Microwave Forum

kleiner-onkel · Administrator Messages: 412 Location: South-West-G

@ mujeeb

100nF or 0.1uF

viki · Guest

help me friends

just want to know how can o tune MaX VCO nand how much noise is eoungh for test cricuit.......

richy_64 · Administrator Messages: 198

To tune the MAX VCO use its datasheet. Just google for it: "MAX2623 pdf". Look for the suitable tuning voltage... ~2V DC.

The noise signal should be around 1V peak-peak. Modulate the tuning voltage with the noise signal with two adjustable resistors, like i do in my circuit:
http://file.carookee.com/forum/broadcasting/1/file/220791/jammer3.gif?w

Look for the two adjustable resistors: Mean frequency and noise amplitude.

viki · Guest

hi
as cricuits shows the output of VCO is going into MAX

1) how to modulate is VCO after tuning into 950Hmz.. or u want me to tune with the N-Gen output
2) cricuit show 5 V VCC of MAX. may i give %5v to VCC and TUNE 2v dc

pleaase in detail

viki · Guest

here is my VCO . i have N-gen in my College LAB just tell me step by step how to modulate N-gen with VCO

i have to give 2V DC to tune VCO at 950mhz with the N-gen output or ......

viki · Guest

see this

richy_64 · Administrator Messages: 198

Hello,
ok, step by step.

Look at the picture below:
R3 is a voltage divider which produces 0...5 V (V+ =5V) to tune the MAX2622. The datasheet of the MAX2623 says that we have to tune it with 2V to get ~930MHz. This is the mean (=middle) frequency of the gsm downlink band.

The next step is to add noise to let the tuning voltage spin around. With R3 I use a second adjustable resistor to influence the 2V-tuning-voltage. Because the impedance of the voltage divider with R3 is lower (~100k against ~500k of R2), the voltage of R3 causes a little deviation of the tuning voltage.

richy_64 · Administrator Messages: 198

This shows exactly what I want to explain:

http://homepages.compuserve.de/richardkotte/IM002312_.jpg

So what do we see here? A mixed signal at the tune pin of the MAX2623 (This is your question: There is 2V DC AND the noise signal)

Noise (=AC) with ~1V peak-peak and
a DC offset voltage, ~2V.

This weird tuning voltage causes the vco to produce a wide spectrum of frequencies ... to jam gsm :-)
-----------------

Have you got an oscilloscope? Without it building such circuits is almost impossible.

viki · Guest

thx,s man

i have oscilloscope... so u wnat me to apply noise from R1 and tune voltage from R3.

and plesae post this jammer 3 cricuit in good qulity like thsi u post

kleiner-onkel · Administrator Messages: 412 Location: South-West-G

@ vici ...

remember .. you need to programm the AVR ...

so you wave to build the programming circuit ,too!!!

richy_64 · Administrator Messages: 198

Hello viki,
yes, you got it.

Instead of using the avr microcontroller you can use your noise generator circuit from above, too. Generally you can try very noise or sawtooth generator you can find. But required is that the output amplitude of the generator is at least 1V peak-peak.

Jammer 0.3 some bigger:

http://file.carookee.com/forum/broadcasting/1/file/220791/jammer3.gif?d