Episode 1729 use your VNA to tune a antenna transmatch there is minimal loss, the match is there to provide maximum power transfer, learn more: web.ece.ucsb.edu/~long/ece145... Be a Patron: / imsaiguy
I hated smith charts back in college. We didn't have a VNA and our microwave electronics course was all classroom. It was terrible. Now 20 years later I have a NanoVNA and it all makes so much more sense now. Really neat seeing the arcs from the variable capacitors and inductor. Makes me want to go dig out my old tuner and play with it.
The best Elmer on the Web. Thank you. The only problem with a matcher in the shack is that all you've done is to make your transmitter happy. But you are now feeding your coax and antenna with the wrong impedance, causing loss. Folks need to be aware of exactly what they've done, so they can optimize it, or just know that what they are doing is an imperfect fix.
For viewers who aren’t familiar with such tuners this video suggests that it’s a totally inclusive solution to obtaining the “perfect” antenna solution. The tuner only presents a good match (SWR) to your transmitters. Apply some RF and insert an SWR bridge or even a second VNA after the tuner. Your SWR will be off the chart. There is no equivalent to using a truly resonant antenna. I used a tuner and created a situation where I had so much stray RF in the shack radiated by the coax after the tuner.
You may have to reconcile your ideas that may be based on your own experience or wisdom; yes, you are wrong. Take your time to understand the principles involved in using the antenna matching units. Resonance occurs only on one frequency only; away from that frequency (up or down) the antenna is no more resonant. You may say near resonance. Many simply claim that their antennas are resonant and hence effective radiators. No, you are wrong. For an antenna to be an effective radiator it needs not to be resonant always. There are some wise guys who say that you are cheating your radio by showing a 50 ohm pure resistive load by introducing the AMU while the actual load on the other side of the AMU is something very different with some resistance and reactance. Yes, it is true. Here, the transmitter puts out all the power it has into the tuner or AMU. Because the transmitter (and receiver too) is designed for the designated 50 ohm system impedance. Once the power is in there, the AMU becomes the source of RF energy. It can very well work into impedances of various kinds that are presented to it by the antenna system at the shack end. If the tuner or AMU is made with fresh, good quality (high Q) components and tuned correctly the loss of the precious RF energy is very minimum that can be ignored. Here, the T match is advantageous in handling a wide range of impedances but the correct setting of the capacitors and the inductor is mandatory to deliver all the power to the antenna system. You may see reduced reflected power reading on the meter on more than one setting while actually some or more of the RF power will be heating up the roller inductor or causing arcing in the capacitor plates. The most effective tuner or AMU will be an L match to interface with both low or high impedance loads by positioning the shunt component on either side of the series component; yes this system involves only two lumped components. There are many materials (on the subject) available on line for you to read apart from standard texts. Hope this helps. De VU2RZA
I disagree. Here is an example. I was able to use a tuner with a 43 ft piece of wire on 160m. The antenna “radiated” a signal so based on your logic it works. I compared how well it worked to dipole and a resonant full wave loop both cut for 160m - no tuner required. While a tuner will get you on the air, a dedicated antenna designed for the intended frequency is going to outperform an an antenna that exhibits high SWR’s on frequencies that the antenna was not designed for - especially when the antenna is significantly shorter than it needs to be. 7B DXCC (302 countries)and 54 years respectfully disagrees with your conclusion. Tuners are useful, not magic boxes.
@@bobkozlarekwa2sqq59 I agree with you. The tuner only ensures that maximum energy is transferred to the antenna, but has no influence on the actual performance of the antenna. It is what I call the rusty nail affect: you can tune a rusty nail to a near perfect 50 resistive impedance and still have no antenna. Of course an antenna that is off-frequency will perform better with a tuner, but that is only because you are getting more power to the antenna.
@@gartnl The tuner (in this case a unit marketed to amateurs for use at the radio end of the feeder) only ensures maximum energy is transferred to the FEEDER. After the tuner, all bets are off because everything after the tuner is the antenna. This is why comercial tuners (marketed to a different crowd) are always remote units designed to be at the antenna end of the feeder. Regardless, as you say, a resonant dipole will totally embarrass anything that needed a tuner.
@@digitalradiohacker True. The whole system counts. I did assume that the tuner is at the antenna end. A VNA should also be used at the antenna end of you want to measure the impedance. But having said that: any wire and tuner is better than no antenna. So nothing against a tuner.
We hold an annual Field Day of a college emeritus group up at a cabin that belonged to our professor/elmer. We have multiple antennas, and are always changing, repairing and for years now, the NanoVNA has been a real workhorse in making custom L-networks, stubs and impedance transformers. It also helps you economize on the reactive elements needed to match. Happy New Year & 73… 😊
The Smith Chart is definitely something that YT was made for. Seeing its practical applications makes it seem a lot less scary than the treatments in books
Same here regarding smith charts. I remember the professor passing around these weird things and we did stuff with them and then moved on. My journey in electronics took me in different directions and never saw one of those charts until I retired and started playing with nano VNAs. This week I'm going to dust off a very old home made tuner and play with it using my brand new HP8711b/8712b VNA.
Excellent video! I really like using my NanoVNA to visualize how my T-network tuner matches my antennas - very good learning instrument. Two things you may want to point out in the future: 1) It is very possible to get more than one "match" on an antenna system using one of these tuners, just because there's a low VSWR doesn't mean the antenna will perform well 2) Generally you want the capacitance of the antenna-side capacitor to be as high as possible. A match with an VSWR of 1:1 with a C2 of 30% is going to be far less efficient than a match with a VSWR of 1.3 and a C2 of 90%.
It doesn't have to be a fancy high-end VNA. This works as well with a nanoVNA. It's my preferred method: instead of randomly turning knobs it actually shows what I'm doing. One thing to remember though: tuning does not mean your antenna is working, only that your impedance is correct.
Not necessary or practical. these antennas are physically small so are easy to erect and space considerations are usually not an issue unlike HF antennas. in any case transmission line losses would be horrendous. Which is why microwave radio systems are typically mounted directly to the antenna.
Thank you for the nice demonstration (as promised already) of the AMU in conjunction with the VNA. Incidentally by having a 50 ohm dummy load on the Tx side of the tuner or AMU, and the VNA on the load side one can asses the magnitude of various impedances that can be handled by the said tuner or AMU. I request you to make a video. Thanks again 😊 De VU2RZA
Would it be feasible or worth while to install a nano vna into the case of the antenna tuner? It would certainly look pretty slick. That should go on your project idea list. Design a housing for the tuner, have PCBWay fabricate it, then swap all the innards of the tuner plus vna and display. I’d bet money you’d be able to sale them like hotcakes.
Amazing video! I've only been learning antenna theory for the last couple years as an EE major. When I had to make my own x band horn antenna for my senior project (only a 3D printed horn with some copper tape) I just measured my S11 from 8 to 12 GHz and called it a day xD Here's a question I haven't gotten an intuitive answer to during my studies: what's causing all those resonances in the antenna (apart from the primary one at lambda/2)? And can you get a feel for these things or do you have to get out a VNA or CST simulation every time?
learning the geometry (wavelengths), transmission line theory (power transfer) you can get a gut feel. after that, cutting and measuring will help educate. things like EZNEC make it easy these days. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5uEz1KkHKas.htmlsi=CuWJFW17DiMtDefb
One of the things with tuners I often see misunderstood is how they "tune antennas". No they don't. They don't even improve the SWR in your coax to the antenna. The antenna itself has its radiation properties, like radiation pattern and feedpoint impedance (both as a function of frequency). You can't change that via an external device, only via changing the antenna geometry. A tuner can not "fix" your antenna. What it can do is to match the random impedance of it to the impedance of your system - 50 ohms in most cases. If you have a length of coax between your antenna and the tuner, you can tune the coax + antenna combo. The antenna will still reflect power into the 50 ohm coax, but your tuner will turn it back towards the antenna. You will still have SWR losses in your coax, and an SWR meter connected between the tuner and the antenna will see no improvement. The radiation pattern of your random wire will still be the same. You will put more overall energy into the antenna, and the amp in your radio will still be better off, but the tuner does not at all improve your antenna in any way. (For these reasons, many of us don't like built-in tuners, as they can create the false assumption that you use a good antenna, while doing none of it)
yes, any loss in the system gets magnified and you will have loss in the system. if the antenna is not TOO bad, then the tuner will allow the RF to get multiple chances to get radiated. say the mismatch allows the antenna to only radiate 75% of the power, 25% gets reflected back. if no tuner then that 25% get put back into the radio as heat, with a tuner the 25% gets turned around, then 75% of that 25% get a second chance. unfortunately the coax we use is quite lossy and every trip it will kill some of the power. in bad mismatches, the tuner can cause the coax to become part of the antenna, sometimes OK, sometimes not.
if there's more than 1/4 second lag from adjustment to observation I think you're SOL. If you could adjust the averaging to less you'd be more likely to be able to hit it... So now you just have to do gradient descent on L, C, R and delay to find the optimum achievable in this set up. Or maybe I'm hallucinating. Hallucination - it's not just for LLMs!
I am trying to understand. At 08:41 - "Not a perfect match anywhere but more broad-band." Has the adjusting of the MFJ antenna tuner reduced the Q of the antenna-transmission-line assembly? And thank you for making the video.
Maybe one can narrow the band when getting closer to the 50 Ohm point to get there faster. 50.22 Ohm seems to be not so bad at all for an antenna out in the environmental conditions.
@@IMSAIGuy The feedline is not part of the antenna. What a transmatch does is make the radio “happy” with the terrible impedance it is presented and the resulting high losses in the transmission line. These days of transistor radios, it’s an acceptable configuration. Not the best thought. Using an antenna tuner (e.g. ah-4) between the feedline and the intended radiating elements delivers more RF as the feedline is no longer absorbing so much of the system loss. Another, better case, is the drive a remote tuner and have it deliver out/up to the radiator via ladder / window line. Loss is loss. The less of it the better.
well that's all fine and dandy, but, all that your doing is providing a good match between the instrument and the input of the tuner. Now you are not actually providing a proper match to the COAX and antenna, I'm guessing your not using a ladder line? Correct me if I'm wrong, but then again I do believe these atu's use a "balun" on the output? Then again dealing with the reactance of the "BALUN" and the actual reactance of the antenna? coax/ladderline/balanced line? As for myself I designed and built (took me two years) a remote ATU that does use a quadrature detector to provide me with phase information, (and other sampling devices) aiding in the tuning of the system. I have here in the main cabin a HP8753e that is connected to a 650' length of 1-5/8 line to the transmitter building. Mind you I have to switch out the transmitters at the hill and select the 1-5/8 line. None the less, a good presentation! and yes using a VNA, even those $50 units with a Mini Circuits coupler, ZFDC-20-5 or a HP8721A will do the trick!!! Sure SWR meters will get you close but!......Also the bird Line Sections with the appropriate slugs. The VNA is your God! (Btw, the tuner is a balanced type, using a plethora of Vacuum relays, hence a stepped tuner, MCU controlled). Cheers, 73's
Some hams bitch and moan the internal matching network of the radio is limited to 3:1 VSWR. Here are a few reasons why limiting to 3:1 is the sane choice. The "Antenna Tuner" (a very poor name BTW) does not and can not tune the antenna it merely transforms the impedance present at the feed end of the coax to match the impedance of the radio. Since the matching is done at the feed end, a significant transmission line (coax) power loss occurs when the VSWR is large. Matching large impedance mismatches will result in heating, large circulating currents and voltages which means the components used must be robust and typically large. Too large to fit into a modern transceiver. Now think about the radio manufacturer's position if it were to squeeze in a 10:1 capable matching network. With a poorly matched antenna system the power losses in the transmission line make the radio look like a dog with poor reception and low power delivered to the antenna. So in effect they are saving the ill informed operator from themselves while ensuring the radio is able to perform close to it's potential.
