I am not familiar with your particular CG decoder, but I would guess that it is a phase lock loop type decoder, and you are adjusting the pot to set the center frequency of the PLL decoder. I have had best luck when adjusting this type decoder by having the normal discriminator noise at the input of the decoder and adjusting the loop frequency with a counter on the PLL test point. Fish around with a scope and find a place on the decoder that you can count, using a 10:1 probe to avoid loading the test point, and put the same 10:1 probe on your counter for the final count adjustment. I have a digital multimeter with an internal counter function that will count the low frequency just fine.
When the adjustment is finished, input a signal generator with about 12 dB quieting and modulate it with your 103.5 tone at 500 Hz deviation and verify that the tone is detected. Then change the tone frequency to 100 Hz and verify that this tone is not detected, and likewise change to the 107.x tone and verify that it is not detected. If the tone above or below the correct frequency is detected, remove the input signal from the receiver and adjust the at-rest frequency up or down to favor the direction the detector needs to go. Then repeat the process to check for proper decode of only the desired frequency. A final test is to put the 103.5 tone back in the generator and add a 1 kHz tone at the same time and bring the total deviation up to 5 kHz and verify that the decoder is still working. If you have a level control between the decoder and the discriminator input you can jocky with the level to allow decode while the input deviation is varied over the range you expect to see. Sometimes a PL type decoder will drop out under voice peaks if the level to the decoder is set too high. I hope this helps - 73 - Jim W5ZIT -----Original Message----- From: [EMAIL PROTECTED] To: [email protected] Sent: Wed, 31 Jan 2007 9:35 PM Subject: [Repeater-Builder] Help CG Decoder Mastr ExecII Hello, anybody of you can tell me how can I retune the band pass filter on CG Decoder into Mastr ExecII? This module is made by Glenayre for GE and the part # is 134D6663G1 (G2 & G3) The module is set to decode CG only. I want to tune at 103.5Hz. and I use another encoder for the TX. Maybe the best procedure is to put jumper to force the module to encode at 103.5 and after adjust the band pass decode pot for the best decoding… If you have other solution, let me know. Thank you. Eric VE2VXT ________________________________________________________________________ Check Out the new free AIM(R) Mail -- 2 GB of storage and industry-leading spam and email virus protection.
