Swr’s

[Cahtrina]

I’m sure there are a lot of threads about swr’s and trying to find one with my situation would probably take hours to find so imma just make a new thread.
First, is it true that you should use a 4 watt radio to tune the swr’s? (Assuming I’m tuning the swr’s and not a cb shop). Second, I went to a cb shop that had a antenna analyzer to test my setup and their machine came up with a 1.08 on channel 20 but when I use a dosy meter to test my swr’s it way off the charts, like a 3 or 4 to 1. Now the radio I’m using on the dosy is the connex turbo N1 with the rf power all the up and with it all the way down the swr’s are around a 1.8. Any advice would ge greatly appreciated.

 

[999]

Check the grounding of your antenna.

 

[fourstringburn]

Swr's???

How about SWR! The abbreviation isn't to be pluralized.

Things to consider is at what point in your antenna system is the SWR measurement to be taken.

With an analyzer, it should be checked with a short jumper at the antenna feedpoint. This will tell you the information of the antenna with no influence from the main coax.

If the CB shop did it this way, that's what your antenna really is. You want to check and tune the antenna, not the coax! If there is a significant difference between the main coax and jumper measurements, this tells you have problems in your feedline or connectors.

With your Dosey, where in the antenna system do you check it at? Also a 3:1 SWR across the whole band is typical of a bad D.C. ground. If this was so, the analyzer would have caught this.

It could be a bad jumper if that's what you used or a loose SO-239 in the Dosey causing a bad ground.

As for your radio's built in SWR meter, I wouldn't put much stock in those. These are generally good for a quick easy reference. My experience with them is when they show a high SWR, then it probably really is but the reverse isn't always true.

Yes, low power like 4 watts is good for SWR checks. Higher power can cause RF issues if present and give inaccurate or quirky readings.

Hope that helps!

 

[Cahtrina]

Lets go with your 4watts theory fourstringburn. Say I did calibrate my antennas with a 4watt radio and lets say its a 1.1 across the board. Now lets say that I unhooked the 4watt radio and hooked up an 200watt radio. Now the SWR readings are 3.1 across the board. Wouldn’t this affect my TX?

 

[fourstringburn]

Lets go with your 4watts theory fourstringburn. Say I did calibrate my antennas with a 4watt radio and lets say its a 1.1 across the board. Now lets say that I unhooked the 4watt radio and hooked up an 200watt radio. Now the SWR readings are 3.1 across the board. Wouldn’t this affect my TX?

Can't really answer a hypothetical question like that. But, if the SWR jumps up like that using higher power then it's likely some serious RFI issues like common mode currents on the coax line. This could affect your audio on TX with a loading up feedback sound or distortion.

Like I said before, an analyzer (if used properly) tells the antenna condition at the source like at the feedpoint. Once the antenna is tuned, the SWR at the antenna doesn't change just because of power levels.

The analyzer should check the antenna at the source and be checked again at the radio end and compare the difference. A slight increase in SWR is nothing to be concerned with.

An analyzer is the more accurate way to check antennas and feedline and most analyzers power output is in milliwatts.

So if your radio or Dosey meters say otherwise at any wattage, then you have to question their accuracy. If high power causes such a significant jump in SWR, then you most likely have RFI problems.

 

[sp5it]

Lets go with your 4watts theory fourstringburn. Say I did calibrate my antennas with a 4watt radio and lets say its a 1.1 across the board. Now lets say that I unhooked the 4watt radio and hooked up an 200watt radio. Now the SWR readings are 3.1 across the board. Wouldn’t this affect my TX?

SWR ratio is not power dependent.
Cause of higher SWR reading might be parasitic oscillation of PA stage. I saw that many times in the past.
Mike

 

[Handy Andy]

Or just pain "Bad Amp" in need to have a tune up done to it - so it doesn't blow up - and take the radio along with it.

 

[midnight special]

when ya put dosy in it probably picks up harmonics from the connex turbo radio, i would trust what the analizer says and not the dosy,,, harmonics tend to throw external meter readings wacky,,,

 

[freecell]

Can't really answer a hypothetical question like that. But, if the SWR jumps up like that using higher power then it's likely some serious RFI issues like common mode currents on the coax line. This could affect your audio on TX with a loading up feedback sound or distortion.

Like I said before, an analyzer (if used properly) tells the antenna condition at the source like at the feedpoint. Once the antenna is tuned, the SWR at the antenna doesn't change just because of power levels.

The analyzer should check the antenna at the source and be checked again at the radio end and compare the difference. A slight increase in SWR is nothing to be concerned with.

An analyzer is the more accurate way to check antennas and feedline and most analyzers power output is in milliwatts.

So if your radio or Dosey meters say otherwise at any wattage, then you have to question their accuracy. If high power causes such a significant jump in SWR, then you most likely have RFI problems.

when using swr measuring equipment that requires a set reading calibration prior to measurement, USE ONLY THE MINIMUM AMOUNT OF POWER NECESSARY TO OBTAIN A SET METER READING. overall this procedure will produce a lower and more accurate measurement of the swr existing on the feedline.

in the case of a stock 40 channel transceiver producing 4 watts of carrier, most swr meters designed for cb use will allow set meter calibration with less than 4 watts.

in contrast, analyzers use power levels in the milliwatt range for swr measurements.

 

[Cahtrina]

SWR ratio is not power dependent.
Cause of higher SWR reading might be parasitic oscillation of PA stage. I saw that many times in the past.
Mike

ok that makes sense.

 

[Cahtrina]

Or just pain "Bad Amp" in need to have a tune up done to it - so it doesn't blow up - and take the radio along with it.

actually does the same thing with the rci 99.

 

[Cahtrina]

Can't really answer a hypothetical question like that. But, if the SWR jumps up like that using higher power then it's likely some serious RFI issues like common mode currents on the coax line. This could affect your audio on TX with a loading up feedback sound or distortion.

Like I said before, an analyzer (if used properly) tells the antenna condition at the source like at the feedpoint. Once the antenna is tuned, the SWR at the antenna doesn't change just because of power levels.

The analyzer should check the antenna at the source and be checked again at the radio end and compare the difference. A slight increase in SWR is nothing to be concerned with.

An analyzer is the more accurate way to check antennas and feedline and most analyzers power output is in milliwatts.

So if your radio or Dosey meters say otherwise at any wattage, then you have to question their accuracy. If high power causes such a significant jump in SWR, then you most likely have RFI problems.

Thank you sir. I don’t think they used the analyzer correctly. They went of the coax and not directly to the antenna but off the coax it read a 1.08. Im going to go with the harmonic therory that some of the other members are saying.

 

[Cahtrina]

when using swr measuring equipment that requires a set reading calibration prior to measurement, USE ONLY THE MINIMUM AMOUNT OF POWER NECESSARY TO OBTAIN A SET METER READING. overall this procedure will produce a lower and more accurate measurement of the swr existing on the feedline.

in the case of a stock 40 channel transceiver producing 4 watts of carrier, most swr meters designed for cb use will allow set meter calibration with less than 4 watts.

in contrast, analyzers use power levels in the milliwatt range for swr measurements.

ok got it. Thanks.

 

[freecell]

you're welcome.

 

[Cahtrina]

I appreciate everybody’s feedback. I never had this problem when i ran a radio with an external amp. I’m thinking these radios with built-in amps are the root cause of my problem.