Latest project built on a stormy day. Outside the weather was awful, Storm Doris has hit us hard and my poor antennas are suffering!
Not a good day to go out, so I decided to stay in my shack and do some building. I want to build a morse code oscillator so that I can practice my morse using my old 1940 morse key. Favourite is to make an oscillator using a 555 timer ic. I have lots of these, so I found a suitable circuit and started to build it. Works fine, can adjust volume and tone using the small presets. A nice little project to keep me busy on a wet and windy day!
I am really enjoying having a stock of components to build projects again, last year I bought some great packs of components from ebay and now I am using them with my projects.
This was a classic project! Back in 1969 there were very few Radio Amateurs transmitting on VHF (2 metres) along came this project in Practical Wireless which used a previously unknown device called an FET (Field Effect Transistor) these devices could work at very high frequencies (VHF) so I decided to have a go at this one!
After spending all my pocket money on a 2N3819 FET, the CQ2 began to take shape. I mounted the receiver on an aluminum front panel which was originally built to house an oscilloscope that I began to build when I was at school. (not a good idea!!) The metal chassis caused havoc with the tuned circuit, so I rebuilt it on a piece of plywood! When the receiver was built I made a QUAD ANTENNA for 2m. The receiver was tuned by squeezing or lengthening the coil and fine tuning with the variable capacitor. Very tricky, as the receiver was a super-regen it was inclined to ‘take off’ without warning. This is what first got me into listening on 2m, I was able to listen to local amateurs using this little beast…
Now, almost 50 years later, I decided to build another CQ2 just out of curiosity to see if I can build a simple project from scratch. This included collecting all the necessary components. One obvious problem is the audio output stage. In the original circuit it used an OC44, OC71 and OC81 transistor (state of the art in 1969) I decided to use a TBA820M for the audio output stage and proceeded to build it first just to make sure that it would work.
This time I built the CQ2 on single sided copper clad board, so much easier to mount components in the ‘dead bug’ style.
The completed circuit used a 2N3819 FET and BC108 in the RF circuit. The audio output worked fine, but had problems with the RF side. As it is a super-regen receiver one of the potentiometers controlled the ‘regeneration’ trouble was…no regen! First it turned out that pot was open circuit, so I replaced it with another, but still no regen. Hmmm…I seem to remember having this problem the first time around! After some thought I remembered that the pin out drawing of the 2N3819 FET in the article is wrong, the source and drain are back to front! Great…so I reversed the leads, still no regen. Then I remembered the same problem last time…the 10pf capacitor across the source and drain…it don’t work with a fixed capacitor, it needs to be a ‘twisted wire’ to get the right feedback. When I changed this the CQ2 sprung into life! Now I can listen to all kinds of VHF data transmissions and random audio signals, working fine… just got to find 144mhz and listen to some amateur stations.
I have been saving this kit for the long dark Winter nights. I bought the JJJ Electronics kit back in April last year after spotting it on E-bay. It is a direct conversion receiver that covers 80m and 40m with an option to add an extra board for 20m and 15m. I chose to add 20m and the extra board was included with the kit. The receiver comes with a very nice white case complete with decals and frequency counter for the front panel display.
I started to build the board by following the very comprehensive instructions which are supplied with the kit. I took my time with this one as this is probably the most complex project I have attempted recently. I have to say that the instructions and parts for the kit, including all the wires, which are colour coded, have been well thought out. The capacitors in the VFO are separate and marked ‘NFO’ as they have a higher tolerance than the other capacitors. I spent about an hour each night for about a week to complete the board. I spent a bit more time wiring up the switch and other wiring. Again, the instructions were easy to follow.
When I had completed the receiver it was time to test it. When I switched it on it worked!
You have to set the VFO coil and filter to make sure that the digital frequency counter is displaying the correct frequency for each band. I connected my antenna tuned the large knob, I could hear lots of stations on 40m, particularly on cw. The cw filter works well and is also best for ssb stations as well. The ssb filter is a little wide and tends to reduce the output.
I am quite impressed with this little receiver considering it is direct conversion. It seems quite sensitive and the audio output quality is good, the simple RF gain is very effective. Only one problem is the tuning, the gear system has a lot of backlash and it is tricky to tune in a station on ssb, however, once tuned it seems quite stable.
When I first bought this kit I wondered if the receiver could be used on Topband 160m. JJJ Electronics don’t supply a board kit for 160m so I sent an e-mail to them asking if it would work on 160m with the coils being changed on one of the add-on boards. The reply was yes it is possible, but they don’t make the components for 160m. I decided to order a couple of coils from Spectrum Communications after another e-mail to recommend the correct coils. The coils arrived a couple of days later and I fitted them into the 20m add-on board replacing the TOKO coils that came with the kit. The new coils worked perfectly! So now I can listen on Topband as well as 80m and 40m.
Conclusion…A nice simple little receiver, works well and easy to build by just following the very clear instructions. Reminds me of my very first receiver kit back in 1969 called a Roamer 7 which was a DC super regen receiver which worked on ‘Trawler Band’ I later found out that this was Topband and heard my very first radio amateurs!
Gosh…how things have changed, I remember building a simple transistor tester back in 1969 taken from an old Practical Wireless magazine.
Tonight I have just finished building this nice little kit. Measures transistors, diodes, L, C, R, frequency counter, function generator and a host of other things. Works well and has nice display.
Got it from ebay for less than £10.
A few weeks on and my ‘toys for boys’ train set is coming on well. I have been adding some content to the rather 2D trackmat in the way of trees and hedges. I have to say that this modelling lark is a bit addictive and you really have to be careful what you spend. Some small things are quite expensive, even from eBay, you have to hunt to find bargains.
My layout at the moment with added walls, hedges and buildings.
My Christmas present was a Flying Scotsman train set, the detail is awesome and runs like a dream on my track. With the rest of my Christmas money I also bought the Tornado Pullman set, again, the detail is amazing and goes well with my Flying Scotsman.
So having come this far, what shall I do next? How about controlling the trains using a laptop computer? The next logical step with Hornby is to change the analogue set up to the DCC digital controlled set up. This is expensive, so I came up with a nice analogue version…
Searching the internet for ideas I stumbled across a company called ‘PC Control’ www.pc-control.co.uk they produce a very easy to use interface and software to control motors in model trains or other things including servos. I was impressed with ‘Motor Bee’ interface board and ‘Motorway’ software, ideal for my next step without spending a fortune. www.pc-control.co.uk/control/products/boards/motorbee.php I ordered the board and tonight I set it up with the railway layout. It works well! The board is easy to wire up and I can control two motors that run both forward and reverse. The ‘Motorway’ software allows to program the motors and follow sequences of instructions. The interface also has digital outputs and digital sensor inputs as well. (This is a nice project for the future) You can also program DLL with Visual Basic to take things even further. I found this quite helpful www.pc-control.co.uk/computrain.htm
The Motor Bee interface board
Motorway Software controller screen.
Today I came across an interesting website http://www.heywhatsthat.com A strange name, but this site will plot your line of sight RF take off from your VHF / UHF antennas showing the torrain and hills in the way. It is also what you can see on a clear day from your own QTH or portable site.
Here is my take off from my QTH. (The crosses show hills in the way)
Looks like I have a good take off due South!
I have always been fascinated with steam railways. Recently I have spent quite a while at the East Lancs Railway at Bury and Ramsbottom. It is so amazing watching these renovated steam trains running. A few weeks ago I watched the Flying Scotsman and Golden Arrow at ELR. Today I watched the Santa Special leave with my daughter Jacquie and grandson Cameron for a fun day. Now it is coming up to Christmas, my wife Kath has bought me a Hornby Flying Scotsman train set.
I already have a train set, bought it a few years ago and set it up on the floor in my attic. It was just a simple oval, nothing special. After a while I put it away and didn’t do anything else because it is such a pain to set up. When I knew that I was about to aquire a Flying Scotsman I thought about how I could set this up on a table in the attic. With help from my son Paul we decided to build a table and layout. This has been an interesting project, I used the track that I already had along with some more bought from ebay and found a great model shop in Whitefield that sold just about everything both new and second hand.
Now I have a nice model train layout, today I bought the stations from Argos, which although a bit expensive, is a worthwhile addition. I’m not a real enthusiast, but have always wanted to build my own permanant set up and be able to play with it whenever I want to!
Still working on the project…more later!