Bitx3B VFO

The Bitx3B has a Varactor tuned VFO using MV209 and the stability is controlled with the Ik3OIL FLL Freq counter which has an inbuilt software to correct the drift in the VFO.

Building a stable vfo is an art and if not built correctly it would not perform optimum.

Picture and Video  below outlines some important factors that could enhance the performance.

BITX 3 B VFO SECTION

Outlined below are some points that need to be performed on the VFO section of Bitx3b for a drift free VFO

1.  VFO Capacitors to be NPO or Polystyrene

2. L5 VFO coil to be wounded tightly, placed flat on board and   applied  with thin layer of glue, quick fix is preferred as it has a thin layer, not very much to be applied, just enough to cover it.

3.MV209 And BB204  legs to be trimmed so that they may be just about near the board and soldered. A thin coating of quick fix could be applied on their sides, this way it becomes a sealed unit and gets protection from any air currents to extremely temperature.

4.It is better to use X position with 0.1uf  preferred Silver Mica /NPO or Polystyrene capacitor.  If you place a jumper across X then you may experience some drift, with 0.1uf in place the drift is manageable with the FLL counter attached.

5.  For FLL Freq counter Input and Contol it is recommended to use Rg174u coax

 6. Adjustment of Trimmer on control side of FLL is very important. The trimmer on extreme end of board is the trimmer that connects to the FLL control unit. Remember to fully mesh the trimmer or the vfo may drift.

The vfo was tested using the above recommendations and the test results:  2 Hours VFO On with max drift of 25Herts 

                   

Audio Mute Circuit For Bitx

Bitx had a problem of  noise being generated on pressing the PTT button. The usual way of muting the PIN 3 of LM386 did work  to solve the problem much, although to some extend, while working with Bitx3b i had discussion regarding this problem with Om Blake Bartosh from USA who was also building the Bitx Version3b  and who has also put in a great effort in bringing out the new Bitx3b construction manual.

The idea was to make a project to mute the audio of LM386 completely.
Presented below is a schematic of the audio mute circuit designed and tested by OM Blake Bartosh.

I myself build it and its working perfectly with my bitx3b. This circuit can be used for any tcvr.
The complete assembled kit will be available very soon.


                                           SCHEMATIC OF BITX AUDIO MUTE CIRCUIT                          

                                           VIDEO OF BITX AUDIO MUTE CIRCUIT                          

 

New Ham Radio TCVR Minima

Om Farhan from India has come up with another Ham Radio project. The new project is named Minima, which means a project with minimum components.

Minima is a complete ssb/cw tcvr with Arduino in it and an Si570.

Farhan's home page on minima is found here  http://www.phonestack.com/farhan/minima.html

 To carry on with our services we have decided to help amateurs buy our various products based on  Minima.

We are starting by selling the PCB developed by our forum member as very low cost, as to promote the building of Minima. Very soon we will provide a complete kit with case for Minima .

Please look out the availability  of the PCB set for Minima, which will be available very soon on our new blog meant for Minima.  http://cqminima.blogspot.com


We have also set up a new blog for  bitx version 3 B, which will be updated with all info on Bitx3B
http://bitxversion3b.blogspot.in/

Best of 73s

Sunil VU3SUA

Posted here are some pictures of my second built Bitx3B this one is with agc working. The earlier agc pcb had to be modified. The present agc/s.meter pcb mounts on the vu meter.

Bitx Ver 3 B RX demo

Some more new videos of Bitx Ver 3 B in receive mode.

Bitx Version 3 B Demo 3

Bitx Version 3 B Demo 2

Bitx Version 3 B SSB TCVR . Demo of RX

Here is a video i took last night for the Bitx Version 3 B in receive mode.

I have taken some more videos which i will post soon.

The receiver is quite sensitive and the VFO is quite stable.  Since it is a var actor VFO i am quite satisfied with its stability .  The maximum drift i observed in 12 to 15 hours not more then 50 to max 100 hertz in a period of 12  to 15 hours time.

More news of Bitx Version 3 coming soon.

Pictures of Working Bitx Ver 3B

It is a pleasure to present  pictures for a complete working Bitx B . 

The Bitx Ver 3B has not been put on sale as yet, although i have sold 3 sets on request.

Two radio amateurs are building the set but are facing some problem in their sets audio.

I will also upload a video very soon giving a live demo of the working Bitx Ver3B in receive and a modulation test on a dummy load and swr bridge and modulation monitored on a commercial receiver.


The Bitx Ver 3 B has some changes that were made to make it much more convenient for operational use.

The changes were.

1. Stable VFO  drift with in 50 to 100 hertz   in time span of few hours

2. Mic Preamp so that there no need to shout in the mic.. hi hi

3. FLL Freq counter connectivity with a buffer added in the vfo

4. Aluminum case

5. Mic PTT and Speaker

                                  PICTURES OF BITX VERSION 3 B