Wednesday, August 29, 2012

Toroids and an Audio Amp for the RockMite

I’m still awaiting the arrival of the 30 meter RockMite, but its early days yet and normally takes around a week to ten days to arrive.
I plan to add all the mods I’ve done for the 40 and 20 but also have a play at changing L1 for a toroid. I’ve taken the details off the RockMite forum and its look pretty easy to do, but as I’ve never done any windings before I’m a little nervous; there are many claims from hams that winding a toroid can be a painful experience!
Well I gave it a quick go last night and in all honesty I didn’t seem to have a problem, I had to do 7 bifilar turns on a T37 core, it was just a matter of making sure that the enamel copper wire didn’t twist and obviously had the correct number of turns and the connections were correctly linked together.
You’ll notice I describe all this in a distinctively non-technical manner. I must admit I’m not really a technical person and my electrical capabilities are fairly basic, but I do believe that by reading up and asking questions you can learn so much, this by the way does not just apply to electronics but everything. My motto is never be afraid to ask even if you think its the most dumb question, someone will know the answer!
My electronic knowledge is as I said basic, but I passed the amateur radio exams and I understand enough to get by. I still get confused by schematics, I know all the components but I make the common mistake of not separating the drawing from how it will actually be laid out on the circuit board and also I get confused with ground and wonder why the ground connections are not shown connecting to “something”.
But I’ll persevere and no doubt eventually in a few years’ time when I read back on this post I will wonder what all the fuss was! I look at all these RockMite projects as a bit of fun but also a big learning curve. In the near future there is no doubt I will buy a larger transceiver project, I don’t want to purchase an expensive kit radio and then halfway through find out I’m stuck, I want to be able to build it and be confident in understanding how it works.
The other project I’m attempting is a simple audio amp using an LM 386 chip. I found a You Tube instructional video and decided to give it a go. My first attempt ended in failure because the chip I was using (pinched out of an old Lake morse oscillator) had failed and when I had completed all the wiring and gave it a test I could hear sounds but they were not amplified.
I rechecked the entire wiring etc. and came to the conclusion that the chip was definitely faulty. So at the moment I am awaiting another chip which hopefully will arrive in the next day or two.
Unfortunately I never got round to servicing the cobweb, bad weather and other jobs got in the way, but I have some holiday coming up and I will finally get round to giving it a good clean.

Thursday, August 23, 2012

Cleaning the Cobweb and Playing with the RM's

I’ve still not got round to taking the Cobweb down for its annual service, I guess I’ve been too busy building all the RockMites, but hopefully as this weekend is a UK bank Holiday I shall climb the ladder and remove the Cobweb from the mast and give it a good checking over.
I suspect the wire contacts within the main junction box will need a good clean and probably re-water proofing, also I need to recheck the SWR on some the bands especially on 20 meters as the wire has drooped and stretched from last winter’s gales and the odd bird perching on the antenna.
For a home brew antenna it’s pretty rugged and it does take a beating especially in the winter storms. As it’s been up for two years now without me tinkering it really does need to be just checked over. Hopefully it will require little work and I'm counting on the old adage “if it ain’t broke don’t fix it”!
 I’ve been looking at replacing the inductor L1 in both RockMites with a simple toroid mod which evidently improves power and stability, I’ve never wound a toroid so it’s a first for me, but I need to learn this skill especially if I am going to be buying more kits which will certainly have toroids!
Since my success with the RM20 I have replaced the 2N2222A transistor in the RM40 with the more powerful 2N3053 and also switched R18 to a lower value. Also like the RM20 I soldered in some sockets so that I could swap out components if required. This minor mod should change the power output on the RM40 to approximately a watt. 
I've yet to test though as I thought this wouldn’t take me very long but once the mod had been completed there was silence when I fired up the rig. After much muttering and investigating I traced the problem back to R5 a simple case of one of the potentiometer wires coming loose. which I will resolder as soon as I get the chance.
Finally I've decided to complete the RM collection by purchasing the RockMite 30; well readers must have realised by now, I'm hooked!

Monday, August 20, 2012

First QSO with the RM 20

Just completed my first QSO with the 20 meter Rockmite.

After returning home from work I decided to fire up the RM 20 to see what was about. The band was pretty quiet so I prepared myself for a CQ call when all of a sudden a station came up right bang on the frequency calling CQ.

I quickly replied with my callsign and Erkki, OH7QR came back immediately and gave me a nice 579 report with some QSB.

Well it took a while but the conditions were not brilliant over the weekend, lots of noise, so I've had to wait patiently and just bide my time for the band to quieten down.

I'm pleased as punch, a distance of 1346 miles with power roughly at 800mw on a 9v battery.

I love this QRP stuff!

Thursday, August 16, 2012

Rock-Mite 20 Completed

The new 2N3053 transistor complete with heat sink and the pack of 2.2 ohm resistors arrived so last night I managed to complete the build of the RM-20.

The smoke test worked with no problems and I was soon listening on 20 meters to see what was about. I hooked up the RM to a dummy load and gave a tap on the key, all seemed to be working OK and I was keen to see what output I was getting with the new transistor upgrade.

First impressions look like about 800mw with my 9v battery so hopefully with a 12v power supply I may well get over a watt.

I also changed the zener diode on D5 as suggested by Colin M0CGH to give a wider RX/TX at around 700Hz.

With the upgrade of the transistor I installed some sockets in to the PCB so that if need be I can chop and change transistor/resistor value to see what matches best for getting maximum output.

The sockets also raise up the transistor (which is considerably larger than the original 2N2222A) above the surrounding bits and bods so that I can fit the heat sink and it doesn't get in the way of anything else.
The heat sink maybe be a bit over the top but the enclosure is quite large so there is no issue when fitting.

Can't wait now to have my first QSO, although I'll doubt I'll beat Colin's distance who emailed me to say he had got the States on one of his first calls, a small distance of some 3000 miles!

Saturday, August 11, 2012

RM-20 Build Gets Started

I managed to start the build for the RM20 yesterday and so far I have soldered the Surface mount chip and added the resistors and all the Capacitors. Just the Crystals and diodes to go and finally all the controls.

I've left out R5 as I have the volume pot and also R18 which is a 10 ohm resistor as I'm going to replace the final transistor 2N2222 and therefore reduce the value of R18 but I'll put in sockets so that I can adjust the value.

It's looking good so far, a much cleaner attempt than when I was making the RM-40 but I guess that's to be expected as you get better with practice. I was hoping to have it completed by the end of the weekend, but since I'm upgrading I will need to wait for the spare parts so it looks like it will be completed mid week.

Some good news on the RM-40, I managed to have a QSO with an MI station in Northern Ireland some 250 miles away. Mick in Armagh gave me a 449 which in the circumstances was not bad and we had a good QSO. I'll try and break that distance record this weekend!

Friday, August 10, 2012

Rock-Mite 20 Arrival

The Rock-Mite 20 arrived this week and I’m hoping to have it built over the weekend. I’ve got myself in to the habit of checking everything by lining all the parts up in an old foam pad before I start the build. 

So far everything is there so I can go ahead and start soldering U1 the only Surface mount piece, this is probably the trickiest bit to get right, but if you take your time and solder with care you should be OK.

I’ve also taken Colin M0CGH advice from the Yahoo RM forum about replace the D5 diode 4v7 with a 5v1 zener which should give RX/TX shift of around 700Hz instead of the 400Hz from the 4v7. 

Do you like the anti-static mat? This is an old disc Record mat that I've had for years and never actually placed on the record player, I knew it would come in handy one day!

The parts laid out for checking

Further updates to follow and hopefully some more pictures as the build progresses. 

Saturday, August 4, 2012

Finally a QSO With The Rock-Mite

The stereo key jack arrived on Friday from Wonderlabs and I installed it in to the RM40 that evening, Soldering completed I plugged in the key and all worked well. 

I had a quick attempt at calling CQ but the band was noisy and I knew pretty well straight away I wasn’t going to get answer.

This morning I gave it another shot but after an hour of key tapping I gave up as all seemed quiet and had a play with the FT 1000MP V instead. 
Then as these things seem to happen I gave it one more shot around lunchtime and within a few minutes bingo, I got a reply! 

G0OTT in Coventry gave me a 559 and we exchanged a quick QSO as there was heavy QSB but I was chuffed to bits. I had built my first transceiver and finally had a QSO even if it was only 42 miles away. 

I will have some more fun tomorrow seeing how far I can make contact, I've got to beat Coventry! Just waiting for the Rock-Mite 20 to arrive now and I have to say I can’t wait, I’m really beginning to get the bug!

Wednesday, August 1, 2012

CW Secrets and My Keys

After I’d gained my Morse ticket I remember thinking that I would soon be chatting away with the big boys hammering out 30 wpm, how wrong I was!
I got my ticket back in the 90s and it took me quite a while to get up to around 20 wpm! The reason I took so long was just not enough practise.
The secret to learning the code is simple, there is no secret, it's just loads and loads of practise, you just cannot do enough practise. 
Back when I had to take the test, the pass rate was 12 wpm and it took me 3 months of daily half hour to an hour grind to get up to the standard. I was lucky in the fact that I did a course of sorts with a very knowledgeable ham who was happy to to coach both myself and my Brother in law at the same time. His favoroute saying was "use your ears"! How he had the patience I'll never know, but he got both of us through the test and I am forever grateful.

I always found I was hitting barriers, somedays I would be great and others it felt like I was getting nowhere. This my teacher told me was completely normal and suprisingly it continues on even when trying to learn to speed up. You'll find you will be stuck at a certain speed and then suddenly it will all click in to place and the barrier is lifted.

I once heard an old amateur telling another that the way he got up to a higher rate of speed quickly was to force himself no matter what to do 5 QSO’s every day. Within 2 months he gone from 12 to 30 wpm. OK so some of us cannot do 5 QSO’s a day but we surely can do at least 1 or 2 and I guarantee you will be amazed at the improvement you get.
In my case I hung around at 14/16 wpm for quite a few years simply because I was not doing enough QSO’s. It’s only in the last few years that I’ve really pushed myself and that the speed has come up. The nice thing now is that I can happily do other work in the shack with radio on low in the background and instantly pick up any CW station that sounds interesting without really having to think about it.
Nowadays I rarely do SSB, (I think my last QSO using SSB was about 2 years ago and that was for a chap who wanted a radio check and nobody was answering him)! Give me CW anytime, I just find it more of a challenge, but obviously each to their own.

I own a number of morse keys, all straight as I have never been able to get on with paddles. The ridiculous thing is I have owned some very nice paddle keys and endeavoured to learn the dark art of “swiping” but just never really been able to master it. It's of course through lack of patience and perseverance and one day I will actually get round to learning the art.
The main key I use is a Czech army issue, a little strange looking compared to normal keys but very smooth and easy to use. 
Czech army issue
I also have a standard Himound which is another nice key but occasionally sticks if the contacts are set too close. I like to have a fairly tight spring and the contacts literally set to a gap of about a cigarettes papers width, so I guess that’s fairly tight.
Another great key I have is a handmade Stillwell, made by Derek Stillwell from Shrewsbury, given to me as a present many years ago. They are quite rare now, excellent chunky keys with a very smooth action, ideal for an operator just learning the mysteries of morse code.
I don’t use it that often because again setting the tight requirements I like (tight spring and close contacts), puts undue pressure on the old girl and she’s too nice and valuable to mess up. Besides having a beautiful brass Stillwell on the mantel piece does make a wonderful site!