Sunday, 12 April 2020


Steve KD1JV announced that his kit for 2015 would be a five band version of the MTR and this time it would include an LCD. I'd missed out on the three band MTR kit, but I was going to do all I could to get my hands on a five band version! Steve restricted ordering of the MTR-5B to the USA only, I can understand the reasoning behind his decision, as filling in overseas paperwork for every single shipment would be very tedious. It was a bit frustrating, but as least ordering was first come, first served like before. Thankfully I found a kind ham based in NY State to help me out and MTR-5B kit #70 of 98 kits was soon in my hands!

The MTR-5B specs from the build instructions -

 Switch selected 40/30/20/17/15 meter bands
(no band modules to lose or change out)
Wide operating voltage range, 6 to 12 volts
15 ma Rx current at 12V supply
Efficient transmitter. Low current with 4W output
LCD display
Push button or Optional rotary tuning
24 hour clock built in, with battery back up
Three 63 character programmable message memories
Message beacon mode with adjustable pause time
Small size: can fit into a 4” x 3” x 3/4” box

The build was fairly straight forward but there were a few issues that had been flagged up by other builders before I had started my kit. It turned out that the supplied reference oscillator was not suitable, so Steve sent new oscillators out via mail. The replacement oscillator caused a slight increase in current consumption, so the rig does not quite meet the 15mA quoted in the specs. The original firmware was found to have some bugs, so replacement firmware was deposited in the AT Sprint Yahoo Group (now files area, in order that builders could update the firmware via a TI Launchpad. The new firmware was self executing, so updating the rig was as easy as connecting up the correct wires to the interface and double clicking a file on the computer.
MTR-5B during build. A number of through-hole parts still need adding.

Reflashing firmware with TI LaunchPad Development board

Case made from sheet aluminuim and sprayed with primer

MTR-070 just prior to final assembly

 This was an article that I wrote for SPRAT -

KD1JV Designs MTR-5B

Colin Evans, M1BUU

I discovered Steve Weber KD1JV’s rigs a few years ago. I built the first version Mountain Topper CW rig (AKA ‘MTR’) in 2012, it was a two band model supplied without a case. I housed my kit in an Altoids tin and selected the 40m and 20m bands. I liked the rig so much, that, when the second version was released, I opted to buy another, this time building for 30m and 20m bands!

KD1JV’s kit for 2015 was the fourth in the MTR series, called the MTR-5B. The rig now includes operation on five bands, a backlit four line LCD and optional rotary encoder.

The MTR-5B kit was a limited run of just under 100, all with a serial number. My kit has serial number 070. The kit was supplied as a board plus parts, including solder and connectors, but minus an enclosure. The components are almost entirely SMD, 0805 size for most resistors and capacitors. The hardest part of the build was probably mounting the processor and DDS chips as these are TSSOP devices (Thin-shrink small outline package).

The build went smoothly and the rig fired up first time without any troubleshooting. There had been a few issues with original firmware, so I knew, even before having the kit in my hands, that an update would be needed. Updating the firmware for the MTR series has been made very easy for us. The MTR series rigs use the TI MSP430 family of processors, the development tool / interface for these chips is called LaunchPad, and costs around £10 delivered to your door. To update the firmware, I simply had to connect three wires from the LaunchPad to the three programming pads provided on the MTR PCB, then it was a just a matter of double clicking the correct file downloaded in a .zip folder. Job Done!

I made my own enclosure from a piece of aluminium sheet ordered from EBay. I hadn’t tried making my own cases before, I wish I had tried it sooner! Using a vice that I made at college, it was easy to bend the aluminium sheet into the shape I wanted. I copied the case style of previous versions of MTR but I sprayed my rig bright orange as it’s my 3yr old son’s favourite colour (might also prevent me leaving it behind after a SOTA activation!). I opted to leave off the optional rotary encoder to make the radio as small as possible, and I also saved around 10 grams in weight.

The MTR-5B is a pleasure to use, the receiver is very quiet, by that I mean that there is very little audio chain noise. There is no volume control, the AF level is simply limited above a certain point. The sidetone, although generated by the processor, is very smooth as it is injected before the final AF stage and is subsequently filtered. The band switching can take a bit of getting used to as it uses a combination of six slide switches, however previous versions of MTR have used this system and I don’t have a problem with it. The most impressive feature of this rig, despite the permanently backlit display, is it’s extremely low current consumption. Another feature which I really like is the real time clock, the clock is surprisingly accurate and I find it very useful for SOTA logging, it will be especially useful to keep set to UTC when summer time comes along. The clock is kept running by a small button cell when the rig is not connected to an external supply.

Some statistics for MTR-5B s/n#070

160g (5.6oz)
106mm x 82mm x 30mm (~4.25” x 3.25” x 1.25”) excluding protrusions.
Built in Iambic (B) keyer with three 63 character programmable messages
Single conversion superhet, ~500Hz bandwidth
High efficiency transmitter using 3 off TO92 BS170
4 line backlit LCD with frequency, RIT, battery voltage, time display.
Full coverage of 40m/30m/20m/17m and 15m. (Option for 80m in any one of slots)
Operating voltage range 6 to 12 Volts, nominal 9V

RX mA 9V
RX mA 12V
TX mA 9V
Power W
Power W 12V

Notes -
RX current measured with no signal present so will be higher in actual use.
TX power measured using 4SQRP QRPometer, in turn compared with Nissei RX-203.
A supply voltage of 7.3V gives approximately 2 watts output on each band.
TX power output and efficiency is influenced by the spacing of turns (inductance) on the low pass filter toroids, I just spaced mine neatly and didn’t mess around too much.

Thanks go to Steve KD1JV for designing and supplying such a great QRP kit!

I've had my MTR-5B for about 5 years now and it has been, and is, a superb radio. I've only had a couple of incidents where the rig froze, cycling the power took care of those, other than that the rig has been totally reliable and never needed any repair. I use my MTR-5B more than any other radio I've owned, it just does exactly what I want.

Friday, 13 March 2015

BITX20 Project

I was listening to the SolderSmoke podcast and Bill, N2CQR, the host was talking about his 'BITX' radio. 'BITX' is a design by VU2ESE of India, it uses the same basic amplifier block throughout, and uses a 'bidirectional' architecture. A lot of the circuit is shared between RX and TX. The beauty and appeal of the BITX design is that it uses very common (cheap!) parts and there's lot of troubleshooting information available at the BITX Yahoo group.

The BITX design appealed to me, because, for the last few years, I've had the desire to have a transatlantic QSO with a home made radio via voice. I haven't actually managed a contact to North America with a home brew radio, although I've done it many times on CW with rigs built from kits. I contacted Bill, N2CQR, and asked his opinion as to whether a common or garden ham like myself could build a BITX. The answer was simple - go for it!

I intended to build my radio with a traditional VFO, true to the VU2ESE design. Recent episodes of SolderSmoke have featured Pete Juliano, N6QW. Bill had copied Pete in on the emails and Pete put forward his case for a DDS VFO. At first I resisted, but then having thought about the benefit of stability, especially as my rig would be used outdoors, I decided that the DDS VFO would actually be a very sensible idea.

I'd seen a presentation by Paul M0XPD at Rishworth convention about the use of Arduino in ham radio in October 2013, I came away feeling inspired. Microcontrollers and programming is not an area of electronics that I'm particularly interested in, but I could see the benefits of Arduino. soon after the presentation, I ordered an Arduino Uno and AD9850 DDS module. I managed to get the Arduino Uno and DDS module running, but then put them in the drawer, like you do!

Pete, N6QW, told me that instead of using an Arduino Uno board, for more permanent applications, an Arduino Pro Mini or Arduino Nano is a cheaper and smaller solution. There's a lot of stuff packed on to an Arduino Uno board, most of it is not actually used once the sketch (Arduino code) is up and running. The Arduino Pro Mini is a very basic Arduino board, it consists of the microprocessor chip and crystal plus voltage regulators. The Arduino Nano is similar to the Pro Mini but has an on-board USB programmer. To program a Pro Mini, you have to use an external programmer. The benefit of the Arduino Pro Mini is that you only have the hardware that you need to run the code, this makes it very cheap and also very small.

I ordered an Arduino Pro Mini clone board via Ebay from a UK seller, they're cheaper from overseas, but at £3.35 posted to your door within a couple of days, I think you can't go wrong. I also ordered another AD9850 module. The price of the AD9850 modules seems to be steadily going up, this is probably because supply is drying up.

Pete N6QW kindly sent me his Arduino sketch and also a wiring diagram for interfacing the DDS to the Pro Mini. It took a few weeks to get things working, I had trouble with my first external programmer, it had been fitted with a fake FTDI chip and FTDI had sent out some code via Windows update to 'brick' fake chips. The programmer worked for a few minutes and then the computer failed to recognise it. I obtained another programmer board, this time fitted with a CH430G chip, this one has worked flawlessly. At some point, I'd managed to copy a schematic mistake from one of the web resources regarding the connections for I2C from the Arduino into my lab book. I battled for ages trying to get my display working, it turned out that I had A4 and A5 (I2C output) transposed. I learned some useful stuff whilst getting the LCD working, so I'm thankful for the initial mistake!

By late October 2014, I had the Arduino controlled DDS up and running, complete with a cool looking white on blue, four line by twenty character, display.

Bill, N2CQR put a picture of his layout diagram on the BITX Yahoo group, I used this to start my BITX build. I replaced the VFO section with my Arduino VFO module. I used the original BITX schematic, starting with the microphone amplifier in the bottom right corner of my single sided copper clad 10"x8" board. I chose to use 2N3904 transistors. I built a few sections, including the BFO, balanced modulator and IF amps, before applying power for the first time. I checked that the oscillator was working and also tested the mic amp and balanced modulator by hooking up a microphone temporarily. My Tektronix 465 scope was very useful at this point. All checked out OK, so I proceeded to add the crystal filter.

Next to be added was the second IF amplifier and balanced mixer. Pete N6QW's Youtube channel came in very useful, it helped a lot whilst winding the trifilar transformers. I fixed the Arduino DDS module in place with M2 countersunk screws and stand off sleeves. With the addition of the LM386 audio amplifier and another IF amplifier, I was in a position to try the receiver for the first time. Some signals were heard, so at that point I was happy. It wasn't until later that I discovered that I had put a resistor in the wrong place in one of the IF amps (This was my only mistake in the build, and I found it straight away whilst sweeping the crystal filter to measure it's response.) By the end of November 2014, I had a working BITX receiver.

I used the original version BITX band pass filter, the later versions use different designs, but I wanted to go with something simple, I wasn't looking for ultimate performance. I used the excellent blog site of Edwin Groot, PA1ED for information about the band pass filter. After the addition of the BPF, I terminated the end with a 50R load and then tested my circuit in TX. It was great to see home brew SSB signals on my 'scope!

The final stages to be added were the RX/TX switching stage, low pass filter and TX amplifier
stage. Against advice, I chose to build the TX power amplifier stage on the same board as the rest of the circuit. At first, I thought all was fine, the rig seemed to work perfectly, with nice sounding transmitted audio (received on FT817 in another room, whilst TXing into dummy load) and just over 5w showing on the meter. I was high on my success and decided to take a break for a while. I came back to the circuit with a view to getting it ready for an on air test and I thought I'd give the circuit a thorough check over. I soon discovered that no matter how much I tried to null the residual carrier by using the variable resistor and capacitor on the balanced modulator, the lowest I could get it to was 400mW. I thought about the problem for a day or so and then decided that it must be some of the output leaking back into the input of the TX stage at the join to the shared band pass filter. Bill N2CQR had also had this problem with his circuit. To test my theory, I simply disconnected the coax connecting the LPF and BPF, sure enough, I could null out the TX carrier to a very low level. The solution was to add another relay in order to disconnect the RX line, both at the LPF end and at the BPF end. Luckily, there was just enough room on the board to add the third relay. By sheer luck, at each stage of the build, I just seemed to have enough board space for the circuit - I think this project was just meant to be!

Three relays to switch between RX and TX may seem excessive, but I had them to hand. One relay switches 12v to either RX circuits or TX circuits and grounds the line not being used. Another relay disconnects the RX path from the LPF and grounds the TX sense pin on the Arduino. The last relay isolates the RX path before the BPF and has one spare switching section, I thought this might be useful in future to possibly control a linear amplifier.

Once I'd solved to residual carrier issue, I was ready to try for my first QSO by the end of January 2015. Bill N2CQR encouraged me to try the circuit as just a bare board in keeping with ham tradition. I don't have a permanent antenna so I had to wait for a dry day and I put up a temporary 20m dipole in the garden. On 1st February 2015, I set up a table in the garden and took the BITX outside as a circuit board. I heard a German station calling CQ with a very strong signal, so I decided to give him a call. I was amazed that he picked me up with the first call. (I later found out that OM Edwin had also had a BITX QSO with the same station!)

It really was a magical moment having a QSO with a home made radio, something that took me about two years to achieve from first having the idea to having the QSO.

With the successful completion of the circuit, it was time to put the rig in a case robust enough for SOTA use. A case was made from half hard aluminium sheet, to fit the circuit board nicely. To compliment the blue LCD, I used blue push switches for the menu functions and also as finishing touch, I added a dual colour LED to indicate RX and TX; blue for RX and red for TX.

The rig was ready for it's first SOTA activation. I hadn't actually tried the rig into an antenna since the first test in the garden as bare circuit board. I do SOTA during the winter as you get bonus points between December and March. I looked at the weather forecast for my chosen weekend to activate and it was due to be very windy. I had to change my plans to a morning activation on Saturday 28th February. It just so happens that the long path propagation works well to VK at this time of year at around 0800utc.

I activated Sharp Haw (SOTA G/NP-029) on 28/02/2015, getting on air by around 0725utc with the BITX20 into an inverted vee dipole suspended by a 7m fishing pole. I called CQ a couple of times before being answered by Vlado OM1AX. I was relieved that my rig was still working well. I worked another five European stations before I heard VK1DI calling me. at first I thought I was dreaming or something, but sure enough, VK1DI was in the log at 0737utc. By 0755, my log included contacts with four VK stations! What an amazing experience! Picture at the top of this article shows my BITX SOTA activation.

I still have to achieve my goal of a home brew transatlantic QSO, but I'm fairly confident that I will be able to achieve this in the coming months.

Thanks expressed to Bill, N2CQR, and Pete, N6QW, for technical advice and encouragement, Paul M0XPD for Arduino code resources, Edwin Groot, PA1ED, for his excellent home brew BITX articles, and finally Graham, G3MFJ for supplying parts.

Wednesday, 12 November 2014

New workbench!

It's about time that I updated this, spare time when you have kids seems in short supply!

I didn't have an area for doing my hobby, but this summer that changed. I have installed a simple workbench in the attic, consisting of two tables form Ikea. I bought one table and then decided that it would be great to have another one to put my Oscilloscope on. I made a small free standing shelf by using a shelf board, along with some adjustable legs, from Ikea. I already had an ESD mat and wristband. I bought an adjustable desk lamp with LED bulb, I find the colour of the light is excellent and the bulb runs very cool. It's nice to have a properly lit work area, the main lighting system uses dichroic bulbs, so I find it very easy to read the colour bands on resistors etc. I find that with traditional incandescent bulbs, it can be very difficult to distinguish the colour bands on resistors.

Despite having limited spare time, I have managed to complete a few projects over the year, although progress was painfully slow at times. Firstly I built a Manhattan style RockMite 40 as a surprise gift for Pete, G4ISJ ( After attending the Blackpool Radio Rally in April, I came home with a RockMite 80 kit (W1REX version) and an OpenQRP 7MHz CW rig kit from Kanga Products, I also commited to building two RockMites for another another ham. I finished the 'customer' RockMites and started to build my OpenQRP and RockMite kits in late spring, but then I put everything away for the summer. I spent my spare time in the summer doing stuff with the family, we had quite a few trips away and had lots of fun chasing the two Lancaster bombers up and down the country on their 2014 Two Lancs Tour. I heard about the Canadian Lancaster's tour of the UK and felt that I could not miss the once in a lifetime opportunity to see two Lancaster bombers flying together in formation.

With the establishment of my new workbench in late summer, I have recently finished a few of my projects. I got my OpenQRP rig working eventually after swapping out some of the components, I battled with VFO drift and problems with the firmware not booting correctly; I replaced the IC socket for the Arduino chip which cured the firmware problem and the drift was cured by replacing a capacitor in the VFO circuit. I finished building my NEQRP NEScaf audio filter which had been lying around since 2013! I also completed a 'customer' build of a Cumbria Designs MicroCode DSP CW reader, and my RockMite 80 was finally wired into it's Zomboids tin this week.

For the last year or so, I've had the ambition of building an SSB rig. I have always been fascinated by contacting hams in the USA, I don't know where this comes from, but it gives me a buzz whenever I manage a contact across the pond. I've had a few contacts across the pond with home built gear (read 'kits'), which I find magical, although I've never managed it with a scratch built rig, this is probably due to the fact that my scratch built rigs work on 30m. I find that for the times I operate, 20m is the best band for US contacts. (I really ought to build a home brew 20m CW rig!). I came up with a personal goal of having a contact with a US station using a scratch built SSB rig.

I have spoken to various hams about my idea and I decided upon the BITX design for my rig. I consulted Bill N2CQR of SolderSmoke podcast fame as he has built a couple of these rigs from scratch. Bill has hooked up with Pete Juliano N6QW for the last few episodes of SolderSmoke and Bill passed my email on to Pete. Pete very soon steered me away from using a traditional VFO for my BITX, suggesting that a DDS VFO would be better. At first I resisted, but I soon came to realise that, as I operate almost entirely from SOTA summits, I'd be using my rig in a VFO hostile environment. I have used my MKARS80 rig a couple of times for SOTA and the VFO tends to drift quite a bit, thankfully Steve, G6ALU the MKARS80 designer, had implemented a very neat solution for this problem in the form of Huff and Puff correction. The Huff and Puff circuit does a very good job at keeping me on frequency.

I have started work on my BITX20, I began by putting together the Arduino controlled DDS VFO, with much help from Pete N6QW (thanks Pete!). I used a cheap Pro Mini Arduino clone board, an AD9850 DDS module from Ebay, and the system drives a neat looking four line LCD display. The original code used in the Arduino was put out by Paul, M0XPD.

I hope to write up my progress with my BITX rig as I go along.

I want to end by expressing my thanks to Pete Juliano, N6QW, Bill Meara, N2CQR and Paul M0XPD who have been great in providing advice, resources and encouragement.

Wednesday, 30 October 2013

Two Tinned Tunas

I came away from the G-QRP convention with a number of goodies, including a Two Tinned Tunas EZ build kit. The kit comes as a pull top tuna can and a PCB.

Open the can to find the parts :-)

Follow the excellent step by step guide to build into a 350mW transmitter!

The kit worked first time and the step by step guide was excellent. My meter was showing around 400mW output on 7.030MHz from 13V supply. (The gold base does not come with the kit.)

It does what it says on the tin! :-)

Tuesday, 29 October 2013

2013 Rishworth G-QRP Convention

The annual G-QRP convention held at Rishworth School near to Halifax is the highlight of the amateur radio calendar for me. In 2011, it was no longer permitted to hold the usual 'Buildathon' in the school laboratories, so instead it was decided to hold the Buildathon at the Premier Inn, at Salterhebble not too far away, on the evening before the main event and thus turn the convention into a two day affair.

There seemed to be a very good atmosphere during that first Friday night construction evening, I took part in the construction myself and successfully completed a Manhattan style Z match ATU. I enjoyed building the project but I found that I rather missed out on the social activity.

This year the Friday night event seemed better than ever, all seemed to be enjoying the conversation and free buffet. I was very pleased to meet Rex, W1REX, for the first time. I have built a number of Rex's QRPme kits since buying my first SUPER Tuna ][ kit from G-QRP club sales at the 2011 convention. Rex had brought the original 1976 Tuna Tin 2 transmitter built by Doug Demaw, W1FB, with him from Maine. I spent most of the evening chatting with Rex about RockMites and Tuna can kits. George Dobbs G3RJV kindly signed my copy of his new QRP book. The Buildathon project this year was the RSGB centenary 20m PSK receiver, I heard that ten builds were attempted and all ten were working at the end of the night.

By 1130pm there were only four people left in the room, including myself; we decided to retire for the evening. Rex picked up his soldering ironing and headed off for his room to do a couple of hours of kit building, whilst I drove the 12 miles to my home QTH.

Saturday 26th October.

I left home at about 9am and stopped off at the convenience store to pick up some sandwiches and drinks for the day. The convention is famous for it's pie and peas, but as I'm vegetarian it's not much good for me! I managed to find a space on the main road outside the school not too far from the entrance, I got there about fifteen minutes before the 10am convention start time. The queue to get in had started to form but I was pleased to be reasonably near to the front.

Unlike previous years, the event opened pretty much exactly at 10am, in the past the doors seemed to be open earlier than this. I heard the usual reports that the traders had all looked at each other's stalls before the official opening and snapped up all the good stuff - I guess that's a perk of being a trader!

My first port of call was to find the book stall run by Richard G3UGF. I bumped into fellow SOTA enthuiast Mike, 2E0YYY whilst trying to locate the book stall. Eventually I spotted Richard at the other end of the hall and dropped off my donation of books, it was a relief as those books were heavy! The book stall had lots of stock and lots of them were interesting historic titles, including some copies of the famous 'Solid State Design for the Radio Amateur' (SSDRA) by Wes Hayward W7ZOI.

The lecture stream started at 11am, first up was a talk by Ian Keyser G3ROO about spy sets. Ian was also joined on the stage by Roy GM4VKI and Johnny Apell SM7UCZ and there were a number of radio sets to look at after the talk.

After Ian's talk it was time to head back to the main hall for lunch. Lots of people were enjoying the pie and peas, whilst I took the opportunity to have a look around the stalls whilst it was a little bit quieter. I bought a new G-QRP club mug as the one that I bought last year got smashed at work; a bargain at only £1! I also picked up a free bag of 2N3866 transistors, I need to find a suitable project now to use them!

The second talk, after lunch,  was by Paul Darlington M0XPD about using the Arduino and similar platforms as a basis for radio projects.. Paul's talk was very well delivered and quite inspiring. I came away thinking about having a play with an Arduino myself, so Paul's talk certainly worked on me! Paul's blog here -

The next talk was by Colin G3VTT. Colin's talk was about his adventures with AM broadcasting from ships at sea. The talk was very entertaining and a good insight in to the technical challenges of operating a high power radio system away from the comforts of land. I felt a little connection with the story as Colin described operating his Elecraft K1 from the Radio Seagull ship. Colin described how he used the Rishworth Buildathon ATU project as a 'sacrificial ATU' to protect his K1 from the AM transmitter. That particular ATU was built by his wife who was sat next to me when we built the kits together!

The rest of my afternoon was then spent chatting with friends and Rex on his QRPme stand. I got to see the original Tuna Tin transmitter again and pose for a photo with it.

Tuesday, 6 August 2013

MTR version2

I was lucky enough to secure another MTR (Mountain Top'er) kit from Steven Weber, this from his second batch released at the end of March 2013. I had been keeping an eagle eye on the AT Sprint Yahoo group for news of the release of another 149 MTR kits. I was amazed when an email came through just as I was getting up for work early one morning announcing that orders were being taken for the new run of MTRs. I ordered straight away but I was worried that I might have missed my chance to own another MTR as I worked out that it had taken 40 minutes for the original email to come through to my phone. I need not have worried though as I later learned that only twelve kits had been spoken for by the time I ordered.

My order confirmation came through pretty quickly from Steve, I was over the moon to have secured another MTR, this time with a neat custom case. The package arrived around 2 weeks after ordering, Steve stated that he had bought the entire stock of shipping boxes from his local Post Office and did not have enough to send out all the orders! My kit had been held back a while whilst Steve sourced some more boxes.

The kit was neatly sealed in plastic and the components were grouped together to make finding them a bit easier. Thankfully all the components were there with none missing. I think Steve does a great job with his kitting, it must be a nightmare with so many tiny components to count out. There were 149 kits made available this time around and just as with the last run, each kit was given a unique serial number, my kit being #267. The numbers for the second run started at #151, as they followed on from the last number of the first run kits.

 The board went together well, although it was time consuming; there are more components than you realise and you have to build on both sides of the board. The processor and DDS chips were mounted first of all and I had learnt from my experience with my first MTR, so this time the chips went on pretty smoothly. I followed the assembly sequence suggested by Steven, KD1JV.

 The build instructions had a few small mistakes, mostly due to the fact that the manual had been modified from the one for the first run kits. It didn't take much thinking to work things out though, the provided schematic helped out here. The obligatory PCB trace error had crept into the design just for a bit of interest,  so a small wire jumper from Q2 (top left) was needed. The ground pad for the antenna connector also needed modifying, it had been flagged as a via by mistake so the solder resist had to be scraped off with a sharp knife.The smoke test went well and soon I was ready to fit the final inductor (L14) for the PA and perform the alignment. The alignment firstly consists of putting the rig into calibration mode by powering up the board whilst pressing two front panel buttons. The rig then sets up a 10MHz signal from the DDS, this signal is measured using a frequency counter at the provided test point. Using the up and down buttons, the signal is calibrated to exactly 10MHz.

Once the reference oscillator is set, the BFO needs to adjusted, this is simply a case of measuring the audio output with an oscillscope and peaking the internally generated audio tone for maximum amplitude using a single trimmer capacitor (CT1).

All that is needed to be done after calibration and setting of the BFO is the align the RX band trimmers. I used my FT817 (my only commercial HF rig) to provide a signal to tune my SOTA dipole using a manual ATU. I tuned for 1:1 VSWR  at the radio and then swapped the FT817 for the MTR and peaked the two trimmers for the first band for maximum response. I then repeated the whole operation again for the second band.

The board had already been tried into the case in order to cut the wires to the correct length for attaching to the external sockets. Putting the PCB into the case was just a matter of disconnecting the power and antenna jacks, as these pass through the case from the outside, and then resoldering them when in the final positions. The board is held in place by  four screws through the top of the case and into the stand offs soldered into the PCB at each corner - a neat solution. A strip of felt across the four push buttons gives a tidy appearance along with the red transparent plastic window for the display.

The rig is very pleasing to use, I built my second MTR for 20m and 30m, and I find 30m is great for weekend SOTA when there is also a big contest on the bands. I like the new case, but I probably prefer my original Altoids tin MTR, it's so much more compact and lighter too! My Altoids tin MTR weighs in at 80g, whilst my new MTR with it's pretty case weighs in at 170g! There are some minor circuit board changes to the second run kits and it might be all in the mind but i find I prefer the audio of my first run MTR.

KD1JV has produced a great little kit that works very well. I'm sure these MTR's will be sought after for years to come. There are apparently 299 MTRs out in the wild and it's unclear whether there will be any more produced, Steven was making noises about making a more complex rig next time including DSP.

1% of the world's population of MTRs!


Sunday, 24 March 2013

SW-20+ Keyer speed control

After all this time I finally got around to fitting a CW speed control to the front panel of my SW-20+
This rig has been a 'work in progress' for a long time. I intended to use the rig for SOTA as my main 20m rig but then I managed to secure one of the limited run of KD1JV's Mountain Toppers (aka 'MTR'). I did manage to work a few contacts with the SW-20+ during testing, including a QSO with Bill, NG2D, in Pleasant Valley, New York.

I tried the rig out on one SOTA activation from Rombalds Moor G/NP-028, and the rig seemed to do OK, but I found that it was a bit tedious to change the speed of the keyer chip that I had fitted to the rig. I had used the PicoKeyer chip from Dale, N0XAS, and built a little Manhattan style keyer circuit fixed the the rear of the SW-20+ case. I had omitted the speed control potentiometer for simplicity, the speed can be set through the menu accessed by pressing the front panel button. I found that I wished that I had fitted the speed control.

During building and testing of the rig, I decided to tweak the tuning range to cover a larger portion of 20m rather than the standard 30 to 40kHz. There is a capacitor that sets the tuning range, I had changed the value to give me band coverage from 13.999 MHz to around 14.070 MHz, I found that the tuning was a little on the difficult side, a slight touch of the tuning knob and you would QSY a number of kHz. Whilst I was inside the rig to fit the speed control, I swapped out the capacitor that sets the tuning range, I now get around 37kHz of swing from about 14.026 to 14.063MHz, this should make the tuning a little easier. I noticed that a lot of the SOTA ops in NA tend to operate above 14.060 MHz, usually 14.061 or 14.062MHz, I thought it was important to have these frequencies covered, whilst still allowing as much tuning below 14.060 as possible.

I ordered the 50k potentiometer from Ebay one afternoon and the very next morning it arrived in the mail, it almost seemed as though the vendor had posted it before I had ordered it! Fitting the potentiometer took quite a bit of work, I had to remove the FreqMite (PIC based frequency counter) from it's front panel bracket first. I left the FreqMite hanging from it's wires and as to be expected I suppose, some of the wires broke off. I then had to remove the fixing screws for the main PCB and move the entire PCB sideways out of the enclosure because I had broken one of the cover fixing brackets, doh! Luckily there is just enough gap between the cover fixing brackets to squeeze the PCB through - good design or pure luck? :-) I repaired the cover fixing bracket and then I removed the sticker on the front panel that said 'SW-20+', of course the sticker had to bring some of the silver front panel paint didn't it?!

Drilling the hole for the potentiometer actually went very well, I managed it without damaging any more of the silver paint. The potentiometer was finally wiggled in to its hole after a bit of persuasion; one of the IC's on the main PCB was just in the wrong place and was fouling. The next task was to rebuild the rig; the main PCB was pushed back into it's correct position and screwed into place. Then all the broken wires had to be fixed to and from the FreqMite. The FreqMite would no longer fit in the same place as before; I had to move the board away from the front panel a little bit and make a bracket extension to support it.

I wired up the new speed control pot to the PicoKeyer board and then it was time for a test - the usual law states that all potentiometers will be wired up 'backwards' i.e. the speed will go from fast to slow, rather than the expected slow to fast. Upon powering up the rig, I was greeted by the usual '73' from the PicoKeyer and the usual babble from the FreqMite asking it's questions, I tried the speed control and I had actually wired it up correctly! How I managed that, I will never know!

Whilst the cover was off the rig, I gave it a re-alignment just to make sure it was properly set up. I found that I could squeeze 2 watts on transmit from a 12v supply, so I think that's pretty good. I backed the power down to 1.5w and left it set at that.

So now the rig is just about finished I reckon, there is not much more room left in the case for further additions. I gave the top cover a quick polish up with some car polish, it's now super shiny! I could do with touching up the silver paint sometime and putting some lettering over the speed control knob, just to finish the rig off.

I am determined that I will do a proper SOTA activation with this rig, it's too nice to just have stored away in some cupboard.

Well, that's it for now folks, my next blog entry will probably be about building an MTR from the second batch of 149 kits - yes, I managed to secure another one! :-)