DSB Digital: Friend, or Foe?

Time Lapse Camera with the Raspberry Pi Zero W: Part 2

The BITX40 is dead. Long Live the BITX40!

In December 2016, Ashhar Farhan and the company HF Signals in India released the BITX40, a simple SSB radio for 40 meter HF. For $45, one could buy the kit with its preassembled board and minimal soldering required to be on the air. Soon after, it was packaged with an Arduino/si5351 based digital tuning mechanism called the Raduino. A digitally tuned HF radio, even as a kit, was only $59!

Up until recently, you could still buy a BITX40. But HF Signals has decided instead to focus on the BITX40’s, the uBITX. We’ve not covered the uBITX here for various reasons, but it’s a multi-band dual conversion SuperHet that has its roots in the original BITX20/40 design. Wait, BITX20?

BITX Roots: Homebrew Radio

That’s right, the BITX40 was not the original BITX. In the early 2000’s, work being done in the homebrew community, along with work by Farhan himself, culminated in the BITX20- a QRP 20 meter radio putting out 5 watts of power. It featured Bidirectional amplification stages, which greatly simplified the topology of the radio and therefore its construction. It was a homebrew hit, and many were built from schematics. Interestingly, the first group buy of parts was arranged by none other than Hans Summers, who now runs QRP Labs.

It wasn’t until 2016 that the BITX40 was made available as a pre-built kit. the BITX20 design was optimized for small scale mass production, and the BITX40 was born. So, what happened? Why is the BITX40 dead? Are there other options? Read on to find out.

The End of The BITX40

In the last week of October 2019, Farhan announced the end of the BITX40 as sold by HF Signals. He posted in the BITX20 group at Groups.io. Here’s an excerpt of what he said:

So Long, BITX40.

This is a little disappointing, but we had to pull the plug on the bitx40 run… We will miss this one, but all is not gone. Sunil continues to ship the bitx20v3 kits which can be modded to 40 meters. If time permits… we could update the original bitx with a more contemporary design… Until then, we will continue to see more scratch built bitxs, a kind of return to the roots.

Ashhar Farhan

And so it is. No longer can you buy a pre-built BITX40 from HF Signals. But this is not the end of the BITX, and it’s not the BITX20v3 kit Farhan mentioned. Read on!

The BITX Lives on: BITX Easy

One of the beautiful things about the BITX design is that it’s Open Source. Anybody can build one or improve on it as they wish, and they can also sell a kit if they want. Farhan has encouraged this from day one, and it is exactly what Sunil and friends at InKits (amateurradiokits.in) are doing. They’ve been making cases, accessories, and BITX20 kits for quite some time. They have a new product coming out called the BITX Easy.

The BITX Easy is a kit- soldering of thru-hole components will be required, and will be a lot of fun! It’ll be available on 80, 40, or 20 meters- the only difference in them is the filters. Otherwise, it’s the same radio. The board layout is improved over the BITX40 as put out by HF Signals, and there are other improvements too. I had a chat with Sunil and got some information about the BITX Easy and the improvements over the BITX40

BITX Easy Improvements

The BITX40 had some annoyances that, while not significant, impeded somewhat on its ease of use. Lets look at them one-by-one.

PTT Noise
When transitioning from transmit to receive and back, the BITX40 had some noise due to some minor design flaws. The BITX Easy includes the necessary changes to eliminate PT noise.

Birdies at 7200khz on 40m
The BITX40 has a very bad birdie at 7200khz,and it’s got to do with the Intermediate Frequency being at 12mhz. The BITX Easy uses a 10mhz IF, which solves this problem.

Mic Preamp
The Mic Preamp is improved, so no mods are required to re-bias the mic preamp to get sufficient output. With the BITX40, one has to either modify the radio slightly with a different resistor, or shout into the mic to get sufficient modulation and be heard. The BITX Easy solves this problem.

Synthesized BFO and VFO
The BITX40 originally had a crystal oscillator for the BFO (the IF frequency) and the VFO was VCO (Voltage Controlled Oscillator). The Raduino synthesized the VFO, but the BFO was still crystal controlled. The BITX Easy has both synthesized by the si5351 and so it is trivial to switch from Lower to Upper Sideband directly in software. On the BITX40 this would require modifications.

Improved Circuit Layout
The BIX40’s final amplifier (PA) was IRF510 based, and so is the BITX Easy. Unfortunately to use the BITX40 on 20 meters, major modifications were needed because the circuit layout itself caused problems that hindered power output. If one were to modify the BITX40 to work on 20 meters, they could expect only 1 watt of output. The BITX Easy will produce 3-4W output- Much better! The PA can also be ran at higher voltages (24V) so that it can put out 10-12W, even on 20 meters. This is a drastic improvement.

Where can I get a BITX Easy?

No release date or pricing has been announced, but you can be sure we’ll be posting about it here at MiscDotGeek when the the time comes. There’s also a 40W Amp kit that will be coming out for the BITX Easy to really boost output during this solar minimum. For now, feast your eyes on the PCB and prototype below. 73!

1 comment

    • Robin on November 6, 2019 at 9:13 AM
    • Reply

    While I am aware that many purchased the BITX40 as a cheap transceiver, it seems to me that only a few took advantage of the learning experience Ashhar’s design provided. It was an opportunity to not simply see, but to experiment with how a basic, somewhat “old school” heterodyne transceiver functions.

    Would be nice to see Ashhar enter the SDR arena with a new “basic” transceiver design.

    🙂

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