Modifications

Cobra 146 GTL

Realistic TRC-453

Uniden PC-122 & AR-144

Uniden Pro -810e Base

PC122XL


Clarifier modification: Cobra 146 & AR-144


1) Lift anode of D-30 and connect a 5.6 uH choke in series.
2) Cut D-32.
3) Cut both traces on the PCB going to the clarifier .
4) Solder one wire to PCB ground.
5) Solder a wire from the other cut trace to an 8 VDC source
(note: 8 volts can be found on the cathode of D-50)
6)This should give you 5 kc of slide.If more slide is wanted then change D-30 to a super slide doide.


Clarifier modification: TRC-453 and Uniden PC-122 (PB-062)


1) Disconnect the clarifiers terminal from the RX only supply and connect it to a constant supply that is found at pin 3 of IC4 (the main 8V regulator, usually marked as HA17808 or similar).
2) Replace D24 with a jumper wire (this will increase the control voltage).
3) Remove D25 and R119 (6.8K) to disable RX only voltages.


Clarifier modification: Uniden Pro-810e


1) Cut D-25.
2) Cut D-32.
3) Cut both traces on the PCB going to the clarifier .
4) Solder one wire to PCB ground.
5) Solder a wire from the other cut trace to an 8 VDC source
(note: 8 volts can be found on the trace that connects R-107 & R-106
6)This should give you 3 kc of slide.If more slide is wanted then jump D-24 with a piece of wire.(Sometimes it works)


Channel Expansion


1)Unsolder the PLL chip.UPD2824 or D2824.
2)Throw it away.Its can't be modified. (or send it to me for spare parts! E-mail me here )
3)Solder in a new PLL UPD2816.
4)Connect pin #20 to pin #21 GROUND.
5)Solder a wire from pin #9 to one side of a SPST switch.
6)Solder a wire from PCB GROUND to the other side of the switch.
7)If all goes well this should give you 27.420 - 27.860 Mhz.
Yes, i know 27.420 in between the channel SO use the clarifier for the 5 kc offset.
8)If you can't get all the frequency coverage then adjust L-14 the VCO coil.


Peaks and Tweaks


VR 10 is AM power
VR 6 is ALC
VR 5 is AM Modulation
VR 7 is RF Power meter
VR 1 is S-meter adjust

TX coils- L34, L35, L36 and L26

RX coils- L3 - L8, L10 and L11

VCO Broadband modification: TRC-453 and Uniden PC-122 (PB-062)


1) Replace C72 (47pF) with a 0.001µF.

2) Replace both R102 (330 Ohm) and R103 (56 Ohm) with 220 Ohm (the parts are inside the wax around VCO coil L13).

 


SuperSwing Mod for the TRC 453, TRC 465 and Uniden PC122



1.  Remove Q27 (located UNDER mic socket)
2.  Change the 10k resistor between mic white audio wire and collector of Q27 to 1k ohm.
3.  Change the 10k resistor at base of Q26 and disc capacitor from collector of Q27 to 1k ohm.

YOU WILL NOT SEE A BIG INCREASE IN WATTAGE BUT THE MIC AMPLIFICATION WILL BE IMPROVED AND/OR LOUDER.


4.   Do the retuning for your maximun forward gain.
5.   Now you could try and adjust the final bias and driver bias (@ left rear of radio) along with the the AMC and SSB/AM power tweeks. The VR's have their functions printed right on the board.

This was sent to me by DJ Weber


AMC range mod for the PC122XL


I have noticed that on the PC122 XL that the AMC adjustment does not have enough range, on the track side of the PCB there is a resistor near the preset resistor location, removing it gives more AMC adjustment range, see my pics below.

 


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