SGC SMARTUNER SG-237 Technical Information download pdf (Page 11)

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VSWR is greater than 2:1 or a difference in frequency is detected, the

program branches to the re-tune program. If it is determined that the

VSWR is less than 2:1 and the frequency has not changed, the com-

puter returns to the Stop mode. Re-tuning. Once it is determined that

re-tuning is necessary, a test is made to see if JP3 is set to tune from

memory. If the result is re-tuning from memory, settings are recalled

from the EEPROM based on the frequency measured. The recalled

data is then tested for validity. If the data proves invalid, it is bypassed

and re-tuning is performed. If the data recalled proves valid, the data is

sent to the relays and the VSWR is checked. If the VSWR is less than

2:1, the program branches to the “OK Tuned” section of the program.

If the VSWR is found to be greater than 2:1, the program branches to

the “re-tune” program.

Selecting tuning path. Several tests are made to determine which tun-

ing algorithm or path should be used to tune the coupler. These tests

are based on frequency, antenna input impedance, antenna phase, and

VSWR. Numerous subroutines are executed repeatedly, depending on

the status of the criteria mentioned above, in order to achieve proper

tuning.

Signaling “no-tune.” Should the initial primary tuning sequence prove

unsuccessful, secondary algorithms are attempted until all possible

routines have been exhausted. If, after the secondary attempts, the cou-

pler still cannot achieve a proper VSWR, the program branches to a

“no-tune” program. Here, the LED's and remote tune indicator will

blink on and off for about 15 seconds to tell the user a proper VSWR

could not be found. After the indicators stop blinking, the program

waits for forward power to cease (if it has not ceased already) and re-

turns to stop mode. At this point the user should try several other fre-

quencies. If the “no-tune” condition persists, check the installation of

the antenna, coupler, radio, and ground system for possible problems.

Signaling “OK tune.” If the coupler achieves a good VSWR during the

tuning sequence, the program branches to the “OK Tune” section of

the code. Here, the tune indicators are engaged. A test is then made to

check if JP3 is set to tune from memory. If so, the frequency is meas-

ured and the tuning elements used are saved in memory coupled with a

verification code. Once saved, a test is made on JP1 to check if the

SG-237 Manual

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Thursday, July 26, 2001 16:13

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SGC SMARTUNER SG-237 Technical Information Page 11

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