KD1JV MTR-5B

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 ATSprint@groups.io) 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    colin.evans2@gmail.com

 
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

BAND	RX mA 9V	RX mA 12V	TX mA 9V	TX mA 12V	Power W 9V	Power W 12V
40m	23.5	18.6	440	580	2.82	4.90
30m	23.7	18.8	490	660	3.06	5.33
20m	23.8	18.8	530	700	3.15	5.40
17m	23.9	18.9	530	690	3.06	5.26
15m	23.9	18.9	620	800	3.12	5.13

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.