Issue #26: Guest Article - The RFBitBanger Transceiver and SCAMP Digital Mode

Hello T&E readers on QRZ.com . . . Our latest article is all about a brand new QRP transceiver, developed by Dr. Daniel Marks to support emergency communications. Dan's article details the radio, now a very unique kit being offered for $150, and describes the new Digital Mode he developed to support this radio. Now, alpha-numeric messages can be sent without the need for an external computer, making it the perfect mode for EmComm. And, on top of that, it sends CW and SSB! Dan and Dave will answer your questions in this forum discussion. If you missed the original discussion, it is available at this link on the QRZ home page. (You're missing quite a bit if you have QRZ access set up for some page other than Home). Regards, Dave Jensen W7DGJ

 

What a fantastic idea! This kit will be on my ever growing bucket list...

 

Thanks Chuck. I'm hankering to order one of these as well. I really like the idea of the new digital mode, and I can definitely see how this will impact the "prepper" ham community in particular. But, it would be great fun to have a digital mode that worked from a mountaintop without a laptop computer to drag along! And, what's the worst case here, you plug in a key and do CW? Cool! Dave

 

I am aware of the potential utility of the RFBitBanger to preppers, which is fine, but I have more generally been uneasy at what's been going on for the last few years. I think what the electronic industry material shortages show is that unfortunately the virtuous cycle of technological improvement can go backwards because if one industry falters, other industries that depend on that industry can also falter as well, and many industries are now dependent on electronics and computers to function. The RFBitBanger is intended to be an example of technological resilience which minimizes the need for the most advanced electronics to make a long distance communications radio.

Thanks for your interest because I think the ideas of technological resilience should get more attention.

 

Very interesting, probably need to do more research on this topic!

73

 

I have a question for Dan . . . I know when you developed it, Dan, that SCAMP was for emergency use as you wanted an easy-to-build radio that could send and receive a digital mode without needing an external computer. But was it also something that could be picked up by the digital ham to have fun with on a Saturday morning? Or is it a mode that you think will only be for EmComm use in some future scenario?

 

I have been corresponding with W1HKJ regarding possibly including SCAMP as a mode supported by fldigi so that it can be a mode usable for ordinary QSOs and not just for emergencies. It is quite possible to implement SCAMP on a standard computer, soundcard, and transceiver setup. Communication between the RFBitBanger as a DSB receiver and a transceiver in USB should be relatively straightforward. One potential difference is that SCAMP is designed to be usable even if the sideband setting is reversed (that is, LSB is configured for USB or vice-versa) as this just swaps the mark and space tones. An implementation on a SSB receiver needs to determine at the beginning of a transmission if the space tone frequency is less than or greater than the mark tone frequency, in case the transmitter has its sideband setting wrong.

Some have asked for a version of the RFBitBanger that basically acts just as a modem without including the RF transceiver so that it could be connected between a computer and a transceiver. I have not quite worked out all of the details of this. If the transceiver is configured with the correct RIT (receiver incremental tuning) this should work fine, but if for some reason it is not possible to configure RIT getting the modem to work correctly with the transceiver gets more complicated. I would like SCAMP to be somewhat tolerant of configuration errors or radio limitations.

So the short answer is yes, it should be quite usable as a mode for ordinary QSOs. A complication comes in to ensure that two stations with opposite sideband configurations can still talk to each other, but I think that will be worked out.

 

The initial 95 RFBitBanger kits have sold out. More will be offered soon.

 

This is great Dan! I hope that one reason for this was your article here, Dave

 

I would buy this just for SCAMP.

 

I've been following this for a little while, hoping to see a computer software implementation of SCAMP available to experiment with, perhaps even on my little QRP Labs QDX data transceiver.
It's been six months - is there any updates of interest for us?

Thanks, and best wishes on this project, both hard and soft sides of it!

 

Hi Franz. I was just talking to Dan Marks the other day . . . I'll ask him to come back here and update you, either online with the forum or in a direct QRZ message. Dave J, W7DGJ

 

I have to say that Dr Marks efforts to move the ARS community forward with a new mode is most commendable.

In looking closely at the finished product, I believe the good Dr Marks has overestimated the 'average hobbyist" this seems to be targeted at. Both from a skill level and from the 'what parts are on hand or might be gotten' for building such a device. I've no doubt that a few to several handful of folks could make this happen - but the 'few' part is, IMO, more realistic.

Along the lines of 'last ditch communications' is the example of the 8-part transmitter for 40m or 30M. One of the parts is, by necessity, a crystal - and likely the hardest to source. To support this as a system, it supposes a common portable Shortwave set with BFO/USB/LSB would be available.
(The EMTX: How to build an 8 component 40/30 meter QRP emergency transmitter | The SWLing Post)
It also supposes a skilled CW operator and a ready audience at the other end.

All the other bits - functioning nets, a known and open frequency, trained operators and an overarching agency (of any kind) to act upon any 'emergency' communication as well as to control said communications -- has to be part of the total package. If any of the items listed in this past paragraph are missing - you have something that will result in a net zero gain.
***

As for the SCAMP part - getting this ported into a commonly available application, as noted elsewhere, would probably be the best chance for use - again, presupposing the "functioning nets, a known and open frequency, trained operators and an overarching agency" as noted above. Nothing operates in a vacuum.

Finally, these is at least some competition for this segment of the communications continuum. The most prominent one that comes to mind is the PrepperCom product. It is nearly 'plug and play' and requires little skill past typing and antenna setup. At nearly $400 for just the modem part, I've not seen any chatter showing the level of acceptance/use within the ARS community. I doubt the vendor will release any sales figures and that is as it should be.

Next, the QRP Labs QMX (about$200 for a completed unit, shipped) which supports several existing/popular modes to include WSJT-X, JS8Call, some fldigi modes e.g. RTTY, Olivia and more. A PC/tablet is required to play with the digimodes. These little rigs often appear in UTOOB videos and posts here on the Zed. The QRP Laabs page would indicate sales of both the kits and completed units is brisk. 'Wildly popular' might be a bit of an exaggeration, but not by much.

In the same class (5 watts) is the SW3B,($180) which supports CW and SSB/SWBCB for RX. Dale has noted the sale of "Over 1000 SW-3B’s have been sold to 43 countries worldwide." These little rigs often appear in UTOOB videos and posts here on the Zed as well.

The 'functioning nets, a known and open frequency, trained operators and an overarching agency' comment applies to all of these units as well.
***

Thanks for the update, hoping Dr Marks drops by to comment on observations here.

 

To comment on some of your observations:

- It's a tall order to ask the average hobbyist to improvise a radio. My intention was to make a radio using the most commonly available parts, not the fewest parts. The ATMEGA328P and the SI5351A are very common and there are even Chinese clones of these parts. My thinking is that many of these other designs use parts that may be harder to find in the future than these parts. Even if ATMEGA328Ps and SI5351A stopped being made today, there would be millions available, and given how many of these are being used, these are not likely to be discontinued soon. Other parts are generic, and even parts like ferrites could be scrounged from EFI beads if needed. Compared to most transceivers with similar capability, the RFBitBanger uses relatively few parts.
- It is designed to be self-contained, and not require any other computer or radio for receiving. It has a built-in keyer, automatic sender, and morse code decoder, and the decoder works well with machine sent code and decently well with paddle-sent code, and can be operated using a keyboard rather than a paddle. In this respect, it is like the PreppCom radio, but can be built from found parts, more like a true "prepper" radio as one can build and repair it oneself. The radio also send/receives RTTY 45/170 as well. The radio supports external control, so one can also use FT8 or other digimodes using a computer or tablet, like the ADX or QMX. The main disadvantage is that one needs to use the ADC/DAC of the tablet or a soundcard, as there is no USB soundcard.
- SCAMP is quite new and I am still working on getting it more widely adopted. But its intention is to be the most simple and reliable digimode that can be implemented in a simple 8-bit microcontroller. It supports features like FT8 such as synchronous signaling and forward error correction despite its simplicity. It is also designed to have a user selectable level of redundancy at the transmitter so that one can spend a long time getting a critical message through if necessary. In this way I hope to get a simple radio with a few watts of transmit power to be able to reliably communicate in unfavorable band conditions in an emergency. But the benefit of SCAMP over CW is that nets could be more automated, yet not require a full digimode setup including a PC or tablet and a transceiver to be able to access it.
- The cost of the components is quite low: a PCB populated with only the surface mount parts, including the microcontroller and PLL costs about $6.50 in qty 100. The most expensive part is about $2.00, which is the ATMEGA328P microcontroller itself. The cost of the magnetics (toroids, about $0.50 each), jacks ($0.15 to $0.60), and the display ($1.25) dominates the rest of the cost. Still, it has a component cost much less than $20 if only a couple of band modules are desired.

I agree adoption is likely to be an uphill battle, and I have not been able to put the time I would like to into moving that forward lately. It was already two and a half years of work to design a new radio and digimode to go with it. I hope that lots of others sell kits of it, as all the plans are completely open, and it can be made and sold by anyone. It could likely be as cheap or cheaper than any of other mentioned radios, except for the simplest radios like the Pixie for example, but the RFBitBanger offers features and automation that would be very helpful even for an experienced user. I think there is a need for a simplified transceiver that is not as rudimentary as the one-transistor transceiver, but not as complicated as a full computer and HF transceiver setup, especially one that could potentially cost in the tens of dollars and be widely deployed and kept in reserve, and that is what I intend with the RFBitBanger.

73,
Dan
KW4TI

 

Why yet another conversational digital mode?

There are lots of asynchronous digital modes out there that are extremely hardy and noise resistant.
I believe many are public licensed.

I was having an Olivia 8/250 conversation the other day and there was an operator who decided he needed to TX on PSK31 on my freq.
There was no change in the copy rate, still 100%