Tracking Generator

External tracking generator from 100kHz to 1000 MHz (sweep analyzer)

( Thanks to my friend Simeon Hristov for help !!! )

At the beginning of the year 2000 I and my good friend Simeon Hristov realized our project of External Tracking Generator.

We made it as an appliance to a standard oscilloscope type C1-94 (Russian model) . Our External Tracking Generator rep-

resents an analogue measurement device with sweep output signal for measuring Frequency Characteristics of filters

(LPF , HPF , BPF , DUPLEXERS , TRAPS) , SWR , amplifiers and other RF passive or active devices .

Features :

1) Wide frequency range from 100 kHz to 1000 MHz

2) Output level 0 ... 300 mV p-p

3) Automatic level control (ALC)

4) 50 ohm output impedance

Block Diagram

A flow chart of application the External Tracking Generator with an oscilloscope C1-94 is shown in Fig.1 This idea can be

used for realization of such generator working together with other types of oscilloscopes . With a view to simplification

of the technical decision we used the power supply from the stabilized rectifier of the oscilloscope and that force us to

distribute the load on the both arms - +12V and -12V , shown in Fig.2 . This influenced upon the technical performance in

some measure .The second very important moment is the use of saw-tooth signal of the generator's sweep which is

necessary for realization of a Sweep Generator . The tirth moment is the way of feeding marks to "Y" input of the oscillos-

cope . This must happen after the input prescaler of "Y" input . So the level of marks will not be influenced by the indica-

tion of the prescaler of "Y" channel but only by the indication of the trimmer "mark level" .The wide band detector used

an option is shown in Fig.3 Figure 4 shows the full flow chart of the External Tracking Generator , where the separate

connection between the blocks as well the way of control of parameters of the generator - "level output signal","frequency",

"fine frequency","deviation" and "marks level" are shown .Our External Tracking Generator has two outputs :

- the first one for UHF range measurement (400 ... 1000 MHz)

- the second one for VHF range measurement (0.08 ... 400 MHz)

The Generator 400 ... 1000 MHz is performed with a system for ALC which influences upon the power supply of the genera-

tor realized by Q1 BFR91A transistor (Fig.5) .The Generator from 0.08 MHz to 400 MHz consist of two other generators :

- the first one for 0.08 MHz ... 50 MHz range (Fig.6)

- the second one for 50 MHz ... 400 MHz range (Fig.7)

Both generators have a common system for ALC . The output signal from both of the generators is gained by a wide band

amplifier (Fig.8) , where ALC is performed by using of a Dual Gate MOSFET Transistor BF966 (Q1, Q5)- Fig.8 . Figure 9 shows

the scheme of the marker generator . It can generate marks through 1 , 10 and 50 MHz . The 10 MHz mark is a basic one

and it is obtained by the generator performed by U1 - 74LS00 . The prescaler U3 - 74LS90 is used for getting 1 MHz mark .

Commutation from 1 - 10 MHz is provided by SW2 and SW3 . Another important moment is obtaining of short pulses . This is

achieved by U2A ,U2B and U4A and U4B . For this purpose IC - 74S00 is used . The marker amplifier is performed by U5 - MA741.

There is a filter at theU5 output R14 , C19 and C18 , which shortens the mark additionally .The mixing of marks with the output

signal from Tracking Generator is made by Q3 BF680 . Fig 10 shows a construction of the mixer .

At the end we should notice that unknown frequency (fx) can be measured by our generator using fx - input with

accuracy +/- 1 MHz .