In the past few years I’ve used several rigs that were at least partially software-defined, but they offered few opportunities to dig into parameters and internal operations. Several years ago I decided I wanted to go deeper so went looking for a SDR that would provide that experience. It had to be compact, portable, flexible, ergonomically-friendly - a very useable cw rig. I wanted some interesting new challenges, but ones that were not overwhelming. The Risen RS-918 turned out to be all of this and more, though there are some caveats that I will explain later.
The Chinese-made RS-918 is a compact, multi-band, HF rig with a maximum output of 10W. Its touchscreen display includes a colorful bandscope with waterfall option and provides readout of various parameters such as frequency, DSP and noise reduction settings, SWR, S-meter, RF power and more. It even includes a workable cw decoder. Many of the parameters are user-configurable through the menu. A speaker is built-in.
This is an all-mode unit that includes SSB, digital modes and even FreeDV. It can be connected to a computer via two USB ports. However, as a hardcore cw operator, I have only used it in cw mode and my comments are based only that; I have not tested other modes.
One of the useful and fun characteristics of the rig is that it is easy to update the firmware, and an active group of international developers regularly provides updates that either tweak existing functions or add new ones.[i] I’ve found them to be responsive to suggestions and feedback.
Other “pros” include easily-selectable output power levels (including .5, 1, 2, 5 watts (perfect for QRP), a tune button, a zero-beat indicator (though the indicator jumps around and takes some getting used to), an easily-adjusted iambic keyer with speed readout, and dual VFOs. Both the DSP and the NR (noise reduction) are adjustable and function well. There is an adjustable RF gain/AGC control. Bandswitching is done through up/down buttons. Sidetone/offset frequency is selectable.
Calibration, adjustment and parameters are set through extensive menus, but once set, the menu rarely needs to be accessed.[ii]
The rig has a 2 ¾ x 7” faceplate, with a built-in tilt stand. Knobs are nicely-machined metal and many of the push-buttons have dual functions, but they are organized in a logical way. Once I’d figured it out, I found the layout convenient and comfortable to use.
A dedicated user group, though small, provides useful support and resources, including some files with simplified instructions for updates, etc .[iii]
The rig does have some downsides. Some of the parameters can be accessed through the touchscreen, but some of the touchscreens aren’t very responsive. Fortunately, most things also can be accessed in other ways. Plug wiring for a straight key is not standard.[iv] The built-in SMD fuse is hard to change, so it’s best to use an additional in-line fuse in the DC line. There is no built-in antenna tuner.
This rig is not plug-and-play. It comes from the factory without being calibrated, so a number of parameters like PA bias must be adjusted immediately. Documentation is on line but it isn’t always easy to decipher and with firmware updates, may not be totally current. Much of the operation is different than a conventional, non-SDR rig. Consequently, there is a fairly steep learning curve involved. In addition, quality control is not great, and factory support is poor, so there are significant risks in buying from China, eBay or Amazon. Fortunately, however, Mike, K0JTA, who started the user group for this rig, also sold the rig after testing it, updating the firmware, setting the basic parameters including the built-in TCXO, and generally ensuring that the rig is working well and ready to go. This is now being done by Pete, AD0MV, and the few extra dollars he charges are well worth the cost. (His notice on the RS-918 group may be found here.)
The RS-918 is a Chinese ready-built version of the mcHF rig designed and sold as a kit by Chris, M0NKA, in the U.K. I considered buying this kit but unfortunately, information about it was very had to decipher from the website.[vi] At the time I was looking, at least, the kit was sold as two boards, without the Mofsets, speaker, mic, case etc. Just what was involved in assembling and getting it going is not clear from the website. Like others I have heard from, I wasn’t at all sure what I would be getting into, especially since I am relatively new to SDR. Though I would have preferred to buy the “original,” it seemed safer and less frustrating to get one that was already assembled, and to get it pre-tested and adjusted.
I have had great fun with this rig, With its many features, including DSP and TCXO and the smaller size, I found I liked it better than my Elecraft K2 (its power draw is similar to the K2) and eventually sold the latter. Once you get the hang of it, it is very easy to use and allows for customization by the user. I’m on the developers’ email list and have enjoyed monitoring their chatter, even though I don’t understand a lot of it, and keeping up with firmware updates. It has provided what I wanted: experience with SDR, some manageable challenges, and solid operating experience. It’s been a good way to operate QRP while keeping a septuagenarian’s brain active.
(A version of this article was originally published in "QRP Quarterly."
Notes: [i] A Wiki description of the project may be found here: https://github.com/df8oe/UHSDR/wiki [ii] Hint: Once the menu button is pushed, the submenus are selected using the middle knob (labelled RF) to highlight the word SHOW for the submenu you want. Then use the RIT knob to open that submenu. Use DSP to select the item you want within that submenu. Then use RIT to HIDE that submenu. Finally, press and hold them menu button to save the settings and again to hide the menu. [iii] https://groups.io/g/RS-918-HF-SDR-Transceiver [iv] Some diagrams show a 4-wire jack and others a 3-wire stereo jack. I am using the latter. A SK uses the common/ground and the center ring, not the point. [v]https://groups.io/g/RS-918-HF-SDR-Transceiver/topic/new_pricing_and_current/75530694?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,75530694
[vi] http://www.m0nka.co.uk
Comentários