2. Solid State Amps
3. Book Reviews
Some time back, I felt the need for a piece of software that would enable me to capture occasional QSOís "off air", and record the Sunday morning WIA broadcasts, etc. I cast around the net and came across "Audacity", a free, "Open Source" program, which has proved to more than meet my requirements.
Since then I have discovered that Audacity also enables me to "capture" some of my favourite classical music programs which are only available as audio streams (not as MP3 downloads). Once captured to hard disk, I can export the program as a "wave" file and burn it to CD. This enables me to "time-shift" my favourite programs and listen to them later on CD in the car, etc.
In fact, Audacity will capture and store on your hard disk, any audio input that is available to your computer. These inputs might come from the Internet as streaming audio; microphone input; record or cassette player, etc. The following is a detailed explanation of the features and benefits of Audacity. The program can be downloaded free from http://audacity.sourceforge.net/
Audacity is a free, easy-to-use audio editor and recorder for Windows, Mac OS X, GNU/Linux, and other operating systems. You can use Audacity to:
Record live audio.
Convert tapes and records into digital recordings or CDs.
Edit Ogg Vorbis, MP3, and WAV sound files.
Cut, copy, splice, and mix sounds together.
Change the speed or pitch of a recording.
And more! See the complete below for a list of features.
This is a list of features in Audacity, the free audio editor.
Audacity can record live audio through a microphone or mixer, or digitize recordings from cassette tapes, vinyl records, or minidiscs. With some sound cards, it can also capture streaming audio.
Record from microphone, line input, or other sources.
Dub over existing tracks to create multi-track recordings.
Record up to 16 channels at once (requires multi-channel hardware).
Level meters can monitor volume levels before, during, and after recording.
Import sound files, edit them, and combine them with other files or new recordings. Export your recordings in several common file formats.
Import and export WAV, AIFF, AU, and Ogg Vorbis files.
Import MPEG audio (including MP2 and MP3 files) with libmad.
Export MP3s with the optional LAME encoder library.
Create WAV or AIFF files suitable for burning to CD.
Import and export all file formats supported by libsndfile.
Open raw (headerless) audio files using the "Import Raw" command.
Note:Audacity does not currently support WMA, AAC, or most other proprietary or restricted file formats.
Easy editing with Cut, Copy, Paste, and Delete.
Use unlimited Undo (and Redo) to go back any number of steps.
Very fast editing of large files.
Edit and mix an unlimited number of tracks.
Use the Drawing tool to alter individual sample points.
Fade the volume up or down smoothly with the Envelope tool.
Change the pitch without altering the tempo, or vice-versa.
Remove static, hiss, hum, or other constant background noises.
Alter frequencies with Equalization, FFT Filter, and Bass Boost effects.
Adjust volumes with Compressor, Amplify, and Normalize effects.
Other built-in effects include:
Record and edit 16-bit, 24-bit, and 32-bit (floating point) samples.
Record at up to 96 KHz.
Sample rates and formats are converted using high-quality resampling and dithering.
Mix tracks with different sample rates or formats, and Audacity will convert them automatically in realtime.
Add new effects with LADSPA plugins.
Audacity includes some sample plugins by Steve Harris.
Load VST plugins for Windows and Mac, with the optional VST Enabler.
Write new effects with the built-in Nyquist programming language.
Spectrogram mode for visualizing frequencies.
"Plot Spectrum" command for detailed frequency analysis.
Licensed under the GNU General Public License (GPL).
Runs on Mac OS X, Windows, and GNU/Linux.
Audacity includes extensive Help files, FAQís Tutorials, etc
Back To Top
HF Solid State Linear Amplifiers Ė A Review
By Bob Mutton Ė VK2ZRM
Firstly, this is not a product review, nor is it a project, but hopefully readers will gain enough information from this article to assist them in furthering their interest and knowledge in this class of amplifiers.
Before we go any further, we must pause and pay homage to Helge Granberg Ė the "Father" of high power HF solid state amplifier design. Granberg was an RF Engineer with Motorola and was responsible for the seminal Motorola "ANís" (Application Notes) and "EB"s (Engineering Briefs) on this topic. Anyone with an interest in solid state RF amplifiers must read these documents, which can be found here
I draw your attention in particular to AN-758 and EB-104
All of the solid state amps discussed in this article are based on the work of Grandberg.
HF Solid State linear amplifiers designed for ham radio fall into three main groups. Those designed to run on 12 Volts; those designed to run on 28 Volts; and those designed to run on 50 Volts.
The 12 Volt amplifiers are aimed primarily at the mobile market and generally top out at around 500 Watts PEP.
The 28 Volt amplifiers are less common and appear in several commercial high power transceivers.
The 50 Volt amplifiers are aimed at base station use and commonly provide powers up to around one Kilowatt PEP.
It might be worth noting here that commercial broadcast transmitters are almost all solid state these days and offer output powers in tens to hundreds of kilowatts.
For more extensive information read this excellent article by Adam Farson, VA7OJ/AB4OJ, titled "What makes a good solid-state Amp?"
So Why Would You Go Solid State?
Unconditionally stable at all frequencies of operation
No tuning required when switching bands
Easily implemented automatic band selection
No life threatening voltages inside
More up to date technology
12 Volt linears makes high power mobile operation feasible
More distortion if not designed, driven and filtered properly
Less robust than valve amps if abused
Less Efficient (50% efficiency versus 70% for valves)
So why would you want to go solid state? Well this is sort of the same question as "why climb Mt Everest"? Because itís there! Isnít Ham Radio all about experimentation and innovation? Valves have been around for about 80 or 90 years. Should we all be still driving around in model T fords, simply because they are less complicated than the current crop of technologically advanced and complex cars?
Solid State Amplifiers Produce More Distortion Than Valve Amps (Not)
Letís put this old chestnut to rest right now!
I should preface my following remarks by saying that the output of a Solid State amp will be clean when used within specs and not overdriven! I think that most criticism of Solid State amps comes from the fact that many amateurs do not know how to properly set up their rigs and are guilty of overdriving their amps to try and squeeze out that extra few watts.
So what do I mean by "properly set up"? I mean that the exciter (transceiver) mic gain, ALC, compression and output power are all adjusted correctly in order not to cause distortion in the transceiver or overdrive the linear amplifier. Incorrect settings will not increase power and will probably make your signal on SSB less intelligible and cause "splatter" and interference to other hams on adjacent frequencies.
Valve amps are forgiving of this sort of misuse and abuse, while Solid State amps are not. The reason behind this fact is that when a valve amp is overdriven it goes into "soft clipping", while a Solid State amp will "hard clip". The peaks of the wave from an over driven valve amp will be rounded, while the peaks of the wave from an over driven Solid State amp will be square. This squaring produces harmonics and general "crap" on the signal.
Yes a mediocre valve amp will perform better than a poorly designed solid state amp. But surely, the vast majority of us Hams use solid state transceivers every day and I donít hear any complaints about distortion from a properly set-up solid state rig running at 100 Watts, so why would it be any different with a properly designed and operated solid state linear. And it isnít!
I refer you to RSGB Radio Communications, June 1983, where three commercial HF linears, two valve units and one solid state linear were tested and compared. The linears were the Yaesu FL-2100Z, Kenwood TL922 (both valve units and the Icom IC2KL (solid state). The testerís comments were, and I quote, "The harmonic output was generally lower (with the IC2KL) than the valve units, while the intermodulation products were generally higher.
When you look at the test results in this article, there is very little to choose between the three linears as far as distortion goes. The Solid State linear was much more pleasant to use as all tuning and band switching was controlled automatically from the transceiver.
The output from the current crop of solid state linears such as the Yaesu Quadra and the Icom PW1 is as clean as any valve amp, when the exciter (transceiver) is properly set up and the amps are used within specs and not overdriven.
Commercial Solid State HF Linear Amplifiers
These fall into two categories, mobile units and base station units.
Letís look at base station units:
These range from a (relatively) affordable 600W unit from Ameritron, to hideously expensive units from Yaesu and Icom.
You will need to own the bank to buy either of the latter units. Budget on between $7,000 and $10,000 each.
Here the choice is much wider. Starting at few hundred dollars for poorly designed 11 Meter (chook band) units, to more sophisticated units for the Ham bands from the likes of Ameritron and RF Electronics and others.
Homebrewing A Solid State HF Linear
This is not a project for the foolhardy or financially challenged. Curiously, the issue is not the amplifier itself as there are a number of sources for complete kits of parts to enable you to assemble an amp capable of up to one kilowatt PEP. More of that in a moment.
The issue is the power supply and protection circuitry. If you go down the 12 Volt route, you will need to provide a power supply of between 12 and 14 Volts at up to 80 Amps. Now I bet you donít have one of those hanging around the shack. OK you could use a battery, but who wants a lead acid battery venting hydrogen into the shack, as your amp draws 80 Amps on peaks? Fortuitously, there are several sources of both linear and switch mode, 12 Volt high current power supplies right here in Sydney.
If you go down the 50 Volt route you will need to find a 50 Volt power supply capable of delivering 20 Amps. Not many of those lying around either. If you can find one, an ex-Telstra 48 Volt, 25 Amp battery charger might be worth looking at. These were available in both linear and switch mode varieties.
In addition you will need to design protection circuitry for, Over Volts; Over Amps; Over Temperature; high SWR, output band filtering etc. You will need to take extreme care when first powering up the unit as the RF output transistors can be killed in the blink of an eye and MRF150 FETS at US$150 each are not something you will want to be replacing too often.
However, a well designed and well protected Solid State Amp with proper protection and output filtering will be every bit as robust and clean as a valve linear.
Well, as a former Australian Prime Minister once famously said, "life was never meant to be easy", and none of the above issues are insurmountable as you will see from the following information. So if you are still interested in the challenge of homebrewing an amp, then take a look at the following two sites. Both offer kits of part for the basic amplifier.
Communications Concepts offers kits based on Grandbergís designs.
RF Electronics offer completed units or kits of parts to enable you to build 500W or one-Kilowatt amps. Chris, VK1GG has one of these 500W babies and is one of the cleanest and strongest signals in the eastern states of Australia. His mobile signal has to be heard to be believed! These amps use the 2SC2879 transistors at 12 to 14 Volts. These transistors are well proven and offer an economical solution, at about US$25 each. RF Electronics offer a kit of parts at US$250 or a complete unit at US$420.
Here is a web site that describes a complete end-to-end HF Linear project. This is the basis for an article appearing in a recent issue of QST. Well worth a read.
Here is another project for a high power amp, delivering 1300 Watts
Additionally, there is a new breed of very fast, lower cost plastic RF power transistors that will ultimately take over from the expensive ceramic RF transistors.
The APT ARF463A and ARF463B are examples.
Elecraft will shortly release a kit for a 1500 Watt linear using these transistors. You can see this amp here:
Tokyo Hy-Power is about to release an amp with these plastic transistors, as well.
Well, there we have it. I have been toying with the idea of a homebrew HF amp for some time. I have even bought some of the components and designed the protection circuitry. Many other hams have also expressed a similar interest. I hope this article at least provides some interest and may even spur some of you to "have a go".
Back To Top
With a number of new amateurs coming onto the HF bands, particularly the Foundation calls, it might be timely to have a look at several Ham Radio related books that will help expand the knowledge of Hams and perhaps stimulate some experimentation in our exciting and interesting hobby.
Some of the books that we will review here will be familiar to most amateurs and some (hopefully) will be new to readers. They range from the highly technical, requiring considerable application by the reader to wade through the theory, to the very practical, with lots of designs that the average amateur can "have a go" at.
The publications in question are:
ARRL Handbook Published by the ARRL in the USA
ARRL Antenna Book Published by the ARRL in the USA
HF Antennas For All Locations Published by the RSGB in the UK
Backyard Antennas Published by the RSGB in the UK
The VK Antenna Handbook for Restricted Spaces Published by Phil Grimshaw VK4KVK
Letís start with the ARRL publications. The ARRL (American Radio Relay League) is the US equivalent of the WIA and they publish a range of books, CDís etc that can be purchased direct or through the WIA bookshop.
The ARRL Handbook has been published annually since 1926 and can be described (along with the ARRL Antenna Book) as the "bible" for radio amateurs. In fact the 2006 issue of the ARRL handbook has a reproduction of the very first handbook Ė 1926 addition, which of course makes fascinating reading.
I have a small collection of ARRL Handbooks from each decade since the 1940ís. The interesting thing you learn from reading handbooks from earlier decades is while the technological change has been dramatic, the underlying principals remain the same. This is particularly apparent with antenna theory.
Both the Handbook and the Antenna Book are large and expensive publications costing around $70 to $80 each and while it is nice to have the latest issue, this is not strictly necessary. If you can find second hand copies anything up to 10 years old, you will find that the content is still very relevant.
Anyway, I digress. The 2006 issue of the ARRL Handbook is 1 Ĺ inches (35mm) thick with 26 chapters and countless pictures, tables and diagrams. I donít know how many pages the Handbook has, as they are not numbered sequentially, but rather are numbered per chapter. The index alone is 23 pages long. The Handbook covers virtually every topic of relevance and interest to Hams, from safety, to fundamental theory, to practical projects, antennas, Digital Signal Processing, etc. The list goes on! There is also a soft copy of the Handbook on CD provided with the hard copy book.
ARRL Antenna Book. I have the 19th Edition of the Antenna Book. The 20th edition is now available. My comments on the Handbook are equally relevant to the Antenna Book. With 28 chapters and hundreds of pictures, charts, diagrams, etc, the Antenna Book makes compelling reading for anyone interested in antenna theory or those contemplating putting up an antenna.
It is impossible to do justice to these two publications in this short review. Needless to say, no Ham shack should be without the ARRL Handbook and the ARRL Antenna Book!
HF Antennas For All Locations- By Les Moxon, G6XN. Well, where do you start? This is no doubt the most comprehensive book on HF antennas available anywhere. With over 300 pages, the book is broken roughly into two halves, the first half dealing with theory and the second half providing practical designs for virtually all types of HF antennas.
For the enthusiastic amateur such as myself, the theory can make for some heavy going. But Moxon ties his practical designs back to the theory ,which helps in understanding the fundamentals.
Both the theory and practical sections are supported by countless diagrams and charts, that illustrate the theoretical point or antenna design that Moxon is describing.
If you are interested in HF antennas and you only ever buy one book on the topic, then this is probably the one to buy. There is an early edition of this book available in the Hornsby Shire Library.
Backyard Antennas Ė By Peter Dodd, G3ldo. After you have numbed your brain wading through the theory in Moxonís book, you will find this book refreshingly practical and easy to assimilate and understand.
There is virtually no theory in this book, but rather it is 200 pages of descriptions, designs diagrams and illustrations of antennas that virtually anyone can stick up in their own backyard. Of course there is some discussion of how and why the antennas work, which is an easy entry into the underlying antenna theory. Highly recommended for both beginners and experienced Hams.
The VK Antenna Handbook For Restricted Spaces Ė By Phil Gromshaw, VK4KVK. This book is written and published by VK4KVK and is available in both hard copy and on CD. I have had mixed reaction to this book, but I must say that I like it and do not regret buying it. With approximately 300 pages, there is nothing fundamentally new in the book and it is slightly repetitive.
What VK4KVK has done is create a "compendium" of information on a range of antennas suitable for space restricted locations (like my own backyard) and I find this information very valuable. There is information that is not widely available, in amateur radio circles anyway, on topics such as "shielded balanced feedlines". I have seen reference to these on the "net" but never in an amateur related publication.
Those who have done any research into miniature beam antennas will already be familiar with the work of VK2ABQ, the late Fred Canton. Fred published a series of articles on very small directional beams, mostly in the RSGB magazine. VK4KVK has "commercialised" Fredís work and produced an antenna he calls The "NU-Beam" You will have to look hard and long to find more comprehensive information on this family of small, directional antennas.
VK4KVK also describes in detail, other antennas suitable for restricted spaces. Both wire antennas and beam antennas are addressed, including antennas that VK4KVK calls the "Vipole", a trapped, multi-band rotatable dipole antenna and the "QFD", a Quad, Folded, Loop antenna.
The antennas that VK4KVK describes are supported by diagrams, dimensions and computer models, to enable the enthusiastic amateur to build their own examples of these antennas.
I recommend this book.
Conclusion. Well I hope that these few brief words are of interest and assistance to budding antenna builders.
Happy Homebrewing (of the antenna kind).
Back To Top