SWR

[magpie]

Hi all, Im a bit of a novice and have a dual needle SWR.
I understand the concepts of forward and reverse and standing waves, however, I,m not sure how to read the meter. Do I read off where the needles cross and take the ratio of the forward reading to the reverse reading ?
Also, Im not sure how to calibrate this device since there is no forward, reverse or cal switch. Do i just connect is up and transmitt?
Any help greatly appreciated.

 

[Beetle]

The manual should describe the meter -- you DID get one with the meter, I hope.

If not, set it on the highest scale, key briefly, and read the point where the two needles cross (as you said). The SWR scale should be on some somewhat vertical lines. Don't use the wattmeters' scales for SWR.

If the highest scale doesn't give a good upscale power reading, UNKEY and change to the next-lower position, then key again.

No adjusting required; just watch out for the maximum power the meter can read, and make sure you don't apply that much unless you're on the correct range.

Looking back on your post, I note you didn't mention a range switch. What exact make and model of meter are you using?

 

[magpie]

Hey mate, yeh i have a Daiwa cross needle SWR and power meter CN 100 series. I brought it a couple of years ago and yes i lost the instruction manual. The device has a power range from 15 to 150 to 1.5K watts (this can be adjusted). A frequency range from 1.8 to 150MHz (the freq range appears to have no adjustment)
The only other adjustment is an: avg and pep ( not sure what this is)
the left needle has forward written on it and the other reverse.
I cant see any scale for power on the screen of the swr

 

[W5LZ]

The idea is to have the lowest 'Reverse' reading. So, use that as a reference if/when making adjustments to the antenna (or tuner/impedance matching device if used). SWR is the relation between forward power and reverse power, yes you've got that right. But, it's not a simple divide one by the other thingy. I would suggest 'googling' for the equation.
- 'Doc

 

[Blackcat630]

Well I Googled that model and it looks similar to the comet meter I use. The left needle is your power output depending on your range setting. Right needle is swr or reflected power. No calibration needed. As you probably know the lower the better! Avg is average power or rms power I believe and pep is peak envelope power or your peak power. That's how how I understand the functions....hope that helps..73

 

[Beetle]

Hey mate, yeh i have a Daiwa cross needle SWR and power meter CN 100 series. I brought it a couple of years ago and yes i lost the instruction manual. The device has a power range from 15 to 150 to 1.5K watts (this can be adjusted). A frequency range from 1.8 to 150MHz (the freq range appears to have no adjustment)
The only other adjustment is an: avg and pep ( not sure what this is)
the left needle has forward written on it and the other reverse.
I cant see any scale for power on the screen of the swr

1. There is no adjustment for frequency range. This one is for ~160 meters through 2 meters -- quite a wide range, actually. I wouldn't try it on any higher frequency.

2. Looking at the picture of the CN101B I Googled, I can clearly see the meter scale that starts in the lower left corner at zero and curves up and to the right. It's marked from zero to 15, and that's the 15 watt scale (the lowest power range). If your transmitter output is higher than 15 watts but below 150, you'd use that switch position and add a zero to the reading: the end scale reading would be 15"0" - or 150 watts. The "5" in the middle of the scale would be "50", and so on. Transmitter greater than 150 watts? Use the 1500 watt range and add TWO zeroes: 15 becomes 1500.

3. Unless your meter has an external wall-wart power source or uses internal batteries, that "PEP" function is worthless. Leave it on "AVG" (average).

4. When you're measuring SWR, use an UNMODULATED carrier, either AM, FM or CW. You can't measure it with SSB.

 

[Captain Kilowatt]

The forward scale is your power output. The reverse scale is the power being reflected due to SWR. The point where the two needles cross over each other is the point where you read the SW. It is read on the red scale.

 

[magpie]

Thanks W5LZ

 

[magpie]

Thanks Black Cat

 

[magpie]

Thanks Beetle

 

[magpie]

Thanks Captain Kilowatt