External SWR Meter Placement
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- Опубліковано 27 лис 2024
- In this video we will look at using an external SWR/Power meter and how it's location in your station wiring affects what it is telling you.
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Great video Tom! In aviation what we call the tuner is usually called a coupler. A much more appropriate name. If you have a tool like the Nano VNA its also good to capture and store a sweep of your antenna system once your tuning is complete. You can then use it as a reference for any comparisons in future troubleshooting of the antenna system. 73
I agree, coupler makes more sense. The Johnson Viking Match Box, a vintage manual tuner, also had a much better name.
Thanks, Tom. Nice easy to understand explaination as usual! Back when I was first licensed (1963) we didn’t have SWR meters… just cut a dipole and hope for the best. Cheers and a happy holiday season to you and your family. Rob W2RSB | F4WCM
You put things in terms that are useful and meaningful. I am looking forward to more of your videos as they demystify the hobby rather than try to prove who is the smartest ham on the planet. Thank you.
I enjoyed the video very much, even though I’m a ham operator, I didn’t know this, you learn something every day, thank you very much. I’ll be subscribing and listening to your other videos. Joey.
Thanks!
Thank You! As a newer ham I have asked this question many times and never got a clear answer. Nicely explained, thanks. Gotta go hook up the meter again....
Thanks for reaching out! Glad it was helpful.
As always, fantastic job Tom 👍
Great video Tom, thanks never thought of it way. Happy holidays stay safe. Ron
Excellent explanation ! It's cleared things up in my mind as I have an swr meter in my manual tuner after my radio and a seperate power/SWR meter after my tuner. I tune my manual tuner to minimim swr but my SWR power meter AFTER my tuner reads a bit higher. Its my antenna that needs a tweak to lower the swr as its reading the true swr in the transmission line. Thank you!
thank you for the information, always good watching your programs. all the best from the UK.
Thank you very much Tom for your contribution with this video, I have checked if I am using my external tuner correctly, I very much appreciate you sharing your experience!!
73s/ XESWL-3017
Another great video. I will think about it then watch it again.
Thanks Tom!
Thanks Tom for your input on my problem.I will try the tests you suggest.That should tell me something. I checked all the instructions on the install of the soft start soft key from Harbach Electronics and all the wiring looks to be just as instructions state. Thanks again for your suggestions.Ron NB3W
My left ear definitely enjoyed the intro and outro more than my right ear 😉
Oops! Sorry about that. Using a different camera setup and didn’t make sure things were in mono.
Tom, there are some Station Monitors that use inline couplers. These couplers require 50 Ohms to provide accurate SWR and Power forward/reflected.
Appreciate Your Video - Thx!
Thank you Tom. Great explanation 73 George KK3R
Great job congratulations Tom 73 from kb2uew
Tom is there anything in the IC7300 need to be turned on in the menu to allow the 7300 to key an external amplifier?I am using a Drake L4B with the soft start soft key board installed from Harbach Electronics. I have not been able to get the IC7300 to cause the relay in the amp to close.I tried the phono plugs marked key and alc on the back of the 7300 and also tried using the din plug on the back using the ground pin and send pin.Mot sure if something needed to be turned on in the software to activate these functions.
Not that I know of. The Send phono jack and pin 3 on the accessory jack should go to ground when the 7300 goes into Transmit. I looked up the schematic for your soft start board. It looks like grounding the Key input should work. I would suggest a couple of tests. Try grounding the key pin on the amplifier directly, with a temporary switch or jumper wire to confirm that the amplifier relay closes. 2nd, use a multimeter to confirm that the send pin on the 7300 is going to ground. If it was ever connected to an amp that draws more than about 1/2 amp, or to a relay without a protection diode, the circuit in the 7300 may have been damaged.
Hi Tom! Thanks for the video! Great explanation! I noticed your name plaque on your door. I’m wondering if you’d share what your connection to the C-17 Globemaster is? It’s my favorite airplane!
73!
That was a gift from an engineer at Boeing. The company I worked for produced the flight control computers and other controls for the C-17. I was our on-site systems engineer at Boeing for a couple years during a system upgrade.
do you have the Firmware 1.42 for the 7300/ If what is the advantage of the new firmware?
Have not installed it yet. Looks like a pretty minor update, from what I read. Oh, I think it’s also only available in Japan so far. I forget what website I found that described the update.
Good luck my Friend...
De YD7KQO Lazuardi
73
This is puzzling... 🤯 The radio PA has an output impedance, ideally 50ohm. The built in tuner matches that to whichever complex impedance the antenna (+ feed) has at that single frequency. Which means that looking from the the external SWR meter towards the antenna, you have a complex impedance (Antenna + feed). AND, looking from the SWR meter input back towards the now tuned transceiver, you have the complex conjugate impedance: the tuner did it's job, you have a perfect match and max. power transfer. This is easily verified by a bit of complex circuit analysis or with a Smith Chart. So the transceiver plus built-in tuner now matches the antenna impedance perfectly, there should be no reflected power whatsoever. The SWR meter is not referenced by 50ohms anymore, its reference is the complex conjugate of the antenna. Except I see exactly what you do, I just repeated your experiment .... 🤷♂🤔
I just did the experiment with a 3dB attenuator as 'antenna', also giving an SWR of 1:3, however purely resistive. Same result. Measuring the open-ended attenuator, it equals a 150R resistor, which makes sense. So in order to achieve max power transfer, the tuner will have to present an equal output impedance: 150R.
Now my SWR meter lives in a 150R referenced universe, not 50R. And my 'antenna' is a simple 150R resistor. Yet, it still shows SWR 1:3.
That is what I don't understand.
Fast forward another day: I know whats going on. Your measurement is 'illegal': You can't use a SWR meter designed for a 50 ohm reference impedance in a 150 ohm (or anything other) impedance environment. Once the tuner has matched the antenna by its conjugate, there are no reflections between the two, it's a matched circuit and it's easy to prove in a smith chart. I've decided to build a 'tandem bridge' (Stockton), referenced to 150 ohm. I'm sure it will show a perfect SWR 1:1 between the tuner and a 150R load, which it should :) Best 73
Hi. You are not quite understanding what a tuner does. The tuner does not eliminate reflected power. If you’re feeding an antenna with 50 ohm coax and the antenna does not present a 50 ohm impedance at its feed point, a tuner at the far end of the coax can’t fix that. The reflected power and standing waves are still present. The components of the tuner are absorbing and partly re-reflecting the reflected power and presenting a 50 ohm impedance at the transmitter connector so the radio doesn’t see it. This is partly why tuners have power ratings. So, an SWR meter (directional power meter) placed at the antenna side of the tuner is simply showing the reflected power that the antenna connection on the tuner is seeing.