Swr

[Ziploc]

Sorry guys been a lil , when checking my swr is my mic gain and variable power should be off ? Thanks

 

[M0GVZ]

Doesn't matter what they're at as long as you're transmitting a signal and you calibrate the SWR meter first at whatever setting they are and don't change anything when checking it or if it's a built in one on a modern radio which self calibrates.

 

[Tallman]

No modulation when checking SWR. RF power out do not change after calibration of the SWR meter.

 

[9C1Driver]

If your in a noisy environment then it does help to back the mic gain down. If your radio has variable power you will need enough carrier to calibrate the meter before you switch to the SWR reading.

 

[Handy Andy]

Sorry guys been a lil , when checking my swr is my mic gain and variable power should be off ? Thanks

You raise an excellent question...

I could look at this and ask myself...

IF my SWR is low with No modulation - what does my radio produce when I do modulate?

Which you can also look at the POWER issues too...

Does my SWR stay stable throughout my power level range?

So you'd have to do the check with Mod off and power low, just to make sure your SWR is not over 2 - if so, something is wrong and you need to look into it..

So to start, keep power and Modulation low...check and ADJUST SWR as you need to throughout the band(s) to obtain the best end-to-end performance...

• (You know the steps FWD then calibrate - switch to SWR - tune thru the range of frequencies to locate the lowest dip and try to make the dip in the CENTER or most used frequency you're going to use tune whip accordingly)

Then increase power - and remember your Forward Settings need to be properly set too - otherwise you can mis-read the SWR reading you need to look for and possibly damage the meter if you put too much power thru it in FWD setting with the Calibrate knob too far open (low resistance rotation setting) and causing overswing and damage the coil or jewel movement or the sensor over range and damage the input electronics from excessive power - (Rare - but that is possible).

Now for your quality of output check - you should try this with some modulation - so you can even verify the radio is not producing harmonics with your modulation "spurries" - you'll see this on your SWR side of your readings. Even adjust FWD when you modulate (to make sure your PEAK Envelope (not just PEP - all power inclusive) settings are properly calibrated) and switch to SWR and validate your harmonic output is low and you're not generating spurries - How do you tell? By the extra SWR increase as you modulate even with the FWD peak settings properly set. How? - because your ANTENNA is mis-matched on the 2nd Harmonics and above and you see that in your SWR (reflection) readings.

If it's excessive, you have to address it where it won't damage your equipment..

 

[Tallman]

You raise an excellent question...

I could look at this and ask myself...

IF my SWR is low with No modulation - what does my radio produce when I do modulate?

Which you can also look at the POWER issues too...

Does my SWR stay stable throughout my power level range?

So you'd have to do the check with Mod off and power low, just to make sure your SWR is not over 2 - if so, something is wrong and you need to look into it..

So to start, keep power and Modulation low...check and ADJUST SWR as you need to throughout the band(s) to obtain the best end-to-end performance...

• (You know the steps FWD then calibrate - switch to SWR - tune thru the range of frequencies to locate the lowest dip and try to make the dip in the CENTER or most used frequency you're going to use tune whip accordingly)

Then increase power - and remember your Forward Settings need to be properly set too - otherwise you can mis-read the SWR reading you need to look for and possibly damage the meter if you put too much power thru it in FWD setting with the Calibrate knob too far open (low resistance rotation setting) and causing overswing and damage the coil or jewel movement or the sensor over range and damage the input electronics from excessive power - (Rare - but that is possible).

Now for your quality of output check - you should try this with some modulation - so you can even verify the radio is not producing harmonics with your modulation "spurries" - you'll see this on your SWR side of your readings. Even adjust FWD when you modulate (to make sure your PEAK Envelope (not just PEP - all power inclusive) settings are properly calibrated) and switch to SWR and validate your harmonic output is low and you're not generating spurries - How do you tell? By the extra SWR increase as you modulate even with the FWD peak settings properly set. How? - because your ANTENNA is mis-matched on the 2nd Harmonics and above and you see that in your SWR (reflection) readings.

If it's excessive, you have to address it where it won't damage your equipment..

Andy I am surprised at your incorrect answer. You tune the antenna for the lowest swr to the frequency.
Not the modulation, or power levels. If your antenna is tuned at 4 watts its tuning will not change at 4 Kilowatts.
Also you do not check the "Quality" of your output on a antenna. Dummy loads only for testing "RF quality."

 

[AudioShockwav]

There are problems that will not show up on a dummy load that will manifest when used with a tuned antenna.
Also a badly hacked radio may show low SWR with no modulation, but roll up into a astronomical reading when loaded up with splatter, shit and harmonics.
Sometimed SWR is not so simple.
I would still look at SWR when modulated, it can tell you things.

73
Jeff

 

[AudioShockwav]

Side bar.
This is also were a antenna analyzer can be a great tool.

73
Jeff

 

[Road Squawker]

if your SWR changes with increased power levels, you have other issues, most likely CMC or a radio that has been golden screwdrivered.

 

[Handy Andy]

Please - don't let an Experienced answer be construed as incorrect...

If you overdrive an amp or your own radio. And if you see SWR issues - it needs tuning up - when you see modulation adding to your SWR problem it is is the first sign of many other issues under the hood of that radio...yet to come

Andy I am surprised at your incorrect answer. You tune the antenna for the lowest swr to the frequency.
Not the modulation, or power levels. If your antenna is tuned at 4 watts its tuning will not change at 4 Kilowatts.
Also you do not check the "Quality" of your output on a antenna. Dummy loads only for testing "RF quality."

 

[Tallman]

Please - don't let an Experienced answer be construed as incorrect...

If you overdrive an amp or your own radio. And if you see SWR issues - it needs tuning up - when you see modulation adding to your SWR problem it is is the first sign of many other issues under the hood of that radio...yet to come

With all of my back round in Quality Control and FCC and FAA I tend to be a bit narrow on interpretations and procedures
Experienced? Would an experienced tech overdrive an amplifier with a dirty radio?
If your radio has had a super whack pack tune up you are trying to set up an antenna with a piece of junk. The answer is still flawed and full of inaccuracies. If you are worried about wave form purity it still needs to be on the test bench working in to a dummy load and analyzed with the Spectrum analyzer.

Audioshockwave, Yes I know about harmonics showing up as increased SWR on the meter. The antenna analyzer is the way to go. If the harmonics are that bad off they would need to run two low pass filters or just get the radio repaired from the golden screwdriver.attack.