Mastodawn

Aeaeaeargh.
Some friends have challenged me to design a working ham transceiver I can make an actual QSO with, with a damn one euro (1€) component BOM, from LCSC.
Thankfully excluding shipping, so don't have to build something like 25 or 50pcs to hit the price point. :D
But it's going to be a real challenge, as I don't actually know CW.
And I want a synthetized rig for some band VHF and up. Quite possibly 2m.
As 23cm seems to require a 1,5€ or 2€ BOM to pull off.

Yes, this post is in part to vent and in part to solicit ideas from people.

If you want to see some of my thoughts and LCSC deep dive finds, they can be seen here:
https://prkele.prk.tky.fi/~ftg/files/oneeuroLCSCchallengeRadio.txt

Andrew Zonenberg Dec 25

@ftg a 1eur bom?? That's slightly nuts lol. Good luck.

@azonenberg
Exactly! It's an insidious challenge.
It looks mayyyyyybe doable.
But requires being really thrifty with the parts and if I want it frequency agile, the PLL is going to be hacky as hell.

The person who challenged me has already shared a picture of their 2m rig's board and asked when I'm ordering pcb's for mine. :D
And I'm still like m8, I'm not even sure I can make the PLL work in the way I think I can. :|
So I some prototyping and simulation ahead.

Onno (VK6FLAB)Dec 25

@ftg @azonenberg there are dozens of single transistor transceiver designs, AFAIK, some even do voice.

@vk6flab @azonenberg
But are they frequency agile?
And yeah there are those.
One friend who's not participating, Mr. "Extremely tempting, but I want to get my phase noise measurement set done first."
Was trying to get me to do a 5.6GHz band super regen with separate transmitter VCO that's locked with a translation loop PLL.
But on 2m I have a chance of actually making a non-gimmic QSO.

Andrew Zonenberg Dec 25

@ftg @vk6flab I've never been into the minimalist / hacky side of amateur radio.

I want to be making phased array radars, or moving Gbps of data using high order QAM between X-band dishes, etc. Not going for contacts on FT8.

But have fun, certainly seems like a challenge.

@azonenberg @vk6flab
Yeah there's the pushing the actual state of the art and in general pushing the envelope.

And then there's this side of trying to see if 1eur is too cheap or not.
And can something practical be built.
Tbh I think the minimum for something that's actually enjoyable to use would be around 3-5eur BOM, as that would allow for a screen.

Matt W1CDN Dec 25

@vk6flab I'm interested in some hints on single-transistor SSB designs...

@ftg this is a rad challenge, love it!

Onno (VK6FLAB)Dec 25

@W1CDN @ftg @azonenberg

Starting point is the Pititico

https://yo6dxe.com/pititico-cw-transceiver/

Pititico CW Transceiver - 40m Band / 550mW

Pititico CW transceiver, designed by PY2OHH. One of the smallest and simplest transceivers designed around a single 2N2222 transistor.

DX EXPLORER

@vk6flab @W1CDN @azonenberg
Pititico is very cool, but sadly CW only.
And if I had to learn CW for this challenge, it would never end.

But PY2OHH has piles of neat designs.
https://www.qsl.net/py2ohh/trx.html

QRP Homebrew receivers, transceivers, transmitters

Andrew Zonenberg Dec 25

@ftg at domestic distributors I'm not even sure i could get a fixed frequency 144 MHz oscillator for $1 much less modulating it

@azonenberg
Yeah unless it was some pixie or some AM toy it would be 100% impossible with western distros. Maybe something with TME.eu. But still very hard.
Can't get 7cent MMIC's and 2cent RF transistors locally.
The current PA is going to be a 0.0200eur 2SC3357, for example.
Ancient transistor, but cheap. I hope to get 100mW from it.
Which should allow me to hit the local 2m repeater.
I have had multiple contacts on the 70cm one on the same mast with 50mW.

@azonenberg
Also, speaking of 144MHz and domestic suppliers, I think one could get a TX going and maybe mixing in the PA on RX within it.
Cheapest 24MHz xtal's with TWO in parallel, VXO'd up and then multiplied twice (x2 and then x3). Or maybe 48MHz xtal and just x3. But the 48MHz might be more finicky to VXO up to get over the lower band edge.
But unfortunately it would not be very frequency agile.

There's the whole regenerative angle, but they are hard to impossible to tame into compliance of any sort.

Adrian Studer Dec 25

@ftg there’s the MS5351M, a clone of the venerable Si5351A. Cheap, but it will still use up a substantial portion of your budget

@adistuder
Yeah, a 5351 and a microcontroller to control it would blow the whole budget.
Thus the real challenge in this, if trying to make something frequency agile.

@ftg Single band SSB should be manageable if you do a bunch of bitx-like crystal filtering.

@AMS
Would have to have an analog VFO, but yeah, with a 4xtal SSB filter like in the original BITX20 and not 8xtal Cohn like in the µBITXit might only consume 10% of the budget.
It is a challenge that does look doable, just decently hard.
The tens of cents start to stack up.

Marsh Ray Dec 25

@ftg Perhaps you could use a cheap microcontroller to generate a sub harmonic square wave and filter the heck out of it.
Some open drain outputs could perhaps make a tayloe detector

Philip Bragg Dec 25

@ftg Can you get a 5V regulator, some sort of reference crystal, a 74HC4024, some 1N4148s, 74HC4060 and 74HC4046 for that price? I reckon even that minimal synthesizer, which will still need multiplier chain or mixer to hit 2m, will be past a single €

Philip Bragg Dec 25

@ftg You may be able to do a 1MHz VFO mix synth for less

@synx508
Cheapest 74HC4024 is €0.3458
Cheapest 74HC4046 is €0.3908 (two in stock) or €0.6195. But there's tons of other 4046's as well.
Cheapest 74HC4060 is €0.1093.

So total for those would be 0.8459, before any passives, voltage regulators or even the VCO itself.

Btw a Toshiba 74VHC4040 is specified to 210MHz and costs €0.1879.

Philip Bragg Dec 25

@ftg Maybe you can use a XOR as the PD if you've got a failsafe VCO config

@synx508
Yeah a XOR is the current plan. as a single gate one is cents.
But I'm so tempted to add one 7474 and some BJT's and make it a proper phase frequency detector with charge pump output.
The very strict budget does help with scope creep. 😜

Philip Bragg Dec 25

@ftg I always forget those single gate ICs still exist

Rue Mohr Dec 25

@synx508 @ftg there is an '08 in there I think....

Henning Paul DC4HP Dec 25

@synx508 @ftg What do you mean by "still"? I learnt about their existence only 15 years ago.

Philip Bragg Dec 25

@hennichodernich @ftg There are so many ICs from that era that have since vanished, while older ICs have survived. The last time I tried to source some "tinylogic" devices I found that the range was smaller. I'm not sure if that was a temporary thing, though…

@synx508 @hennichodernich
Yeah that's the problem with the newer logic families. They just go away or are single source.
While 74HC just continues to be available in SOIC.
But the small, single or double gate parts are also good for fast designs that use them for RF, as grounding, bypassing and general layout is much easier to do well.
After other projects are done, I want to see how sharp edges I can get from a single gate NAND or inverter in DFN.

Philip Bragg Dec 25

@ftg @hennichodernich This has reminded me that the venerable 4046 was finally designed properly for typical applications and then discontinued https://www.nexperia.com/product/74HCT9046AD

74HCT9046AD (PLL with band gap controlled VCO)

74HCT9046AD - The 74HCT9046A. This device features reduced input threshold levels to allow interfacing to TTL logic levels. Inputs also include clamp diodes, this enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

Nexperia

Philip Bragg Dec 25

@ftg @hennichodernich (and the 7046 with the actually usable lock detector circuit, but that seems to be available still)

@synx508 @hennichodernich
Yeah the demise of 9046 was a damn shame.
I do still have some 7046's in my stocks, waiting for a project.

Henning Paul DC4HP Dec 25

@ftg @synx508 I consider onsemi's NC7SZ family as second source for 74LVC1G and both are easily available.

@hennichodernich @ftg @synx508 We use these things by the dozen at work for line drivers, re-drivers, signal gating, and voltage translation. Anything doing functional safety uses a pile of them to help manage fault exclusion.

DJ-Bauer Dec 25

@ftg
If it helps you, I'd take one if you can ship within US or Europe and cover shipping.
That sounds like a fun trinket!

@dbauer
It needs to exist and work for that to even be a consideration. :D