XBM80-2 80m ultra-simple rig

This has been on before, I know.

Some years ago, I wanted to see how simple one could make a rig that actually worked. There is no doubt at all that the rig can be made better with more experimentation with values and other things, but I was quite surprised that something this simple worked.

Please do not (ever) be afraid to use my designs as starting points. If you can make something better, great. If it totally fails, just start again! 

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2 .

XBM80-2 transceiver webpage

As Jason M0NYW has kindly done a PCB layout and provided the Gerber files, I was hoping to add a link to these on my website, but I cannot create a public link to my Google Drive zip file. Not sure if this is a temporary issue. 

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2 .

UPDATE 1700z:  I think I have solved the problem and the link to Jason's Gerber file is now on the webpage. 

XBM80-2 transceiver

One of my Facebook memories this week was of some QSOs over 100 miles by AA1TJ using my little XBM80-2 transceiver in 2010. I did not realise it was that old!

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2 .

Ultra simple 80m transceiver

If you get bored this holiday, you may get some ideas from the XBM80-2 transceiver on my website. It really works!! You would be hard pressed to find anything simpler.

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2 .

XBM80-2 QRP transceiver

Today, I had an email from somebody in the Netherlands about this transceiver.  He was getting no audio. Recently someone told me that crystal earpieces do not like DC. If this is correct, I suggest a capacitor is added between the collector of the audio transistor and the crystal earpiece. A 0.1uF or greater should be suitable. I also suggested that the audio transistor must not be in saturation. If need be, the bias can be altered to put the collector of the audio stage to mid-rail.

As I always say, do not be afraid to experiment.  If the circuit works better with different values then change them! With something this simple you could always start again, HI.

How simple can you make a transceiver?

Many years ago, I built the XBM80-2 80m CW transceiver. It never got cased, but shows how simple a transceiver can be! Somewhere recently I was told that it is a good idea to keep DC from hitting the crystal earpiece. If this is the case, it is probably worth adding a DC blocking capacitor between the audio transistor and earpiece. I have no idea if this is an old wive's tale or fact.

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2 .

Ultra-simple 80m transceiver

As mentioned before, there is often a compulsion to get results with the fewest parts. Usually, this involves a compromise, often with the RX. This is the case with this rig. It certainly works, but be careful not to call over a co-channel station.

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2

XBM80-2

 

Yesterday, I posted the 10m Lesser Chirpy. This was based on the 80m XBM80-2 QRP CW transceiver which is shown here. 

You would be hard pressed to make this transceiver much simpler! Do not be afraid to experiment - I am sure you can do better. 

S1 provides offset between RX and TX by shifting the crystal frequency, how much will depend on C1. You could always make C1 adjustable so the offset is what you want.

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/80m-xbm80-2 .

XBM80-2 transceiver

This was a very simple 80m CW transceiver that I designed and built many years ago, apparently in 2010.

Like all my designs please take this as a starting point as you may very well be able to do much better. As you can see this was just experimental. At the time it was fun. These days, such experimental work is probably beyond me since the 2013 stroke.

See https://sites.google.com/site/g3xbmqrp3/hf/80m_xbm80

A very simple QRP transceiver for 80m CW - the XBM80-2

I received this yesterday from Martin G0PJO:

Hi Roger,

G0PJO's rig in the field

I thought you might like to know that the QRP rig works and I’ve just returned from the field (the only place I can put up my 80m dipole) having had a successful QSO with G3XVL just over 4.5 miles away in Ipswich. He gave me a report of 599. The only issue that I had was with the audio level on receive. I’m using a crystal earpiece and I really had to listen but we managed a 30 minute+ QSO!

Many thanks for publishing the design.

Martin

G0PJO

This very very simple transceiver for 80m CW is on my website. See the direct link at  https://sites.google.com/site/g3xbmqrp3/hf/80m_xbm80.  There is also a video link. 

For all my projects go to http://www.g3xbm.co.uk . Because of my poor health I have not built anything original for some years.  I very much hope to get back to experiments soon.

VK2ZAY's version of the XBM80-2 transceiver

A few more people have been making the XBM80-2 transceiver. One is Alan Yates VK2ZAY who has made a de-luxe version with some refinements and additions. See it on his blog at http://www.vk2zay.net/article/238

Problem with Sprint Layout 4 PCB package

Trying to do a small PCB for the XBM80-2 80m micro-transceiver using the Sprint Layout 4 PCB layout package I hit a problem: wanting to use a single sided PCB for low cost I did a groundplane fill. Then I wanted to connect certain pads to this. I cannot see how to do this! Several people have offered advice, but nothing seems to work: any attempt just results in a new clearance area being created. In the end I gave up and filled in the ground as another track and join it to the pads manually. The resultant draft PCB (1 inch square)  is shown here. I have not built it on a PCB yet, so this is only a suggestion. An SMT version could be half the size - i.e. VERY tiny indeed.

XBM80-2 video and PCB (draft)

A short video about the XBM80-2 80m CW micro-transceiver. This is built "ugly style" on a piece of copper clad board. It will get put in a box soon! I've also been having a go at a PCB (just 1 inch square - 25mm x 25mm).

Improvements to the XBM80-2 80m QRP transceiver

A few small value optimisations have improved the XBM80-2 transceiver. I've optimised the collector circuit values and this has resulted in 120mW output (was 60mW) from a 12V supply. The sensitivity is a little higher, the backwave level is lower, the amount of AM breakthrough from medium wave broadcasters is lower. At 4pm I was hearing DR2010O in the Ruhr area of Germany working all over Europe and could copy almost all the stations that he was working but I failed to break the pileup with 120mW. I'm beginning to think this little transceiver could be really useful. There is no reason why it should not work well on any band up to 28MHz (with less output) with a fundamental crystal. I'm wondering how it will perform on 50MHz with the collector tuned to x2 crystal?

XBM80-2 heard at 430kms

This evening I tried listening for my 60mW CW signal from my XBM80-2 80m micro-transceiver on the on-line SDR at Twente in Holland. The signal was clearly audible at RST529 when I keyed the transmitter slowly! Distance is 430kms (267miles).

Another XBM80-2 QSO tonight

This evening I worked G6ALB 3kms away on the XBM80-2 60mW ultra-simple 80m transceiver getting a 599 report. Andrew was copied at 599 when he was using his 300mW TR6C4 simple valve transceiver which has a regen RX. Andrew also sent test transmissions using his signal generator and I was able to copy his signal when he was running 3mW output. So, the conclusion is, as AA1TJ has already proven, the design is quite a useful one and VERY simple.

AA1TJ's success with the XBM80-2

Mike Rainey AA1TJ has built his version of the XBM80-2, but LESS the audio stage, using instead his 600 ohm magnetic headphones via a transformer, and has managed some QSOs well over 100 miles. He changed the emitter resistor to 15k to reduce the signal radiated on key-up (backwave) as well as made a link coupled bandpass filter output/input circuit. This would reduce the amount of AM breakthrough usefully.

XBM80-2: a 2-way QSO and report

This morning I worked M0DRK using my tiny 60mW XBM80-2 transceiver I designed last week. It uses just 13 parts plus the crystal, earpiece and optional frequency offset switch. My report for Derek was 599 and he gave me 599+40dB. Derek is in the same village. Also monitoring was G4LHI in Huntingdon 32kms away and he reported my signal was as strong as Derek who was running 5W.  In fact 60mW is only going to be about 3 S points down on 5W. I also heard GM3JUD when listening on the XBM80-2 on 3.560, but was unable to raise him.

Simple 80m CW transceiver

Want to try something really simple?  I am now waiting to have a QSO on 80m CW using my XBM80-2 transceiver that I put together in the week. Pout is 60mW. The only switching between TX and RX is by the morse key. Additional offset can be had with the switch in series with the crystal. Skeds with local stations are being arranged.