Electronics · Ham Radio

Bitx Progressing

The Bitx completed

My bitx project has been lying dormant for a couple of months now. I completed wiring about 2 months back. The transmitter was working properly. But the receiver was not receiving anything . When I tried to increase volume, it started howling. After initial testing, I became QRL with lot of other activities. This weekend I decided to look at bitx board again. I carefully rechecked all stages and found out that I had made 2 mistakes in wiring components , a 22 ohms resistor was in the place of 220 ohm and at another place I put a 1k instead of 100 ohm. After correcting the mistakes I fired up the receiver , I could hear some CW transmission around 14.01Mhz. When I increased the volume, the audio stage was howling. I decided to discard the audio stage and build a new one. I bought a small audio module form local market for Rs 25 and fixed it to the board. Now the audio is clean even when the volume is maximum. I am still not satisfied with the sensitivity of the receiver. I made the following measurements on various transistors today. The table of the voltages on transistors are given below. The transistors numbers are based on Bitx V3 diagram by OM vu2wmj Rahul.

BitX20 Voltage chart

Voltages on Receiver Chain  Supply voltage 12 V.  Transistor used 2N3904

Transistor Emitter Base Collector
Q1 1.64 2.38 8.22
Q2 1.8 2.5 8.14
Q3a 0 .6 4.46
Q3 4.04 4.76 10.6
Q4 0 .6 2.04

Voltages on Transmitter Chain, Supply Voltage 12V

Transistor Emitter Base Collector
Q10 1.72 2.33 7.7
Q11 1.5 2.1 7.3
Q12 1.31 1.95 6.2
Q13 1.41 1.96 6.4
Q14 2.2 2.9 9.5

I think I need to verify the voltages with some other builder.

3 thoughts on “Bitx Progressing

  1. How about using a bread board? 🙂 srry no offense meant but I was surprised by the messy circuit. 🙂 …. Couldn’t find your background work on the subject. Mind posting a link along with it.?

  2. I think you could shorten those leads, else it will make distortion. Me living at Keshavadasapuram. Please send me your number, I will try to reach you.

    VU3MMU – Mohan

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