Highfields Amateur Radio Club
Repair Assistance & Modifications.

Note: This mod was posted prior to David Harms posting (with the permission of the manufacturer) the factory method of frequency adjustment on the same Facebook group. I have reproduced David's post at the bottom of this page in case the Facebook post is deleted or lost or for those that have not got a Facebook account.

As stock there is no ready means of adjusting the base oscillator frequency to re-align the radio should it drift due to age or other reason. This modification will rectify that failing, adding a trimming capacitor to the circuit.

The first thing to do is to remove the cover from the oscillator section, that's the one with the crystal coming through the lid (highlighted with the orange box in the image, right). It should just prise off (gently).

Once inside the oscillator'ss screened area locate and carefully remove the first capacitor from pin 10 of the LMX2352. In my radio it was a stack of 2 smt capacitors, remove as shown in the second and thrid pictures below (click on them for higher resolution images).

Your radio will have 1 or more smt capacitors as the amount of capacitance required to tune to the correct frequency may vary due to component tolerance and adjustment during manufacture.

Replace the screening cover when done.

On the other side of the board attach a trimmer capacitor (shown below), mine was a random one removed from a scrap board, to one side of crystal and ground and a 150pF cap from the other side to ground. Ensure that the trimmer capacitor will not touch the case when it is replaced (there is plenty of room but just to be sure).

The 2 crystal leads and the ground point I used are shown ringed in the first image above.

Adjust with frequency counter to be exactly on frequency. If the required frequency is not attainable, change value of 150pF cap.

AnyTone AT-5555 Factory Oscillator Adjustment.
By David, N6QLC
Originally posted on the Anytone AT-5555 Facebook group
First posted 29 June 11 and amended on 6 July 11.

Refer to the picture below for the location of the resistor and frequency measurement point.

1. Change the R567 resistance from 56K to 33K.
(This is the resistor that is mentioned in the AnyTone AT-5555 Frequency Stability Mod page. It has been reported that the following adjustment works without changing the resistor. Maybe the change is due to the stability issue noted on the other page? Webmaster).

2. Adjustment:

Press and hold "FUNC" while powering on the radio; then press "RB" once, then press "AN/ANL" once, then press "DW" once, the radio enters adjustment mode when the LCD displays BFXXX, (where XXX is the numeric setting value) and you must make adjustments to the frequency in each mode, one by one:

A. Switch to CW mode. Adjust the CLARIFIER until the frequency counter shows 10.6950 MHz.

B. Switch to FM mode. Adjust the CLARIFIER until the frequency counter shows 10.6950 MHz.

C. Switch to USB mode. Adjust the CLARIFIER until the frequency counter shows 10.6925 MHz.

D. Switch to LSB mode. Adjust the CLARIFIER until the frequency counter shows 10.6975 MHz.

Shut off radio to save data and exit frequency calibration mode.

This is what it should be set to. But, because of circuit loading during measurment, even with isolated counter lead, I found the final transmitted frequency about 40hz low.

What I did to solve this was transmit durring adjustment mode and use a counter on the RF out to set AM/FM mode exact. USB and LSB modes I zero beated it with my TS-2000 which was in alignment. That solved all the issues with being off frequency.

Information provided courtesy of Qixiang Electron Science & Technology Co., Ltd.
          Edited for better English translation by David A Harms, N6QLC.