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Tuesday, January 13, 2015

New Schematic And Mods Bitx3b/3c

The Bitx3b/3c construction manual is being updated and will be available very soon, we are making some corrections to it, also some mods have been done on the exciter and pa  for both versions.
The main mod being oscillation in PA caused by feedback. We have used a diode switching arrangement to cut of the RX antenna on Transmit, the mods were required on both exciter and pa board.
The new schematic for bitx3b/3c and pa can be download from this link.

The new kits that will be sold now will have these mods done, how ever these mods can also be taken up in the existing pcb's you may have purchased.

The following files will been found with the download link.

1. Bitx3B Exciter Sch, with mod done to  disconnect of Exciter RX Ant on Transmit.

2. Bitx3C Exciter Sch, with mod done to  disconnect of Exciter RX Ant on Transmit.

2. New PA Sch with mod done to:
Disconnection of RX Antenna  on Transmit at P5.
Selection of 12 or 24 Volts for Final.

0.01 Capacitors  across all four IN4007 diodes

IN4007 diodes  across both relays.

New Printed Circuit Boards of Bitx3B, Bitx3C Exciter And PA will have these mods done. The earlier Bitx 3B/3C PA boards can be modified as with above details. The earlier boards can also use relay instead of the diode cut off switch for the Rx antenna as per one's wish as both systems work.

Thursday, November 6, 2014

Bitx3C Pictures

Here are some latest Bitx3C pictures .   I hope these pictures help Bitx3B And Bitx3C  builders .

Later I will be posting some Videos  of Bitx3C  .

Best Wishes.

Monday, November 3, 2014

Correct Sch Bitx3B AGC

Kindly find the correct Bitx3B AGC  complete details of schematic, silkscreen , components layout.

I am extremely sorry that we had earlier uploaded and sent a wrong schematic of the Bitx3B AGC.

Note:R16  Value 10k to 15k.  10k works ok

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


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