Category Archives: Homebrewing

Wideband Transmission #1

This is the first in a series of blog posts covering a wide variety of topics. In the past, I have used Twitter for my microblogging needs. For a variety of reasons, I'm on a Twitter hiatus right now, so I'll be using this series to convey some of the disconnected (and possibly connected) random thoughts that I feel I need to get out there. I don't think I'll be abandoning Twitter completely, but I will be reworking the ways in which I use it once I come back.

I'm also in the process of disconnecting completely from Google, so I wanted to give fair warning to those who correspond with me via my Gmail account that I will be abandoning that service very soon. I've already deleted my Google+ profile, and will be deactivating the rest shortly. I'll probably describe my rationale for this later, but keep in mind that I've been a Google customer data mine for nearly a decade, so this is not something that I undertake lightly. I'll try to get alternate contact information to those of you who regularly correspond with me.

It is an age of new beginnings.

Clackamas 2 Prototype

With the introduction out of the way, let's get down to the good stuff. Above, you can see the latest project on the Etherkit bench. It's a re-work of the receiver from the Clackamas transceiver (the rig that I submitted to the 2010 FDIM 72-part challenge). I've decided to make this receiver into a cheap & cheerful little kit to get people warmed up for building the CC1. It's currently for 40 meters only, is a superhet, and is VXO tuned (covers 7.030 MHz plus a bit more). It is 100% discrete component (you can see a TDA7052 IC above, but I've abandoned it for a different AF amp) and will be SMT construction. The receiver itself is pretty simple, but you can see there's a fair bit of other circuitry on there. That stuff is mute and sidetone circuits. It's easy enough to design a standalone receiver, but most of them will probably just gather dust after being built unless they can interface to a transmitter easily. With this extra circuitry, you can just split off your transmitter's key line and connect it to this receiver to have built-in muting and sidetone. My goal is to make this project cheap and fun to build. I'll be fast-tracking this one so I can get back to the CC1 soon.

Oddly enough, another project from the FDIM Class of 2010 is also coming out soon. As spotted on The QRPer, the Cyclone 40 transceiver is based on the rig that Dave Cripe, NM0S submitted as his 2010 FDIM 72-part challenge entry. I recall that the rig had a very unique design and that the specs were impressive. Dave's a great designer, so be sure to buy one to get a rig unlike anything else you've seen before and to support 4SQRP.

Choking off the Internet firehose that I had previously directed at me has allowed me to devote a bit more time to enjoyable activities that I've neglected, one of those being reading. I'm currently enjoying a book I've had on my shelf for a while now called Seeing in the Dark by Timothy Ferris. It's billed about being about amateur astronomers, but it does get into the professional side quite a bit as well. It's a good read and very entertaining, and I can't help but see a lot of parallels between amateur radio and amateur astronomy.

That's a great segue to the final item, which is a bit of fun from our favorite Canuck astronaut, Cmdr Hadfield. He's leaving ISS in a few days and just released a surprisingly touching (although obviously light-hearted) rendition of Space Oddity by David Bowie (one of my guilty favorites). Cmdr Hadfield may not be on the level of Neil Armstrong or Yuri Gagarin, but he's definitely making a play for Coolest Astronaut Ever.

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.

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!

Homebrewing Hangout

As I mentioned in the previous post, I wanted to try the Google+ Hangouts feature to attempt to do a video chat version of the old EchoLink chat that some of us used to have a few years ago on Saturdays. Today we took it for a spin, and I think I really like how it shaped up. We ended up having a total of 12 participants, with about half of the people actively participating, including AK6L, OK4BX, W0EA, LA3PNA, and WG0AT (Steve the Goathiker).

I've never used the G+ Hangouts before, so I didn't really know what to expect, other than a video chat. It turns out that it's quite a bit more useful than that. For example, you can do screensharing with your PC desktop or a particular window. Tomas OK4BX came prepared with an excellent slideshow presentation of the DDS-driven MEPT that he and his father recently put on the air. W0EA was able to show us the schematic and PCB layout of the amplifier T/R switch that he just sent out for manufacturing. You are also able to switch between multiple cams while in the Hangout, which AK6L used to give us some nice closeups of his projects. I've got a USB microscope which is basically a webcam with a high-power lens, so it would work great for showing off close-ups of things as necessary. We also got a neat treat to a live view of WG0AT's goats Rooster and Peanut, courtesy of his iPhone connection to the Hangout.

The only potential downside that I could see when compared to EchoLink is the free-for-all format versus the way that EchoLink facilitates traditional roundtables. It wasn't really a problem for our group, but I was at a bit of a loss on how to handle moderation. In the future, I think we'll start off with a sign-up queue to speak, then end with a free-form chat. There's also no native list of callsigns to call upon, but using a Hangout plugin (Lower Third), you can add a caption to your video stream with your name and callsign just like a TV chyron.

The overall impression was that the hangout went better than expected. We had some really interesting information presented and the turnout was excellent for a first time. I think this definitely is superior to the EchoLink chat. Now that I have an idea of what's going on, it should run even smoother next time. If you are not already a member, go to our Google+ Community page (Ham Radio Homebrewing) and join. The next time there is a Hangout, you'll get an invitation. We've scheduled the next one for two weeks from today due to it being close to Christmas next weekend. I'm not sure if this will continue on a weekly or every other week schedule in the future, but we will continue these Hangouts on a regular schedule.

Community

OpenBeaconMini

I recently did quite a bit of pontificating about the diminished state of our online communities. It's easy enough to complain, but the real measure of devotion is actually taking positive actions to help move things along. In that spirit, I was inspired by the recent announcement of Google+ Communities (a development that's been sorely needed for a long time) to create a new group there called "Ham Radio Homebrewing".

The nice thing about G+ Communities is that is supports a better range of communication possibilities than a traditional listserv or forum can provide. Photos, videos, and links to interesting projects can be very easily shared, in an instantly accessible graphical format. G+ also has the "Hangouts" feature, which allows you to video conference with other members of the group. I envision this could be like a souped-up version of the EchoLink QRP chats, where we could show off projects to each other, in live video chat.

I'm also planning on using the Ham Radio Homebrewing group to organize a small group build of a simple Manhattan construction project based on the OpenBeacon MEPT kit. This little project will be called OpenBeaconMini, and will be a very simple QRSS/DFCW QRPp transmitter kit for the frequency of 14.140 MHz (and if the project goes well, a second run of the project for 3.852 MHz). Keep an eye on the Ham Radio Homebrewing group and this blog for further details as this progresses.

SSB In A Box

Unnamed SSB QRP Rig

For the first time in quite a while, I've taken a project from start to a complete finish in an enclosure. I wanted to have my prototype SSB QRP rig ready to take with me to Salmoncon, so I busted a move this weekend to tweak the last bits of the circuitry to my liking, build an enclosure, and get it properly mounted. You can see the results to the left. I have an assortment of Ten Tec enclosures on hand, but none of them were large enough to accommodate the bulky circuit board that I used, so I had to fabricate my own out of copper clad based on the WA4MNT instructions (such as AA7EE did with his wonderful CC-20 beta build). I would say that my mechanical construction skills are average at best, so it's not the nicest looking enclosure, but I guess it's OK for a first try (the perfectionist in me sees lots of flaws). The two-tone blue and grey doesn't look too bad from a distance. Regardless of the aesthetics, the final enclosure is quite sturdy and will work well to keep the radio safe.

SSB Rig Guts

Here to the right, you can see the insides of the radio (sorry for the crummy photo, it was taken with my phone). The mainboard is the one laying horizontally and filling most of the room in the enclosure. To the left of the mainboard is the microcontroller/DDS board, standing vertically. Crammed in right in front of that, is the 4-digit LED frequency display and all of the other controls. Unseen and in the top cover, is a 1 watt, 8 ohm speaker. The LM380 AF amplifier can easily drive it to room-filling audio.

Here are some preliminary specs so you can get some idea of the performance:

  • Tuning range: 14.000 to 14.350 MHz (DDS)
  • IF BW: 2.3 kHz (3 dB), 6 crystal ladder filter
  • Current consumption: ~150 mA RX (not optimized for current yet)
  • TX Power: ~8 watts @ +13.7 VDC
  • MDS, IP3, etc.: not measured yet, see below

I haven't measured any of the important RX specifications yet, but I'll give you some subjective operating impressions. Compared to my IC-718, the sensitivity is very close. Maybe a few dB down but not much. Noise seems pretty good, a bit better than the IC-718. A rough guess of dynamic range and intermod distortion is that it is decent as well. Haven't heard much in the way of distortion products or "crunching" in the pileups that I've tuned through. There's no AGC, so you can listen to some pretty weak DX signals, then have the local guy replying really blast through but sound relatively clean. Since the architecture is based on ADE-1 mixers and low-noise MMIC IF amplifiers, it's what you would expect. There's no preamp, but that doesn't seem to be much of a handicap on 20 meters. In fact, I think it would probably be counterproductive, especially since you probably aren't working any stations that far into the mud that you need a preamp to hear them.

As I previously alluded to, my mechanical skills are a bit suspect at times, so I needed to have a test QSO with the radio once it was all buttoned up to make sure that it was working correctly. So I did a bit of tuning around at about 9 PM local and heard K2L, the South Carolina station for the Original 13 Colonies special event station, thumping my speaker off at well over S9. He was working stations at an easy clip with fairly short exchanges, so it was perfect for a quick test. I snagged him on the first call with an honest 59 report (at least I think it was honest...I heard him giving other stations lower reports so I assume I was really a 59) with approximately 8 watts PEP into my ZS6BKW at 30 feet. Mission accomplished!

It will be fun to take this rig to Salmoncon for some camping portable operation. I've never attended a Salmoncon before, but I think any of the attendees can use the special K7S callsign, so maybe I can do some CQing on 20 meters SSB with the short call and attract some stations. We won't be up there until Friday evening, so I think we'll miss the SOTA runs, but hopefully I can also get the radio out to a SOTA peak near here when I return. It might be too ambitious, but before Salmoncon I would also like to finish a 40 meter CW rig based on my Clackamas design that I entered into the 2010 FDIM contest. We'll see if I can actually pull that off.

Stay tuned for more news on Salmoncon as it gets closer and hopefully I can get a video of the SSB rig on YouTube so that you can see it in action for yourself soon.

Inkscape Manhattan Layout Template

I had a lot of requests for the Manhattan Layout Template that I mentioned in my FDIM seminar. Here's a quick & dirty link to the file. I consider it licensed under Creative Commons CC-BY-SA, although I haven't indicated it on the document yet. Hope you enjoy and put it to good use!

Manhattan Layout Template

Single-Ended Mixers and Reverse Isolation

Progress on CC-Series development proceeds at a reasonably-good clip right now. One of my last big hardware bugs to stamp out is some nasty microphonics that seem to be generated by the combination product detector/BFO. Today, I believe that I made some significant progress towards solving it and wanted to share what I learned.

IF Amp & Product Detector from CC-20 Beta 1

I've done a lot of reading in Experimental Methods in RF Design (EMRFD) about microphonics in DC receivers (read chapter 8!), and the number one cause of it is poor LO-RF port isolation in the mixer. The CC-Series uses a venerable old circuit which hasn't seen much use in a while. A dual-gate MOSFET is pressed into double-duty as a product detector and BFO (see above). Since the dual-gate MOSFET product detector is in a single-ended configuration, it inherently has bad LO-RF isolation. This allows VFO (or BFO in this case) signal to leak out the product detector input, and have a good portion of that signal reflect back into the product detector. So naturally, the CC-20 could be experiencing the microphonics because of this phenomena. One of the solutions mentioned in EMRFD is to put an amp in front of the mixer which has excellent reverse isolation (signals coming into the amp output don't tend to get out of the input, and therefore can't reflect back in again).

I had the suspicion that the common-source JFET amp in front of the product detector might be the culprit. So what's the best type of amp to place in front of a single-ended mixer? The common-gate JFET amp is a good and popular choice. However, VE7BPO notes on a recently published web page that the best commonly found amp configuration for this particular parameter appears to be the cascode (see the bottom of the page).

In order to test this theory, I went to work on a project that I had set aside earier: a direct conversion receiver based on the CC-Series product detector. When there was no preamp in front of it, the microphonics were unbearable. I figured that a good way to test my theory would be to put a cascode amp in front of this mixer and see how much it helped. I decided to put a dual-gate MOSFET preamp in front of it, as this is essentially a cascode amp and it fits with the dual-gate MOSFET product detector. Once the new preamp was added, the change was dramatic. The microphonics were gone.

Next, I decided to be a bit more rigorous in my study and quantify the exact difference between the common-source JFET amp and the dual-gate MOSFET amp. First I breadboarded the common-source JFET amp and ran it through the test procedure in the page linked above (at 18 MHz). The results were atrocious. Only 30 dB of reverse isolation, which is worse than the worst amp listed there (the feedback amp). Next, I dug out an old dual-gate MOSFET amp I had breadboarded for my 2008 investigations and ran it through the same test. As expected, the results were vastly superior: 68 dB of reverse isolation. This lines up nicely with Todd's measured results of >64 dB for the hybrid cascode (I used a spectrum analyzer while he used an oscilloscope, so I was able to get a pretty good measurement down to low signal levels).

So this appears to be strong evidence that the IF amp is the problem. It seems certain that the next version of the CC-Series is going to scrap those awful common-source amps for a much nicer dual-gate MOSFET amp. The lesson to take away from this is that if you are going to use a single-ended mixer for any but the most simplistic applications, it must be fronted with an amplifier with an excellent reverse isolation. While the typical common-gate JFET amp will work OK, for best results it looks like a cascode or dual-gate MOSFET amp is the way to go.

Creating PCBs with "PCB Fab-in-a-Box"

G3UUR Crystal Checker

G3UUR Crystal Checker

I decided to make my initial Project X prototype PCBs at home using the old tried-and-true method of toner transfer (via Pulsar Professional paper and foil). Since I'm a novice at PCB layout, I didn't feel comfortable paying the money for a few proto PCBs from a board house, then finding out that I did something wrong and flushing that money down the drain. Instead of buying Pulsar's starter kit, I just purchased a pack of the transfer paper and a roll of the green foil. I also got the required GBC laminator from Amazon instead of paying significantly more for it from Pulsar.

Last night, it was time to give the process a whirl, so I decided to make a PCB of the G3UUR crystal checker circuit that was printed in the Fall 2010 QRP Quarterly (an excellent article, by the way). The instructions seemed clear enough, but I had about five failures before I finally figured out how to make the process work correctly. I was just about ready to chuck the whole thing in the trash bin, but I managed to keep my wits and persevere through it. For those who might be new to the process, let me help you to avoid some of the problems that I had:

  • Give yourself at least 0.5 inches of copper clad clearance on each margin of the final board edge in order to give the laminator good purchase on the board and transfer paper. Putting the toner traces too close to the edge will result in those edges failing to adhere to the board. There's just not enough heat and pressure to do the job properly at the edge.
  • When passing the copper clad plus transfer paper through the GBC laminator, I found that it worked better with four passes. Pass the board once, turn it 90°, pass it again, etc., until all four edges have been the leading edge through the laminator.
  • I didn't see this mentioned in the instructions, but after you apply the foil on top of the toner traces, you must let everything cool down to room temperature before attempting to peel the foil off the board. Failing to do so will rip most of your toner off of the board!

Once I got the bugs worked out, I was quite happy with the end result. I also decided to try out a new etching method. Instead of using ferric chloride, I used the hydrogen peroxide/hydrochloric acid recipe that I've seen touted on the Internet. Let me just say that it worked out beautifully and is waaaaay cheaper than buying ferric chloride. It only took about 3 minutes to etch my small board in a Ziploc baggie. No need to mess with expensive equipment or chemicals!

The etched board turned out very well. There are a few places with very close traces, as you can see in the photo above. These etched out perfectly, no problems at all. You might notice some bad copper on the bounding rectangle on my board, but that was because of the close clearance between that trace and the board edges. I know how to avoid that in the future.

Tonight, I got the board all soldered together and it worked perfectly on first power-up! That's always an extremely satisfying feeling. Now that I've got a handle on the process, I feel comfortable using it on the Project X prototype. Stay tuned for more progress on the new radio!

G3UUR Crystal Checker - Bottom

G3UUR Crystal Checker - Bottom

G3UUR Crystal Checker - Top

G3UUR Crystal Checker - Top

A New Toy for the Shack

AmScope SM-4T

I'm starting to build up the gear for the kitbiz to get off the ground, and the first large investment just arrived at the shack. Thanks to some blog posts from Eldon WA0UWH, I found AmScope.com, who sells all manner of microscopes for low prices. I ended up finding a scope that was very similar to the one that I worked with at Tek; the SM-4T. It's a 7x-45x trinocular stereo zoom scope with a double-arm boom. I also ordered a 80-LED ring light with a variable brightness control. The beast barely fits on my tiny construction bench, but I'll have to deal with the cramped space for now.

Here's some of my impressions after assembling and using it. First off, the base is massively heavy; which is great for stability but no fun when transporting it. I thought the poor UPS drive was going to get a hernia getting it off of his truck. The fit-and-finish is pretty good. Not quite the same as the high-quality brand name microscope at Tek, but I felt like it was good for the price I paid. The manual is terrible. I'm still not sure that they sent me the right manual, since the diagrams in the once I received show a completely different model. But the back of the manual does show the parts for my microscope, so who knows, maybe you just get some generic manual for all of the different models. The Engrish factor is pretty high, as you might expect. Fortunately, I was still able to easily assemble the microscope by referencing the photos on the AmScope website.

The image quality is quite good, although the field of view is a bit smaller than my Tek microscope. The interpupillary distance and diopter setting is fully adjustable. Once I got them set correctly, the microscope was a pleasure to use. The 80-LED light did a good job of providing bright white illumination for the circuit boards that I examined. My first impression is that I've received a good value for my money. AmScope claims that their production line is the same one that manufactures microscope for Zeiss, Leica, Nikon, and Olympus. Based on the quality, that certainly seems like a credible claim. It's a bit spendy for the average homebrewer to purchase, but if you are serious about doing a lot of SMT work, I think that these microscopes would be an excellent choice for the shack.