These instructions are to broadband your radio if you have the 24.000Mhz mod or the ChipSwitch installed.
#1. Take the four screws out of the speaker cover on the radio.
#2. With the radio upside down and the PLL board facing you, Remove the four screws in each corner of the pll board.
#3. Loosen the four screws on the sides of the radio that hold the PLL tray in the radio. Loosen them all the way before they come completely out.
#4. Pull the PLL board out towards you so the bottom of the PLL board is upside down.
#5. Look at the diagram below and locate C304, C326, & C327. At the point where they connect together, you will place 1 leg of a 50V 220pf capacitor (Radio Shack P/N 272-124) and the other leg to Ground of the board.
#6. Check your work and make sure you did not short anything out and that you placed the capacitor in the right place.
#7. Reassemble the PLL board and connect power to the radio.
#8. Connect a watt meter and a dummy load to the antenna jack.
#9. Put the radio on 29.500.Mhz and peak L310 for maximum output power.
#10. Now put the radio on 25.500Mhz and peak L319 for maximim output power.
#11. Reassemble your radio and your ready to go.
MOD #2 A simpler method...
Here is a simpler method of increasing the VCO coverage on the HR2510. If your HR2510 is Chipswitched, but doesn't lock on 12 Meters, this mod will take care of the problem without having to access the underside of the synth PCB.
Remove the four screws from the bottom cover and remove the cover.
On the PLL board locate L307 (TP306).
Install a small ceramic capacitor between the long lead of L307 and ground. Any value between 180 and 220 picofarad (pf) will do. There is a convenient ground loacted just behind L307. this locationis a plate-through hole (it looks like a shiny solder dot showing through the silk screening.)
The set should now lock from 24.800 to 29.900Mhz without further adjustment.
If you have access to a scope, the radio can easily be broadbanded for better performance in this new frequency range. to broadband, monitor the output at J311 and adjust L310 and L319 for equal output at the upper and lower limit of your operating range.
More information to be added soon so come back often.
For the HR2510 Modification Main Page . Click Here.
If you have any Questions or Comments, you can E-Mail me at Rogerbird