveguide, here they sell a kind of silver compound that you can rub onto old silvered objects to restore the silvering, might help to get a bit less loss from your waveguide
Interesting stuff. Thanks Joe.
A+ joesmith! A few mech e ideas for those who might want to take this a step further:
1)Differential fine pitch screws will let you adjust, with a backlash of maybe 10 thou, off the shelf from McMaster. (Use the it like you would for any other linear drive mechanism.) Using a teflon/nylon bearing block is surprisingly good for backlash-resistance. Alternatively, you can do the old "overrun past your critical measurement points, then start feeding in to take up the gearing slack" trick.
2) Using a slide vernier caliper, you can detach the moving jaw and attach that to your movable component in the slotted line. Then take the 'fixed jaw' part of the caliper, and use that as your static ruler (e.g.affixed to the wg). In fact, you can skip the differential screw step and build around grainger's 4KU78 for 30$ (on closeout, get it quick!), giving you both locking mechanisms as well as fine-resolution adjustment. It's not going to be as good as that $300 Starett mic, but it'll get you 90% of the way there.
3: Depending on what y'all have in your garage, you might be able to do better than the ball peen hammer in a vice. It's the contour of the internal radius that determines the wg performance. A sheet metal brake if you happen to have one is probably the best option. If you have a >2 ton hydraulic press, even those mini harbor freight 100$ ones, and a vice, you can metal-form a nearly perfect 90. Put it into a machinists vice (so you have reliable 90s, and planar surfaces) and you should be good to go unless you're using some crazy Aquamat or Hastelloy or crazy stainless
-2x2l
As I have stated in the these two videos, the internal radii must be less than 10% of the broad width. The main contributor of error was the WGs width. If you want to make a better slotted line, buy a section of WG with proper dimensions and make it longer than I show.
Your home made waveguide is doing exceptionally well. Commercial machined waveguide is very expensive.
I would think an suitable sensitive analog meter would be better to find minimums than the DVM.
Perhaps the issue you are having with seeing the minimums with the diode detector may be there is not enough signal to turn on the diode. A backwards tunnel diode might work better to see the minimums since they respond to lower level signals.
The demonstrations with the magnet was great for showing the effect of fixed biasing the ferrite. The bias increases the resonant frequency of and lowers the permeability of the ferrite, thus reducing the loss.
This was a great video! Thank you.
Working with higher power would have helped. The notches are very sharp,
Exceptionally well done diy homemade Waveguide & informative video !! ....You might try making an "Iris" Coupled Cavity Notch Filter. The Cavity Waveguide section is soldered on at a Right angle to the Main guide, electrically in Parallel.....Makes a great, deep Skirt Notch low loss filter....Experimenting with the "Iris" Diameter is a lot of fun & helpful when you need to notch out a Narrow BW offending signal....
The video I watched from the Signal Path where he was attempting to 3D print some WGs showed a iris filter. I may give it a try.
I have the GR900 slotted line from General radio, including the cal kit and adapters to other connectors. I use for all my RF stuff GR874 connectors. They go to about 6 GHz and I have a lot of accessoires like trombones, air-line, mixers, detectors, attenuators, component fixtures, T , L, U shapes, sliding loads, variable capacitors, all kinds of adapters etc. Most were given or bought cheap because there most people over here have no clue what they are.
The slotted line uses a detector/voltmeter that has 3 uV full scale sensibility if I remember wel.
You should be making these videos!!! I thought about getting a used WR90 slotted line and transition for it. The costs far exceeded what I planned to use it for. I think going much further with these experiments will require I purchase some actual hardware.
@@joesmith-je3tq Yes, they are expensive and rare. Also not really usable other then educational fun (for me)
I got mine from a friend who used to be a GR salesman in the 60-70's . Payed 200 euro for it. It is complete with all GR900 adapters, even to sma. A toolkit for servicing GR900 connectors. I al ready had GR900 airline.
But I had a problem with getting the correct unit-oscillators. I build a sweeping RF generator that does 25 to 2000 MHz and that is the highest I could go. But the liteVNA should be able generate 6 GHz (If I am correct)_
The other problem was the SWR meter, but I had one from HP. I found some GR stuff since, but had no time due to work.
I now am partly retired and I am living on my sailboat. If I sell my house the hardest part, mentally, is getting rid of my GR collection (the bridges for most, the small stuff is already aboard.) I have a GR1620 A that was used by GR in their cal lab (confirmed by Henry Hall, the man who designed bridges for GR for 40 years, a great and smart guy, still active in the GR collectiors world. I think he is over 90 by now. That thing is huge, and bizar, it can measure down to aF.
I amgoing to play with a satelite LNB to downconvert X-band to less than 6GHz so I can play around with radar (a friend has aan old radar from his ship for me to play around and restore so I can mount it on my boat. It works just over 9 GHz.
I did not know you were in to RF, the videos about waveguides are great. I made a few videos in the past but then got to busy with work and it is a lot of work and I hate editing.
@@pa4tim The LiteVNA is rated to 6.3GHz without harmonics and 9.3GHz with. As I have shown, things are pretty poor even at 8GHz. That's the whole reason I needed the frequency extender.
You could see if one of the local museums would like your collection. You could then just donate them to a good home.
My main interest in electronics is digital. Digital = analog = RF. When it comes to editing, you and me both!!!
An idea for the slotted waveguide, or any sliding load, you could buy a cheap digital caliper from Amazon and solder/glue it in place. You will get fast precise readouts, a thumb wheel for precision adjustments, and a locking screw. Once again, great work!
As I demonstrated during the video, the largest error contributor is the dimensions of the waveguide. For making the measurement, I was going to use a grease pen, mark it, then measure it after the fact with calipers. No point in wasting a lot of time on a one off experiment.
@@joesmith-je3tq Agreed, I only meant that cheap digital calipers are now cheap enough that you can solder/desolder them to different pieces of equipment whenever you need some precise positioning control. I've been meaning to drill a hole in a set so I can add 3D printed hooks to insert to control positioning.
Great series, Joe! Please keep them coming! I've got some microwave experiments sitting on the back burner for the time being, but I've looked into 3D printed waveguides/horns a bit. The conductive paints seem a bit expensive, so I was thinking about copper sprays used for things like automotive head gaskets that you can buy from auto parts stores. It mostly consists of copper particles, propellants and volatiles (which might help smooth out the printed parts?). I don't recall this being tried, but it might be the cheapest and most convenient method to add conductive coatings. I suspect the effectiveness significantly depends on the number of coats applied. I'm looking forwards to more of these videos!
I tried one of the copper dressings I use and posted a few pictures for you on EEVBLOG. If you have something that hardens and is actually conductive, post some details. I have some that will somewhat harden but a higher temperatures than the plastic would withstand. Even then, I doubt it would be conductive.
I did try to copper plate some conductive PLA filament. This does seem to work to some degree and may be an option. I found a paper and posted it but the results were poor. Looking at the photos, the workmanship was so poor, it never had a chance.
y6g
y6g
Another great video! Regarding 3D printing, you can buy conductive filament. It's a bit resistive, but you could assist it with conductive paint on the lining or just line with copper tape, allowing the filament to make the joins between faces. With a 3D print that beautiful slotted wave guide could have the slot closed too, very excited to see your next videos!
Post the MFG and PN for the material you are suggesting.
@@joesmith-je3tq I can't seem to post links, my posts are deleted, but Protopasta has one, but I think it's US supply so may be expensive to import. There's a very basic review of conductive filaments on All3D for alternatives. Interestingly, you can buy filament loaded with 80% copper (not sure if that's weight or volume on RS components and Amazon in the UK. No idea if it's conductive but might be worth testing. There are several conductive resins too but I can't remember how I found them last time.
@@bansci Most likely hits the filter is all. It's much more conductive than I was guessing. Maybe it could be directly plated with copper. Have you ran any experiments with it?
@@joesmith-je3tq I've not tested it, sorry. I can see suppliers for Protopasta in the UK. Farnell will have some stock next month, and there's other suppliers like Ram peripherals who have it right now.
I have no idea if the filament will work well for RF, you might be able to electroplate it but it's fairly high resistance. I think conductive paint or foil lining of 3D prints might still be the best way to go, especially resin prints which can be very dimensionally precise and smooth. If you have a design for something roughly hand sized, I'd be happy to resin print it for you and post it for you to paint and assemble. I can even do some cad work if needed, this series is great and I'd like to see it continue
@@bansci I posted a link on EEVBLOG to a paper where they are directly plating a conductive plastic. One of their experiments was a horn antenna. They show the radiation pattern prior to and with the plating but the test seemed rather poor at best. We have a few different products on order. I also wrote Signal Path to see if they would be interested in making a followup video where they showed attempting to print a few waveguides.
Really enjoying your endeavors and appreciate the hard work to produce all of this and then video it!
On the 'slotted-line'; maybe you could make a long screw that is threaded on the base and captive (but able to rotate) on the movable slide block.
I realize that you are just demonstrating the concept and with the looseness of the waveguide dimensions that is is probable not worth it.
Anyway, great content and helps us without the lab to sit alongside of you and feel a part of the journey. Thanks Joe!
No doubt that many things could be done to improve the mechanical slotted line, but did you notice that old HP microwave counter tied to the GPS receiver? If in battle, one is like playing with rocks and sticks, the other an F-35B Lightning II. Both can kill....
Hi Joe, really enjoying this series! I maintained a 19 hop 6 gig digital microwave system for many years and just retired. But never did much experimenting as the system just worked. I am realizing more and more that having a variety of attenuators is essential when doing RF measurements whether that be for HF or Microwave. Would you be willing to share the source of the inexpensive yet decent quality SMA attenuator kit you referred in the video? ebay vendor or link to the kit? (I realize that it is a gamble as to quality) Thank you for sharing your knowledge of RF measurement techniques!
The problem with that is I have no idea if you would get the same parts from the same distributor. Maybe use the search engine on EEVBLOG. This topic comes up from time to time. For example: www.eevblog.com/forum/testgear/amazon-attenuators-any-good/msg5277016/#msg5277016
If the diameter of those attns is consistent, you could probably make a clamp to hold them while torquing.
I've been known to just wrap some tape around a set of pliers.
Hi what kind of torque wrench are you using? And how much Nm are you using!
What about having a look at the ZERO IF transceiver for 10Ghz
I don't have a lot of interest in radio and don't hold a amateur radio license. That said, they do use 10GHz and I would guess some of the amateur radio YT'ers would be more than willing to put together a review for you. Wouldn't hurt to ask them.
Hi
Will your software work with a vnwa spectrum and ?
Allan pierron
N8zhc
Does it follow the exact same protocol?
How did you build the freq extender?
Assuming you watched part 1, do you have a specific question? Or just in general, like I used a drill, nuts, bolts, wrenches, screwdrivers.
Hi
What I want to no what mixers you used amp, a. Copy of the circuit
I would like to build one
Allan pierron
N8zhc
Any interested people out there following along stay away from 11.0Ghz as this is used for satellite Broadcasting.
A VNA presents very low power.