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Radio swap high swr?

'As long as you don't move the antenna you can switch to any radio and not have to worry."

I disagree. The swr CAN vary from radio to radio even if it is "matched" well with the first radio.

This is due to the various "states" of tuning inside the radio as one with a higher Harmonic and IMD content will show a higher swr.

Wether it is a "worry" or not is a matter for another discussion.
 
You've seen that SWR varies quite a bit for various reasons. That won't change by using a 'more accurate' meter, it's still going to happen.
How about swapping radios and seeing a change? Certainly possible, but probably not for the reasons you think. SWR deals with impedance matching, that's all. If there's a difference in impedance because of a radio change, and if the antenna really was close to 'right' to start with, then it's a fair assumption that the radio's output impedance may not be what it could be. Maybe! BUt trying to determine if it is or not by using an antenna is not the way to go about it, too many possible variables. Check that radio's impedance output with a dummy load. A dummy load doesn't have the reactances possible with any antenna.
The 'quality'/'purity' of a transmitter's signal has very little, if anything, to do with SWR. That SWR still only deals with impedances and if they aren't the same. That 'quality/purity' thingy just doesn't apply to SWR.
- 'Doc
 
W5LZ said:
You've seen that SWR varies quite a bit for various reasons. That won't change by using a 'more accurate' meter, it's still going to happen.
How about swapping radios and seeing a change? Certainly possible, but probably not for the reasons you think. SWR deals with impedance matching, that's all. If there's a difference in impedance because of a radio change, and if the antenna really was close to 'right' to start with, then it's a fair assumption that the radio's output impedance may not be what it could be. Maybe! BUt trying to determine if it is or not by using an antenna is not the way to go about it, too many possible variables. Check that radio's impedance output with a dummy load. A dummy load doesn't have the reactances possible with any antenna.
The 'quality'/'purity' of a transmitter's signal has very little, if anything, to do with SWR. That SWR still only deals with impedances and if they aren't the same. That 'quality/purity' thingy just doesn't apply to SWR.
- 'Doc
Click to expand...
Ummm . . . That isn't exactly so . . .
Of course Doc, this isn't a common problem with Hammies like yourself. However, when someone gets into a CB/Export radio and purposely mangles the 54mhz trap coils and effectively disabling them - as well as yanking out the AM Limiter - then all manner of harmonics besides the fundamental freq are fed through and can/do create SWR problems. Some of those spurs and harmonics really are strong enough to make the SWR meter see reflected power and thereby show a poor SWR.

Is this the problem in this situation? Doubt it. Since there is inconsistent readings from the SWR meter with movement to the cable; then I gotta blame the cable or the connections/connectors.
 
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anytone

my anytone was never peaked etc just tuned by me via the menu never inside the radio.My 2950dx was a shop job peak and tune that shows teh higher swr.I also think higher power output may have a effect.
 
The spectral 'purity' of a signal has little to do with SWR. It certainly can have a lot to do with the apparent power being transmitted and the quality of the transmitted signal. Keep in mind just exactly what SWR is. It's a ratio between forward and reverse power (actually measured by voltages but in this sort of thing they amount to the same thing). That means that depending on how bad the impedance mismatch is, so much of the signal, no matter what that signal consists of, is 'reflected' back down the feed line. That antenna or SWR meter doesn't know a 'good' signal from a 'bad' signal, both are treated the same. You should think of that signal as a 'whole', not what it's made up from.
Modifying a transmitter, in most cases, doesn't produce enough additional power output to make any significant difference in the strength of a signal. All those 'parts'/circuits in that transmitter's 'string' really are there for a legitimate purpose, not just to reduce power output. They do reduce power output of the 'wrong' kind, which you don't want to start with. In some very rare instances, usually where those additional parts aren't really needed, they aren't doing anything constructive, preventing something getting 'out' that shouldn't be getting out. But that's very rare. (The manufacturer isn't going to waste money on something that doesn't have to be there for some reason.) It isn't a matter of it being 'ham' or 'CB'er' radio, it's a matter of the signal being 'good' or not. It applies to any service, not just CB or ham stuff. Cell phones are radios, it applies to them too.
SWR only applies to impedance matching, it provides no useful information about anything else. It can't tell you anything about signal 'quality', if it has unwanted frequency characteristics or 'purity', or anything else. Unfortunately, it doesn't tell you all of what you need to know about that impedance matching to be very useful either. That SWR meter can be 'fooled' easily. To really understand that you have to know just what impedance is, and that is NOT something simple.
- 'Doc
 
Those cross hatch meters that indicates forward and reflected power. Those would be more useful than a simple SWR meter I'm guessing. I used a antenna matcher on my home base radio with that homemade inverted v antenna. I adjusted it to get the SWR at optimum and then fine tuned it to get the rf power going out right. Forward power I'm guessing.
 
123kid said:
my anytone was never peaked etc just tuned by me via the menu never inside the radio.My 2950dx was a shop job peak and tune that shows teh higher swr.I also think higher power output may have a effect.
Click to expand...

My SWR isn't as much on low power but increases slightly with more rf power dialed in
 
Lil'Yeshua said:
My SWR isn't as much on low power but increases slightly with more rf power dialed in
Click to expand...

thats just shows ya how a meter can be fooled easily. w5lz explains it best it
all deals with impedance matching. and i dont know or understand it all
but this IS what i uderstand
1]radio jack -50 ohms by design
2]amp 50 ohms by design
3]coax -50 ohms by design NO MATTER THE LENTH
antenna 50ohms or close after being tuned in.
so what yourdoing is matching the antenna to everything else 1-3
you need a anylizer that shows impedance . mfj 259,269 do might be more not sure
this is my understanding of it and i know theres more to it but this is what i understand
 
Reguardless of your antenna "tuning" IMD and Harmonics WILL have an effect on your swr meter reading.

when your signal is full of unwanted products it makes a true swr reading impossible. You normally do not see this in ham equiptment as you do in export rigs.
 
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The Mad Scientist said:
Reguardless of your antenna "tuning" IMD and Harmonics WILL have an effect on your swr meter reading.
Click to expand...

Yup.


Doc:

When the 54mhz trap in a radio has been disabled by the golden screwdriver, it will allow for the 2nd harmonic to pass through w/o any attenuation. Yes; that trap is necessary. No modulation is necessary to get this condition either. Since the antenna is already tuned for the 11m band and the radio is also TXing a small portion of 54mhz harmonic, that 11m tuned antenna will have a poor SWR at that freq and return the SWR meter returned current for 54mhz. This is mixed with the 11m return; so the meter reads both at the same time (an average of the two) as a net result.

Now, when modulating into a radio that has the AM Limter and the 54mhz trap disabled, it will return a SWR to the meter that will 'swing' upwards as the spurious and 2nd harmonics are fuller and stronger.

I know you don't use 10m Export or CB radios Doc; but these are the pitfalls of these radio when in the hands of golden screwdriver jockeys and ill-informed CB radio operators. That is just the way it is . . .
 
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Robb said:
Yup.


Doc:

When the 54mhz trap in a radio has been disabled by the golden screwdriver, it will allow for the 2nd harmonic to pass through w/o any attenuation. No modulation is necessary to get this condition either. Since the antenna is already tuned for the 11m band and the radio is also TXing a small portion of 54mhz harmonic, that 11m tuned antenna will have a poor SWR at that freq and return the SWR meter returned current for 54mhz. This is mixed with the 11m return; so the meter reads both at the same time (an average of the two) as a net result.

Now, when modulating into a radio that has the AM Limter and the 54mhz trap disabled, it will return a SWR to the meter that will 'swing' upwards as the spurious and 2nd harmonics are fuller and stronger.

I know you don't use 10m Export or CB radios Doc; but these are the pitfalls of these radio when in the hands of golden screwdriver jockeys and ill-informed CB radio operators. That is just the way it is . . .
Click to expand...


yes, The masters of the golden screwdriver. It is nice when they pull out the 54 MHz trap ground caps and damn near rip out the step up coil. Makes a real mess out of things. :mad:
 
I read a very good explanation of exactly what SWR is and does not too long ago. It was in 'plain language' mostly, and was very clear, easy to understand. I thought I had saved the address but now can't find it. It doesn't matter if it's CB radio or ham radio, it's all radio and SWR behaves the same with all of it.
- 'Doc
 

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