This information is for firmware version 2.48 & greater
WARNING:
This test turns on the transceiver transmitter.
Pay attention in case a fault condition causes unintended issues
Overview
SWR screen allows you to visualize the Standing Wave Ratio (SWR) of your antenna system across the band you are currently tuned to.
This feature gives you a complete picture of the system’s SWR, including the internal transmission path, tuner, and antenna.
SWR is measured using the lowest FM power level to ensure safe and reliable readings.
The results are displayed as a graph, providing clear visual feedback on your antenna’s performance.
If an SD card is inserted, CatTouch can store SWR data and display historical plots.
These are color-coded and timestamped, so you can compare performance over time.
The chart legend displays the date and time of each test, making it easy to track changes.
To use the SWR screen, first go to the MTR screen, tune to a valid amateur frequency, and ensure VFO A is selected.
Switch to the SWR screen and follow the prompts. CatTouch will handle mode and power settings automatically.
For transceivers without a clock, such as the FTdx1200, the SWR screen will still work.
However the date and time on the plots will not be correct.
The test process temporarily changes the transceiver’s frequency, mode, and power level.
These settings are restored automatically once the test is complete.
SWR tests can only be performed within allocated amateur bands.
Attempting to test outside these bands will result in an error.
If an SD card is inserted, the SWR data is stored in a CSV file named swr.csv.
This file can be opened on a computer for further analysis.
Each line of the file includes the band, frequency, SWR value, date, time, and transceiver model.
CatTouch does not control tuners directly.
You must configure any internal or external tuners manually before starting the test.
NOTES:
The lowest FM power level is used to test SWR
During testing, transceiver frequency will change & transmitter will turn on & off
Once testing has completed, the original frequency, mode & power is restored
Trying to test SWR outside an allocated amateur band, will error & CatTouch will restart
Bands are determined by IARU zones which you can change on the CFG screen
CatTouch has no provision for MARS / no frequency limit SWR testing
Once a SWR measurement starts, the only way to stop it is to remove power to CatTouch & Transceiver
Yaesu transceivers report SWR as a value 0~255 & not a ratio of forward & reflected power
There is no magic table that converts Yaesu's value to actual SWR
Different transceivers report different SWR values for the same antenna
If dial frequency changes after SWR test, go to transceiver CW setting & set CW FREQ DISPLAY > DIRECT FREQ
During SWR testing, it may try to transmit on a frequency not allowed by your transceiver, in which case a high SWR will be reported
CatTouch does not control any tuner - internal or external. You must manually set this yourself
SWR data is stored in the CSV file swr.csv which is formatted like this:
# band,F(Hz),SWR(0~255),YYYY-MM-DD,HHMM,RIG
20m,14000000,98,2023-05-08,01:38,FT991A
Date & time is Zulu
Why FM for SWR measurements?
Accurately measuring SWR requires a stable carrier signal and frequency, along with sufficient power.
The carrier bandwidth should be as narrow as possible to minimize interference with other users.
Yaesu transceivers have many modes that can be summarized by:
CW fits all the criteria, but a transceiver can be set up so the CAT TX command won't produce a carrier.
AM takes too long to stabilize, probably due to the way Yaesu uses ALC action to limit AM PA power.
SSB requires external modulation to generate a carrier.
RTTY contains additional frequency components (mark & space tones) that interfere with measurements.
PSK contains additional components like RTTY and varying power levels per frequency component.
FM has a constant amplitude carrier. If not modulated, it is a constant frequency. It requires no additional configuration to TX via CAT.
An often misunderstood fact about FM is that if it is not modulated, its carrier occupies the same bandwidth as CW.