If you enjoy ham radio kit building, then you are definitely going to want to hear about the MDT DSB QRP transceiver kit from ozQRP. This article will be more of a real-world, operational performance review of this radios’ capabilities, not a walkthrough on how to build it.
The 40 meter MDT kit (Minimalist Double Sideband Transceiver) is produced by ozQRP, a company based in Australia. This is an absolutely amazing QRP radio kit for the 40 meter band and is a great option for those ham radio operators who are new to HF and are looking for affordable means of getting on the air, for those looking for lightweight/compact rigs for camping/backpacking, or for those who just love kit building and are looking for their next project.
By making this transceiver Double Sideband (DSB), rather than Single Sideband (SSB), the MDT should be much easier to build than any SSB transceiver kit on the market. I didn’t personally build this one, but after opening it up to peak inside, I have to agree that this radio would not be that difficult to construct.
Utilizing this DSB deign also eliminates the need to align the receiver after building the kit. All that is necessary is balancing the mixer to null out the carrier and setting the microphone gain. All user-installed components are “through hole” type. There is one SMD tuning diode, but luckily, this part comes pre- installed. You will also be winding some toroids but this is not a difficult task.
All of these design elements add up to what may be one of the easiest to build voice capable, VFO, HF ham radio kits on the market today, thus making this kit a great option for kit builders who are ready to move a step up from building single frequency CW kits such as the Pixie or Rockmite. If you want the MDT, but don’t have any experience with kit building, I recommend finding a local elmer or ham club that can help you out. With any luck, ozQRP might someday make the MDT available for sale as a fully finished product at a reasonably increased price point.
The MDT kit can cover one of two frequency range options: 7.050 – 7.130MHz or 7.215 – 7.300MHz. I received the 7.215 – 7.300 MHz version since that falls within the voice portion of the USA 40m band plan. Using my frequency counter and a second 40m rig for testing, I found the MDT to be very accurate to its specified frequency range coverage. One thing to keep in mind, however, is that since this is a DSB transceiver that utilizes a ceramic resonator instead of a crystal, you will experience a little bit of frequency drift. This was not really much of a problem for me for if the frequency drifted, I just had to compensate a little with the tuning knob.
I also found the MDT to have a very sensitive receiver that did a magnificent job at pulling out those weak signals from all over the world. The audio output jack can easily power a small self-powered external speaker if you prefer not to use headphones. On the transmit side of things, this rig is capable of putting out 1.5 – 2 watts when using a 13.8 volt power source. During my tests, I ran the MDT from a 13.6 volt power supply, which registered on my SWR/Power meter as just a little below the full 2 watts max stated by the manufacturer. When tested with my portable 12 volt SLA and lithium ion battery packs, I was able to achieve nearly 1.5 watts of output power.
Now, many of you may be thinking that 1.5 – 2 watts isn’t enough power to accomplish anything. Well, I am glad to report that nothing could be further from the truth. Shortly after hooking up the MDT for the first time (and without much effort at all), I easily made multiple contacts up and down the US west coast. I even checked into a few west coast nets as well. So far, the antennas I have used with the MDT are as follows: Carolina Windom 40, Alpha EzMilitary Vertical, and even a short MFJ-1840T telescopic antenna. Each time I used the MDT, I found myself pleasantly surprised by its performance.
At first, I found it a little difficult to dial in signals without the use of a fine tune knob. Luckily, within the first hour or so of use, I started getting accustomed to the single tuning knob, and it became almost second nature to me later that evening. I also highly recommend taking the time to properly place numbered marks evenly spaced around the dial from which you can then use to create a frequency chart that you can tape to the top of the MDT’s case. That way, you can have a good idea of where you are on the band.
The MDT transceiver doesn’t come with a microphone or power supply so you will have to source those yourself. I ended up using an inexpensive 4 pin CB mic (which I had to re-wire to work with the MDT) and a small external 12 volt lithium ion battery pack. Both of these items can easily be found online.
The MDT measures 5.12”x3.94”x1.97” and, based on my little postage scale, it weighs in at roughly 0.625 pounds (microphone not included). This makes the MDT one of the smallest, lightest, and easiest to build complete HF voice transceiver kits currently on the market.
After inspecting the internal layout, size of the circuit board, and quantity of components, I have concluded that the MDT circuit board and enclosure could be easily re-designed to fit into a taller and narrower handheld/HT (handie talkie) form factor. This would be quite amazing if ozQRP implemented this idea especially considering the category of handheld HF kit radios is essentially extinct and ripe for the picking. (YouKits doesn’t offer their TJ2B SSB HT as a kit anymore and DZKit has completely discontinued their single frequency HT-7 40M AM Handie-Talkie). ozQRP could easily and quickly position themselves as the only company on the market to offer a 40 meter DSB handheld ham radio kit. With more and more young outdoorsy hams filling our ranks, this could be the perfect opportunity for ozQRP to make this move.
I have a few simple modification suggestions for those who are planning to build this kit that other hams have implemented:
1. Add a power on/off switch (switch not included in kit, you will need to drill a hole though part of the case as well).
2. Add a second switch to easily choose between the upper or lower half of the specified frequency coverage. (This is covered in the user manual as well as by other hams on Youtube and the QRZ forums.)
3. Consider adding a small internal loud speaker. (Not included, & you will need to modify the case.)
4. Add 4 little stick on rubber feet to the bottom of the radio so it doesn’t slide around. (Probably the most important and simplest mod you can do. This radio is so lightweight that it easily slides around on table-tops.)
5. Another possible improvement would be to attempt to find a battery pack small enough to be mounted inside the MDT against the top of the case.
The MDT DSB 40 meter transceivers small lightweight spartan design is perfect for portable operations such as backpacking trips or SOTA activations (Summits On The Air) where lightweight gear is a top priority. It’s also a great option for amateur radio operators who recently earned their General Class License and want an affordable method of getting on the air with HF without breaking the bank.
To sum things up, I love this little rig. Its performance is awesome, it’s easy to operate, and it’s just plain fun to use. Talking to people hundreds of miles away using a radio that is smaller and lighter than a small box of cookies really brings out the magic in ham radio. I highly recommend the MDT kit from ozQRP for any ham who enjoys intermediate level kit building.
73! from James Hannibal – KH2SR
Made in Australia
Price: $86 Australian Dollars ($68 US Dollars) Plus Shipping
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I love mine and have used it portable with a EFHW antenna with great results. I also found that flooding the area of the ceramic resonator with hot glue will insulate It enough to minimize the frequency drift. I use a Baofeng speaker/mic with great results. Great radio and great review.
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