Specifications - SG-237  HF Frequency Range: 1.8 to 60 MHz  Power Input Range: 3 to 100 watts (PEP) —  40 watts max. on CW  Input Impedance Range: 45 to 55 ohms  VSWR: (Typical) Typically less than 1.4:1  DC Input Requirement: + 13.8 VDC (nominal)  DC Operating Range: +10.5 to 18 VDC  Input Current: Average: 300 milli amps  Random set time: Typical: less than 2 seconds  Recurrent set time: Typical: less than 10 milliseconds  Memory Capacity: 170 locations  Antenna Length: Minimum length of 7 ft. - 3.5 to 60 MHz  Minimum length of 23 ft. - 1.8 to 60  Installation: Any position  Operating Temperature: -35° to +70° C  Size: 9 x 7 x 1.5 inches (PCB 5.5 x 6 x 1 inches)  Weight: 2 pounds (PCB 1.25 pounds)  Case Construction: ABS plastic cover on an anodized aluminum base  Control Cable: Shielded 4 conductor RG-58 coax with PL-259 connector  Control Cable Length: 9 feet in length

OE1MHA: The tuner is not tuning every length of wire, but just very specific random wire lengths seem to work well. Especially 23m long wire seems to work very well on all HF bands. 

OE3JKS: could not tune my wire at all! Possibly it was mounted too low? ( just 2 meters above ground) 

OE5MZC: Tuner hangs as soon as I try to match on 50 Mhz. After this it does not retune on HF. No action at all. Reset or Power-Off necessary to cure the problem. But all other bands work well with the Smartuner in the middle of my multiband dipole ( instead of a balun ) Also the cover is not waterproof! The screws often come loose and they are difficult to refit, since they are hidden in the rear aluminium panel. 

OE1PYA: used SGC-237 with a 10m high fibreglass fishing rod vertical ,close to the car. Antenna wire run through the plastic bumper of car and tuner was safely inside the trunk, tuning well on all HF bands. 

OE3XMU: 25m long helically wound wire around 10m long fibreglass tower on top of  7m aluminium mast  with 15m long counterpoise on the ground performed very  well on HF bands. ( worked 28 ITU-zones during one night ) but also problems on 6 meter !? 

Answer from SGC Tech Support: 

Thank you for your email regarding the group of SG-237 owners.  We 
appreciate your comments. 

The SG-237 should provide excellent performance on all bands and 
antennas, as we specify.  However, in your particular situation,  it 
appears that there was corrupted firmware in the MCU.  Replacing the MCU 
should resolve the problem. 

Please advise where and how to dispatch 6 new MCU chips for 
replacement.  We are confident that this will clear up the problem. 

Looking forward to your response. 

Best regards 
SGC Tech Dept. 

If you encounter erratic tuning behavier of your SGC Smartuner a defective firmware might be the reason. However it is more likely that bad grounding system is the reason for malefunction of this tuner!. To change the firmware , remove power supply, loosen all screws and remove the cover. Do not forget to loosen the thightener for the coaxcable before opening the cover. Locate the MCU chip ( see photo ) .Use the rifght tool to remove the IC from socket. Fit the new MCU-chip in same direction as the old one. Observe polarity. Do NOT use force! Assemble in reverse order and apply power to check improved performance of your SG-237 Smartuner.

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