High SWR

[salcia]

I have a Kenwood 7180H with a Comet CA-2x4srb antenna in my vehicle. While on 2 meters and low power (10w), my SWR is 1.2. When I go to high power (50w), my SWR jumps to from 10 to infinity. Should there be such a drastic difference in SWR? Any ideas?

 

[TheJerk]

I have a Kenwood 7180H with a Comet CA-2x4srb antenna in my vehicle. While on 2 meters and low power (10w), my SWR is 1.2. When I go to high power (50w), my SWR jumps to from 10 to infinity. Should there be such a drastic difference in SWR? Any ideas?

Are you recalibrating the SWR when you switch to high power?

Are you modulating when looking at the SWR?

Is the meter capable of reading SWR at the power you are trying to read?

 

[kb2vxa]

You're doing something wrong, SWR is a function of impedance matching and has nothing to do with power. If the meter has a power range switch (ugh) you're not on the proper range or if it has a FWD-REF switch (much better) you forgot to calibrate to full scale on FWD when you changed power. Either way it's rather unimportant, if you have a good match that's all that matters. Once accomplished you can remove the meter, you don't need it anymore.

 

[TheJerk]

You're doing something wrong, SWR is a function of impedance matching and has nothing to do with power. If the meter has a power range switch (ugh) you're not on the proper range or if it has a FWD-REF switch (much better) you forgot to calibrate to full scale on FWD when you changed power. Either way it's rather unimportant, if you have a good match that's all that matters. Once accomplished you can remove the meter, you don't need it anymore.

While power has nothing to do with SWR, it can (and does) affect the meter's ability to read SWR. This is most common in the cheaper meters, and some are not able to read SWR under even a small amount of power.

I have three SWR meters...only the digital (fully automatic) meter will accurately read SWR with any power under 500 watts, the others need recalibrated/re-zero'd as soon as the switch is flipped.

 

[salcia]

Are you recalibrating the SWR when you switch to high power?

Are you modulating when looking at the SWR?

Is the meter capable of reading SWR at the power you are trying to read?

The SWR meter is a Comet CP5M SO-239 which is good up to 2kw. It has no zero adjust.

 

[N_Jay]

CP5M is an antenna mount?

 

[zz0468]

There's a whole lot that doesn't make sense to me here...

1. This is the CB forum.
2. The radio is a Kenwood 7180H, which is a VHF high band radio, not a CB.
3. The antenna is a VHF/UHF dual band antenna.
4. The Comet CP5M SO-239 is an antenna mount, not a SWR meter.

So, some pieces necessary for a good answer are missing. But based on the statement that the SWR meter is good to 2 KW, it might be a good assumption that what you have is an HF meter. It may act quite unpredictably (and unreliably) when used on VHF.

Fill in the missing pieces, and correct what information appears to be wrong, and maybe we can help you.

 

[zz0468]

CP5M is an antenna mount?

Good. So it's not just me that can't find a CP5M SWR meter!

 

[salcia]

There's a whole lot that doesn't make sense to me here...

1. This is the CB forum.
2. The radio is a Kenwood 7180H, which is a VHF high band radio, not a CB.
3. The antenna is a VHF/UHF dual band antenna.
4. The Comet CP5M SO-239 is an antenna mount, not a SWR meter.

So, some pieces necessary for a good answer are missing. But based on the statement that the SWR meter is good to 2 KW, it might be a good assumption that what you have is an HF meter. It may act quite unpredictably (and unreliably) when used on VHF.

Fill in the missing pieces, and correct what information appears to be wrong, and maybe we can help you.

I thought this was the Antenna and Coax forum, sorry. The reason I got the dual band antenna is to be able to accomodate my IC-W32A. But I did find my problem, when I ordered the SWR meter, I ordered the wrong one, oh well. Sorry for the confusion.