Microwave local oscillator ZLPLL 14G
VK2JDS > 09-12-2019, 04:26 PM
My own use of the ZLPLL 14G as a multiband local oscillator source.
Local oscillators for microwave transverters need to be clean output, ultra low phase noise, lockable to 10MHz, small , portable and programmable (and affordable).
The 14 GHz version of the ever popular ZLPLL satifies all these requirements. It uses a ADF5355 with some clever design work to optimise it, producing over +12dBm out.
Here is how I retasked mine to do a few more bands than just feeding my diode mixer on 122 GHz.
Utilising the 8 pin J1 channel change header it's easy to add a 3 or 4 position switch to select LO outputs for 122, 76, 47 and 24 GHz bands as required to run the transverter offset you want.
I use 433 MHz on my FT817. What is also handy is a 'direct transmit' option so the local oscillator can generate a carrier (for CW etc) right on the transmit frequency, e.g 122250.100.
To do this a single transistor (bc547 etc) and a 4k7 resistor is employed to toggle the D0 pair of pins and is driven by the transmit 12volt line via a switch.
This allows automatic PLL frequency shift from transverter receive, to direct transmit mode if you want the extra carrier power rather than using the transverter on TX.
The required direct transmit frequencies are then programmed into the ZLPLL on channel positions 1 3 5 and 9, while the transverted LO frequencies are loaded into positions 0 2 4 and 8.
How to program the ZLPLL :
This can be done easily with a ebay usb to serial adapter, using 3 wires : transmit data, receive data and ground.
Plug in the USB adapter flying leads to J7 RXD TXD and GND on the ZLPLL
Plug the usb end of the adapter into your laptop.
Power up the ZLPLL, it doesn't need a 10 MHz source attached to do the programming, a yellow led will be lit.
Use device manager to see what port number the USB adapter is showing as, then open a tty program like putty and open a serial port (5 for example on mine) at 9600 baud.
Press enter to get a prompt from the ZLPLL.
Now, the commands show and ? will bring up lots of useful info on how to drive the pcb.
Refer to the screen shots. EDIT cant add the screenshots due to size restriction on the forum, i will have to type them up in another post.
show will display what the pcb is currently outputting and what channels are programmed.
? will display the help list of commands you can use.
For example lets program up a signal source for 24048.100 MHz.
type in
freq 24048.100
multiplier 2
This will enable the output running at 12024.0500 MHz.
freq 10368.000
multiplier 1
It now runs as a beacon for 10 GHz directly.
freq 122250.100
multiplier 9
This will give you a signal source for that new transverter using the silicon radar chip !
Type diag for more info on what the pll is doing.
To save this setting in memory 1 for example, just type save 1 , and its done. So easy.
Refer to the screen shots for the frequencies and multipliers required for what I wanted to do with mine.
I just added a 3 position toggle switch to give me transverter LO frequencies for 122, 76 and 47 GHz bands, with the option of direct transmit on each one.
It just connects to D1 D2 and D3 on J1, so the box just plugs into power, 10 MHz, direct TX dc input, and screws onto the sma on the multiplier CMA382400AUP for 122 and 76, direct to pcb for 47.
73 Dave vk2jds
photos edited (fingers crossed they are small enough)