RC-14 - An Old Project Revisited

Way back in June 1987, the RSGB published an article in RadCom describing the "RC-14", a relatively simple "beginners" single band (20m) direct conversion receiver.    This was "kitted" by the then popular "Cirkit" emporium, and was offered at an attractive price to RSGB members.

This was, in my view a very well designed piece of equipment, and contained only three integrated circuits (one of the famous and rather splendid Plessey "SL" ICs and a couple of op amps configured as active filters with characteristics very similar to those of a high-performance crystal SSB filter) plus a varactor-tuned VFO, and the end result was a very pleasing receiver.

I built the receiver not long after it was published using the approved kit, and adapted it to my "bespoke" requirements - I disliked the flimsy enclosure provided and moved it to a more mechanically sound but less aesthetically pleasing aluminium die-cast box, and replaced the linear slider tuning pot (remember it was a varactor based design) with a rotary multiturn unit, albeit at great expense, and used it for a while (as you do) and moved on . . .

My version of the RSGB RC-14

Recently, I have become interested in the "QRSS" aspect of the hobby which is based around the transmission of very low power, low signalling rate beacon signals for extended periods which are received at various locations around the globe using PC-based "grabber" software.

Participation in this requires either the setting up of a "grabber" receiving station, or the use of a low power "MEPT" (Manned Experimental Propagation Transmitter), or in some cases both, though not necessarily at the same time!

Over the last few weeks I have been doing either and even occasionally both (!) using conventional equipment, and by "conventional" I mean "High Performance Japanese Transceivers", certainly as the receiving station, but it occurred to me recently that it was possible overkill using such high-spec equipment to perform such relatively mundane tasks.   In a flash of inspiration (or something!) I remembered my RC-14, and began to wonder if that could be dragooned into service as a QRSS receiver.

The built-in VFO, though adequate for general receiving purposes was certainly not of the required specification as a QRSS receiver, where frequency stability is a primary requirement, but the substitution of the built-in VFO with a crystal-based, or even synthesiser-based local oscillator would seem to be a Good Idea.

If you are following the argument, then by now you will surely have picked up on the mental thread . . .

And so, another project is born!

QRSS - And More on the Fascination with Propagation

I would be the first to admit that I'm a bit of an "odd fish".   Regarding my radio on-air activities I am most content just lurking in the background, listening and watching and taking note of what goes on whilst my transmitting activities are very sporadic.

I accept that in a way this is quite a selfish attitude - if all the other enthusiasts in the world did what I did, there would be very little for those like me to listen to!

Thankfully, we are all just that bit different, and the mathematics of probability dictate that the mainstream provides the required fodder for practically all of us.

However what I have learned to do over recent years is to make a contribution to the world of Amateur Radio in another way, by uploading information to the Internet in such a way that fellow enthusiasts can make use of it.

There are many ways of making this kind of contribution, all you need is a computer or computers, an Internet connection, and software which allows the uploading of information automatically.  There are a number of ways of doing this, each serving its own particular niche interest.

One I have been doing for quite a long time now is participating in the WSPR (Weak Signal Propagation Reporting) network.   This is actually one activity in which I make a regular transmitting contribution though that isn't essential.

One I have started to make a contribution to more recently is the self-administered network of QRSS enthusiasts.

For those not in the know, QRSS, which has been around for a number of years is a very slow signalling system, usually our old friend Morse Code but sent VERY slowly, used to modulate very low power (usually less than one watt) transmitters, and the reception of these transmitters is recorded using a suitable piece of DSP-based software, and the screen displays of these programs are uploaded to the Internet where they can be seen by interested parties.   The web pages displaying these are known as "grabbers"  Claudio, I2NDT maintains a web page of links to many of these "grabbers" - he calls it his "Compendium" and I would encourage you to click on the link to have a look.  In QRSS terminology, these low power transmitters are often referred to as "MEPTs" (Manned Experimental Propagation Transmitters) to distinguish them from "Beacon" transmitters, as there are licensing issues with the use of the latter terminology in some parts of the world.

I have built a little web page showing my own contribution to this system which can be found HERE. This will only be active for some of the time, as it does tie up equipment, but when it is active I make an announcement on the "KnightsQRSS" EMailing list, likewise when it is shut down.

I also have on the bench as a construction project a little QRSS transmitter from a QRP Labs (brainchild of Hans Summers, G0UPL) which will hopefully take to the airwaves on 30m very soon.  This will use my alternate callsign of G8LBT which, in Morse Code terms has a more even distribution of dots and dashes, and should, I think be slightly more useful as a QRSS source.

Expect more Blog contributions relating to this fascinating arm of the hobby, and in the meantime if you want to have a look for yourself at "live" QRSS transmissions, I would suggest you dial in either 7.000MHz USB or 10.139MHz USB into your HF receiver, and feed the output into a PC soundcard, and run appropriate FREE software such as ARGO or Spectran (my personal favourite is Spectrum Laboratory by DL4YHF), and see what crawls across your PC screen. www.weaksignals.com/ is one good source, as is DL4YHF's page if you want to download Spectrum Laboratory.