Sunday, 1 March 2015

Pluggin' Away

More development of the Plug-In BITX Module concept...

Having taken delivery of a bumper bundle of 40 pin 0.1 inch female header connectors from Banggood for the price of a pint of beer (including shipping a third of the way around the world)...


I was in a position to move my plugin BITX from its premium plot on a solderless breadboard to a permanent and inexpensive brownfield location...


My three K and H AD-13 breadboards are great for the development of pretty sophisticated projects. But recently, they have become the homes of almost permanent installations, blocking them for their intended function of development canvasses.

Until yesterday, there's been the aforementioned BITX, the Arduino SDR system and the Digital Tube Screamer squandering premium space on my large breadboards...


Some correspondents have asked about these breadboards - including questions about suppliers. I took a look a few days ago and it seems that my original supplier (Maplin here in the UK) no longer stocks this model - so even I can't replace these  precious resources. Freeing up the land for more development is important - but it wasn't my only motive.

I've a couple of talks coming up this month at radio clubs in the North West of England, where I'll be mentioning the Parallel IF method, and having a convenient, robust demo system will be an advantage. Plus, I wanted a system I could put into my luggage for the big trip to Ohio for FDIM.

Here's an aerial view of the (nearly) finished, but fully working unit...


Power comes in at the top, RF from the antenna in at the left hand side of the picture and AF output to speaker or 'phones from the right. I built a tuning control, push-buttons and space for the display onto the board - to form a complete user interface. The system is self-contained apart from power supply, speaker and antenna.

The elements of the system are emphasised in the annotated image below...


Most important is the pair of parallel IF plug-in crystal filters seen close to the middle of the system. Otherwise, there's a straight-through signal path from left to right (for receive).

As I write, I've been listening to the build-up to the RSGB news on 40m, with the unequal struggle between people exciting the ether at 7150 kHz with UK legal limit and "QSY Old Man" and others from across the seas with a more cavalier approach. Highly entertaining!

To close, a little story for St David's Day...

I was inspired by Mike Richards, g4wnc's writing in the current number of RadCom - so I splashed out on a new Raspberry Pi 2 Model B...


As you see, I got my Pi (and a little 8GB SD card with an OS already on it) from the nice folks at The Pi Hut (usual disclaimer).

I'm no stranger to Raspberries - here's the newcomer sat next to the slower original model B, which it is now upstaging...


Following g4wnc's suggestion, I thought I'd try the Pi with FLDIGI - so, at risk of poisoning the feckless, I set about ordering a Daffodil USB Sound card. Those of you who have been near Google today will know that the Daffodil is the national flower of Wales, of which David is patron Saint...



I could have ordered a "Daff" from a certain global on-line retailer (of which I am a frequent and satisfied customer) associated with powerful women and rain forests.

Instead, I ordered from an outfit called Digital Daffodil through that equally ubiquitous on-line auction site you will have heard about. I handed over less than half the money I was asked for by the on-line retailer (postage and package included) and my Soundcard was in my grubby hands in LESS THAN 24 HOURS. That's what I call good service! No affiliation - except as satisfied customer.



The new Pi - and FLDIGI - work FB.

Let's hope Digital Daffodil's premises are nowhere near food outlets!

...-.- de m0xpd


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