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Reviews Categories | Antenna Analyzers | AMQRP AA-908/Micro-908 Antenna Analyst Help


Reviews Summary for AMQRP AA-908/Micro-908 Antenna Analyst
AMQRP AA-908/Micro-908 Antenna Analyst Reviews: 10 Average rating: 3.3/5 MSRP: $230
Description: A microcomputer-controlled DDS-based antenna analyzer with a range of <1 MHz to 60 MHz. It is also a platform for the AMQRP Micro-908 daughterboard and will support the (optional) KK7P DSP board, providing DSP-based audio filtering as well as numerous other functions. Fully software configurable with available source code to allow the user to download and/or write new features and/or fix problems.
It has been offered primarily as a kit (check website for availability) but it should be possible to find someone that will assemble it if you do not wish to tackle the installation of SMD components.
Product is in production.
More info: http://www.amqrp.org/kits/micro908/index.html
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W3FPR Rating: 0/5 Sep 22, 2012 20:20 Send this review to a friend
An expensive doorstop  Time owned: more than 12 months
I purchased the AA908 in good faith based on the promises that were made by AmQRP - not only an antenna analyzer, but a standalone PSK31 function from a keyboard, and a DSP audio filter.

It soon became obvious that the AA908 was only good if the impedance was close to 50 ohms. After many emails on the Micro908 reflector, the improved reflectometer was promised. 3 years later, I paid for my reflectometer upgrade, and found that there was a small but inadequate improvement.

So bottom line, I have a very expensive doorstop. Oh yes, there are auxiliary applications that will produce nice plots of the antenna, but if the impedance is not near 50+j0 ohms, I would not place any faith in those plots.

As for the promised PSK31 functions, yes, I was hopeful and purchased the keyboard too. That function was never provided, so I wasted more of my money on the keyboard.

I don't usually give a negative review, but this experience has not been very good. I do not have a functioning AA908 antenna analyzer, the promised PSK31 function has been replaced by the AmQRP ENU-PSK device, and this has been a string of promises made, but not fulfilled.

I continue to use my MFJ-259B. There was hope that the AA908 would replace that analyzer, but those hopes have been shattered many years ago.

As I indicated, if hams just want to check their resonant antennas that show an impedance near 50 ohms, the AA908 will give them pretty plots, but if what is needed is a good reading of the actual antenna impedance even though it is far different than 50 ohms (one application of this information is to design a matching nework), the AA908 is woefully inadequate.
 
G3TJP Rating: 1/5 Sep 22, 2012 19:02 Send this review to a friend
Lots of promises and great excuses, but no follow-through  Time owned: more than 12 months
After reading the product spec. friends and I bought three.. All worked first time and went through the calibration phase without apparent problem, then to the real world where the three of us tried to use them in a world that wasn’t a resistive 50 ohms.

The further the impedance moved from 50 ohms, the more inaccurate these units became. Some users who heap praise on these analysers only seek to confirm resonance, but they were dire for the experimenter. We discovered that all three units behaved equally badly.

A revised reflectometer was promised three or four years ago and the main complainers on the reflector were offered a chance to beta test it. Parts were sent out and then we were told how much out of pocket the designer was, so we all coughed up around another 50 bucks for the new and wonderful reflectometer. Frankly, it wasn't much better, so the development "goes on." What a joke! They have moved on to other items and only pay occasional lip service when their feathers are ruffled. The exciting list of enhancements never happened and the users who hoped it would help them experiment have reverted to MFJ259's or similar, that give more believable readings. The AA908 is a very expensive doorstop and I am amazed that these boxes of snake oil are STILL being sold, but then, we were gullible too, a few years ago.

It’s no use extolling its virtues as a signal source and a great VFO to a guy who bought it to use as an antenna analyser! That doesn’t cut the mustard. Quite simply, it doesn’t match its specification and I doubt if a genuine experimenter exists who relies on and trusts this device. Brown-nosing the salesman still doesn’t make it work to specification, but some will never learn and they’ll toss the Mk., 1 in a corner and buy the Mk. 2 and so on. Personally, I won’t spend good money after bad and frankly, I would like my money back!

Definitely the Edsel of antenna analysers.
 
KC2JDY Rating: 2/5 Nov 23, 2010 03:34 Send this review to a friend
Devalued - no warranty  Time owned: 6 to 12 months
Tested OK and worked for a short while then fried its DDS-60 daughterboard. No real recourse. Now is an expensive brick.
 
W1RIK Rating: 5/5 Aug 22, 2010 11:51 Send this review to a friend
Works Great, Unbelievable Support  Time owned: 0 to 3 months
I purchased this kit mostly because I love to build kits and I needed an antenna analyzer. I also ordered the DSP option with it. This was my first foray into surface mount components. I was amazed that I had no problem working with them. Of course a magnifying light and the proper tools helped a lot.
I had a problem with a defective component, not the fault of the manufacturer, and George Heron who was instrumental in the design was a phenomenal help. We quickly got it up and running and it is now functioning as an antenna analyzer that allows me many different outputs and charting capability.
I think the best part of this experience was what I learned during the process, both during the building, and with programming the HC908 and understanding what I did.
This is a high quality product. Fit and finish was very good, with just a couple of minor tweaks, and the components in the kit were top shelf. Technical support was incredible.
If you're looking for a fun project, here it is!
 
K2RNY Rating: 5/5 Feb 11, 2010 13:32 Send this review to a friend
Great Analyzer and more at a good price!  Time owned: 3 to 6 months
I ordered my micro908 over the Holiday's. The package arrived in no time and the contents were layed out a very nice order. All the parts for a particluar part of the assembly are packaged together. All SMT is packaged on cards in the order you need to use them in.

Yes, there is SMT involved and the landscape can get busy in areas of the PCB. I found that with a lit magnifier and the proper tools, assembly was not a problem. Remember to only unpack the parts you are going to solder in at one time.

The manual is great. All steps are fully described and there were plenty of pictures and diagrams for me to refer to in order to insure I was doing things right.

The DDS-60 can be a bit tricky only because of its size.

George Heron is absolutely great at answering your questions. Heck, he even tested my DDS-60 for me to insure it was operating right.

After a few retouches with the soldering iron, my Micro908 works great.

I recommend getting the parts for the backlit display.

In summary, this is a great kit priced right with plenty of support behind it. A definite 5 from this reviewer.
 
KC7FYS Rating: 2/5 Oct 14, 2009 19:51 Send this review to a friend
Wont be surprised to see one at a garage sale soon.  Time owned: more than 12 months
I hesitate to tender a negative review for several reasons. Chief among them is my respect for the man behind this project and his stature in the homebrew community. I am also not a super technical ham, but have successfully built several kits--the AA908, however, was purchased built from a rather smart ham who unloaded it on me when the project had shown some signs of being dead. That was about 2007. Now on the reflector, you will periodically hear the intrepid voice of yet another bitter AA908 owner ask, Is this project dead? Folks are respectful, but generally consider it a project that started out with a big puff of steam, but now smells like a dead fish. The USB port will likely never happen, nor will the PSK31 functionality. Its kind of quaint to watch the video documentation that came with this rather large unit--which seems to get larger every time I sit it next to my Autek analyzer on the same shelf. It works, but it is not a work in progress at all. I regret having bought it sometimes, and other times consider it the way the hobby is. Buy it, but dont expect it ever to change at this point. Visit the AMQRP website to see the rather cute ^Roadmap^ of what was to be. One might just as easily photoshop on a Vegematic: it slices, dices, and makes julienne fries in seconds.

Actually, the vegematic is cheaper and maybe more fun.
 
WB2SRF Rating: 4/5 Jun 15, 2006 13:16 Send this review to a friend
Great learning experience  Time owned: more than 12 months
I agree with the other reviewer's comments. To keep things in perspective, this is a great project if you wish to have hands on experience and learn about how things work. The source code is available and is good to study the framework to see how the microcontroller is being used to perform the computations and measurements. This project is evolving and seems to have many future applications.
 
KC7ULI Rating: 5/5 Jan 3, 2006 11:17 Send this review to a friend
more than the sum of the parts  Time owned: 3 to 6 months
Well, this is a kitted project and it is a well done kit. Rough edges, yes, but consider that this is produced by the AMQRP group who are doing this through their love of the hobby. As stated, the kit is well done with pretty good documentation. It's a complex electronic device that is well designed for its price class, with good quality parts and a lot of existing features and lots and lots of potential. And the rough edges are getting smoother all the time.

A work in progress to be sure, but that is part of the allure of this. If you want an MFJ269, get one, but if you don't like MFJ or if you want to have some pretty good fun, then this tool is what you might want to consider. The Palstar ZM30 antenna analyzer is a commercialized version of this design, and the software is essentially the same. The layout in that design is different for their mechanical implementation, but that device gets great reviews (12 of 12 are 5's so far). The Palstar doesn't have provisions for the DSP, as far as I recall, and it probably isn't ever going to be anything more than an antenna analyzer like the AA908 (well, it probably can work as a stable programmable VFO just like the AA908, since the DDS system used is one of the neat features of this design).

The Palstar isn't a kit, so when you buy it (for not a lot more than the kit version of the AA908 plus DSP, etc.) it works out of the box. But the AA908 is a growing, evolving project that should continue to add features and capabilities. It will provide a lot of satisfaction in the building process, it will hone your construction skills, it will work as an excellent and flexible test and measurement tool for your shack (much more than just an antenna analyzer).

Finally, the user community is growing, the support network is superb (and very helpful) and about the only issue I see is with the continued availability of the kits. I suspect that George and crew at AMQRP don't want to make a career out of kitting this project, so I wouldn't be surprised if they aren't working to move this over to another small company that will continue to produce the product into perpetuity. Watch the kit user reflector for unbuilt kits if AMQRP is out. They do come up once in a while and they are well worth building up.

Larry
 
AA2YS Rating: 4/5 Jan 3, 2006 07:09 Send this review to a friend
Nice and flexible, but some rough edges  Time owned: more than 12 months
The first review covers all of the technical aspects very well, so I won't repeat them.

I don't think it quite emphasized enough, though, that the AA-908 really is a "work in progress". It's not unusual to have several firmware releases over the course of a few days to fix problems that come up.

The intention for the AA-908 was always advertised to be a "general computing platform" that could be used for an antenna analyzer, audio filter, portab le PSK interface, rig control, etc. The antenna analyzer and audio filter apps are there, but the others have been coming "real soon now" for well over a year, and don't even get mentioned any longer, so I presume that they've stagnated.

Don't get me wrong - this is a fine device, and fun to build, but don't go into it with the expectation that you're going to be getting something that "just works" out of the box.
 
KA7OEI Rating: 5/5 Dec 29, 2005 17:34 Send this review to a friend
If it won't do what you want it to do, change it!  Time owned: 3 to 6 months
This unit is primarily offered as a kit. Be forewarned that it has a lot of surface-mount parts, so if you aren't prepared to do some fine detail work, you might want to consider other options - like finding someone (a friend or a "kitbuilders" group) that can help! I personally enjoy kits and "getting my hands dirty" in building/improving them - but this may not be everyone's "cup of tea."

Originally designed for use up to 30 MHz, a newly-available DDS synthesizer board (and a firmware upgrade) expands its range up to 60 MHz. This unit will display the frequency, the resistance, and the reactance - and it can determine the sign of the reactance. It tunes in 10 Hz steps and its frequency accuracy/stability is that of the crystal reference oscillator onboard.

It also has a serial port to allow updating of the firmware when new features/bugfixes come out as well as providing remote control by a computer allowing one to graphically plot the SWR/Z/X of an antenna: It is really quite neat to be able to sweep your antenna system across all of HF to see if it *really* resonates where it is supposed to!

Also available is the KK7P DSPx board (see the TAPR site for more info) that allows one to provide a suite of audio DSP filtering capabilities such as noise reduction, bandpass filtering, automatic notching, etc. The software for this filter, too, is upgradable via the serial port.

Future capabilities include the possibility of a standalone PSK31 terminal without a PC (using a computer keyboard that can plug into a jack) and using the '908's LCD readout on TX/RX. Of course, you could theoretically program whatever DSP/DDS project you think of.

In addition to measuring antenna properties, it will also measure the value of a capacitor or inductor and can function as a signal generator/VFO with an output in the 0 to 5 dBm area (more or less...)

Caveats: As mentioned, it comes as a kit, so you'll want to keep that in mind if you want to get one. Also, it is a "work in progress" so the firmware is constantly evolving (but getting better!) If you are able to do 'HC908 assembly language (the source code for this is available freely) you'll be able to contribute to the effort! While there are a few bugs and quirks in the system, it does, for the most part, work very well! Note that it isn't an ultra-precision instrument and its best accuracy occurs when reading nearest to 50 ohms, but it is certainly good enough to tell you what's going on with your antenna system.

As a side comment: The main thing that limits the low end frequency response of this unit are the coupling capacitors in the reflectometer bridge and DDS board. As they are, they are usable down to about 500 KHz (maybe a bit lower) but theoretically, it should be able to go down to a few 10's of KHz with some capacitor changes - something that could be of interest to a LowFER. (The DDS synthesizer itself is capabile of generating frequencies down to 10 Hz with this software.)

Note that this kit is not always available: The "kitting" will only occur if/when there is deemed sufficient demand (and available time by those doing it!) so you'd have to check the web site - but it may be possible to find one (assembled or not) that someone else is selling. When I got my AA-908/Micro908 kit (with DSP board, which added around $70 or so) it was approx. $300 - but the price is certainly likely to vary over time and with availability.
 


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