HP 5086-7582 YIG

I bought this YIG to use in a signal generator, just for the fun of it.  No idea what it came out of, but I have found some details on a similar unit.



I found this note:  http://www.electro-tech-online.com/attachments/hp7067-jpg.7100/

so I have tried it out and it looks as though those details are about right.  Mine has the following pinout and characteristics:



I’ll do some measurements on the actual range and the FM coil sensitivity later.  Looks like this is going to be a useful YIG to make a signal generator as planned.

116MHz LO using PIC12F629 and ADF4351

After replacing the fake synth chip with a real one, I needed a small and reliable controller to upload the parameters to the six registers in the ADF4351.  I decided to use a PIC instead of an Arduino as it is about 12 years since I last used a PIC and back then it was a UV-erasure job (16C74A I think?) and a programmer with a ZIF socket, and an early version of MPASM.

Part of the reason was a request for advice on the rsgbtech Yahoo group from Mike G6TRM, so grateful thanks to Mike for providing the spur.  The rest of the reason is all of the pieces written by Andy Talbot G4JNT that use a PIC.  Andy makes it seem quite straightforward, so I thought I’d better get the soldering iron out and just get on with learning about new-fangled chips and in-circuit programming.

I decided to push myself a bit and learn how to use the PICkit3 in-circuit programmer and MPLAB-X IDE, coding in C using XC8.

The project is a 116MHz local oscillator with dual outputs via a 5th order Chebyshev LPF with a corner at 140MHz and 0.1dB ripple.  I edge-soldered the Chinese ADF4351 board into a tinplate box and fitted a 5V regulator and protection diode.  As I wasn’t sure about the design of the PIC daughterboard, I decided to go back to the 1970s and use Veroboard for a change.

I need a few more of these little controllers, so I might order a batch of PCBs and use a surface-mount PIC and level-shifting resistors.  For now, the Veroboard is doing a fine job.


The 6-pin and 2-pin sockets fit the ADF4351 board.  The 6-pin header is for the PICkit3 in-circuit programmer.  The resistors are required because the PIC is a 5V version and the 4351 is 3.3V.  The PIC runs fine on 3.3V, but I can’t then use the in-circuit programmer.

It all works fine, the output looks clean enough at 116MHz.  I am using it as an injection-lock stabiliser for the Anglian overtone crystal LOs.

The code is still rather ugly and uncommented.

#define _XTAL_FREQ 1000000
// Change these parameters    //
// This is for 116MHz, with   //
// 3712MHz VCO divided by 32  //
// and 10 MHz PFD so INT=371  //
// FRAC=1, MOD=5 and DIV=32   //
#define FRAC 1
#define INT 371
#define MOD 5
#define DIV 32
#define R0 (INT*32768)+(FRAC*8)
#define R1 (0x08008001)+(MOD*8)
#define R2 0x78004E42
#define R3 0xB
#define R5 0x580005
#if DIV == 64
#define DIVX 6
#elif DIV == 32
#define DIVX 5
#elif DIV == 16
#define DIVX 4
#elif DIV == 8
#define DIVX 3
#elif DIV == 4
#define DIVX 2
#elif DIV == 2
#define DIVX 1
#elif DIV == 1
#define DIVX 0
#define R4 (0x84003C)+(DIVX*1048576)
#define SEN GPIO5
#define SCL GPIO4
#define SDA GPIO2
#if defined(__XC)
 #include <xc.h> /* XC8 General Include File */
#elif defined(HI_TECH_C)
 #include <htc.h> /* HiTech General Include File */

#include <stdint.h> /* For uint8_t definition */
#include <stdbool.h> /* For true/false definition */

#include "system.h" /* System funct/params, like osc/peripheral config */
#include "user.h" /* User funct/params, such as InitApp */

void send(void)
void SPIsend(uint32_t reg)
 for(int n=31;n>=0;n--)
void SPIsetup(void)
void main(void) 

Fixing a fake ADF4351 synth board

A couple of months ago, I bought some ADF4351 synthesizer boards at a very attractive price from a Chinese supplier.  Sadly, the supplied boards turned out to have fake, or out of spec, 4351 chips which actually behaved like 4350s, with no /32 or /64 divisor.  As a result, it was impossible to use them below about 130MHz.  Several UK microwavers including RadCom columnist Andy Talbot G4JNT were also supplied with these fakes

Following up Andy’s suggestion in his Design Notes column in the Nov 2016 RadCom , I decided to swap one of the fake devices for a new  ADF4351BCPZ bought from RS (stock no 796-8710, £9) and can confirm that the board now behaves correctly at /32 and /64.  It just needed a bit of concentration, a fine soldering iron, lots of flux and a stereo microscope, then a 100W iron to flow the solder into the heat transfer pad from the underside.

I removed the fake chip by applying the 100W iron to the underside of the board beneath the chip, then used a hot-air blower to melt the solder on the top side of the board, lifting the chip away with tweezers.  Next, I applied a good dose of liquid flux, then cleaned off the pads with desolder wick.  I applied a bit of solder to one of the pads, then more flux, positioned the new chip, melted the solder to attach the device with the chip firmly held down, then did the same at the opposite side, but followed the technique recommended by Andy and others, using a flood of flux and a fair excess of solder.

I ran the iron across all of the pins and pads on each edge of the chip, then removed the excess using desolder wick, ensuring I cleared all bridges. Surface tension did the hard work, although I did have to reflow two of the pins after close examination under the microscope.

The repaired board is in the picture. The chip is 5mm square. Notice that the markings appear very sharp and the pin-1 dot is very distinct,.

Replacement ADF4351 ship mounted on a green PCB

Now compare one of the fake originals. The soldering is much better of course, but the label is indistinct and the dot is almost absent, as though the top surface of the chip was abraded and then printed with a new identifier. The lettering does look 100% the same.

Fake ADF4351 before replacement- actually a re-marked ADF4350