Measuring Antenna Tuner Insertion Loss - Ham Radio
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- Опубликовано: 28 авг 2024
- In this video, we take a look at insertion loss or line loss resulting from using an antenna tuner in ham radio. In the video, we use a MFJ-901B Antenna Tuner.
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Just bought a brand new 901-B a month ago and today I decided to check it out on 40 meters using a 10 ohm, 50 ohm, and 1000 ohm resistive load. Used NanoVNA to adjust the tuner for a 1 to 1 match (NanoVNA seeing 50 + j0 ohms on the input of the tuner) and then replaced the NanoVNA with a 50 ohm output signal generator using a sine wave output and connected my Oscilloscope to the input of the tuner (output of the signal generator) and the load connected to the output of the tuner. Then used my Oscilloscope measured RMS voltages to calculate the input power to the tuner and the load resistor power and then calculated the tuner loss. Results are as follows:
10 ohm load: Loss = 0.85 dB
50 ohm load: Loss = 0.60 dB
1000 ohm load: Loss = 0.75 dB
My setup including scope probe impedance may have influenced the results a little bit but believe my quick test was reasonable.
Unfortunately it looks like inventory of new 901-B tuners has dried up within the last week or so due to MFJ stopping US production and glad I snagged a new one just in time.
Note: I went back and also did a through loss test on 40 meters using my NanoVNA when the tuner was adjusted for a perfect match using a 50 ohm load and I came up with a loss of 0.22 dB using this method which is pretty close with what you saw and slightly lower than the 0.60 dB loss I obtained using my Oscilloscope method. Also repeated the through test with the NanoVNA in which I did not use an external 50 ohm resistor to adjust the tuner, I adjusted the tuner for a perfect match when it's output was looking into the S21 port, and came up with a loss of 0.21 dB which is basically identical with what I came up with when using an external load to adjust the tuner.
73 and thanks for the video.
Don wd8dsb
Hey Don, that sounds like an awesome test. Thank you for sharing. Glad to hear you were able to get the 901-B they are getting hard to find these days and they are nice little tuners.
Excellent video describing the smith chart and measuring insertion loss. I have learned something new today. Thanks Ape !
Awesome, thanks for checking it out Kevin!
Thanks!
Thank you 🙏
i run all bands no tuner.No losses.Nice video, thanks for posting K1LLR
Hey Paul, thanks for checking it out!
Nice job Ape. Your experiments are in the steps of the late Stan Gibilisco, who passed away just a couple days after he posted his final ham RUclips video. Guess it's gonna be time soon for you to write a book too, eh? Thanks for your diligence. K7KS
Stan was extremely intelligent. Big shoes to fill
Thanks for the kind words Alan, Stan was great.. love his videos and I recently picked up one of his books.
I rather have a little loss from the tuner than massive loss or blown finals from an antenna system with out of control SWR.
I agree Dominic, thanks for watching 👍
Great video. You've also got something interesting in the insertion loss chart at the end. It shows the high-pass characteristic of that configuration of T-network tuner.
Thanks for checking it out Stuart, glad you liked it!
You should try connecting a 1:2 or 1:4 balun transformer between the tuner and the S2 port. Also with some length of coax. To simulate a bad match antenna with a length of 50 ohm coax that needs tuning. What you had in the video was a perfect match antenna and the tuner was basically asked to do nothing.
Fair point Baldur, thanks for watching!
Thought the video was on insertion loss of the tuner ? Adding lossy components is obviously going to add loss
@@paulm0hpd319 a balun transformer is not lossy. A length of coax is lossy depending on the length. Expected outcome is that the tuner will match the SWR mismatch with minimum loss with a short coax and increasing loss with longer coax. A misconception in the HAM community is that using a tuner is always lossy but it depends greatly on the coax length and frequency.
@@BaldurNorddahl a balun transformer is not lossy mmmmm ,yes it is a common misconception that a tuner is lossy, think there's a big misconception on tuners matching swr full stop
@@paulm0hpd319 a transformer is indeed a lossless component. Of course real world components have losses, but assuming low power and a well made balun for the frequency in use, this will be very little. A coax cable will however have real loss depending on the length used and the frequency and this loss increases with high SWR. Therefore the coax has to be as short as possible when using a tuner to cancel out large mismatches.
Great video. I would love to see how to measure insertion loss of various antennas such as 9:1 unun, 49:1, screwdriver antennas such as wrc etc. we may be surprised to see how much loss each system presents for qrp hams.
Thanks Kyle, glad you liked it. I do have some videos measure loss on toroidal cores used in wire antennas: ruclips.net/video/6j1Yc1Y4Ly0/видео.html
I will check that out! Wonder how you would measure antennas like wrc? I know coils have loss. Just curious how much.
Great video. Your pace and high level content is perfect for my old brain. Always wondered what one would do with the second channel on the VNA. Now I know. 73.
Hey Jeff, glad you liked it 👍
Thanks for the video! Good to see some more empirical evidence. I generally agreed with your conclusion but I did wonder, however, about losses at lower frequencies - especially for the T-match. If you had done a sweep from 1.7 to 4mhz and tuned the MFJ to 3.6mhz or 1.9mhz - what loss do you see?
Hey SWL, anything in the transmission line will cause loss, while I didn't test the lower bands I'm sure it's there too... maybe I will do a new video?
@@TheSmokinApe I don’t think you need to do a new video. I just wanted to see insertion losses when the MFJ is tuned in the low bands. I don’t think the loss would be much different, but, tuning the T-match on each amateur band from 160 to say 6m and noting the loss in each band would be interesting if the values were different than where you tuned the MFJ in the video. I have the 971 which is really the same device and will try my NanoVNA. Thx!!
The antenna the tuner and the feed line all become part of antenna system
Correct
Very good demonstration. I've heard folks say the same thing about insertion loss associated with tuners. I do a lot of QRP work (exclusively so) and all contacts - including DX - are at 5 Watts and less. I use a random wire with a portable tuner and prefer the widebandedness of this setup cuz I cannot afford a lot of weight and gear for two/ three day hikes into the Cascades. I don't imagine I'd be able to be heard if antenna tuners were as lossy as people say. I do just fine; of course I optimize the radiated signal by making sure the inductance and capacitance are properly adjusted and that's my gears in top shape. Your demonstration seems to confirm my experience. 73, K7GYB.
"I do just fine; of course I optimize the radiated signal by making sure the inductance and capacitance are properly adjusted" I'm curious: Do you do something with your turner other than match using VSWR? Tnx and 73, Bob WK2Y
Thanks for the detailed post and for watching David.
@@bobgerzoff5072 I make sure the contacts are clean and that it's grounded... but I mentioned about the operation of it because I was merely confirming to the author that adjusting for minimum VSWR assures minimum loss - at least for me... this may not be true for folks running higher power. Other than that I don't do anything different than operating the tuner in a conventional manner.
He's talking about a real tuner, not an auto tuner. On a real, manual tuner - you have a main inductor coil and then two adjustments, one for the radio and one for the antenna. @@bobgerzoff5072
@@davidvaughn7752which tuner do you use? I was looking at the AH-705.
Makes me wish I was a newbie NOW. This type of instructional content is priceless in helping grasp concepts. Thanks for your service Ape! 73 - KF6IF
Thanks for watching Phil!
While I disagree with your over simplification of the topic and have witnessed the difference using a watt meter and pass through capable tuner I appreciate your video and effort
Howdy Nick, thanks for the feedback. I did make is simple to illustrate a point that I know is “dramatical”. I appreciate what your saying and will likely expand on the topic 👍
What tests have you done? If you're testing it in pass-through mode isn't that just bypassing the internals? What wattage did you use relative to the wattage rating of the unit? I'm trying to understand both how things work from the theoretical side as well as real-world measurements.
I believe insertion loss starts to become a real issue if the tuner has either poor quality or dirty/worn contacts on the rotary switch or any other contacts.
Fair point Harry, thanks!
Nice job. I think Ape is secretly an electrical engineer and is just too humble to admit it. 😉
LOL, thanks for watching TR!
How did you get your NanoVNA on your PC? How did you hook it up live and what software did you use? I thought you could do it via an app on your phone but that this was now discontinued. I had no idea you could do it on a pc.
Hey Nick, its called NanoVNA Saver: ruclips.net/video/2S0dt0bYoLs/видео.html
Thanx nice presentation
Thanks Gail, glad you liked it!
good video, I agree that there shouldn't be loss if tuned.
It was a fun video to make, thanks for checking it out Thump!
Is there a benefit to optimizing your antenna for resonance over just getting an ATU and letting it handle it? If there aren't meaningful insertion losses, why would anybody set up a full-sized antenna for 80m or 160m?
I think you want the antenna close, when you start to play games to get a match the antenna generally isn't as efficient.
@@TheSmokinApe the antenna itself will radiate all the energy that reaches it ,the efficiency of the antenna would be down to it length/radiation pattern, the efficiency of the antenna system would be down to every component in that system, the job of the tuner is to allow the transmitter to produce its full power into the system, many blame the tuner for lost efficiency when other components in that system are to blame ,resonance is also misunderstood, it doesn't guarantee efficiency just as a non resonant antenna doesn't guarantee lack of efficiency
You have to balance losses against versatility. HF radios are rare in just one band, we buy units capable of using most of the HF bands, and we need antennas that can utilize that capability, without tuners no antenna system really does that.
Agreed, thanks for the comment LC 👍
Good job. Isn't insertion loss is inversely proportional to VSWR? I think those 2 readings track each other.
I think it's inversely proportional to the angle of the dangle.
@@TheSmokinApe squared by the dip in the hip.
Exactly FYL!
When you say far field plots, are you speaking of software plots? I use field strength meters and leave the ffp for reference and RUclipsrs.
I think I am saying both, obviously the FSM is the more practical approach. Thanks for watching and for the comment Jay.
@@TheSmokinApe other than getting bitten by the neighbors dog 🤣
Yeah, I don't what that!
What's old is new (or what's new is old?). In the dim dark ages of radio, everyone used a pair of #12's spaced 6-inches as their feed line. And everyone had a link coupled plate tank in their transmitter that could match whatever impedance was presented at the shack. Everyone effectively had an antenna tuner. Fast forward to current times and we find through your experimental set-up that the old-fashioned antenna tuner is still an efficient way to present a 50-ohm load to the modern transmitters. The simple fact is that a doublet of almost any reasonable length, when fed with a parallel conductor line through a tuner, is probably more efficient than coax-fed half-wave dipoles and has the advantage of being practically frequency independent.
Now a challenge for you: Repeat the experiment with a set of baluns in the signal path. Parallel conductor feedlines have a reputation for radiating due to imbalance. Some of that imbalance is from proximity effects, but some of it is the balance created by the balun now in the output of most antenna tuners. The effectiveness and efficiency of baluns needs investigated just like the tuners they support.
Well said, the voltage baluns incorporated in most commercial tuners are bad news, you want the feeder CURRENTS equal and 180 degrees out of phase, not the VOLTAGES. plus the transformers produce a non 180 degree phase shift. Also they tend to be 4:1, why do that? The transformation of impedance to a lower value is likely itself to increase tuner losses.
I have made common mode chokes to drive open wire fed antennas from the tuner unbalanced output, I think it is a better solution. Tuners get a lot of bad press, they can introduce significant loss under some conditions, however they can have benefits even in matched systems. I used to live near to a MW broadcaster, a T-match ATU helped a lot to protect the receiver from the battering it was getting from the broadcaster....
Thanks for the idea Bill
Well done on the video, unfortunately the tuner in this instance is having a very easy time so the losses are minimal, I do realise it is messy to deviate from 50 ohms for your level measurements. A random point that might be fun to investigate is that some rigs themselves are not optimal (depending on band etc) driving a 50 ohm load, and will deliver more real power into a slightly different impedance. I remember years ago finding that one of my rigs delivered a little more power into a 70 ohm load than it did into a 50 ohm one. I know your video does not address this but in some instances even with a 50ohm load you can actually get a little more power out with a tuner in circuit. A tuner like yours with a high pass characteristic can help with BC overloading in some radios if you are close to a site.
Thanks for the detail G0FVT, I didn't consider that point. I appreciate it!
@@TheSmokinApe , thank you for making the video, my comment was not meant in a snarky way but I also realise that it takes a while to set up a demonstration. A lot of people that claim tuners have huge loss should bear in mind that even high power tuners frequently don't even need ventilation.
I didn't take it that way, thanks for the comment G0FVT
That's a really good point; we assume that all finals are set up to maximize power transfer at 50Ω, but that's not always an accurate assumption, especially since nearly every TX design will have variable power output across different frequencies...
Is there a good mechanism for determining a transmitter's real output impedance? Will an ATU or even a manual transmatch take this into account?
@@oasntet good question, you could probably run a tuner into a power meter and dummy load (unusually in that order) adjust the tuner for maximum power transfer into the load, then replace the transmitter with a VNA to see what impedance the rig was seeing.
Always great videos❗️73 KV5P
Glad you like them!