Improve your Bitx40 with these simple upgrades

Making your own Bitx40 HF transceiver can be fun, the kit is low-cost and well supported on the internet.

However, this is not the most refined radio you will use. Out of the box, it's basic, but it does work. For me, the minimal nature of this radio makes those Bitx40  contacts so much more satisfying.

This radio can be improved, modified and upgraded. There are plenty of resources on-line to cover most things, many of these are relatively easy to do. Each enhancement makes the radio a little better, it appears there are always features and upgrades to be added.

When I mention my Bitx40, I'm often asked 'so what have you done to it?'. To help me answer this question I thought I'd share the modification I've made on this web-page. I've listed all the useful modifications that have been made to my Bitx40 radio below.

I hope you find this page useful, maybe it will help improve your experience of this little radio as well.

What is a Bitx40

The Bitx40 is a 40m 7 watt transceiver kit purchased from India. It is an open source design made into a kit by HF-Signals. Everything is provided in the kit to make a fully functioning transceiver (a speaker or headphones must be sourced separately). However, the transceiver kit is minimal. With the use of a purpose made case and a couple of simple mods this kit can turned into a fun radio for your shack.

You can buy one from here: 

Recommended modifications to improve the Bitx40

Below is a list of the modification I've made to my radio. All have been successful implemented on my own Bitx40 radio. 

Metal case

You can buy this smart metal case from here: 

Its a solid metal enclosure which looks great and has enough space for your modifications and wiring. Pre-cut holes, painted and screen printed, a great place to start your project.This case could save you a lot of time and effort if making enclosures is not your thing. 

Also, these cases come with a speaker, pots, screws and connectors. Everything you'll need to complete your Bitx40 is included. Okay, you may need some wire for the power cable, but the plug is included with this case!

Tip: I used the 'Universal Case Blue II For Bitx40' as seen in the images on this web site.

Wire up the microphone like a KX3

Why? Because these connections are logical, available and easy to achieve.

I had an Elecraft compatible microphone knocking around which I knew worked well, so this was the most logical connection method for me.

Using the KX3 connections I ended up with a dedicated headphone socket, and a dedicated microphone and PTT socket. Nice and simple. This also made connecting the Bitx40 to Signalink sound card (for data modes) simple.

Low cost microphone

Compatible Elecraft microphones can be low cost if you buy them from here: 

Microphone jack socket (4 way)

You'll also need a four-way 3.5mm jack socket available online.

 

Microphone socket pinning

Here are the pin connections: 

  • Tip=Microphone
  • Ring 1=Microphone 0v
  • Ring 2=PTT
  • Base=PTT 0V

Firmware, function button, ten turn pot, and more

Bitx40 function button
Bitx40 function button

All of the above tips will give you a working radio. Now to really add some bells and whistles go to this page and add a function button and new menu items!  

Here is the reference link:

 Essential mods found on this page include:

  • Firmware - Menu options and more!
  • Function button - Used with the firmware
  • PTT seance - Also required to eliminate pops and squeaks!

Important: Follow the firmware setting steps after installing the firmware!

Tip: Use a header pin to make the PTT seance connection (so you can disconnect the board)

Tip: Set the ten turn pot to cover half the band only. This makes tuning  a breeze and is much nicer to use.

RF gain control

Rf gain modification for the Bitx40
Rf gain modification for the Bitx40

If you want to turn down all that QRM noise, then this feature will be high up on your to-do list. An RF gain control can be added with the use of a 1K pot connected in series with the RF track.This mod actually adds an attenuator to the RF input of the receiver.

You'll need a two pin header, some screened cable and a header connector.

The RF track is broken on the PCB and a header is attached to the board (as shown on the left), a 1K pot is connected to the new header to complete the circuit.

Here is the reference link: 

Tip: I glued the header to the board using epoxy glue. Super glue does not work.



Get rid of the hiss

The basic Bitx40 kit comes with a lot of audio hiss. It's darn annoying. For me, this mod is essential. Removing the hiss and improving the audio quality totally transforms the radio.

You'll need to add a 0.01uF capacitor and 10k resistor to the LM386 amplifier (across pins 5 & 8).

It's the only 8 pin device on the board, and this can be added to the top of the board if you can't be bothered to remove the PCB.

Here is the reference link: 

Bitx40 audio hiss removal modification
Bitx40 audio hiss removal modification