Hey gang, I was wondering if I could get some help on installing a vfo windup mod in a Uniden grant xl. I’ve done a couple 29s but can’t find any instructions on how to do it on this grant. A friend of mine wants it installed. Thanks
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Uniden Grant xl vfo windup mod
- Thread starter Ocean cruiser
- Start date
Doing this to a sideband radio is a bit different.
Anyone who wants to use the radio for sideband will routinely have the receive-only clarifier changed to lock his transmit to his receive frequency. This is the only way a group can all be transmitting on the same slot. Move the clarifier knob and your transmit frequency follows your receive frequency. FCC says that's not legal, so the clarifier knob is locked out in transmit when the radio is made.
The slide-in trick requires the clarifier to be stock, more or less. That means the knob on the front panel must work only in receive mode. The transmit-side circuit that substitutes a trimpot for the front-panel clarifier control while transmitting is what gets modified for the slide-in trick.
If you just don't care about sideband, it can be done. Just don't have a schemo of that radio here at home to make a specific suggestion where to connect the capacitor.
With any luck I'll get time to look at the diagram on file at work and suggest the hookup.
Good chance that the wiper pin of the "tx frequency" trimpot is where the cap should go. Positive side there, negative side to ground. I would try 220uf to start. Might need more, might need less.
And if you don't restore the radio to the factory-original non-sideband operating setup it won't work anyway.
73
Anyone who wants to use the radio for sideband will routinely have the receive-only clarifier changed to lock his transmit to his receive frequency. This is the only way a group can all be transmitting on the same slot. Move the clarifier knob and your transmit frequency follows your receive frequency. FCC says that's not legal, so the clarifier knob is locked out in transmit when the radio is made.
The slide-in trick requires the clarifier to be stock, more or less. That means the knob on the front panel must work only in receive mode. The transmit-side circuit that substitutes a trimpot for the front-panel clarifier control while transmitting is what gets modified for the slide-in trick.
If you just don't care about sideband, it can be done. Just don't have a schemo of that radio here at home to make a specific suggestion where to connect the capacitor.
With any luck I'll get time to look at the diagram on file at work and suggest the hookup.
Good chance that the wiper pin of the "tx frequency" trimpot is where the cap should go. Positive side there, negative side to ground. I would try 220uf to start. Might need more, might need less.
And if you don't restore the radio to the factory-original non-sideband operating setup it won't work anyway.
73
Don't have instructions for restoring the clarifier to it's original factory setup.
A readable schematic file for the Grant XL has been conspicuously absent from the web for decades.
The Grant LT schematic should offer some guidance. Good chance D52 and/or D75 was removed or just unhooked at one end. Other half of the proposition would be for the red wire on the clockwise lug of the clarifier to get moved from the continuous 8 Volts to the receive-only 8 Volt source. And if R44, R175 or R175 was removed or shorted across, those would have to be restored as well.
Best I can do with only the LT schematic to work with.
73
A readable schematic file for the Grant XL has been conspicuously absent from the web for decades.
The Grant LT schematic should offer some guidance. Good chance D52 and/or D75 was removed or just unhooked at one end. Other half of the proposition would be for the red wire on the clockwise lug of the clarifier to get moved from the continuous 8 Volts to the receive-only 8 Volt source. And if R44, R175 or R175 was removed or shorted across, those would have to be restored as well.
Best I can do with only the LT schematic to work with.
73
Thank you but The clarifier is ok, it’s factory and locked. Just need to find where to hook the positive of the cap to.
The wiper pin is the center pin of the transmit-frequency trimpot. Might be labeled "VR5". The positive side of the capacitor goes here. The negative side to ground. And if you want to shut this feature off, insert a switch between the capacitor's negative side and ground.
73
73
That is only true if you rely on the voltage change at VR-5 to charge and discharge the cap between RX and TX. This can easily be done on a radio with an unlocked clarifier, by using the wiper of that clarifier. Just attach the cap there and the other side to a voltage that changes between RX and TX, like the 8 volt line.
I installed one on my D201 and got it to work with the unlocked clarifier and VFO on AM. When on SSB, the mode switch automatically disconnects the mod.
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