开云体育

SR2000 /SR400 RX/TX offset fix

W7WRX All Messages By This Member #30088 Edited These radios drop approximately 40 cycles on TX.? This is annoying in modern times. This drop happens in ALL modes.? I isolated the VFO from the radio and found the issue is the VFO itself. It's not a voltage regulation problem.? The 12ba6 is an odd ball vfo tube and why they used a sharp cutoff tube like this I do not know.? Rather than rebuild and modify the radio, my friend, Jim k7jeb and I decided to offset the TX voltage to the varactor.? This is done with a 1meg resistor and a 10K.?? Place the 1meg from terminal 12 on relay to the ground terminal next to it.? Next, unhook the wire from pin 8 on relay.? Insert a 10K resistor in series with relays terminal and the wire.? That's it.? The offset is gone..it will be within a cycle.? The rit and cal pot all work normally.?? Hope this helps someone.?
Jeff AC0C All Messages By This Member #30092 Edited 开云体育 Great idea! 73/jeff/ac0c alpha-charlie-zero-charlie On 5/2/2024 6:40 PM, W7WRX wrote: toggle quoted message Show quoted text These radios drop approximately 40 cycles on TX.? This is annoying in modern times. This drop happens in ALL modes.? I isolated the VFO from the radio and found the issue is the VFO itself. It's not a voltage regulation problem.? The 12ba6 is an odd ball vfo tube and why they used a sharp cutoff tube like this I do not know.? Rather than rebuild and modify the radio, my friend, Jim k7jeb and I decided to offset the TX voltage to the varactor.? This is done with a 1meg resistor and a 10K.?? Place the 1meg from terminal 12 on relay to the ground terminal next to it.? Next, unhook the wire from pin 8 on relay.? Insert a 10K resistor in series with relays terminal and the wire.? That's it.? The offset is gone..it will be within a cycle.? The rit and cal pot all work normally.?? Hope this helps someone.?
W7WRX All Messages By This Member #30093 Edited 开云体育 Yes!? ?I now have 2 hours of talk time on it. With the dd 103 counter, there is nonoffset and everyone is happy. C On May 2, 2024 8:24 PM, "Jeff AC0C via groups.io" <keepwalking188@...> wrote: Great idea! 73/jeff/ac0c alpha-charlie-zero-charlie On 5/2/2024 6:40 PM, W7WRX wrote: toggle quoted message Show quoted text These radios drop approximately 40 cycles on TX.? This is annoying in modern times. This drop happens in ALL modes.? I isolated the VFO from the radio and found the issue is the VFO itself. It's not a voltage regulation problem.? The 12ba6 is an odd ball vfo tube and why they used a sharp cutoff tube like this I do not know.? Rather than rebuild and modify the radio, my friend, Jim k7jeb and I decided to offset the TX voltage to the varactor.? This is done with a 1meg resistor and a 10K.?? Place the 1meg from terminal 12 on relay to the ground terminal next to it.? Next, unhook the wire from pin 8 on relay.? Insert a 10K resistor in series with relays terminal and the wire.? That's it.? The offset is gone..it will be within a cycle.? The rit and cal pot all work normally.?? Hope this helps someone.?
Dave Jordan All Messages By This Member #30097 Edited Very Cool, In the Yaesu FT-857 the radio had a feature that allowed the operator to adjust the Carrier Point for either lower or upper sideband in receive or transmit?+/- 300Hz (p.97 of the operations manual).?? This tweak reminds me of that Carrier Point feature. Makes me think one could substitute a 10k pot for the fixed resistor and have one more adjustment to tinker with....;-) 73 dave wa3gin toggle quoted message Show quoted text On Fri, May 3, 2024 at 12:00?AM W7WRX via <clark=[email protected]> wrote: Yes!? ?I now have 2 hours of talk time on it. With the dd 103 counter, there is nonoffset and everyone is happy. C On May 2, 2024 8:24 PM, "Jeff AC0C via " <keepwalking188=[email protected]> wrote: Great idea! 73/jeff/ac0c alpha-charlie-zero-charlie On 5/2/2024 6:40 PM, W7WRX wrote: These radios drop approximately 40 cycles on TX.? This is annoying in modern times. This drop happens in ALL modes.? I isolated the VFO from the radio and found the issue is the VFO itself. It's not a voltage regulation problem.? The 12ba6 is an odd ball vfo tube and why they used a sharp cutoff tube like this I do not know.? Rather than rebuild and modify the radio, my friend, Jim k7jeb and I decided to offset the TX voltage to the varactor.? This is done with a 1meg resistor and a 10K.?? Place the 1meg from terminal 12 on relay to the ground terminal next to it.? Next, unhook the wire from pin 8 on relay.? Insert a 10K resistor in series with relays terminal and the wire.? That's it.? The offset is gone..it will be within a cycle.? The rit and cal pot all work normally.?? Hope this helps someone.?
W7WRX All Messages By This Member #30099 Edited 开云体育 Dave, if you move the carrier point you are just changing the pass band.? Not the frequency.? This would be like adjusting a PBT on icom or shift on yaesu. Only it works on TX also.?? On this radio and others, there is a shift of tx frequency.? If you tune in a station, when you tx you will be off freq when you reply.?? I thought about a pot.? You could put it up top on a bracket for easy adjustment. But I decided on fixed value.?? I have a few hours of talk time on this radio now and get good reports back. Thr rx and tx is within a cycle. Thats gokd enough for me. This should be a standard fix for all the radios in this series.? You will need to calibrate the vfo center after this change.? Set cal pot to middle. Set dial to 0.? Then adjust the slug on bottom of vfo for center.? C On May 3, 2024 6:59 AM, "Dave Jordan via groups.io" <wa3gin@...> wrote: Very Cool, In the Yaesu FT-857 the radio had a feature that allowed the operator to adjust the Carrier Point for either lower or upper sideband in receive or transmit?+/- 300Hz (p.97 of the operations manual).?? This tweak reminds me of that Carrier Point feature. Makes me think one could substitute a 10k pot for the fixed resistor and have one more adjustment to tinker with....;-) 73 dave wa3gin On Fri, May 3, 2024 at 12:00?AM W7WRX via <clark=[email protected]> wrote: toggle quoted message Show quoted text Yes!? ?I now have 2 hours of talk time on it. With the dd 103 counter, there is nonoffset and everyone is happy. C On May 2, 2024 8:24 PM, "Jeff AC0C via " <keepwalking188=[email protected]> wrote: Great idea! 73/jeff/ac0c alpha-charlie-zero-charlie On 5/2/2024 6:40 PM, W7WRX wrote: These radios drop approximately 40 cycles on TX.? This is annoying in modern times. This drop happens in ALL modes.? I isolated the VFO from the radio and found the issue is the VFO itself. It's not a voltage regulation problem.? The 12ba6 is an odd ball vfo tube and why they used a sharp cutoff tube like this I do not know.? Rather than rebuild and modify the radio, my friend, Jim k7jeb and I decided to offset the TX voltage to the varactor.? This is done with a 1meg resistor and a 10K.?? Place the 1meg from terminal 12 on relay to the ground terminal next to it.? Next, unhook the wire from pin 8 on relay.? Insert a 10K resistor in series with relays terminal and the wire.? That's it.? The offset is gone..it will be within a cycle.? The rit and cal pot all work normally.?? Hope this helps someone.?

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