Review of the Elecraft KX3 Ultra Portable HF/2m Transceiver

[Moleculo]

I found out in 2011 that Elecraft was working on a small, ultra portable HF/2m SDR rig and my interest was immediately piqued for quite a few reasons. First, as an owner of the K3, I was confident that any new transceiver that Elecraft put out would have terrific specifications. Secondly, I like putting together kits, and Elecraft always makes their products available in kit form. I already had the Yaesu FT-897D as my portable rig, but the thought of something 1/10th the size was very appealing. Given Elecraft's reputation for customer support and their unique approach to software defined radios, I decided to promptly sell the Yaesu FT-897D and pre-ordered a KX3 kit within minutes of receiving the pre-order announcement.

After several months, I received my kit and hastily took all of the components out of the box and laid them out:

Keep in mind that the KX3 is available in either assembled or kit form. I was one of the very first customers to receive the KX3 in kit form. You can follow along with my build process which includes detailed photos in this article. The entire build process only took a few hours and is no more difficult than assembling a basic PC. I really think that anyone that can use basic hand tools can have a lot of fun assembling the kit, although if that's not for you then for an extra $100, Elecraft will provide you with an assembled rig.

Here is the cost breakdown of my initial order (rounded to whole dollars):

Item | Price
KX3 Kit|$900
MH3 Microphone|$60
KXFL3 dual-Passband Roofing Filter|$130
KXAT3 Internal, 20-W Automatic Antenna Tuner|$170
KXBC3 Internal NiMH Charger with Real-Time Clock|$60

Total|1320​

I later picked up the KXPD3 Precision Iambic Keyer Paddle which has a price tag of $130.

Physical Attributes
Here is a picture of the fully assembled radio with the paddle, microphone, power, and antenna attached:

The dimension of the KX3 are 3.4" high x 7.4" wide x 1.7" deep. It weighs about 18 ounces without batteries and options. To give some perspective on how small this rig actually is, I took this picture:

The left side contains all of the interface ports (more on these in a later update):

The right side contains the BNC HF antenna jack and the location of the future 2 meter SMA antenna jack:

The thumb screws on either side are how you open the rig to install the batteries:

Note that you do not need to install batteries if you have an external power source. It is also safe to install the batteries while the rig is powered by external DC. In this picture, the optional battery charger is not installed because it is not currently being shipped. When it does ship, I will be trying various other types of batteries and reporting back on the lifespan and performance using this power configuration.

The optional paddle installs on the radio face using the thumb screws:

This paddle is really an ingenious design, well built, and is adjustable via the small allan screws in the top and sides.

In the next update, I'll cover the basics of the operational controls and discuss some of the more detailed specifications of this completely software defined radio.

 

[Moleculo]

Basic Operation

Elecraft has stated that the goal of the KX3 was to build a portable rig that would appeal to both novice and expert users alike. The KX3 user interface demonstrates these goals in practice in every way.

Here is a sample picture of a typical operating display:

If you've ever seen the K3 display, the KX3 looks very familiar. Working from the top left, the meter shows received signal strength, SWR, and RF power. This meter also shows Mic Gain and Compression when you are adjusting those values. The frequency, mode, antenna selection, and sub band are all easily readable, as expected. A graphic that represents pass band filter width is on the bottom left, next to the AGC and actual filter selection setting. You can change what is displayed in place of VFO B - one of the settings I find most useful while portable is the operating battery voltage. Overall, I find the display well thought out and easy to determine basic operating parameters at a glance.

Here is a close-up pic of the left side controls on the rig:

As expected, you tap the button for the function printed on the button, and hold the button down for the function in yellow printed below the button. If the button below one of the dials is an adjustable function, after pressing the button, you make adjustments using the dial directly above. For example, if you wnat to adjust the Compression, you simply press the CMP button and then dial the knob above labeled KEYER/MIC.

Each of the three dials also have alternate functions indicated in yellow that are accessible by pushing the dial in. The button functions take a few minutes to get used to, but are easy to remember once you understand the principles.

The right side of the rig has buttons that function similarly:

The dial on the right has several functions. The obvious function is that it serves as the adjustment for VFO B. It also is always set up to make fine adjustments to VFO A when not selected to change VFO B. If you have RIT enabled, pushing the dial resets the clarifier to the VFO A display frequency. Lastly, you use it to change display or menu options.

Pressing and holding the MENU button gives you all of the advanced configuration and setting functions which will be highlighted later. As you can tell, the basic operation of this rig is really fairly straight forward.

 

[Moleculo]

Transceiver Interfaces

As mentioned earlier, The left side of the radio is where you'll find all of the interfaces.

The obvious ports are for the mic, key, and stereo headphones. There are several configuration options available for this port depending on what type of paddle or key you will use. ACC1 is the PC interface for use with the included USB or Serial (depending on which you ordered) cable. ACC2 is the general purpose I/O port, used to provide PTT to external devices (like a linear amplifier), as well as several other functions like providing transverter control, or controlling PTT On the KX3. Again, the menu options provide settings to allow you to select how you wish to use this port.
The RX I/Q port is a quadrature output which allows you to interface the radio to a stereo PC soundcard input and use various panadapter types of software like HDSDR and NaP3.

Because the KX3 is first and foremost intended to be a portable radio, extra sound card interfaces are not provided. If you wish to use soundcard modes, you need to build or acquire a sound card interface that use the stereo headphone and microphone jacks on the KX3.


Basic Specifications

Elecraft lists the specifications in detail on their website, so I will only highlight a few of the more interesting specs. First, the rig will use a fairly wide operating voltage: 8v-15v. While the maximum power output is 10 watts, when voltage drops below 11v, it will automatically reduce power output to 5 watts. The rig is designed from the ground up to consume as little power as necessary and can be configured to consume as little as 150ma while receiving. To achieve 150ma of RX current drain, perform the following (courtesy of Wayne at Elecraft):

• Use headphones (10-100 mA saved depending on volume level)
• Turn off the LCD backlight (25 mA)
• Turn off the RX I/Q port when not needed (10 mA; see MENU:RX I/Q)
• Turn off the preamp (5 mA saved for the 20 dB preamp, 10-15 mA for the 10-dB preamp)
• turn off the RX isolation amp (10-15 mA; see MENU:RX ISO)

On transmit, the rig will automatically change to a higher-impedance PA output transformer winding to reduce current drain when power output is reduced to 3 watts or certain other conditions are met when operating below 5 watts. This neat design feature can result in about a 50% TX current drain savings!

While the KX3 is a direct conversion, zero-IF receiver much like other SDRs, the optional dual bandwidth roofing filter is an intelligent design that overcomes receiver blocking from adjacent signals. This is especially useful for field day and other activities where other transceivers may be operating nearby.

It's important not to overlook a few other built in features like an 8 band TX and RX equalizer, adjustable speech compression, and even DVR!

Coming next, testing out the optional auto-tuner...

 

[Moleculo]

Auto Tuner Performance

The fact that an HF rig this small has an optional auto tuner is almost an anomaly all by itself. QRP rigs like the Yaesu FT-817 don't have an auto tuner feature and it is just as uncommon in mobile HF rigs. Even entry level base station HF rigs leave often leave out the auto tuner.

Not only does the KX3 offer one that fits neatly within the chassis, it's also extremely capable, handling loads in excess of 20:1 SWR!

This is my KX3 Auto Tuner Torture Test:

I placed the KX3 in the middle of my den with a 6 foot telescoping whip attached. Ground for the antenna was only supplied via the electrical chassis ground going to the power supply plugged into the house mains. While this setup is completely impractical, it should give you an idea of the types of loads you could tune with a very compromised antenna in the field. The following is a table that shows what the KX3 auto tuner was able to do with this short indoor antenna:

Frequency | Tuned SWR
50.125|1.0:1
28.410|1.0:1
24.930|4.9:1
21.275|2.3:1
18.125|1.0:1
14.200|1.7:1
10.125|1.6:1
7.200|12:1
5.330.5|16.6:1
3.900|15.1:1

As you can see, on almost all of the bands 30 meters and above, the rig is actually useable! A much more practical application is to use a reasonable length of wire, 20-30 feet or longer, tossed in a tree with a reasonable trailing ground wire. The KX3 should have no problems loading up an antenna like this so you can have fun with the worst antenna conditions.

Next up, I'll cover some of the more advanced features of the radio, although if anyone has specific questions about the rig, I'll be happy to answer those first.

 

[AudioShockwav]

I will say the results on the Auto tuner are very nice indeed.
When I bought my 897D I got the FC-30 with it because it matched the radio and I was very disappointed by its performance.
So bad in fact I sold it at a loss a couple of month's later.
I often go camping and use some very basic antennas, to see the Elecraft tuner work that well with a 6 foot telescoping whip is nice.
At what SWR set point will the PA start folding back power?


73
Jeff

 

[Moleculo]

At what SWR set point will the PA start folding back power?

I did a quick test to see if I could answer that question. I used a cross needle meter, so it's difficult to say exactly, but it looks to me like the point where power starts to fold back is something greater than 4:1 SWR.

The way the ATU works is actually really convenient. With the unit installed, you can set the radio via menu options to either BYPASS the tuner or put it in AUTO mode. AUTO mode is the only choice if you want it enabled.

While using the radio, whenever you key up on a new frequency, the radio automatically determines if it should do a quick tune using one of its stored tune parameters or quickly find a new setting. If you press the ATU TUNE button, the radio will do an extensive search to find the best match and then store that in the memory. ATU parameters are saved every 20khz for each band, so once the rig learns the antenna you're using, retunes are very quick.

 

[vagrant]

Thank you for the write up. The KX3 pretty much kills my 817ND for hiking and air travel and should work well with the mini-buddipole to keep things compact. So many features it's impossible to resist. My want would be a good case to protect it, but should fare well in my carry on with the camera & computer. Ughh...too many hobbies.

Still, I'll wait another six months for things to shake out and improve. I think a foldable solar mat is in my future as well.

* That tuner is incredible!

 

[Moleculo]

My want would be a good case to protect it

I picked up the perfect case for it. I'll take pictures tonight and post it in another thread with a link here.

 

[Moleculo]

Sherwood Engineering Test Results

Sherwood Engineering just released their test results for the KX3 receiver, which are unbelievably outstanding. The KX3 Dynamic range is currently shown as the best on the market! The tests results are quite interesting and can be found at:

Receiver Test Data

 

[Moleculo]

As promised, I posted pictures and comments about a perfect case solution for the KX3, which can be found here:

http://www.worldwidedx.com/elecraft-kx3/140715-kx3-carry-case-recommendation.html

IMO, this is the perfect case for this rig and will protect your investment while transporting for a long time.

 

[Moleculo]

I went on a search to provide cost effective, long lasting portable battery power for the KX3. I posted the results of my search here:

http://www.worldwidedx.com/elecraft-kx3/143215-ultimate-portable-power-elecraft-kx3.html

In my next updates, I'll continue on with some of the neat, built in features of this amazing portable rig.

 

[Moleculo]

I had to take a little break on my review of the KX3 while I had some family vacation and some work engagements. It's now time to pick up where I left off and discuss some of the interesting features of this unique rig.

Internal vs. External Speakers

The KX3 includes a small, built in speaker. The little speaker is fairly powerful for its size, but it is not what you will want to use to realize the rig's full potential.

There are reports of mechanical buzzing generated by the internal speaker due to the case design, but Elecraft says they are working on it. I did a small modification to my case to add clearance around the speaker which helped me quite a bit, but there seems to be more than one issue causing this buzz. Keep in mind that using the external speaker causes additional battery drain that can be avoided by using headphones or external powered speakers.

For me, a set of decent ear buds is the way to go because you get to take advantage of some features only available with two speakers. Also, headphones allow for more volume than the internal speaker is capable of. Two key options are that are only available with stereo speakers are the simulated stereo effects and the dual receive.

KX3 Stereo Audio Effects

Plug in a set of headphones, go into the Menu settings, and select the AFX MD (Audio Effects Mode) menu. Set it to "Delay" and you get a simulated stereo effect on the received stations. Couple this with the RX 8 band EQ and the pleasantness of the received audio is amazing, and listening fatigue is eased at the same time. It's just too difficult to describe how nice this rig sounds - you just have to hear it for yourself. The other option you can select is "Pitch", which maps received stations between right and left depending on the pitch of the signal. The most practical use for this is when you're listening to multiple stations - it adds some separation to the signals sending stations to either ear. Personally, I prefer the Delay setting, but you may have your own preference.

Dual RX

Another impressive feature you get when using stereo headphones or external speakers is the Dual RX capability. This feature is like having a second receiver with some limitations. Set the VFO A to one frequency and VFO B to a different frequency within 15KHz of each other. Go to the menu options and change the DUAL RX to "Auto". The rig will send VFO A to the left ear and VFO B to the right ear. This feature is especially helpful when trying to work a DX station operating split! Unlike a true dual RX radio, you don't get separate volume and filter controls, but this still is a really nice feature for rig at this price point.

I use the radio both with just the internal speaker and with headphones and hope that Elecraft will solve the mechanical buzz issue created by the internal speaker. Regardless, using headphones adds a whole level of enjoyment to this rig.

 

[Moleculo]

Noise Reduction

Elecraft recently added Receive Noise Reduction to the firmware, which is not described in the manual at the time of this writing. Since I live in a high noise area in the city, this is a very important function that can make or break an HF rig for me. I've used it for a while, and all I have to say is "WOW". This implementation of NR is probably the most flexible implementation on the market today. That said, it's still a work in progress and a few refinements on the user interface for this function could probably be made.

Because there is not a dedicated knob to NR on this little radio, you have to go to the Menu settings and find the entry called "RX NR". It is locked by default, so you have to hold down the RATE button for about 3 seconds to unlock it for adjustment. This is the first thing that needs to be tweaked, in my opinion: I wish there was a quicker way to to adjust it under changing band conditions or when changing bands. An cool feature is that the rig actually allows you to have different stored settings for CW vs the voice modes.

There are actually THREE adjustments that can be made that affect how the DSP works. They are named Beta, Decay, and Mix. Here is the overview from Wayne on the effect of these settings:

The default beta is 5 for CW and 10 for voice modes. A lower beta will further reduce noise, but may attenuate weak signals. The default decay is 240. A much lower decay value will allow NR to track fading signals better, at the expense of somewhat worse noise rejection. The mix value determines how much of the signal is “dry” (unprocessed) vs. “wet” (processed). The default is 220 in CW mode and 250 in voice modes — essentially “all wet”. You might want to use a lower mix number to reduce the “hollow” sound or to minimize the effect of NR on weak signals.

I had to read that a few times while playing with the settings, but it makes the NR almost infinitely adjustable to suit your liking. Once you have it set, you can turn the NR on and off by just pressing the NR button on face. I can honestly say that the DSP in the KX3 works better for me than the K3. I have not owned any of the other "high end" radios, to compare to but it's far more flexible and works far better than any of the "mid range" rigs I've owned.

Some things I would like to see improved with the NR usability: I already mentioned the ability to change the settings quicker. Along with this, I don't think you really need the range of adjustment (1-250) on each of the three settings. The net effect of this is that it takes a really long time to move from minimum to extreme trying to find the setting you like. The reality is that once you find the settings you like, you get accustomed to the one adjustment that impacts what you like the most and tend to just tweak that one.

Wayne indicated to me that there may be some more tweaks made with the usability of the NR, but it sure does work well with the current setup.

 

[Moleculo]

KX3 Paddle Upgrade Kit

People often wonder why Elecraft customers tend to be a little fanatical about the Elecraft company and brand. The KX3 paddle is a great example of how this happens. While the idea of a small paddle that attaches to the rig was universally loved, some of the hard-core CW guys have been a little disappointed by the feel of the paddle while some others actually experienced a few minor technical issues caused by it's design. Several users reported that it was difficult to send beyond 30-35wpm with the supplied paddle.

Elecraft heard the feedback and went to work to find a solution to make the product as good as it can be. Today, they announced the availability of an "upgrade kit" for all owners of paddles before Sept 2012 that would be free of charge. The kit basically consists of two new sets of springs with differing tension and new contacts. Those who have tested the upgrade have reported that they are very satisfied, even calling it "near-Begali" feel, making faster sending finally possible with the little key.

I'm not trying to turn this review into an advertisement for Elecraft, but I was quite impressed by this level of service.

 

[Moleculo]

KX3 as a Mobile HF Rig

I've been asked a few times about my thoughts on how the KX3 would fare as a mobile rig, mounted in a vehicle. After using this rig for a while, I believe I have enough information to give an informed opinion. First let me point out the KX3 Mobile Installation & Operations guide on Elecraft's website: http://www.elecraft.com/manual/Rev1.2-KX3-Mobile-Owners.pdf. It's worth reading this guide if you are thinking about installing any HF rig in a vehicle as it contains some important principles, as well as some interesting ideas that you may choose to implement.

I have installed and used several HF rigs in vehicles. I currently use an Icom IC-7000 in my Jeep. While the KX3 bests every other mobile rig I've ever used in terms of performance (at it's power level), I can't see myself attempting to use it as a dedicated mobile rig right now. There are three main design choices that I feel will frustrate most hams who would try this:

1. VFO Knob - The VFO knob is touchy on the KX3. You can adjust the drag on it a bit, but you cannot adjust it so it is tight enough to stay on frequency for bouncing down the road in a vehicle. In my opinion, the IC-7000 is the standard for how mobile VFO's should operate and everyone should either blatantly copy their design or come up with a better implementation of the same idea. To be fair, the KX3 does have a VFO lock function (hold down KHz for 3 seconds), but that is only practical if you want to stay on that particular frequency for an extended period. Often when operating mobile, I reach over and dial around, listening for QSO's. If I find one, I listen for a few minutes to see if I want to join in and spin the dial if I don't. I don't think you could keep the KX3 VFO on frequency for even one minute while driving down the busy Southern California freeways in my Jeep.

2. Display - I really like the KX3 display and think that the layout is well designed. However, an effective LCD display used in a mobile environment is affected by constantly changing lighting conditions. The radios designed for the best mobile experience give the user options for brightness and contrast as well as various color choices to suit the individual user. The KX3 does not have a color screen (which is fine by me) but only has the capability to turn the back light on or off. If the KX3 were to implement some of the display features of the K3, the display would be better suited for mobile use.

3. Overall Design - I think the KX3 UI is fantastic for a portable or desk radio, which is what it appears to be optimized for. I don't think the radio was designed with effective mobile operations in mind. I won't dwell on every little feature, but I'll give a few examples of what I'm referring to:

• Size and location of radio and interfaces - The radio is too deep and slightly too large for most vehicles' mounting locations. One interesting way to fix this would be to offer a case option that would not accept batteries. Also, all of the interfaces are on the side of the radio which cause you to need even more horizontal space for installation.
• Frequency entry - the KX3's frequency entry is clever but not very useful while driving. Input on a mic would be better. To be fair, other rigs like the Yaesu FT-857D have this same issue, but the KX3 is also twice the price. A mic with keypad frequency entry should be offered.
• Parameter adjustments - This functionality may change over time, but as of right now some of the parameters that I like to change while driving are too cumbersome, causing me to take my eyes off the road too much. This is really nit-picking, but NR, NB, and PBT adjustments are areas that could be improved a bit.
• External speaker PA - doesn't deliver enough volume to external speakers in a noisy vehicle. If your vehicle is noisy, you really need a powered external speaker.

I think most of the issues I outline here could be addressed fairly easily. With the pending release of the 100 watt amplifier with built-in tuner option, I think it would be a smart move for Elecraft to consider offering a slimmed down "mobile" version of the KX3 that eliminated batteries and all interfaces except for the mic and possibly the key. For a true mobile radio, all other interfaces should be housed in the remote mount chassis.

That's my opinion on the KX3 as a mobile subject; what's yours?