Uniden Grant XL Mods

You can perform PLL, clarifier, audio, AGC, receive, SSB detector, 10 meter conversion and NPC-RC mods on the Uniden Grant XL. You can also add Schottky diodes, improve various components and increase the Tx range.

Are you curious about how to perform these mods to your Uniden Grant XL? Read this article to learn more.

What Are Some of The Most Popular Uniden Grant XL Mods?

 The Uniden Grant XL is a popular radio among radio enthusiasts for doing custom modifications. Some of the modifications commonly done by the enthusiast community are given down below:

  1. PLL (Phase Locked Loop) Modifications
  2. Clarifier Mods (Slider)
  3. Power output and Audio Modifications
  4. AGC Modification
  5. Receive Modifications
  6. SSB Detector Upgrade
  7. Schottky Diode Upgrades
  8. 10 Meter Conversion
  9. Widebanding the TX range
  10. Misc. Component Upgrades
  11. Negative peak compression – Reduced carrier (NPC-RC) mod

How to Perform The Different Uniden Grant XL Mods?

PLL (Phase Locked Loop) Modifications:

PLL modifications are among the first modifications you should consider for your Uniden Grant XL.


The advantage of PLL modding is the increase in frequency coverage beyond its design limitations. The design limitations are often the result of FCC monitoring. PLL mod will also increase the performance of your radio.


Follow this diagram to do the PLL mod:

PLL mod
Source: usermanual.wiki

Now, perform these steps serially  to successfully PLL mod your Uniden Grant XL set:

  • Locate 8719 chip at the bottom of the circuit board.
  • Find the 14th pin on the chip.
  • Carefully cut the trace of the 14th pin.
  • Reconnect the 14th pin to the trace using a 4.7 KOhm 0.25 W resistor.
  • Install 3 micro SPST switches on a suitable spot on the radio
  • Connect the first switch to the 11th and 12th pins.
  • Then connect the second switch to the 10th pin and board ground.
  • Connect the third switch to pin 9 and pin 14.

Now take a look at this diagram:

diagram and wire
Source: usermanual.wiki

All the diodes here are 1N914 or 1N4148 and the rotary switch is 2 pole/ 6 positions. Follow the diagram and wire the rotary switch accordingly. 

After wiring the switch according to the diagram you need to connect the switch to the pins on the chip. Follow these steps to connect the rotary switch to the chip:

  • Connect A5 to the 10th pin of the chip.
  • Likewise, connect the 11th pin to A1.
  • Then connect the 9th pin to B
  • Connect B3 to pin number 14.
  • Finally, connect A to ground.

Your PLL mod has now been successfully completed.

Clarifier Mods (Slider):

This is another commonly done mod to the Uniden Grant XL radio. 


The advantage of this mod is that it allows you to fine tune the received signal more precisely. It results in a more clarified signal.


The process for performing this mod is a bit easier compared to the PLL mod. Here are the steps you could follow to complete this mod:

  • Locate the R44 and D52 on the circuit board.
  • Remove both the R44 and the D52 from the board.
  • Find the R174 on the board and bypass it by adding a shunt. Alternatively, you could simply remove the resistor and add a jumper in its spot.
  • Disconnect the red wire that connects the clarifier with the PCB of the radio.
  • Ground the red wire.
  • Then disconnect the orange wire which attaches to the PCB as well.
  • Connect the orange wire to the 3rd pin of the mb3756 chip on the board.

Your clarifier mod is now complete. This should be enough to give you about 6KHz of slide. 

If you want -6KHz to +6KHz with the 0 right at the middle you should follow these steps:

  • Locate the R175 and short it.
  • Now find the D51 on the PCB and short it as well.
  • Then remove the R149, R188 and the R44 from the board.
  • Disconnect the wire from the clarifier’s high side.
  • Connect the wire to the 3rd pin of the IC4,
  • Find the R174 on the board and replace it with a resistor of 3.3K resistance.
  • Join the shorted D51 to the 3rd pin of the IC4 with an added 12,000 resistor.

The Tx will now track with the Rx.

Power Output and Audio Modifications:

Advantage :

By doing this mod you will be able to increase the loudness of your transmitted signal. It will increase your volume in the channel. 

Modding Process:

To perform this custom modification follow these steps:

  1. Find the R131 resistor in the PCB of your Uniden Grant XL.
  2. Cut the trace to the R131. Alternatively, you could cut one of the legs of the resistor for ease.
  3. Reconnect the R131 to the PCB using a couple of wires and a switch.
  4. Put ferrite beads on both the wires.
  5. Mount the switch on a convenient location on the back of the radio.

Your modification is now completed successfully. 

AGC Modification:

The AGC or Automatic Gain Control modification can also be done to the Uniden Grant XL radio set.


The advantage of modding the AGC is that you can now increase your signal to noise ratio. The AGC essentially prevents the Rx output from varying too much.

Modding Process:

Look at the wiring diagram shown in this picture:

Modding Process diagram
Source: usermanual.wiki

Based on this picture, follow these steps to mod the AGC of the radio:

  1. Locate the C23 at the underside of the PCB.
  2. Mount a switch to the back of the radio at a convenient spot.
  3. Connect the switch to either end of the C23 with a 10 microFarad 25V or 16V electrolytic capacitor in series with the switch. 
  4. Ensure the correct polarity of the capacitor. The new capacitor should be connected in such a way that the positive end connects with the positive end of the C23 capacitor. Likewise, the negative end of the new capacitor should touch the negative end of C23.

Your AGC mod is now complete. You can now switch the AGC of your Uniden Grant XL to fast or slow mode as needed.

Receive Modifications:

Modifying the receive is another modification often performed in the amateur radio enthusiast community. It reduces the noise floor which is generated by the radio itself.


The advantage of performing this particular mod is the resulting gain improvement. You will notice about a 4 dB to 6 dB increase in gain while keeping the signal to noise ratio constant.

Modding Process:

To do this modification follow these steps:

  1. Locate the Q14 on the board.
  2. Replace the Q14 with a 2SC2999 or a NTE 107.
  3. When using a NTE 107, slightly readjust the L4, L5 and L6 legs if needed.

Your receive mod is now completed.

SSB Detector Upgrade:

This is a very simple mod you could do to the Uniden Grant XL which is a SSB CB radio.


By performing this modification you improve the capability of your SSB detector. Having a better SSB detector lets you demodulate SSB signals with less noise, increasing the clarity of the Rx audio.

Modding Process:

Follow these steps:

  1. Locate the Q14 transistor and replace it with a better transistor.
  2. Replace the Q19 transistor on the PCB with the Q14.

Your SSB detector has now been upgraded.

Schottky Diode Upgrades:


This mod reduces noise and increases sensitivity of Rx signal on AM communication.

Modding Process:

Follow these steps:

  1. Locate and replace the D1, D2, D21 and D22 diodes with NTE583 diodes.
  2. If NTE583 is not available, use SK9975 diodes instead.

You will notice a big difference in terms of noise in the Rx and Tx signals.

10 Meter Conversion:

This is another mod you could try on the Uniden Grant XL. While the Uniden Grant XL already transmits far for a CB radio, this is still a worthy mod.


You can use your Uniden Grant XL CB radio to communicate in the  10 meter band using this modification.

Modding Process:

The modding process for this mod:

  1. Find the 11.325 MHz X3 crystal.
  2. Change it to a 11.6908 MHz crystal.

Your 10 meter conversion band is now complete.

Widebanding the TX range:

This is another widely used modification among amateur radio enthusiasts.


The advantage of this mod is that it lets you transmit signal at a wider frequency range.

Modding Process:

To do this mod follow these simple steps:

  1. Locate and remove the R206 from the PCB.
  2. In place of the removed resistor put a 33K and a 2.2K resistors in parallel configuration.

You can now emit signals at a wider band.

Misc. Component Upgrades:

You can upgrade different components in the radio set for better performance.

Modding process:

You can upgrade these components:

  1. Replace the 20 W Q41 with a 50 W NTE152.
  2. Replace the 10 V C18 with a 16 V capacitor of similar capacitance.
  3. Short the R180 to reduce distortion of the Tx signal.
  4. Replace C109 with a capacitor of half the  capacitance and the same voltage.
  5. Replace the R114 with a resistor of 10,000 Ohm.

Negative peak compression – Reduced carrier (NPC-RC) mod

This is a more complex mode which you can do to the Uniden Grant XL.


The NPC part of the mod squeezes the negative peaks of your signal to give you a better signal modulation. The RC part reduces the dead key of the radio.

Modding Process:

Follow the steps mentioned here:

  1. Add a 1.5K resistor to the middle leg of Q24.
  2. Replace R126, R124 and R131 with 4.7K resistors.
  3. Adjust VR10 AM to 2.5 W.
  4. Connect the positive end of a 10 microFarad capacitor of pin 9 of IC6 and negative leg to D63.

The NPC-RC mod is now complete.

What to Keep in Mind When Performing Uniden Grant XL Mods?

Some of the modifications mentioned here can be illegal in your country. Modding the Uniden Grant XL can also end up damaging the radio. In addition to this, modding the electrical circuitry can also be dangerous for you. Seek help from a professional if you lack experience on working with electrical circuitry.

Frequently Asked Questions (FAQs):

When did CB radio go to 40 channels?

CB radio started using 40 channels between 26.965 MHz and 27.405 MHz. in 1977. Until 1977 CB radios used only 23 channels in the USA. Having more channels in the CB service helps in short distance communication.

What is the most active CB channel for truckers?

Channels 17 and 19 are the most active CB channels for truckers. Truckers driving on the north and south bound roads prefer channel 17, while others prefer channel 19. Truckers use them for short distance informal communication.

What is the least used CB channel?

The least used CB channel is channel 9. That is because channel 9 is the designated emergency channel. The frequency of CB channel 9 is 27.065 MHz. If you are ever in an emergency you could ask for help using this channel.


Now you know all there is to know about Uniden Grant XL mods.The Uniden Grant XL is a great CB radio that can be upgraded to a great extent through some simple modifications. I hope you got answers to all your questions by reading this article.

That is it for today. Thank you and goodbye.


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