SWR Meter - Internal Vs External (

Eddy, K6SDW, is trying to find out which SWR meter he sould us. He wants to know which SWR meter should he use to tune the antenna circuit, the built-in Icom 7300 meter or the MFJ-945e meter reading.
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[@AC3HT]

IMO, the SWR meter in the radio is giving the correct reading. Since the external SWR meter is after the internal 'matching network' , the external meter will still read an unmatched / higher SWR result. 73, AC3HT

[@daveN2MXX]

This response is absolutely correct....the SWR will be different when comparing readings at after and before the matching unit. Some of these other responses here are absolutely wrong and confusing.

[@donaldsmith3048]

From working with a lot of things I think that where the SWR meter is in the coax. At HF it sometimes makes a difference but at the setup you have there is coax from the radio to the meter. What percent of a wave length is that. I have tested antenna with a Bird meter with different length of jumpers from the radio to the meter. Same radio and antenna with a one foot jumper and a two foot jumper they didn't read the same!

[@4youian]

Maybe use CW mode since the MFJ will average the reading of an SSB signal.

[@KirkMonteux]

exactly and thats why he missed the whole point

[@z95m]

Yes, Dave's totally lost on this.

[@624radicalham]

@@z95m He is lost. And it's a shame he's such a nice guy but he's in over his head on tons of videos. Someone once told me a good teacher is everything and Dave fumbles all over the road trying to explain. Something as simple as saying "buy an ARB-704 to protect your radio when running an old tube amp" turned into a 15 minute video of him struggling to explain the voltage an old amp throws back to a modern radio. None of the are clear concise explanations and never take into account other variables. It truly seems Dave never uses high power amps.

[@xjohn1970]

So which SWR should you believe? The Radio SWR or external SWR meter?

[@BusDriverRFI]

They are both incorrect. VSWR is a measurement of the maximum voltage along the line ratio with the minimum standing voltage along the line. Any "VSWR" meter is a measurement of one point along the line. What these meters actually are is forward and reflected current meters. They are just a guess for VSWR.

[@AlanElBee]

Thanks Dave, for sharing this and giving me something to think about. 73, K7KS

[@eddy2561]

Thanks Dave!! My BAD, I meant to say I always turn off the 7300 internal tuner when using the 945e.....ALWAYS!!! 73/K6SDW

[@BusDriverRFI]

He knows. He just wants to deflect from the real question.

[@Colin_In_VK]

By the looks of that your external swr meter wasn't working, it was only just moving, while the one in the rig was in the red, it should have been showing a high swr?

[@azav8raa]

Like all modern transceivers, the 7300 is pulling back the RF power when it sees the high SWR. This is to protect the final amplifier transistors and to keep you from breaking your radio. You can see this at 6:54 in Dave's video -- look at the forward power on the WM150M. The 7300 is set to 50% RF (~50W) but is only driving ~4W into the high SWR load. The WM150M really needs more power going through it to get a more accurate reading (ie more needle swing). Also as Dave noted, neither 7300 or the WM150M are lab grade instruments so even under more ideal conditions they will not 100% agree. I typically pay more attention to the radio's SWR meter. If it's not happy it will cut the power output to keep those expensive output transistors safe. One thing Dave mentioned that needs to be emphasized more: if you are using an external tuner, make sure the tuner in the radio is bypassed. Otherwise they will fight each other. de KB7ZUT

[@tomw3380]

I have been having the same question as Eddie. I have a Yaesu FTDx10 with a short (18”) low loss coax jumper going to my MFJ 949E manual tuner w/cross needle power/swr meter. It has terminals for ladder line and I have 43 feet of 450ohm ladder line going to a 135 foot horizontal, center fed 10-80 doublet. I do not have the internal radio tuner turned on because the swr on this doublet is too high for the internal tuner to handle. I only tune with the manual tuner. I lower the radio power output to 30 watts for the initial tuning and use the cross needle meter to do the initial adjustments. When the cross needles read close to 1:1, the Yaesu electronic meter is reading about 1.2:1 which is a very safe reading for the radio. But, I then do the fine tuning using the Yaesu swr meter. Since the purpose of tuning is to provide the best protection for the radio, I figure the reading on the Yaesu meter is what the radio is actually seeing. Then to finish, I raise the wattage back up to the desired output and do a final swr check. I can’t carry or whistle a tune in a bucket so I switch modes to CW or FM and use the solid carrier for tuning. I can’t swear that this is the right method, but it is my method until,I discover something wrong with it. Dave, thanks so much for your videos and questions answered. It kept my nose to the grindstone until I go my Extra Class license a couple weeks ago. Tom WA4EOD

[@BartVanAllen]

Going into a valve amplifier, the amp input is not always 50 ohms, and so the load seen by the radio is not always an acceptable match. I use the radio tuner to match to the input of the amp and the tuner after the amp to match load to the antenna. Most of the time that is not needed, but sometimes doing that makes the radio see a better load, sometimes dropping it from the occasional 1.3 to 1.4 down to 1 to 1. Well worth it to me to help the finals stay safe. I tune the ant load first, then hit the radio tuner button if it is not good enough. Yes, the question did not mention an amp, but I mention this to show that sometimes using both is beneficial.

[@daveN2MXX]

At 6:29 it is clearly seen that the "tune" indicator is shown on the 7300 display, indicating that the internal tuner is engaged in the 7300. You then are also looking at the external SWR meter? Of course the readings are different. What is the point of this video?

[@shigityshigityshwa]

Lol just casually spurting out some SSB on a digital only portion of 40m. Nice Dave.

[@shigityshigityshwa]

Didn’t ID on 40 either lol

[@darrellcollins877]

I have a cross needle meter and it is EASY TO READ all the time. When my radio tuner is off, the radio meter and external meter meter will be very close. When I turn tuner on and tune up, the radio meter will show low swr because it is behind the tuner. The external meter will show the swr of the antenna since it is after the tuner. Seems odd to see so much difference in your meters .....

[@mrjones6770]

My 7300 reads as it should with My quad antenna around 1.2....but when I connect my swr meter it reads 1.5 on the 7300 and 1.7 on the meter so why is the happening?..so when connect antenna straight to 7300 and use it's built in meter it's reads correct....but when I add my meter it's goes up across the range from 1.2 to 1.5

[@markrowell7242]

I have an MFJ-969, which is similar to his but has an roller inductor. The -969 also has a bypass selection so you can put it into or out of the circuit. The cross needles are brought down to the center of the meter so reading doesn't have the gap as witnessed on your cross needle SWR meter. I almost always have my -969 in the bypass mode but it still keeps the cross needle in line. I find very little difference between the -969 SWR reading and the -7300 bar graph reading. If there is a differnce, the -7300 bar graph shows a little lower than the -969. The readings you got are REALLY different. Not sure why. 73 N7MHR

[@624radicalham]

I'm going to post this here so it doesn't get buried in the comment replies and hope Dave takes this as constructive. He is constantly lost in almost every single video. And it's a shame because he's such a nice guy but he's in over his head on tons of issues. Someone once told me a good teacher is everything and Dave fumbles all over the road trying to explain. Something as simple as saying "buy an ARB-704 to protect your radio when running an old tube amp" turned into a 15 minute video of him struggling to explain the voltage an old amp throws back to a modern radio. None of these videos are clear concise explanations and never take into account other variables. It truly seems Dave never uses high power amps either. Please Dave clear it up.

[@tonyo93]

should but wont... so?

[@Steven.Cartwright]

Im still confused after watching this video lol Sorry dave lol I just use the radios ATU and dont have an external SWR meter or ATU attached at all i just keep it simple and trust my radio. I do check the SWR with the external meter when first setting up an antenna OR if i notice somethings not right but i then unplug it and take it out the equation.

[@awwaldo]

I can't believe Dave didn't ID on 40 meters! (just kidding) He may have ID'ed off camera. 🙃 I'm so thankful that no one else makes any mistakes. 😇 The SWR meter on the ICOM is much faster than the Cross Needle model. You're not going to get an "accurate" reading chatting into the microphone, you're only going to get an idea of what it might be. You really need a CW type signal to get a steady reading. As Dave said, these are not labratory grade instruments. It's just something you're going to have to learn to live with unless you plan on shelling out some $$$$. 🤑🤑🤑🤑

[@DominicMazoch]

One tuner at a time. Use one bypass the other!

[@eddy2561]

My BAD, I meant to say I always turn off the 7300 internal tuner when using the 945e.....ALWAYS!!! 73/K6SDW

[@subramanianr7206]

@@eddy2561 hi Eddy, you should get the same readings on both the 7300 and the external swr meter in the mfj tuner. Your question is valid and Dave gave incorrect information; he tries to find fault with the differences in the technology involved in the metering. He is quite wrong. Please check the patch cable between the radio and the tuner. You get your radio to work (on all bands) using the same patch cable into a 50 ohm pure resistive dummy load to display 1:1 on the bargraph without using the internal tuner. Then connect the mfj tuner to the radio and put the same dummy load at the output of the tuner. Now make the radio work into the dummy load through the tuner. The readings on the radio and the tuner must be reading the same 1:1 swr at some specific settings of the control knobs. Now connect the antenna at the output of the tuner and using 5-10w on CW you must be able to tune your antenna on whatever bands that's designed for. At any cost you should get both the readings concur with each other if not exactly at least within the ball park region. "S" parameters (except S11) have nothing to do anything at all as Dave is assuming 😀 Wish you all the best. De VU2RZA

[@xjohn1970]

@@subramanianr7206 So which SWR should you believe? The Radio SWR or external SWR meter?

[@xjohn1970]

@@subramanianr7206 my radio SWR reads 1.5 & external SWR meter reads 1.2

[@subramanianr7206]

@@xjohn1970 good question. It should be the other way around by logical deduction and by the way things have been designed. One might argue that an swr of 1.5 on the radio is good (at least not bad for the radio) and some use the phrase "the radio is happy"..😀 Here the scenery is different. Once you add the tuner in between the radio and the antenna the radio is going to deliver all its full power into the tuner as it presents the "mandatory 50 ohm"(assume it's well tuned with the antenna system) Yes, the radio is not going to know whether it's a 50 ohm transmission line or a 50 ohm resistive load. So, now the tuner becomes the source of RF (voltage/current). The radio is relieved with a big sigh. It's the job of the tuner to deliver the RF power that has been borrowed from the radio into the transmission line and the antenna system as a whole. As the tuner contains the needed L/C (inductor and capacitor in the right combination) it cancels out or minimises the reactive part of the antenna system making it more like a resistive load. Now you know the answer well I believe. Yes, your radio should read the minimum swr nearly (1.2:1) and the tuner may read 1.5:1, but not vice versa. In such a situation I will be greatly convinced. Good luck. De VU2RZA

[@karlmadsen3179]

Blah blah blah..... just get to the point.