Saturday, 17 November 2012

MRM-30 goes QRO

One of my first Manhattan style construction projects was a RockMite 30 circuit. I had upgraded my RockMite 20 with a Hamgadgets memory keyer chip, this left me with a spare keyer chip. I thought a great way to use the spare chip was to build a RockMite 30. I had seen pictures of other home brew RockMites on the Internet and I thought it would be something I would be able to do.
I wanted to make an 'ultimate' RockMite, so I put in a VXO circuit and also the output PA transformer modification promoted on the Yahoo RockMite Group. I used a 2N3866 transistor for the PA. I was hoping for about 800mW of RF, but I was disappointed that the rig would only put out 520mW. I then upgraded the output filter, this promotes a super clean transmit signal from the rig, but it introduced another 20mW of loss, I was now only getting 500mW from 12 volts.
I was still pleased with my efforts though, it was the first home brew transceiver that I had attempted and it did work. My local radio club put on a camping and amateur radio weekend in July 2011 and I tried out the newly completed using an inverted vee dipole. I was pleased to work HB9UH with some very shaky QRS CW! It turns out that Hans, HB9UH, is a member of the Helvetia Telegraphy Club, a group dedicated to promoting the use and teaching of Morse Code.
The QSO with Hans remains my only contact with the rig. My CW has improved a bit since then, I have been using another Manhattan style RockMite 30 rig which I built to take part in LA1KHA's PP3 challenge and also an MTR by KD1JV for my SOTA activations this year. The MTR is my favourite rig, I rate it above everything else, so my other rigs have been gathering dust! I decided that I need to try to use my other home built radios.
I was always disappointed with the low power output from the home brew RockMite 30 - (MRM-30), I thought it would be more useful for SOTA if it could put out a bit more power. A couple of watts on 30m should be very useful.
I looked in to a design for a 5 Watt RockMite 80 on the Yahoo group, the design used a CB PA output transistor, a 2SC2166. I thought that I could use a similar scheme for my rig. I managed to locate an Eleflow 2SC2166 at a reasonable price on Ebay.
I replaced the 2N3866 output transistor on my rig with a 2N2222A and I used an adapted version of the 1.5W PA circuit from the Small Wonder Labs SW-30+. I knew that the circuit would be capable of a couple of watts at 10MHz. I built the circuit in to the RockMite this week and I was pleased to measure the output at around 2 watts, I'm well pleased with that! I could probably get a lot more out of the circuit, but I happy to stick at the 2 watt level. The signal still looks very clean, so I'm really happy.
I hope to try the rig from a SOTA summit soon, Winter Bonus is only a couple of weeks away!:-)
I haven't added any RX filtering yet, I'm going to see how bad it is without first!
New 2 watt output stage squeezed in (right hand, middle)

Friday, 16 November 2012

Buckden Pike - Remembrance Sunday

For this years Remembrance day, I decided to go to the Buckden Pike War Memorial to do the two minutes silence at 11am.

A Wellington bomber crashed on Buckden Pike in January 1942, killing all but one of it's crew. The survivor erected a memorial cross at the crash site to pay tribute to his fellow servicemen.

Buckden Pike, 2303ft, is classified as a 'Marilyn', so it is included in the SOTA scheme (G/NP-009), being worth 6 points. My plan was to operate my radio from near to the trig point and claim the SOTA points, before moving on to the War Memorial, something like 1km away.

I parked in the public car at Buckden and set off walking along the bridle path at about 0745utc. I was pleasantly surprised to find that the once boggy path had been properly surfaced and was now easy to walk on.

I gained the summit at just after 0900utc, it had taken around 80 minutes from the car park to the trig point, much faster than previous occasions.
I'd taken along my MTR (Mountain Topper), a little two band CW rig, built into an Altoids tin. Using a 1000mAh LiPo battery, I was on the air on 7.032MHz at about 0925utc with about 2.5W. I was amazed at the pile up that quickly developed! I found after about 20 minutes of operating, my brain got a bit fried and I started making a lot of mistakes. I took a 5 minute break from the pile up, but upon asking 'QRL?', I was greeted with another wall of chasers! I moved on to 14.058MHz, again I was met with a big pile up after only a few minutes. My time soon unfortunately run out, so after working Barry N1EU in Delmar, NY, at 1040utc, I had to leave the chasers and tear down the station. 34 QSO's were in the log, so the little MTR had done a great job, I'm sure I could have worked many more stations given a lot more time. I had actually operated a little too long really, it was 1050utc by the time I left for the memorial, and it was about 1km away!
Unfortunately, the route to the memorial is very boggy indeed! I simply didn't have the time to carefully pick my way through the bogs, I just had to run like mad! I reached the memorial at 1058utc, I'd just made it and I was quite soggy too! There was quite a mixed gathering of people at the memorial, and we all fell silent for two minutes at 11am. I was persuaded to pose for a group photograph, although I didn't know any of the other people there! For once, the photos should turn out OK, the weather was actually very nice, usually the visibility is very poor at that time of year, with thick fog being the normally expected conditions. My camera didn't record the memorial pictures properly, so I don't have any pictures of the people at the cross :-(
As you see, the weather was fantastic -
73 de Colin, M0CGH

Friday, 12 October 2012

Elecraft K1

I was delighted to be asked to build an Elecraft K1 on behalf of a fellow ham a few Month's ago.

The K1 kit had arrived within a few days of ordering direct from the USA. The kit came with a very comprehensive owners manual / builders guide. The K1 was ordered with a 2 band filter module (40/20), LCD back light kit and KAT1 auto ATU.

I was expecting a very high quality kit, and I wasn't disappointed!

First of all, the filter board was constructed. All went together fine, the instructions were very clear indeed.

Next came the front panel. The front panel is the main operations centre, it houses the main processor which controls of all the rig's functions. Components are fitted both to the front and back of the board. Again, the construction was very simple.

The instructions were really good. The front panel LCD backlight kit was also added at this time, it is much easier to do it this way than 'retro fitting' it I am reliably informed from multiple sources!

The main board is constructed last of all, this board contains the receive and transmit circuitry, the receive portion mostly towards the front of the board, whilst the transmit portion is mostly at the back. The RX and TX sections are built and tested in turn.

Left - the K1 main board with receive portion complete just after initial 'smoke test'. Luckily there was no smoke! The board fired up first time without problem and all the voltages checked out OK. The instruction book gives lots of testing opportunities, first of all you do resistance checks to make sure than there aren't any solder bridges etc.

Once you are happy with the resistance checks, you then go on to the voltage checks with power applied. Whilst in theory you could just build the whole K1 and do 'all up' testing, building and testing in small bits gives you confidence that you are doing everything right. It's a great feeling when all checks out OK.

The TX portion of the rig went together really well, the hardest part being the winding of the little transformers. I found it a bit tricky to get them to sit and look neat, but I got there in the end and I'm happy with the result.

The alignment of the rig is pretty simple, first you tweak the inductors on RX before completing the TX build, then after TX build you tweak them again on transmit.

I used the sound card on my laptop to set the BFO offset, although initially I had just done it by ear and the computer confirmed that I had got it pretty close. I found it quite amazing that I was using signals from the US to align the rig - 20m was very lively at the time, W1AW kindly confirmed calibration of the VFO readout on 14.0475 MHz :-)

 There are a few components fitted on the underneath side of the main PCB, I guess that Elecraft ran out of space to put them on the top. The rig uses all through-hole components, there are no SMDs used anywhere in the rig. The components all lie flat on the board too, this is not something I'm used to, the kits I've built recently have all used resistors and diodes in a vertical fashion, I use vertical mounting for my Manhattan rigs too, it just saves so much space.

I think Elecraft made a good decision spacing the board out the way they did, it makes construction easy, especially as all the footprints for the similar components are the same, this makes pre-forming the leads a piece of cake - well done Elecraft! (Note that some component locations are intentionally unused - I haven't missed them off by error!)

I think the assembled rig looks very nice, it certainly doesn't look as though somebody has put it together in an attic in Yorkshire! (yes, it was assembled in an attic in Yorkshire!)

There is a lot of work involved building a K1 - it has taken me a number of weeks to put this one together, but I have been doing a short session at a time, say 1 to 2 hours. There are no really hard bits to the construction, there is just a lot of it! The board solders extremely nicely, you can tell that it is a good quality board. I am very impressed by the overall quality of the kit, there is no wonder that Elecraft kits fetch good money second hand.

I'd definitely recommend the K1 kit and I haven't even tried it out on air yet! I would say that it's the best kit building experience I ever had, it's so nice when the instructions are so confidence inspiring and everything is explained in detail.

I have yet to add the KAT1 ATU board to the K1 - the board is fully populated, but I want to give the K1 a thorough try out first without the ATU to make sure everything is working as it should. I hope to try out the K1 this weekend. Once I'm happy everything is OK with the K1, I'll plumb in the ATU. I have never had the luxury of using an auto ATU, so it will be a new experience for me.

The K1 goes back to it's owner at the end of October - I'll be sad to see it go, but I'm very proud of my work. Hopefully I'll get to build somebody else' Elecraft kit in the not too distant future! Any offers? :-)

Hi Mite 17

Well, hasn't time flown by! I can't believe that we are already well in to October.

Back in August I started to build a HiMite 17, using my usual Manhattan style construction technique.

I got the circuit almost working but have since put the project on hold. I hope to get the project finished in the not too distant future.

I used crystals supplied by Graham G3MFJ at G-QRP club sales. Graham has just started stocking 18.086 MHz crystals, this now being the preferred frequency for QRP CW on 17m. I followed the schematic for the HiMite 17 devised by Dave Benson, K1SWL. Dave uses inductors in series with the VXO crystal to pull it down a bit as the crystals originally used were cut for 18.096MHz. I also used an inductor so my rig operates at slightly lower than 18.086MHz.

The frequency of the rig can be 'wiggled' by the use of 2 potentiometers to change the RX and TX frequency a little bit.

I seem to have lost my supply of violet LEDs, so I used a pink one instead - isn't it pretty? :-)

This rig is still a work in progress, I do hope to get it on the air soon!

Wednesday, 22 August 2012

New RockMite 20

Tom, M1EYP, and I had a discussion about LA1KHA's PP3 challenge a while back. Tom is convinced that 20m is the best band to find SOTA chasers whilst running flea power from a PP3 battery. I had to try out Tom's theory!

I ordered two RockMite 20 kits from Dave, K1SWL at Small Wonder Labs. The kits arrived in about 2 weeks from ordering - Dave had been waiting for parts shortages. I ordered two kits as I wanted to use the parts of the second kit for another project - watch this space!

My original RockMite 20
I already have a RockMite 20 in an Altoids tin. I worked N1WPU, Ted in Stockton Springs, Maine, back in September 2011 with my original RockMite, I cherish my RockMite for that QSO, I had joked to my friend minutes before the QSO that my aim was to have a contact with a US station using my 330mW - I couldn't believe it when it actually happened! Apparently my friend is still telling the tale! I really couldn't bring myself to modify the rig for Kjell, LA1KHA's, challenge, so I decided to order a new kit to modify.

The new kit went together without any problems, but I did substitute the zener diode feeding the varicap with a 5V1, I found the original 4V7 zener did not provide enough TX/RX shift. Dave is now shipping MVAM109 varicaps with his RockMite kits, supplies of our beloved MV1662 have mostly dried up. The MVAM109 is a pretty good substitute for the original varicap, but I find it needs more voltage to provide the same capacitance.

I again decided to build the new RockMite in my usual style, using a box from Maplin. I added a volume control, as  I find this improves both selectivity and  current consumption. I removed the PA collector choke and used a 4z-1z transformer instead, I also switched out the zener/resistor regulators, using a single low drop out 5v regulator instead to supply the mixer and PIC - see previous blog entry about low current mod.

So, how does the rig perform? Pretty well I'd say! I took the rig with me on my recent SOTA activation of Great Whernside, G/NP-008. I connected the rig up to my PP3 challenge battery, now measuring under 8 Volts, and sent an SMS spot to the SOTAwatch spotting service. This was the first time the rig had ever been connected to an antenna, would I get any replies to my flea power (~89mW) CQ's? Well I did get a reply, immediately after my first CQ call, I was answered by Barry, N1EU, in Delmar, Albany County, New York! Talk about an opening score - the QSO was across 3239 Miles, which equates to 36,393 Miles per Watt! I have applied and have been approved for my QRP ARCI 1000 Miles per Watt Award (KMPW), I think I just scraped though the award criteria ;-)

Tuesday, 21 August 2012

A new Son!

I have not updated my blog for a while, but I have a good excuse.

I'm pleased to share news of the birth of my second son, Samuel on July 4th, weighing 9lbs 8oz.

Samuel is doing really well and at 7 weeks he already weighs over 14lbs! We are all managing to get plenty of sleep, so all is good :-)

Wednesday, 27 June 2012

SW-20+ gets a paint job

I finally managed to get a coat of paint on my Small Wonder Labs SW-20+. I tried to make it look at least reminiscent of the case at one time supplied by Dave K1SWL for the SW series.

I'm quite pleased with how the radio turned out, I think it looks quite smart, although I put the labels in the wrong place because I was working from memory! Doh!

Dave K1SWL discontinued the SW series back in March 2012. The Small Wonder Labs website states that an easier to build replacement for the SW series will be available sometime in the future.

Hendricks QRP kits SMK-2

The Hendricks QRP kits SMK-2 is a new kit aimed at letting people have a go at soldering surface mount components. The kit is a complete package including all you need to get the rig up and running. The rig is not really a transceiver, but rather a transmitter and and a receiver combined on the same PCB.

I was really impressed with the quality of the kit, the board is of excellent quality and the screen printing is nice too.

The build instructions by Doug Hendricks are first class. The components are quite large in SMT terms,  -1206 size. I think this was a good choice by the designer. The rig still ends up being tiny, but the components are much easier to handle than the usual 0805 or 0603 sized components.

The case (chassis) is of good quality, but I attacked mine with a file taking off the rough edges. My kit was one of the first batch and unfortunately there was an error made when trimming the PCB's. My PCB was too big to fit inside the chassis. Doug Hendricks, KI6DS was straight on to the problem, letting me know about the mistake before my kit had even arrived in the UK! I trimmed my board using a hobby knife and a straight edge, it was quite tedious, but the end result after finishing with a smooth file was perfect. A day or two later,  a new PCB appeared on my doormat, all the way from California! You can't grumble at that. As I had already sorted my PCB, I sent the new board all the way back to Dos Palos! Poor little PCB, - that's some round trip!

The kit went together without any issues at all and it fired up first time. The receiver seems to work quite well, there is some BCI during the darkness hours, but that is to be expected with such a simple DC receiver and I've heard worse. The transmitter portion seems to put out the stated 300mW or thereabouts. I haven't managed a QSO yet with this little gem, every time I have tried to get on 40m recently there seems to be a contest on!

Whilst this rig is intended as a learning exercise to hone the skills working with surface mount devices, it does seem to work quite well and I think it will be a lot of fun to use in the future.

I liked everything about the kit except for the water slip decals. I used Plastikote clear project paint for my chassis as I had some left over from a previous project. You can see the edges of the decals very clearly through the varnish. Maybe frosted or matt varnish would have been a better choice, but I still think you would be able to see the edges of the decals. I think if I was to build another SMK-2, I'd use my Brother labelling machine to label the controls using clear tape. The water slip decal process was fiddly and labourious.

A great kit and good value for money.

SMK-2 built by M0CGH

Further details can be found at:

Monday, 25 June 2012


Back in April, I read a post by Peter, G4ISJ, on the SOTAwatch reflector about a new kit by Steven Weber, KD1JV. I had studied a few of Steven's designs before, especially the ATS series of rigs. I'm quite new to using CW on the air, and the cost of the ATS kits always put me off - I couldn't justify spending $200 plus on a rig that I didn't have the skills to use.

The post by Peter, G4ISJ, on the SOTAwatch site gave a brief overview of the new 'MTR' or 'Mountain Topper' rig and the fact that, as usual with Steven's kits, the sales had been brisk. I looked at the specifications and thought that it would be a fantastic kit and at $100, I thought it was very good value for money, if not a steal! I thought I had missed  my chance to order a kit as Steven had made only 150 kits available, each with it's own serial number, Elecraft style.

I joined the ATS (Appalachian Trail Sprint) Yahoo group immediately with a view to learning more about the rig and to make sure that I would be informed of any further availability of MTR kits.

I was very pleased to see a post on the Yahoo group a day later stating that around 50 MTR kits remained available. With my 33rd birthday just around the corner, I thought the MTR would make a superb present. With my XYL's permission (!) I placed an order. I had a couple of days of wondering before Steven confirmed via email that my order had been successful.

My kit, serial number 131, arrived just before my birthday, I wanted to start building it straight away, but construction had to wait until after we had been away on a family holiday.

The MTR kit is almost fully based on surface mount components. I don't mind soldering SMD's as I work for an electronics company doing repairs on circuit boards.

I found the quality of the kit and instructions excellent, although I would say that the MTR is not a kit for beginners. I built the kit using a fine tipped, temperature controlled iron, soldering each component by hand, one at a time. I took my time building the kit over a couple of weeks.

The most difficult part of the soldering was to mount the processor chip. Steven, KD1JV kindly sent a replacement chip via airmail, after it was discovered that the original version of the MTR firmware had a serious bug. The yellow dot on the new processor chip, added by Steven, shows that the corrected firmware has been programmed. I kept the yellow dot on the chip as I feel it's an important of the MTR's history.

Unfortunately the replacement processor chip had suffered a bit during it's Atlantic voyage and had bent pins, which took me a while to notice! I tried for ages to mount the processor chip, before I realised that some of the pins weren't actually touching the board! Viewed from above, all looked fine, but when viewed from the side, the problem was obvious. I put the processor chip flat on the desk, holding the body down with one finger whilst I pushed the pins down as firmly as I dared using the butt end of a pair of tweezers. This worked well, the pins now touched the pads on the board. The soldering of the processor then went smoothly.

Unfortunately the board suffered a little bit during my initial attempts to mount the processor, this can be seen if you look carefully at the photo - the solder resist on the right hand side of the processor has been scratched slightly, but these things happen!

The top side of the board went much more smoothly, it was really nice to be soldering the more interesting parts, the little LED display and the push button switches, these are the real interactive bits! The three slide switches are for band switching. All three switches need to be moved to change bands, either all to the left for 40m, or all to the right for 20m. If wanted either of the bands could be swapped for 30m or 80m, it's up to the builder to decide which two of the four bands available to choose. The 'Made in USA' bit makes me chuckle - mine was made in England! (OK, I guess it means the PCB was made in USA!)

Initial testing and alignment was performed in my garden! I was amazed by the performance of the receiver, it is very selective. There is almost no background noise on receive, you almost think that there is a fault with the antenna, but then you tune around and the wanted signals just jump out at you very clearly. The tuning takes some getting used to, it is rather slow if you only use the up and down buttons. The entire CW portion of the chosen bands, in my case 20m and 40m can be tuned. One neat function is 'DFE' or Direct Frequency Entry, this allows you to send the desired frequency to the rig in Morse code via the paddle key. This allows quick QSY to a known frequency. The rig reads back the VFO frequency via Morse code and by flashing up the figures on the display one by one, it works a lot better than the description would lead you to believe.

The MTR was designed to fit inside an Altoids tin and I felt it would not be right to fit it in to anything else but an Altoids tin. I managed to find a tin (and a spare, which would be needed due to drilling mistakes!) of Altoids at my local supermarket, although at £1.25 each, they are not exactly QRP priced these days! ;-)

It took quite a lot of work to get all the holes drilled in the right position, the PCB is quite a 'cosy' fit into the tin, but I managed OK in the end. The connectors can't be fitted low enough down the sides of the tin and still allow the lid to close, this is due to allowing for clearance of the PCB. Notches had to be filed out of the lid with a 'rat tail' file to allow the lid to close. The tin is actually used up side down, as the photos will make clear.

Steven, KD1JV, provides a handy quick reference graphic in the MTR build document, I printed out a copy and laminated it. It just fits inside the tin lid and it comes in handy to jog the memory whilst out in the sticks. It can be seen that this little rig has lots of available functions, there are 3 keyer memories, RIT, battery voltage meter, built in Iambic keyer and also the Direct Frequency Entry feature noted before. A quick press of the 'Menu' button gives a read back of the current operating frequency in Morse code, aswell as in figures via the LED display.

Most builders are using their own graphics for the top of their MTR tins, but I used the one provided by Steven, KD1JV. I like to think that I have done a good job with MTR serial number 131 and I hope that KD1JV himself would be pleased with my efforts.

The specifications of the KD1JV Designs MTR from the build instructions:

Dual band, 20 M and 40 M typical, 30 M and 80 M possible.


MDS: ~0.2 uV

Small signal band width ~ 500 Hz

Audio output limited to ~ 800 mv p-p

Headphone output, 16 ohms min recommended.

Minimum current (no signal) ~35 ma


2.5 watts @ 9 volt supply typical

Spurs -50 dBc or better

I tried the MTR out from my local SOTA summit, Rombalds Moor (G/NP-028) a few weeks ago and I was very impressed with the performance. The receiver is excellent, very quiet indeed and very selective. The lack of volume control is not an issue whatsoever. I have yet to tweak the transmitter portion of the rig, but from 11v supply, my power meter was showing a healthy 4+ Watts on TX.

Overall, the MTR is an amazing rig!

Thursday, 26 April 2012

SW-20+ Gets some new toys!

I finally finished my Small Wonder Labs SW-20+. I had a PicoKeyer chip in my stores which I had originally intended to home brew into a tuna can based keyer project to add to my tuna can rig collection. I never got around to building my tuna can keyer, so my chip sat in it's box for months. After I built the SW-20+ earlier this year, I decided that it would really benefit from an internal keyer. I want to make this rig a good SOTA rig. I threw together a Manhattan style daughterboard, mounting the keyer chip on one of W1REX's MePads. I soldered the daughterboard to the rear panel.

The keyer works really well, although a front panel speed control would be a good idea - maybe I'll implement one in the coming weeks.

I then hit another problem - whilst I can answer CQ's no problem, it's always nice to know roughly where you are in the band, especially if you are sending out an alert for SOTA, stating you are to be found on 'x' frequency. The Small Wonder Labs Freq-Mite was the answer. This was an easy kit to make and it worked first time. I'm pretty impressed by the accuracy, although the readout is only to the nearest 1kHz, it's close enough to be very useful. My hits on the RBN matched with the indicated frequency very well (I also checked with my FT817).

I still think this rig will be excellent for SOTA in the Summer. It doesn't weigh very much, I just need to find a nice lightweight power source to power it!
PicoKeyer on rear panel, Freq-Mite between pots.

Tuesday, 3 April 2012

MRM-30 in the workshop

In Summer last year, I built my first Manhattan style transceiver - I had upgraded my RockMite-20 with a PicoKeyer from Hamgadgets, this left me with a spare RockMite chip. I thought it would be fun to try out the Manhattan technique and build a RockMite 30. I had lots of help via email from Chuck, W5USJ - a great guy, always willing to help out newcomers and he knows his RockMites!

The result was my MRM-30 -

I was slightly disappointed that the rig only puts out 500mW on 10.116MHz - I was hoping for nearer 750mW. The rig does work quite well though, although I've only had it on air a couple of times. Like all RockMites, the receiver is quite wide so many stations can be heard at any one time! I had a nice QSO with HB9UH when I first tried out the rig into an antenna.

The circuit of the MRM-30 is pretty standard, although I have tried to tweak the PA stage for more power. I used a 4:1z transformer instead of the RF choke for the PA load/DC supply. I eventually upgraded the PIC to a PicoKeyer. I have fitted LED's to indicate the 'shift' state and also power on, mainly to make the rig look pretty!

The heat sink on the 2N3866 is a bit overkill - I was thinking that the rig would produce more power than it does, but still it doesn't harm anything and it adds a bit of eye candy! I made the case large on purpose - to allow later upgrades and also to make the rig a little easier to use. My original intention was to build the rig for SOTA use and I thought it would be good to have large controls to enable use with cold hands. I ended up making the rig too pretty - I wouldn't want to risk damaging it out on the hill now!

Ondra, OK1CDJ, announced a neat little kit he had designed, on the Yahoo RockMite Group a couple of weeks ago. The kit is a little audio filter for CW. Ondra had designed the filter for his own use I believe, but quite a few people showed an interest, so a kit was put together and was made available at HamShop Cz. The kits sold out pretty quickly, but I was lucky enough to buy one before they had all gone. I believe that this kit will be available again soon.

The kit arrived from the Czech Republic very quickly (4 days after order!) in a padded envelope. The included instructions were adequate for a seasoned builder. The PCB is of nice quality and the components used are all surface mount type. I like surface mount components, they feed my obsession of making things neat and compact. There are no components smaller than 0805, so soldering was not a problem.

The components soldered on to the board very easily, I again used lead-free solder, as this was on hand. The solder joints seemed to form nicely and were lovely and shiny! The finished PCB looks very professional - it doesn't look like it's been built as a kit at all -

My plan is to fit the little CW filter board in to my MRM-30. I have been planning to add an Op-Amp filter to the MRM-30 for quite some time, I even bought some of the components. The filter kit has made adding a filter really easy!
Two resistors fitted to rear of the PCB

I'm not sure at this stage whether I'll remove the little variable resistor and fit a front panel mounted variable resistor, it might prove useful to be able to adjust the frequency response of the filter during a QSO.

My MRM-30 shows slightly different shift frequencies depending upon which 'channel' is in use, so if the replying station is zero beat, they may be slightly out of the 'peak' of the pass band of the filter, if adjusted for one particular 'channel'.

I hope to fit the filter PCB in to the MRM-30 in the next few days. I have a Freq-Mite on order from Small Wonder Labs, so I hope to be fitting that into the SW-20+ also quite soon.

Tuesday, 27 March 2012

QRPme Sudden Storm

I recently built two versions of the Sudden Storm receiver by W1REX.

The first version I built was the version 4, this was a short lived version - I think Rex, W1REX, once told me he had 45 PCB's available to go out in the field. The version 4 Sudden Storm PCB is red due to a mistake - it was meant to be blue!

The build was very easy and the PCB soldered very nicely, even though I used lead free solder. There is a trace missing from the Tune pot, so this had to be added using a jumper.

Sudden Storm ver4 PCB. See if you can spot the trace fault!
I thnik the rig looks quite smart with it's red PCB, it's a shame that the band module isn't red also. I used the 'soup up' potentiometers which have transparent, hollow shafts. A 3mm LED fits into the shaft so it can be illuminated. In previous rigs I have used blue LEDs, but I have found them to be very bright. Even running them at a very low current doesn't seem to dim them much! This time around I got hold of some purple LED's, I think they look cool because they mostly look blue, but the reflected light is purple, they are a nice intensity too.
Sudden Storm version 4 'red' (Why does John West print his labels upside down?)

 The version 5 board went together extremely well, there are no mistakes on the PCB and the components are very nicely laid out. Again I used the 'soup up' pots with purple LED's. You can see the LEDs sat in the rear of the pot shafts in this photo taken during construction.

 When I had finished the build, I sat the PCB on an old John West tuna tin and applied power. The rig seems to have very low noise, which I think is due to the special filter applied to the LM386. The tuning range is quite limited, but it will work well with a crystal controlled transmitter using the same crystals as the receiver. The crystal can be pulled by an optional capacitor if required. The receiver can be put onto a different band by changing the band module and crystal.

Rex, W1REX, usually supplies a tin, indeed the components are usually sealed inside and you have to open the tin to get the parts out! To save on shipping costs my kits came without tins. Luckily, tuna tins seem to be a standard size all over the world, so my John West tins are just the job. (Thank goodness my wife eats tuna!)

73 de Colin

Wednesday, 14 March 2012

RockMite 40 low current mod

I gained my 500 Activator points certificate for SOTA on Monday, 12th March 2012. I began planning my SOTA expedition the week before. I kept an eye on the weather forecast and the solar conditions and decided that Monday, March 12th would be the day to do my expedition. My boss signed off my holiday, so I was all set - or was I?

Being a Monday, I thought that maybe SOTA chaser stations might be hard to come by. I wanted to continue my theme of activating for SOTA using PP3 powered rigs in order to increase my score for LA1KHA's PP3 SOTA challenge. Would I find enough chasers on 30m or 17m to qualify the three summits needed to increase my SOTA points to at least 500? I thought that it might have been a tall order. Thoughts turned to the 40m band. 7.032MHz has a reputation of being the most used frequency for SOTA.

I had built a RockMite 40 kit a while ago using 7.015MHz crystals, when I connected it to an antenna I discovered that the rig was overloaded with high speed CW. As a CW beginner, I had made a mistake to choose this frequency, so I put in some 7.030MHz crystals instead. The rig then sat in my cupboard for a couple of months.

Regulator fitted top right, next to red capacitor.

 The RockMite seemed a prime candidate for conversion to 9V, so last week I removed the PCB yet again and pulled out the 5.1V zener regulators (R1/D3 and R8/D4). The zener regulators do their job, but they waste lots of current. I replaced the regulators with a single TS2950ct-5.0 ultra low drop out 5V regulator which I hurriedly picked up at Maplin for 99p. The 5V regulator fitted nicely into the holes for R1, although as there are only two holes, an extra hole was drilled through the PCB on to the ground plane on the underside. The solder resist was then scraped off to allow soldering of the regulator ground lead to the ground plane. A 0.33uF capacitor was then soldered into the holes intended for D3. This cap was on the output side of the regulator. A jumper lead was then soldered underneath the board from the output of the regulator to one of the holes left after the removal of R8.

Regulator and capacitor in place of R1/D3

The current consumption in receive reduced by about half to just under 10mA. This is great for battery life! The picture to the right shows a previous conversion of a 30m RockMite (you might spot different coloured capacitors!).

I wasn't sure what the exact frequency of my RockMite 40 would be, all I knew is that it would be below 7.030MHz, as most RockMites run LF of the crystal frequency. I attempted to zero beat the rig with my FT817 to determine the exact frequency, the best match I found had a dial reading of 7.0286MHz. I would have to wait until later to find out how near I had got! I thought that the SOTA chasers wouldn't mind tuning down 3kHz, which would be good, as I would be rockbound!

My dipole on St Sunday Crag G/LD-010
I arrived on my first summit, St Sunday Crag, G/LD-010 for SOTA, at about 1100utc, Monday 12th March. I set up my usual inverted vee dipole, but this time I connected the extra elements for 40m. I sent an alert to the SOTAwatch website via SMS to state I was QRV. After a couple of CQ calls, I was answered by Åge, LA1ENA, who gave me a 559 report. A small run of stations waited in turn to call me, it was fantastic! I had worried about finding contacts to qualify the summit, but in just over 20 minutes, I'd worked 12 stations!

The views were simply stunning -

I moved on to the next summit, Fairfield, G-LD-007 and I was QRV by 1320utc. Another self spot via SMS brought the chasers on to my frequency very quickly, first in the log at 1326utc was Mike ,GM0OAA, giving me a 569 report from Glasgow. Again a nice run of stations called me, the last being George, GI4SRQ, giving me a new DXCC on CW.
Dipole on Fairfield,G/LD-007, above the clouds!

My last summit of the day was Seat Sandal, G/LD-022. I was at 494 points, so I only needed four more QSO's to get to my target of at least 500 points. I decided that it would be nice to finally earn my 500 point certificate using a home brew rig, instead of the RockMite. I fired up my MRM-39 on 30m. Yet again the self spot SMS service was used and I worked six stations including OE7PHI and OK1DVM for two new DXCCs. The RockMite 40 was then connected to the antenna, to allow the 40m chasers to work me. I worked another six stations, with the final contact being Michael, G0BPU, in Ipswich, who gave me a 559 report.

The little RockMite had performed beyond all expectations! I had a great day out and I didn't even feel tired at all considering the 8 Mile hike over the mountains.

My PP3 challenge battery is alive and well, and now I have three bands to choose from - 40m, 30m and 17m. Hmmm, there seems to be one band missing there! ;-)