As with most things in life a change is as good as a rest. As I’ve been reading through the qrp-tech Yahoo group there’s been a host of information and advice regarding building QRP Kit especially the 1Watter and Rockmite ][.
Although I’m the proud owner of my homebrew oscilloscope a lot of the advice is geared towards those who don’t have access to that type of kit and that’s always a good thing. As such if you want to understand the advice, it’s worth having the tools at the lowest common denominator available. Enter the RF probe and the red board CCCC (Cheap Chinese Crystal Calibrator)!
I’ve been toying with the idea of building an RF probe for some time but basically couldn’t be bothered as I had no real need for one, but now I do! Originally I was looking at the plethora of hardcore homebrew ideas on t’internet but once again due to a poorly stocked garage/junk box I would have spent more money buying the bits to bodge in a true homebrew fashion than buying a prebuilt probe. Now that’s just not cricket as making stuff is 90% of the fun!
As a compromise Pacific Antenna’s kit was a reasonable investment and for once entered the country without Border Force inviting it into an interview room and probing it’s orifices and charging it a duty surcharge for the privilege! I’m of the growing opinion that being an amateur radio enthusiast would be better served by emigrating (not wishing to do a disservice to my fellow domestic enthusiasts, kit providers etc etc.) to somewhere warm! Cue Nathan Muir quote from Spy Game! (You can research that one yourself!)
Moving on before I get lynched, the RF Probe is a nifty little kit and if you’re starting out in this game and want a project for your Intermediate ticket, give it a look as it would tick the box for the practical build assessment and give you something in your arsenal if you want to build receivers/transmitters/transceivers at some point.
Not much for your money, but 15 minutes work gives you this
which plugs into your digital multimeter and gives you a useful diagnostic tool for future builds.
They even publish a How To Guide to assist you in getting to know your new toy.
The red board CCCC is another creature altogether. Chuck Adams K7QO who is the lead on the QSB-01 project hosts a site which is well worth a read where he uses the kit as an introduction to kit building as his first exercise.
Again, a simple build worthy of an Intermediate Licence project which gives you something worth having on your bench. When faced with a crystal, firstly don’t always believe what’s stamped on the housing of a crystal. Secondly, if it’s unmarked how do you know what it is? Thirdly, as builds progress in complexity you may be faced with the prospect of installing matched crystals in a transceiver to give a better IF (intermediate frequency).
By way of example, with the 1Watter build, at Phase 3 – Audio Detector Mixer (BFO) Installation, there’s advice to install three crystals from the supplied five which are closest in frequency. Now assuming all crystals are not made equally how do you tell who’s who from the innocuous metal cans? Further on there’s an advanced testing stage where the part built kit is tested against a crystal oscillator.
If you’re going to build something that works it’s worth giving yourself a fighting chance and for a whole £5 and a week/two week wait on delivery for a red board CCCC, on the scale of things it isn’t a bad investment.
Once again you get an assorted bag of goodies for your money.
Which with a little love and attention turns into this –
Here we are at the smoke test with a 12Mhz crystal under test and the board reporting everything correctly.
There is a need for a minor mod. In its native form this board is no good for crystals smaller than 10Mhz. By replacing a few capacitors with something more appropriate you will have a crystal calibrator more in tune to the frequencies utilised in all things amateur radio.