Simulators Window


Choosing a PLL Type


As you can see from the image below, you can choose from several PLL types, each one has a preset N code, carrier oscillator and loop oscillator frequency, usage of this pull down menu is simple, select the PLL type you wish to simulate and then use the simulator.

If a PLL type is not listed please let me know that you wish for it to be included, and if possible tell me some of the details of the radio it is for, such as the carrier oscillator and loop frequencies, and the normal N code range, this will allow me to build the simulator.





Channel Simulator


This pane is used for general information and for conversion simulations

The top section displays the actual "N" code as a decimal value, and as a HEX value, it also shows the physical "N" code for ROM type PLL's, this is displayed inside brackets "( )".

At the very top section of the window you will notice that there are two radio buttons, called "Normal/TX" and "RX", these allow you to select the state of the "T/R" pin of the PLL to simulate a TX or RX condition, which changes the VCO frequency and "N" code, not all PLL's have this option and the radio buttons are greyed out when not required.

The lower section details the carrier oscillator, loop oscillator, VCO and VCO Mixer frequencies, underneath that is the Binary or BCD "N" code as used by the PLL type selected from the menu, some PLL's use a ROM (Read Only Memory) section which converts the "physical" N code into the code it actually requires, when this is the case the physical N code is displayed.

This pane also allows you to substitute a different carrier oscillator or loop oscillator frequency, this is handy if you are planning to do a channel conversion and want to see what crystal frequency will be required, there is an important detail to remember, in many radios the loop oscillator crystal frequency is doubled or tripled, so the resultant frequency is displayed and used in the simulator, you will need to calculate the actual crystal frequency required by dividing it by two or by three (as required).

To substitute a different frequency just select one from the pull down menu, for the loop oscillator you may also enter a frequency manually, just click the check box marked as "Other..." and enter it in the text box, click the button to the left of the menu to transfer it into the simulator.

At the very bottom of the pane is another button, this is used to calculate the channel frequency based upon the N code, carrier, loop and VCO frequencies, so if you substitute a different loop frequency you can see what the new channel frequency will be.




CB Radio Simulator


This pane is used to graphically display the configuration of a radio (based on the PLL type) , you can see what the various frequencies should be for each channel, the graphical display will change depending upon the PLL type selected, as not all CB circuits work the same way.

At the bottom of the pane is a slider, this selects the PLL N code, this allows you to set any N code that is supported by the PLL, so you can see what frequencies should be present for any given N code ! An important note here is that this is the "actual" N code, so if the PLL uses a ROM section it is the code that is actually used by the PLL, not what is present on its programming pins, but usually these types only allow 40 channel operation anyway.

The Decimal N code is shown just above the slider box, this feeds into the PLL (represented by the box), from there you can see the downmix frequency, that is fed back into the progammable divider from the VCO, this is the required frequency to give either a 10KHz or 5KHz output to the phase detector, which alters an output voltage to control the VCO frequency.

The VCO frequency usually mixes with a loop oscillator frequency, to output a signal for the TX and RX mixers, however, some PLL's do not use this method, (the display will show the actual method used), the TX mixer will mix the VCO Mixer output with the carrier oscillator frequency to give the channel frequency, again, not all PLL's work this way.

At the very top section of the window you will notice that there are two radio buttons, called "Normal/TX" and "RX", these allow you to select the state of the "T/R" pin of the PLL to simulate a TX or RX condition, which changes the VCO frequency and "N" code, not all PLL's have this option and they are greyed out when not required.

The 1st RX mixer mixes the channel frequency with the VCO mixer output to give the 1st I.F. frequency (which is shown in the 1st box after the mixer), this will often go to a second mixer to give the second I.F. (usually 455KHz), sometimes a radio may use more than one I.F. frequency.

The loop oscillator frequency can be changed to a different one after selecting a PLL type from the list, so for a radio that uses a different loop frequency to the standard ones you can still see what frequencies should be present, you can also change the loop frequency for simulating an expanded radios coverage.

The end result is that you can choose a PLL type from the menu, and then select a channel frequency or N code using the slider, you can then see what the various frequencies should be, this is a good tool for troubleshooting a radios mixers and I.F. as you can see what they are supposed to be.




PLL "N" Codes


This is a simple one to explain, this pane shows the normal FCC/EU/UK (Legal) band "N" codes for the selected PLL type, so you can look up a channel number and see what the "physical" N code is supposed to be.



 

 


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