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Tuesday, October 28, 2014

Uploading Pictures And Posting On CQ Bitx

We are inviting Bitx version 3 builders to contribute with article and pictures of their built Bitx tcvr on Cq Bitx blog .

To seek an invitation to  Upload  pictures  and Post on our blog , kindly send a scanned picture of your license to establish the authenticity of your Ham Radio Profile, with your name, email etc

The invitation to post pictures and write on CqBitx will be sent as soon as we have your profile details.

Kindly email me at for your request.

Best of 73s

Sunil  VU3SUA

Thursday, August 14, 2014

New Avala PCB

If you are looking to build the Avala 01 sdr tcvr we now have the PCB's for sale.
The present Avala PCB is made with all corrections as per original circuit and with tinning and masking, and a better silk screen  of the pcb.

The PCB will be available from our website and also from our ebay shop.


AGC Pictures

To help in construction the AGC circuit used in Bitx3B or if used in any other receiver , some pictures are being published here. One resistance that was sitting between preset and lm324 is 10K , the value is now shown in the AGC pcb image file

Thursday, July 24, 2014

ADE-1 Mixer for Bitx Version 3

Information is being provided as how to connect the ADE-1 Mixer for the older version of Bitx3 And also for Bitx Version 3B. The Bitx Version 3 C has already been updated with ADE-1 Mixers.


Friday, July 18, 2014

Bitx Version 3C

For those of you wishing to build the Bitx 3 with ADE-1 Mixers the good news is that the PCB's are ready for the Bitx Version 3C.   There have been no other changes in Bitx 3C

The Bitx3C has been tested and performance is good. I shall publish a video soon of a working set.
 Published below are two pictures of Bitx3C.

Bitx Version 3C Solder Side with ADE-1 Mixers
Bitx Version 3C Components Side 
      The Bitx Version 3C PCB And kit will be available by next week onwards.

Thursday, June 26, 2014

Bitx3B VFO complete band coverage with zero drift

A new video of Bitx3B is being shown here, which has the following improvement:

1. Full coverage of 20Mt band from 14.000MHZ to 14.350MHZ
2. Zero drift with varicap tuning diode.

The varicap is 1SV149  .   They work up to a maximum of 10V biasing and capable of a C max of 500pF at 1V bias. so we can manage from 8V regulator easily.

This device was suggested to me by my good friend MVS  Sarma from Hyderabad. India.
After trying this device i did not think twice by replacing it with MV209.

So now we have a very stable VFO with BITX3B giving a complete band coverage, who wants a DDS anyway for a mono  band tcvr ........


Missing ground track in exciter, band pass filter stage.

Kindly correct the band pass filter stage in the Bitx3B pcb which has a missing track that should be connected between 39PF and ground for L1 and L2

Monday, June 16, 2014

How to connect Bitx VFO with Ik3OIL FLL

Many friends had requested me to  show how the Bitx VFO could be connected to the Ik3OIl FLL counter to stop the drift in the Bitx VFO.

Presented here is a video and details as how to connect the Bitx VFO with the Ik3OIL freq counter.

First we present the video with the Bitx VFO that is connected with the Ik3OIL Freq counter.
The FLL control circuit works with combination of some components and software on the counter and some parts are on the IK3OIL VFO pcb. The main part being the BB204 varactor diode. A buffer stage has been taken from the Ik3OIL VFO pcb.

In this demo we powered the bitx VFO and the Ik3OIL Counter . You may observe that after the red led stops to blink the FLL takes control and stabilizes the VFO.
In the demo i have also rotated the main tune and fine tune capacitor which gives complete coverage for the 20mt band. There is no drift as the tuning is stopped and the FLL control takes the new readout and starts to control the VFO.

This demo has been done on the Bitx version 3 exciter.

I would welcome any one who wants any more help.





                        BITX VERSION 3 EXCITER PCB

                           FLL FREQUENCY COUNTER

  1. Some important points to be noted: 
  2.  In VFO use Polystyrene Or NPO capacitors
  3. Use RG174u for all RF connections
  4. 12 Volts can be taken to the FLL VFO pcb from the bitx power supply 

Monday, May 19, 2014

Stacked VFO coil for bitx3b vfo

Bitx3B VFO stage picture has been posted here. The Bitx3B VFO is made with two number's of
T37-6 stacked together and quick fix applied on it.

The trimmer at control of FLL will need to be engaged at such a point as to observe the least drift .
The VFO is rock solid and i did not find any drift .

The FLL menu switch has been soldered on the solder side of PCB, so that it could be easier pressing the switch while adjusting the BFO or VFO to set their frequencies.

Saturday, May 17, 2014

Bitx3B New built

Here are some pictures of my new built Bitx3B .  This new bitx3b set is built on the second batch of PCB for exciter which has some minor changes.
The VFO uses 2 number of T37-6 stacked . The results are very good. I could find no drift at all. very shortly i will publish a video on it. provision is also provided on the new board to add DDS if VFO is not to be used. And yes I have also installed the audio mute circuit in this set.

The power supply used is a 24 Volts 2.5 Amps SMPS Laptop power supply.
The RF output is 4 watts clean.

Power Supply 24 Volts SMPS from my Laptop


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