Dual Gate MOSFET Investigations - Intermodulation

A look into the intermod properties of a BF991 amplifier.

You may have seen in my previous post that I have been working on the latest (and hopefully final) major revision of the CC1. Many of the previous decisions on the radio architecture have been thrown out, perhaps most importantly the decision to use a dual-gate MOSFET as the mixer. In the quest for a replacement, I considered using the old standby, a diode ring mixer, but I wanted to be open to other possibilities as well. As shown in that last post, the KISS mixer from Chris Trask seems to have excellent intermod performance with relative simplicity. So the current plan is to try to build an IF chain using the KISS mixer and see if it will work well in the CC1.

Having quantified the performance of the KISS mixer, the current quest is to find an IF amplifier that will provide decent performance at a reasonable current "price". With an IIP3 of approximately +30 dBm (I believe it should be able to get the mixer there with some improvements in components), the limiting factor for IP3 performance in the IF chain will be the IF amplifiers. Consider that my current goals for the CC1 receiver are:

  • Dynamic range of around 100 dB
  • Decent sensitivity (less than -130 dB MDS in 400 Hz bandwidth)
  • Reasonable current consumption for portable use (< 60 mA)

In order to achieve this, I've determined (using the excellent Cascade08 program from W7ZOI's LADPAC software suite) that the IF amp that I choose will need the following characteristics:

  • OIP3 of at least +20 dBm (although higher is better since the amp is the limiting factor)
  • modest gain

The current candidate for the IF topology is similar to the design seen in Figure 6.89 in Experimental Methods in RF Design, with no gain until after the first IF filter. To that end, I've been looking a various amplifier designs to see if I could find something that would fit (or at least come close to) the requirements above. Bipolar amps are nice, but use a lot of current. MMICs were another possibility; the ones I have found do have about +20 dBm OIP3, but with around 20 mA of current draw and approximately 20 dB of gain, which means the IIP3 is not that great. I figured it wouldn't hurt to take a look at the dual-gate MOSFET again, as I know that at least they can use modest current and many have excellent noise figure.

Without getting into the weeds of every detail of the experiment that I tried, I'll just recap the important parts. Initially I used a BF998 with an L-network on gate 1 to transform the 2.2 kΩ input impedance of the amplifier to 50 Ω. A pot was provided to provide variable voltage bias to gate 2. Different permutations of source resistor and gate 2 bias were tried, and the best IIP3 I could get from that amplifier was about -3 dBm (with perhaps 14 dB of gain). OK, but not great. So I decided to give the BF991 a try and see what I could get out of it. Again, I tried many variations of source resistor and gate 2 bias, and was able to find a configuration that is somewhat promising.

BF991IF

You can see in the schematic above that I settled on a source resistor of 100 Ω and "dipped" the gate 2 pot for best IP3, which came out at 5.6 V of bias. I also found in previous trials that leaving the source bypass capacitor out improved the IP3 a few dB and decreased the gain a few dB, which was a worthy improvement. Input and output was matched for 50 Ω. The current consumption was only 4 mA, which is pretty great for an IF amp in a portable radio.

bf991ip2

Here is the capture of the OIP3 measurement from my DSA815-TG. Only 10 dB of gain, but that is OK as we wanted modest gain. The IIP3 measured +8 dBm, and when you add in the 10 dB of gain, the OIP3 is +18 dBm, which is pretty close to my original spec, and all for only 4 mA.

This all looks very reasonable. But there's one problem. The good IP3 is highly dependent on VDD and VG2, especially the gate 2 voltage. As this is going to be a production radio, there needs to be a reliable way to set VG2 during calibration, every time. Also it appears that I probably need some way to keep VDD stable over a variety of voltage inputs, such as a LDO voltage regulator (maybe 9 or 10 V would work). But I need as much headway as possible in VDD in order to get the most out of my dual-gate MOSFET amp. In my experience, they don't like being voltage-starved. There also appears to be a bit of dependency on the tuning of the input L-network, although that is not as pronounced as the other effects.

As it stands now, this is a promising candidate for the IF amp, but I'll have to find a way to reduce these dependencies quite a bit in order for it to be viable for a commercial product. That's my next line of inquiry, and I'll be sure to have a follow-up post if I am able to get around the remaining limitations

Wideband Transmission #5

Latest CC1 Progress

image

As you can see from the above photo, I have finished a significant portion of the digital side of the newest CC1 prototype and now I'm on to the receiver section. This weekend I finished my first pass of the audio chain and characterized the gain and frequency response of the chain. Next up is the design of the IF and front end of the receiver. This time I plan to do a much better job of characterizing the performance of entire radio, designing for specific critical receiver specifications, and iterating the design as necessary instead of holding on to dodgy performance from circuits.

Mixer Investigations and the Search for Better Dynamic Range

Since I decided to ditch the dual-gate MOSFET mixer front end, I've been considering what to replace it with. At first, I was thinking about using the ADE-1 for the mixer and product detector, but I've been intrigued with reading about H-Mode mixers over the last few weeks, which led me to the similar, but simpler KISS mixer by Chris Trask. That seemed like a good candidate for the CC1, with relative simplicity and better-than-average performance. Since good IP3 performance is the main characteristic of this mixer, I wanted to try measuring IIP3 at my own bench to see how it looked in a home made circuit with less than optimal parts and layout.

To get warmed up, I first attempted to measure the IIP3 of a few parts that I had on hand where I already knew IIP3 values to expect: the SBL-1 and the ADE-1. Using a DG1022 as the signal generators, my HFRLB as a hybrid combiner, and the DSA815TG, I was able to measure an IIP3 of +13 dBm for the SBL-1 and +17 dBm for the ADE-1, which is pretty much right on what other people have published.

image

Here is my test setup for measuring the KISS mixer performance. I deviated from the circuit described in the KISS mixer white paper in a few ways. First, I used a TI TS5A3157 analog switch, as I didn't have any Fairchild FST3157 on hand. I also used a hand-wound trifilar transformer on a BN2402-43 core instead of a nice transfomer from a company like Mini-Circuits. I drove the KISS mixer with +3 dBm from a Si5351. My measurement of IIP3 for this variant of the KISS mixer came out to +27 dBm, which seems reasonable given the poorer components I was using. Conversion loss was 7 dB. I'm going to try to measure it again with an actual FST3157 and a Mini-Circuits transformer in the near future, so it will be interesting to how much that will improve the IMD performance.

But honestly, I probably won't need better than +27 dBm performance if this mixer is used in the CC1. Since the CC1 is meant to be a trail-friendly radio with modest current consumption, I don't think I want to include the high current amplifier needed after the KISS mixer to get maximum performance out of it. Which is kind of a shame, but I figure that I should be able to keep RX current to around 50 to 60 mA and still have a receiver with better IMD performance than your typical level 7 diode ring mixer receiver. Stay tuned for more details on the CC1 front end as they are worked out in the NT7S shack.

10 Meter Contest!

Yes, it's almost time for my favorite contest of the year: the ARRL 10 Meter Contest. Ever since I moved into the current QTH, it has been a bit of a tradition for me to operate the contest as SSB QRP only. By virtue of entering that least-liked category, it has been no problem to collect some modest wallpaper from this contest. That's fun, but my real goal is to beat my previous score. Last year, I think I did fairly well with 7490 using a stock IC-718 and my ZS6BKW doublet. So this year, I'm going to have to step up my equipment game in order to have a good chance of besting last years score. I'm thinking some kind of gain antenna is going to be a must. If I can get a Moxon or small Yagi up around 20 feet and use an Armstrong rotor, that should help give me a little more oomph than last time. We'll see if I can get something built in the less than 3 weeks before the contest.

Wideband Transmission #4

It's been a while since I've posted one of these. I understand that things have been fairly quiet over here in the last few months, so I wanted to let you all know that I'm not dead yet. I've actually been working on Etherkit a fair amount in the background, and that has been eating up most of my free work time. I know that things have looked stagnant, but please understand that I have been putting in time to revamp the business and bring some exciting new things to Etherkit. I have a few different, parallel projects going on right now. Soon I will commit to one of them and move forward on that, depending on how things pan out. I suspect I'll have more to say on the matter in less than a month on where Etherkit will be going in the future.

In related news, I've had a few people ask about what's going on with the CC1. I apologize for the CC1 being a huge bit of vaporware. To be frank, it has been the most frustrating project I've ever worked on, but I believe in it strongly enough to attempt to finish it. At this point, as much as I have had fun with the BF998, I believe that in order to make the CC1 the radio that I want it to be, I will have to abandon using the BF998 as mixers and switch to a balanced mixer design, most likely the ADE-1. I'm also looking into adding a small OLED display to the radio, which will also necessitate a large redesign to the mechanical layout of the radio (I'll probably end up doing the typical TFR design, such as the KX1, KX3, etc.). I'm also impressed enough with the Si5351A that I'm going to try using that as the new VFO and BFO. A brand new CC1 prototype is just getting started on the bench now, so it should be interesting to see how it works out. I'll post some progress photos and videos to my Twitter feed and the blog, as appropriate.

Thanks for hanging in there with me. It has been a real challenge to try to run a business while also being a full-time caregiver to my two boys. I would say that I haven't been very successful in doing both, so naturally, the business took the backseat. But now that my boys are getting older (Noah is 4 and Eli is 2.5, can you believe it?), I'm able to spend a bit more time during the day handing business. Things will be moving forward.

Si5351A Investigations Part 6

The theme of this blog post is not lots of tedious work, but refinement leading to good results.

First off, let's talk about the funny I2C address on the parts which I received from Mouser. Since Digi-Key has no order minimums and very inexpensive shipping available (in the form of USPS First Class mail), I ordered another batch of Si5351As from them so I could see if they would respond to the correct address of 0x60. Sure enough, once I received them and used the Bus Pirate I2C address scan macro, they came up on address 0x60. So it seems obvious that Mouser has some oddball parts; perhaps they were custom parts that inadvertently escaped Silicon Labs. I'm still waiting to hear back from Mouser about the issue, but in the meantime, I would recommend you order from a different distributor until they fix this problem.

I also decided last Friday to try to get my KiCad skills back in order and crank out a cheap and cheerful breakout board for the Si5351A. It didn't take me too long to get back in the groove and design a small, simple PCB that would make it easier to prototype with the Si5351A. The board is 30 mm x 50 mm, with three end launch SMA connectors on the right edge and the power/I2C pins on the other side. I've also added wideband transformers (Mini-Circuits TC1-6X+) to the outputs to isolate them from the breakout board. Below you can see the OSHPark rendering of the board.

Si5351A Breakout Board

They will hopefully be here in about a week or so (one of the benefits of living in the same city as OSHPark). Assuming that they work as expected, there's a chance that I may end up selling these as kits, so stay tuned if that interests you.

Now on to the best news. The last big question in my Si5351 investigations is whether it would be suitable for VFO usage in a standard amateur radio receiver, where it would have to be tuned rapidly. Having seen in a Silicon Labs application note that the Si5351 can be tuned glitch-free by locking the PLL to a fixed frequency and only changing the synth parameters of the attached multisynth, I set out to implement that in the Si5351 avr-gcc library.

Next, I ripped the AD9834 DDS and crystal BFO oscillator out of my last CC1 prototype and substituted the Si5351 for the VFO and BFO. Long story short, after a bit of tweaking, the part performed beautifully! I can crank the tuning encoder knob as fast as I possibly can, and I get no hint of any glitching or other tuning artifacts. The Si5351 has enough oomph to drive the BF998 dual-gate MOSFETs as well. Into a high-impedance, the drive level was over 4 Vpp, which is a decent drive level for that mixer. The only slight hardware change I had to make was to change the I2C pull-up resistors to 10kΩ and reduce the I2C clock speed down to about 100 kHz in order to reduce noise from the I2C line getting into the receiver. This change seemed to have no adverse affect on the tuning speed of the Si5351.

At this point, I believe I have investigated most of the main points that I wanted to look at when this first began. Wonderfully, the Si5351 appears to be a very suitable IC for use in all kinds of amateur radio applications. The multiple independent outputs is a superb feature, and has the potential to greatly reduce parts count and price in ham radio transceivers. I'm already thinking of many applications where this inexpensive, stable, and versatile IC can be used.

Even though the main objectives have been met, I'm still not done with this IC. I would like to look into further details, such as phase noise. I also have a lot of plans, such as building a new radio from scratch using the Si5351, possibly selling the breakout board mentioned above as a kit, and maybe even creating a more complete development board (which could be used as a wide-range VFO) by incorporating a microcontroller, LCD display, and encoder knob. Keep watching the blog for further updates.

Stuff 'n Things

As a mild winter turns into an unusually nice spring here in Beaverton (last week we had multiple days with clear skies and highs in the upper 70s °F), a young ham's thoughts turn to portable activations, Field Day, SOTA, and the like. I've been looking forward to this summer for the opportunity to take the CC1 out in the field, but I may not get to be quite as adventurous as I hoped. Last winter, I slipped in a wet patch on the concrete in the garage and hurt my knee. As a typical guy, I didn't go to the doctor to have it checked out, I decided to "walk it off". It did heal, but not completely. So I finally gave in and saw my doctor about it a few weeks ago. She strongly suspects a torn meniscus, and ordered an MRI to confirm it. Unsurprisingly, my insurance company denied coverage on the MRI, instead expecting me to do a bunch of physical therapy based on at best a guess on what the problem is. Coming from a technical background such as mine, this boggles my mind. When you have a problem and you have the tools to make a measurement, you make the measurement to see what's wrong, not just take a course of action based on a guess! I understand that money is the driving factor behind this decision, but it still seems like a waste of resources for both myself and the insurance company. Not to mention that I don't have the faith in the efficacy of physical therapy that consensus medicine does.

So now I have to decide whether to shell out beaucoup bucks on physical therapy that probably won't do anything other than siphon money from our family to their coffers. And if that fails to miraculously heal the non-specific "knee pain" referred to by the insurance company, then I guess I get the privilege of paying for the MRI that I should have had in the first place.

I'm completely fed up with politics, so I have no desire for a political battle in my comments. I'm quite aware of the history of employer-provided health insurance in the US, and the effect of government distortions in the medical marketplace. There's plenty of blame to be handed out all around, so let's just leave it at that.

Anyway, I may not get to do any SOTA summits this year (except for perhaps a super-easy one such as Cooper Mountain right on the outskirts of Beaverton), but hopefully I can at least get out with the CC1 for portable ops to the park or while camping.

Speaking of the CC1, it's at a bit of a lull in its development right now. I'm waiting for all of the beta builders to complete their construction so I can be sure that I have all of the major hardware bugs worked out (which looks tentatively promising right now). I still have quite a bit of firmware coding to work on, then I'll be ready for the next (and hopefully last) PCB spin. With any luck, that should come in about 8-10 weeks.

In the meantime, I want to work on some side projects, and perhaps some opportunities to raise more capital to fund CC1 development. In that regard, I've been looking at a neat part recently. It's a MEMS VCXO from SiTime called the SiT3808. What's cool about this part is that it has linear voltage tuning, so that you don't have the uneven tuning response like you would from a varactor-tuned VCXO. The phase noise on the spec sheet also looks very good. I ordered some samples for 7.030 MHz and 28.060 MHz and breadboarded them to test the frequency stability. It was nothing short of amazing. The 7.030 MHz part had a long term drift of 5 Hz in 1.5 hours. The 28.060 MHz part drifted only about 20 Hz in 2 hours. That's pretty spectacular for CW use.

Since the 28 MHz part was so stable, I created a QRP transmitter for it by adding on a keying circuit and a couple of BD139 amplifiers. It outputs a very clean and stable 2 watt signal and has a tuning range of about 20 kHz. I also was fairly easily able to create a TX offset circuit, so that the transmitter can be paired with a direct conversion receiver (which I plan to do soon). Since tuning is linear, the offset is the same anywhere in the tuning range, unlike a typical varactor-tuned crystal oscillator.

I've been thinking about a way to introduce these parts to the ham community, since I don't believe that I've seen them mentioned by any homebrewers or used in any kits. Last week on the qrp-tech listserv, K7QO proposed a group build of the venerable NE602/LM386 direct conversion receiver (this one from chapter 1 in Experimental Methods in RF Design). Since this design is so well known, it seems like a "remix" of this design using the SiT3808 as the local oscillator might be a fun way to spread the word about the product. I breadboarded a version with the 7.030 MHz SiT3808 sample, which you can see below (the SiT3808 is in the upper-right corner, and it obscured by the tuning pot wiring).

NE602/LM386 Prototype Receiver with SiT3808
NE602/LM386 Prototype Receiver with SiT3808

It works exactly as expected. Wide open band signals directly dumped down to baseband, and a nice, stable LO. This particular SiT3808 part number only tunes about 4 kHz, but I will be able to get parts with a greater tuning range. I'm consulting with SiTime right now about bulk pricing, and hopefully I'll be able to do a kit run of at least 100 of these bad boys in the near future. Let me know in the comments if this is something that may interest you.

So that's my big rant for the day. Stay tuned for further updates on all of these projects in the near future.

The Thrill of QRP DX

Last night after the rest of the family was in bed, I was hacking on the CC1 firmware to add the BFO calibration routine so that I could get an accurate readout of my receive frequency. After successfully completing that task at the late hour of 0130, I decided to cruise 40 meters to see what was going on. Normally the best time for 40 meter DX at my QTH seems to be from about 0200 or so until sunrise, so I thought I might catch something.

Scanning below 7.030 MHz, I came across a very loud station. I figured it was somebody in CONUS, but decided to listen for an ID just in case. It actually turned out to be PJ2/K8ND in Curaçao. Not exactly rare DX, but it's still quite a ways from my QTH and it's a new one for me. So I figured I would take a crack at it with the CC1. Long story short, I set the CC1 in XIT mode and after an hour of trying, my 3 watt signal finally managed to crack the JA-wall. I was pretty excited! Not exactly a heroic snag in the annals of DXing, but it was a good one for me. My single HF antenna is a ZS6BKW only up about 30 feet, so busting a 40 meter pileup to a station 6000 km away made my night. My first DX contact on the CC1! Even better, I woke up to find that the FB op uploaded his log to LoTW immediately, and I've got +1 to my DXCC count.

QRP is fun!

CC1 #1

A brief post to show you the CC1 prototype, now inside of its aluminum enclosure. This is the actual enclosure that will be used for production, but I will have the end caps custom cut and silkscreened, so you won't have to do it yourself. Pardon my questionable metalworking skills, and please note the the production tuning knob will be different (a bit smaller so as to not interfere with the LEDs). At least this will give you some idea of what the final product will look like. The dimensions of the enclosure is 70 x 100 x 29 mm (or 2.75 x 3.93 x 1.14 inches). The first photo shows a size comparison with a standard deck of cards. The weight is 190 grams (6.7 oz).

After the latest circuit tweaks, everything is looking very good with this beta test. I will have more news for the beta testers in the near future. Exciting!

CC1-40 In Enclosure
CC1-40 In Enclosure
CC1-40 Front
CC1-40 Front
CC1-40 Rear
CC1-40 Rear

First RF

CC1-40 Prototype
CC1-40 Prototype

Two days ago, I received my pack of 10 CC1 prototype PCBs from Seeed Studio. The excitement was too much, so I immediately started building the first CC1 prototype as soon as my wife got home from work. Not surprisingly, I didn't go to bed until I completed the build, sometime around 3 AM. I knew it was futile to even try to sleep, as I'd just lie in bed wondering if I had messed something up with the circuit. The radio seemed to pass all of the basic checks early that morning, but had a few oddities that needed to be worked out.

Yesterday, I was able to tweak some component values and got almost everything in line with my Manhattan-built prototype. I could hear a good rush of band noise as the antenna was connected, signals were coming in, and there was a stable 3 W CW output from the transmitter. Everything was looking great, but by the time the radio was ready to go QRV, 40 meters was closed and I was dead tired anyway.

NT7S CC1 Beta Test QSL
NT7S CC1 Beta Test QSL

Tonight, I tried to make a first QSO with AA7EE, but 40 meters had already gone long by the time I was able to make it to the radio at 6 PM, and Oakland was well out of the skip zone. There were a lot of signals from Rockies and east on the band, so I cruised a bit looking for a CQ. No luck finding anybody CQing, so I found a clear spot just above the QRP watering hole and called CQ with the CC1 keyer memory. Right off the bat, I got a call from WA0JLY! We gave each other 559 reports, but he actually came up to 579 by the end of the QSO. It was a very short QSO, as just as we exchanged reports, I was called away to help with our 10 month old son Eli. So I apologize Denny for the cutting the QSO short and for my shaky fist! Earlier today, I made some special QSL cards to commemorate the occasion and WA0JLY will get the first one. I do plan on getting more on-air time with the CC1 over the next few months, something that I've set aside far too much while I've been doing design.

So the initial verdict for this CC1 beta test is looking good. I will be getting in touch with the original beta testers soon and soon after that will contact those who requested to be in on the next beta (if you are one of those people and you don't hear from me soon, feel free to contact me). As I've been saying recently, I'm cautiously optimistic about this board spin. I hope that I will be able to deliver a good product to my beta testers that has all of the original bugs eliminated.

Edit

I've had a lot of people ask for details about the CC1 and I forgot that it has been a while since I've last reviewed the details about the rig on the blog. So here's a quick list of specs. Please keep in mind that this is strictly preliminary and subject to change for the release version.

  • Monoband CW QRP transceiver kit
  • DDS VFO (AD9834), full band coverage
  • Mostly SMT construction (0805 resistor/capacitors)
  • Initial available bands: 40, 30, 20, 15 (probably will add 80 and 17 if there is demand)
  • ATmega328P microcontroller with built-in keyer and straight key mode, audio frequency annunciation, RIT/XIT, voltage supply readout, breakout headers to UART, I2C, ADC, GPS port for WSPR transmission (and hopefully APRS over PSK63)
  • TX output power: 3 W
  • RX current: ~40 mA
  • TX current (13.7 VDC, 3 W): ~370 mA
  • MDS: -125 dBm
  • IF rejection: 86 dB
  • Image rejection: 95 dB
  • Two-tone, 3rd order IMD dynamic range: 75 dB
  • PCB dimensions: 70 x 99 mm
  • Custom matching aluminum enclosure measuring 70 x 100 x 25 mm will be included

HNY

Yes, a belated Happy New Year greetings! It's hard to believe that 2013 is already well under way. I figured it was about time to give you a quick update on what's going on in the shack right now.

First up is the discrete component grabber receiver for 14.141 MHz that I prototyped to be paired with the OpenBeaconMini project. The receiver itself consists of a roughly 2 kHz wide crystal filter on the front end, feeding into a single-balanced diode ring mixer, which drives an AF amp using 2N4401 and 2N4403 transistors. Because I'm not able to put up a proper outdoor antenna for the grabber right now, I decided to put the VE7BPO cascode active antenna on it instead. It seems to work well, but I don't know for sure because there are basically no signals on this part of the band. I intended to use my Raspberry Pi with the receiver as a grabber, but I had no luck getting either LOPORA or QRSSVD to work properly and reliably. It may just be asking too much of the poor beast. So I'm going to try to appropriate another PC in order to get the grabber receiver QRV so that on-air testing of OpenBeaconMini can begin in earnest.

Discrete component monitor RX for 14.141 MHz
Discrete component monitor RX for 14.141 MHz

Next, I wanted to give you a very brief overview of my most recent purchase for the lab: a Rigol DS1022U arbitrary waveform generator. As far as I can tell, this appears to be pretty much the same as the DS1022A model that is sold in the US. But being a typical ham, I wanted to save a few dollars, so I purchased it off of eBay from seller who says he is an authorized Rigol dealer.

Rigol DG1022U Arbitrary Waveform Generator
Rigol DG1022U Arbitrary Waveform Generator

The DG1022[U|A] has two channels that can output a sine wave up to 25 MHz in 1 mHz (as in millihertz) steps. It can also provide square, ramp, pulse, noise, and arbitrary waveforms at lesser frequencies. It can modulate the waveform in a variety of ways, including AM, FM, PM, PWM, and FSK. It can, of course, also do sweeps of various parameters. The output amplitude into 50 Ω ranges from 10 Vpp on Channel 1 or 3 Vpp on Channel 2 down to 2 mVpp on both channels (or -50 dBm). The shielding on this AWG seems to be excellent. Using my HP 355C/355D attenuator combo, I can get a signal down to about -140 dBm (disclaimer: not a scientific measurement, made using my ear as a detector and listening on my IC-718). The dual outputs makes it very useful for a variety of two-tone receiver measurements, one of the big reasons driving my purchase. The Channel 2 output also doubles as a 200 MHz frequency counter input. Paired with the USB connectivity of the device (it seems to enumerate as a usbtmc device), that will be extremely handy for measuring oscillator drift. The DG1022 can also link the two channels together and give them a specific phase difference, as you can see below. This will make it very handy as a I/Q LO when I want to experiment with phasing and SDR rigs.

I/Q Output from DG1022U

So far, I've been very pleased with my purchase. I don't feel like I've had it or used it long enough to give you a full review, but I thought that this preview would at least be a bit helpful for those thinking about using it. One of my goals for the new year is to do a much better job of characterizing everything that I build. Since I intend to start selling transceivers in the near future, it's doubly-important that I can make accurate measurements of my products so that I can properly state their specifications. To this end, I've decided to sell off a bunch of my unused or replaceable test equipment (please take a look at the for sale posting) in order to finance the new, calibrated test gear. Next up on my purchase list is a Rigol DSA815TG spectrum analyzer (just reviewed favorably in the February 2013 QST), but that's going to require the sale of everything on that page!

Finally, I've got the CC1 prototype PCBs on their way from Seeed Studio right now. It looks like they just cleared customs in the US, so hopefully they will be in my hands in the next few days. With any luck, I'll have the first one built by the weekend and will be well on the way to a new beta test. I'll put up a quick post to show off the PCBs, and when the first prototype unit is completed. Stay tuned!