SWR & Perplexity.AI copied to RadioReference.com

[Samyham]

I hope you all find this interesting and informative. The citation #4 is to a RadioReference.com thread/post.

It's been my experience that AI is not the gospel truth so if any of you Hams know different from it's answers here (or you think you're smarter than AI) please reply.

QUESTION: I have a difference in the SWR reading of about .5 on the SWR scale in my Yaesu FT-891 transceiver in comparison with my MFJ-945E tuner. Which is the one to be more likely accurate?

ANSWER: The SWR reading difference between your Yaesu FT-891 transceiver and MFJ-945E tuner is likely due to the different methods used by each device to measure SWR. The FT-891 transceiver uses a built-in SWR meter, which can be less accurate compared to a dedicated SWR meter like the MFJ-945E tuner.

The built-in SWR meter in the FT-891 transceiver is designed to provide a qualitative measurement of SWR, which can be less precise than the more advanced SWR meters found in dedicated antenna tuners like the MFJ-945E. The MFJ-945E tuner uses a more sophisticated method to measure SWR, which includes a mini cross meter that provides a more detailed and accurate reading of the forward and reverse power levels[1][3][4].

Therefore, it is more likely that the MFJ-945E tuner is providing a more accurate reading of the SWR.

Citations:
[1] Do I need a separate SWR meter if the transceiver has one built-in?
[2] FT-891@groups.io | SWR meter reading problems, or perhaps not?
[3] https://www.eham.net/reviews/view-product?id=1350&page=2&per-page=10
[4] Advice on high SWR with new setup?
[5] Amazon.com: Customer Questions & Answers


QUESTION: Sounds like you've done your homework! Thank you.

ANSWER: You're welcome! I'm glad I could provide a helpful explanation based on the differences between the built-in SWR meter in the Yaesu FT-891 transceiver and the dedicated SWR meter in the MFJ-945E tuner. Comparing the specifications and capabilities of various amateur radio equipment is an important part of making informed decisions and troubleshooting issues. My knowledge comes from researching the technical details of these devices to give you an accurate and well-informed response. Please let me know if you have any other questions!


QUESTION: Great follow up answer. Have a great day!

ANSWER: Thank you! I'm here to help anytime you have questions. Have a wonderful day ahead!

73

 

[RFI-EMI-GUY]

I am confused as to the correct answer. This seems to be an opinion based on random sources. I would rather do my own research as flawed as Google/Internet sources may be than to accept the AI as the arbiter of truth. Folks are buying into this AI craze as a solution to all of the worlds problems.

I would suggest that folks not feed the AI and encourage hackers and pen testers to subject the AI to excruciating punishment.

 

[KF5LJW]

Neither answer is correct. SWR is an outdated CB term. Only hams and CB users still use outdated terms and measurements.

 

[RFI-EMI-GUY]

Neither answer is correct. SWR is an outdated CB term. Only hams and CB users still use outdated terms and measurements.

If you are saying the term "SWR" has been replaced by VSWR (Voltage Standing Wave Ratio) I agree, however the calculation and measurement remain the same. VSWR is still relevant in the LMR world. If someone asked me to measure their antennas "SWR" I would grab the same bird meter that I use to measure "VSWR" and also my calculator. But I would be calculating on the basis of displayed forward and reflected power, not voltage.

The manual for MFJ-945E "Ham radio" tuner mentioned in the OP uses SWR throughout the instructions.

Return Loss (RL) is another representation and is expressed in dB (decibels) which is a logarithmic equivalent to VSWR. RL is typically measured with a network analyzer.

 

[mikewazowski]

Neither answer is correct. SWR is an outdated CB term. Only hams and CB users still use outdated terms and measurements.

So if SWR is an outdated term, what's the modern equivalent?

 

[jeepsandradios]

In my world we dont measure SWR. We measure Return Loss of an antenna then Forward or Reflected power only. Thats how everything is documented. I know with all those numbers you can figure SWR but in the end thats what we look at.

 

[techman210]

A Yaesu FT-891 transceiver and a MFJ-945E are not pieces of calibrated test equipment. A 0.5 difference is splitting hairs. You are lucky the readings are that close.

 

[Samyham]

A Yaesu FT-891 transceiver and a MFJ-945E are not pieces of calibrated test equipment. A 0.5 difference is splitting hairs. You are lucky the readings are that close.

Sometimes it's been more than 1. I think Perplexity had the right general idea. No one so far has disputed the point so I'll be focusing on the MFJ. I'm inexperienced and I'm shocked how sometimes even just barely a nudge can make a big difference - more than a 1.

Also, guys, while AI not-rarely makes mistakes, it's pretty awesome. Perplexity is free and the pro version is also, for a few tries each day, free. There's others with free versions too. I like co-pilotly but I used up my free quota for the month plus other limits. Hammies can't just be left behind on this.

 

[KF5LJW]

If you are saying the term "SWR" has been replaced by VSWR (Voltage Standing Wave Ratio) I agree, however the calculation and measurement remain the same. VSWR is still relevant in the LMR world.

No, sir, that is not what I mean. I am a professional in the LMR world. As you have shown, the only RF industry that uses the term SWR or VSWR is antenna manufacturers to describe the bandwidth of their antennas. Pull out a bird, and you will read Return Loss, which is much more useful and easier to understand. So when I hear someone use the term VSWR, I know they are a CB operator.

This will confuse Cb operators. It is impossible to measure an antenna VSWR from the shack.

 

[AK9R]

Pull out a bird, and you will read Return Loss...

A Bird 43 can read forward or reverse power. To get return loss, you'd have to do some math.

 

[KF5LJW]

A Bird 43 can read forward or reverse power. To get return loss, you'd have to do some math.

It's very outdated equipment, but yes, the math is 5th grade level. 100 out of 10 reflected is an RL = 10 dB or a failed antenna system., and tells you your system is 90% efficient. An SWR of 2 tells you nothing other than the impedance is either 100 or 25 ohms.

 

[RFI-EMI-GUY]

My take on this whole thread?

Pointless.

1) The measurements SWR, VSWR, RL all originate from the detection of a voltage on a transmission line using a diode directional coupler. The instruments described, Yaesu FT-891 transceiver, MFJ-945E tuner and Bird 43 all operate on same principals. Deriving SWR/VSWR or Return Loss from any of them is trivial to do. It is simple math. In fact the lowly MFJ-945E with cross needle meter is most informative of the three.

2) Accuracy which is the point of the discussion, differs among all of the instruments. The Bird 43 is the only instrument with specified accuracy. If I recall it is 8% which is not very stellar.

3) More important is the discussion of measurement methodology. The operator should test the antenna at at least 3 points to determine if the antenna is resonant withing the desired band of operation. If it is resonant, and VSWR is within 1.5:1 it is probably "ok". The AI is apparently clueless on this.

4) All that has been accomplished in this thread has been to stir up animosity over "Ham Operators and CB operators" and their "outdated terms and practices" versus "LMR experts" In that regard the AI has been successful. Look forward to more of this confusion and anger in other realms as the AI rules your world.

 

[mikewazowski]

My take on this whole thread?

Pointless.

1) The measurements SWR, VSWR, RL all originate from the detection of a voltage on a transmission line using a diode directional coupler. The instruments described, Yaesu FT-891 transceiver, MFJ-945E tuner and Bird 43 all operate on same principals. Deriving SWR/VSWR or Return Loss from any of them is trivial to do. It is simple math. In fact the lowly MFJ-945E with cross needle meter is most informative of the three.

Well said. Anyone involved in the LMR world knows that all 3 measurements are equivalent and the terms are interchangeable with a little math.

No, sir, that is not what I mean. I am a professional in the LMR world. As you have shown, the only RF industry that uses the term SWR or VSWR is antenna manufacturers to describe the bandwidth of their antennas.

Real LMR professionals use Smith Charts.

 

[AK9R]

The Bird 43 is the only instrument with specified accuracy. If I recall it is 8% which is not very stellar.

+/- 5% of full scale for a continuous signal. +/- 8% of full scale with a 43P reading peak power.

 

[Chronic]

hook a dummy load up to both and compare test results , and call it what ever you want , maybe the hick-a-majigger is in a satisfactory range.

 

[RFI-EMI-GUY]

+/- 5% of full scale for a continuous signal. +/- 8% of full scale with a 43P reading peak power.

Good enough for government work... Traceable to NIST dumpster.

 

[Samyham]

hook a dummy load up to both and compare test results , and call it what ever you want , maybe the hick-a-majigger is in a satisfactory range.

I have a home-made Dummy with a female-end coax. You mean, plug the far end of my Random Wire antenna into the the female end? Then check the meters for results, with and without the Tuner? Sounds good.

I'll probable double-check the idea with 2 AI's; likely Perplexity and Co-Pilotly. Maybe even a third - Bing (who doesn't love Bill Gates and Microsoft?). I'm sure, you all won't mind. Oh, yea!

 

[AK9R]

Sounds to me like you are shopping for answers. There are a lot of myths and falsehoods out there. AI is not immune from repeating them.

 

[RFI-EMI-GUY]

Sounds to me like you are shopping for answers. There are a lot of myths and falsehoods out there. AI is not immune from repeating them.

But AI must be correct, otherwise why would investors be throwing billions at it? Oh, because the AI told them to... nevermind.

 

[Samyham]

hook a dummy load up to both and compare test results , and call it what ever you want , maybe the hick-a-majigger is in a satisfactory range.

I have a home-made Dummy with a female-end coax. You mean, plug the far end of my Random Wire antenna into the the female end? Then check the meters for results, with and without the Tuner? Sounds good.

Chronic, Joking aside, I was serious about this idea. Will this work or did you have something else in mind.?

I guess I could use a short coax extension I have instead of attaching the dummy load to the far end of my random wire antenna. Then test with the tuner bypass on and off. I'm thinking this would be easier. BTW, the MFJ-945E does not come with a dummy load built into it.