Recently we looked at a digital DSB transceiver kit for FT8 that’s been making the rounds, and talked about the pros and cons of such a design. There’s also been discussion about the DSB digital FT8 rigs on several groups.io and Facebook groups.
Another vendor has entered into the arena of digital-only QRP radios. It advertised as a SSB digital only radio kit for FT8 (and one alternate frequency) and it’s called the Phaser. Let’s have a look!
The Phaser: A first glance
The rig we’re looking at today is called the Phaser, by Midnight Design Solutions. It’s a single band transceiver for either 80, 40, 30, or 20 meters. It was designed by Dave Benson, K1SWL, who also designed many other influential radios through the years.
The Phaser has several advantages over the DSB rigs, but there are still some compromises that need to be examined. Let’s take a look at the design and break it down some of the pros and cons.
Phaser Specifications and Pro’s
Let’s have a look at the transmitter portion. An si5351 clock output is fed into a 74ACT74 flip flop, which is used to generate IQ output into a phasing filter (hence the name “Phaser”), producing a SSB signal which can then be mixed with the audio input.
The si5351 synthesizer is a wise addition to this digital radio. The radio can be programmed to have an alternate frequency in addition to its pre-programmed FT8 frequencies. This will make it great for JS8Call (the default alternate frequency) and other digital modes- even WSPR. Not having to put in a different crystal to change frequencies is very good. This is 2019, after all!
The specs for the transmitter say that it has 30dB of opposite sideband suppression, and that’s far better than DSB. It’s still not as good as the 40db of sideband suppression that most designs strive for. Still, this design is heads and shoulders above the DSB transceivers, and at $50 is only $10 more.
Another benefit of this radio is that owners of these radios can communicate with each other, unlike DSB radios which are unable to communicate directly with each other.
Looking at the Receiver
A look at the receiver portion of the schematic show that the Phaser has a Direct Conversion receiver using the time-proven but dated ne602 mixer. This is okay but not optimal. A standard double balanced diode ring mixer would give the receiver a better performance. The ne602 was probably chosen for low cost and simplicity. To see what a Direct Conversion receiver with a double balanced diode ring mixer looks like, check out the DC40 project on this site.
The Phaser’s page says that it’s a SSB transceiver. And that’s true in the sense that it can transmit and receive SSB signals.
The receiver lacks sideband filtering however, and so this is not a SSB receiver, it is an unfiltered DC receiver that can successfully receive SSB signals. As was mentioned in the DSB Digital article, lack of sideband filtering lowers sensitivity by up to 3dB. It will still receive SSB signals, so not all is lost, but it is a significant compromise in performance. It would have been nice to see them use filtering in this portion of the radio as well, especially since IQ output is already on the board. Granted, this would drive complexity (and price) up a bit.
Other Awesome Things
There are other really good things about this radio. All of the surface mount components are preinstalled. The manual is excellent, and the price/performance ratio is much better than the DSB transceivers. The Phaser puts out 4W of power, and it’s not wasted with the opposite sideband. The radio is small (4.125″ x 3.85″) and only draws 135ma on receive and 1A on transmit. Not bad!
Overall, the Phaser will be a fun radio to operate and will be a better investment than one of the DSB radios. It’s only $50 (their introductory price), and such a small investment in radio gear will surely bring hours of fun in the building and operation of the rig. Be sure to go to their site http://www.midnightdesignsolutions.com/phaser/ and check it out!
It seems that digital-only radios are getting really popular. It’ll be interesting to see what other vendors come up with for this space. If you know of any others, be sure to let us know in the comments below!
12/4/2019: Article updated with the correct company name (Midnight Design Soltuions, not Studio) and to add information about the designer of the radio.
12/5/2019: Updated to remove reference to the Mountain Topper radio which was not designed by K1SWL