Showing posts from March 16, 2008

Bitx By Mark G0MGX [Pictures]

Mark has been very quick in assembling his Bitx version 3, and Mark you have done a great
job,posting your great Bitx pics on CQBITX.

Bitx Version 3 By Arjan Holland DSC02145

Posting some spendid pictures of Bitx version 3 home-brewed by Om Arjan Holland


Frequency Counter Picture

Here is the picture for the frequency counter in power safe mode. I had to take the counter out of the shack to get a good picture of it as I do not own a good camera as yet :))

This is apparently the beta test Pcb,and does not have a switch for programming nor does it have a 5 volt regulator.

A new set of Pcb for counter with a programming switch and a 5 volt regulator will be available for members with-in a few days time.

Frequecy Counter For Bitx


The Bitx Version 3 has company now.A frequency counter designed by Wolfgang "Wolf" Büscher, DL4YHF.
is now available with me for Hams who would like to add it on their Bitx
or use it in their rigs or set it up as a lab instrument.

All the credit goes to Om Rahul VU3WJM for making a fantastic PCB
and also allowing me to offer it to Hams world-wide,we are also full of appreciation to DL4YHF for putting up such a simple design.

I will post the pic of frequency counter soon.

In meantime any interested may contact me.

Many Goodies for Bitx on the way.QRX for them

Wide Band Transformers

Wide-Band Transformers In the Bitx Mixer ContinuedIn the previous web page, we looked at the difference that the number of turns made at the input of the mixer transformer winding. Lets change the viewpoint and look at the input to the diode bridge. We are going to look differentially. That is, across the 2 points rather than from 1 point to ground. The scope will be connected like this using 2 scope probes. This takes a special differential amplifier plug in.First, lets look at the 4 turn, 5.25uH transformer input signal that we left off with in the previous page. The left picture is the signal at the collector of Q7. The right picture is at the input to the diodes after going through the input transformer. The difference in amplitude is due to using a differential input to the scope instead of going from 1 end of the transformer to ground, we are going across the + and - leads of the transformer so we get twice the amplitude. There's not much change going through the transfor…

Stage By Stage Construction

What impressed me most is the way OM Leonard has planned making the Bitx stage by stage.
This method is very secure as you know the particular stage is working after you have constructed and tested it,there is no cause to worry later.

After examining them, I decided to make an "exploded" layout drawing using a section-by-section approach to the assembly and testing. I will function test each section as it is assembled. This will almost insure that the board will function when everything is completed. I already had an head start on the project as this would be the 3rd Bitx I had built. I already knew what the signals should look like in each stage.

RF Amplifier Section [Leonard]

RF Amplifier sectionThe Printed Circuit Boards are furnished with a 2SC2570A RF Amplifier Transistor for Q1. The pads on the board are for that RF transistor and are C-E-B left to right and the board is correct for that device.Using it, the board is correct. If you desire to use a standard C-B-E transistor configuration, go to C-B-E mod for an explanation of the board changes. The amplifiers can be tested individually by connecting +12 volts to the end of the appropriate 100 ohm resistor. Do Not power up both of them at the same time!We have 100 millivolts in and 920 mv's out. db=20log E1/E2 so db=20xlog 9.2 so we have a measured gain of 19.27db. Lets measure from the antenna input to the same output spot. This will send signal through the band pass filter. Simply move the signal generator over to the Rx Antenna point, double check the signal generator output and measure again. 100 mv's in and 720 mv's out. db=20log7.2 so we now have a gain of 17.15db. The differen…