Saturday, 25 February 2012

Difficult to find torroid data

It is remarkably difficult to find the data about a few simple torroids, manufacturers make so many and characterise by just the size, without the essential ferrite characteristics, especially the Al = uH/turn data.

The coils inductance, uH = (Al * t^2)/1000. Dimensions are in mm.

So here are some common ones:

Type Width Thick Al
FT50-43 T37-0 12.7 4.9 440
FT50-61 T37-2 12.7 4.9 69
FT82-43 T37-6 21 6.35 470
FT82-61 T37-7 21 6.35 79

Two hole torroids
Type Width Length Al
BN-43-202 T80-6 13.3 14.35 2220
BN-61-202 T80-10 13.3 14.35 385

More data at, parts available from 'kit parts'.

Afgans, Shnafgans.

It is with some trepidation that I make this blog entry!

So you Afgans want to burn our national flags? And we have burnt your Koran. So what?

Well we are annoyed about you burning the flag that represents our nation, we are not sympathetic to you, we just think you are idiots.

There I have said it. Now sort yourselves out, or maybe we will just leave you to it, to fight it out amoung yourselves. Come to think of it that's a very good idea.

SWR meter

This is the bare bones of a potential design for an SWR meter, to measure the forward and reflected power in an antenna feeder.

25 02 2012 13 12 02
It includes a low power dummy load for transmitter testing. The input and output are 50R impedance. Schottky or Ge diodes should be used, e.g. 1N43A.

Friday, 24 February 2012

Software Defined Radio

Here are the essentials of a Software Defined Radio front end. They are simplified diagrams of the Elektor SDR.


24 02 2012 17 36 40

The input is USB, this provides both power +5V, and the input commands to the FT232R convertor, which converts the USB signals to the serial bus I2C signals for the frequency generator CY27EE16ZE. The VFO has a 10MHz xtal and the x4 tuning frequencies are derived from this.

The VFO is followed by a divide by 4 "johnson" counter which generates four phase signals to drive the mixer. (0, 90, 180, 270 deg)


24 02 2012 17 37 33

The mixer uses a standard CMOS switch 74HC4066 to sample the four clock phases of the input antenna signal. The samples are integrated during the 0, 90, 180 and 270 deg phases on the 2n2 capacitors. The I and Q audio signals are obtained by mixing the outputs of each pair of switches in a couple of op-amps.

This is the bare, and very simple, bones of an SDR receiver. It has to be used with a PC with a good sound card (ideally 24bit/96kHz capability for a tuning range of +/-48kHz around a chosen frequency), and software for driving the VFO, displaying the received signals and decoding them as AM, FM or SSB, such as the SDRadio software for a Windows PC or the DSP Radio software for the Mac running OS X.

iTunes improvement???

Apple has just announced a new section of iTunes, this section will carry music which has been specially encoded to improve the perceived reproduction. I say 'perceived' because in fact it does nothing for the actual reproduction of the original instruments!!

This simply continues the fallacy that since the human ear can only hear 20-20kHz that is all we need to play music. Which is nonsense, to hear the music you need to reproduce the sound of the original instruments, and these produce frequencies much above 20kHz which give them their individual timbre. So any music system needs to be able to manage very low frequencies (organs go down to 16Hz) and very high frequencies (trumpets produce harmonics above 50kHz), a reasonable system should manage 5Hz-50kHz, not the usually quoted 20-20kHz.

Let's see what it is all about

Sound in studios is recorded digitally with 24bit words and at 96kHz. This is the original sound heard by the sound engineer. according to his settings this original can have some clipping on load peaks and some compressed dynamic range as he adjusts the volume. Possible dynamic range or 24bit/96kHz digital recording is 126dB, with a bandwidth of 48kHz.

Apple is now asking the studios to submit to them this 24/96 media. They will then convert it to the CD standard of16bit/44kHz using an Apple CAF 32 bit file intermediary, this will avoid certain distortions introduced in the down-sampling process. A sharp cut off filter will be used at 20kHz, dynamic range will be limited to the CD's 84dB, and only 15% of original data will remain!

Think that a full orchestra has a dynamic range of over 130dB, the CD is a pretty bad medium to carry realistic audio dynamics.

Next Apple will check for clipping, that is where the signal goes upto or over the maximum that the digital representation can handle, known as 0dBS. Beyond that their is no bigger digital number to represent the signal peak and it is chopped off. Any clipping is reported back to the engineers and they can re-master the tracks.

Next Apple will convert the file to AAC 256kbps, eliminating frequencies and harmonics supposedly not perceived by human ears. Cutting data down to 1/5th of the CD size, or just 3% of original.

Thus you get your song on iTunes. But is it any better?

No, it's clever but dumb.

The music industry has resisted higher quality distribution directly to, again, prevent "piracy". They clapped DRM on the 24/96 standard DVD-A or SACD disks and on Blu-ray, which effectively killed their market, but they don't care.

Now I believe Apple is trying slowly to drag the recording industry into the modern digital age. First step, get them to give Apple 24/96 masters. Second step define the best way to get this sound squeezed into 256kbps AAC compressed format, losing as little as possible of the original dynamics (good move but impossible outcome).

Next? If I was asked about the future, then what I would like to see is a two tier music distribution, first getting rid of the oddity, the CD 16/44.1, format and moving this to 16/48 with AAC compression - a standard that existing iPods could play - and a full blown 24/96 format with non-lossy compression.

So iTunes launches 16/48 lossy AAC and true 24/96 distribution in a non-lossy compressed format such as ALAC or FLAC. iPods can handle the 16/48, Macs can today easily handle the 24/96.

That's the goal we are all waiting for.

And next, for Apple to be the first company to produce an "iPod+" capable of storing and processing 24/96 audio files, both on the digital side (requires 32bit processing) and on the storage side (requires x10 increase in memory) and on the analog to digital conversion side (to ensure the device can output up to 48kHz frequencies). All this is technically possible. But it may take a while to update or load your music, even over fast WiFi... at 1GB per album...

There is just one other small copyright problem, that is the studios use of "windowing" to only allow release of tracks in certain countries at certain times, for example today many 24/96 tracks are only available in the USA. This is a misuse of copyright problem that has to be solved by arm twisting or legal changes.

Thursday, 23 February 2012

Too much said, not enough done - TV

There is so much being said these days in the battle to get us to update our TVs. Bigger screens, 1080p reproduction, 3D, surround sound…

But an issue that is now raising its head is Smart TV, that seems to mean the inclusion of a computer (or just a browser) in the TV. But is this the right partitioning of a system? Take this simple diagram:

Screen Shot 2012 02 23 at 10 55 31

Today's TVs include the TV signal Receiver (terrestrial or satellite), and the STB is outside. The STB could be just a cable box, an add-on satellite box, or a smart box like Boxee, Apply TV etc. But why not consider the alternative? Take the receiver out and put the STB in or leave both out?

This last suggestion would make the TV a dumb display device, and thus the price should come down… the input would be HDMI. An alternative is to smarten up the TV and give it a WiFi interface, now that would be something else, a very bright idea. Any external source would then simply connect to your WiFi and address the TV as a peripheral - come to think of it like the Apple TV streams from the Mac or iPad today. Just need to design and build a Cable, Terrestrial, Satellite box that also connects by WiFi and job done. This "tuning" box could easily be controlled by software on the iPhone/iPad (or Android device), to give the ultimate: TV and internet access at the same time

Thursday, 16 February 2012

Proposed DSB TXRX for 80m

So i was reading about a design for a RXTX for DSB on 80m, and I had some thoughts about it, so I designed this circuit - it has not been made, but could inspire someone to have a go:

16 02 2012 12 57 59

There is no RX/TX switching so this has to be done externally, in the PA - the ones I proposed earlier might be modified to do this.

I have researched all the components, the torrid and the MOSFETs and chosen the best ones. The coils are always a problem, finding the right ferrets and variable coils, but I think the Farnell 18009 and 18008 will be OK for the receiver and transmitter, and the Toko A7BRS-T1040Z (Digikey TK2417-ND or TK5117-ND) should be OK for the VFO. The capacitance values may have to be tweaked to get the right frequency coverage.

The MOSFETs BFR31 and 30 seem to be great devices for low level RF use as they are easily biased, actually nnot needing any bias but conducting a few milliamps with VGS = 0.

The audio side has not been thought out and may have the wrong gain needed, again play with the feedback around the op-amps to get this right. The transmit op-amp gain will affect the modulation and needs to be carefully set so not to over-modulate the output.

Tuesday, 14 February 2012

Management is what the NHS wants

The NHS does not need to be "privatised", this is just a way to pour more public money into the hands of insurers and bankers.

The NHS is a "company" today and can run on company lines. If it is not performing then it is not the financial structure that needs reform, nor outside pressures, it is the internal management skills and structures.

The government, and especially that clown Landsley, should be looking at this and stop his threats and unwanted, unnecessary reforms.

The very first thing to look at is customer service. From a welcome at the door, to a proper treatment inside, to a happy departure and follow up. My experience of these aspects of the NHS leaves a great deal to be desired. If you can fix this then tackle medical progress and spending next, and give the technical part of this into the hands of doctors, but keep a firm handle on the costs. Progress has to be made, but costs have to be balanced against what can be achieved.

Monday, 13 February 2012

New single end amplifier for HF 10W

Here is a proposal for a simple single end amplifier for HF (target 7Mhz band):

Single end amplifier

The input is a 4:1 transformer, loaded by a 22R resistor, this means the input impedance is about 90R, a bit high, but the power levels are low. The transformer serves to reduce the drive to the MOSFET, I have assumed that the input will be about 1W from the driving low power TX. With the MOSFET biased at Id = 0.4 - 0.5A a swing of less than 1V is needed on the input for full swing on the output.

Note that there is series capacitor missing on the input, a 0.22uF capacitor should be put in series with the input connection.

The output is also a 1:4 balun so that the impedance seen by the transistor is 50/4 = 12R. This lines up with the output impedance of the single transistor at 10W power and 13.8V Vcc, which is R = Vcc^2/Pout, or 12R.

The output low pass filter is the same as on the previous push-pull amplifier I have described.

The quoted MOSFET IRF530 is a bit over-kill, and the smaller IRF510 will be quite enough. Even smaller would be better (my idea; would be SOT32 package, 40V, 5A max with lw input and output capacitances… I especially like the look of Vishay's IRFIZ14G in the isolated TO220 package - no insulation washers needed, just bolt it down! Maybe this is one to try.

Re-doing HF amplifier output calculations

The critical component is the output transformer, this has to match the push-pull output MOSFETs to the Ro = 50R load.

Load needed

The transistors need a load of RL = (Vcc)^2/Pout. and the transformer ratio to match this has to be n = ns/np = sqrt(Ro/RL). Calculating these things give:

Rl = (13.8)^2/10 = 19R


n = sqrt(50/19) = 1.6 So a transformer with a turns ratio of 3:5 will be good.


But we also have to make sure the core never runs into saturation, to do this we need its primary reactance to be x4 RL, or 76R. The reactance of the primary is given by 2pifL. Calculating we get:

2pi x 7.1 x 10^6 x L = 76, or L = 76/(2pi x 7.1) = 1.7uH minimum.

With a type 61 core, of the chosen Binocular ferrite BN-61-202, with an Al = 385 we have L = n^2 x Al/1000 uH, so for 3t on the primary we get

L = 9 x 385/1000 = 3.2uH which is sufficient.

Here's a repeat of the final proposed circuit:

Amp schematic

As you can see the MOSFETs Vcc is fed by a couple of RFCs, and their is the 3:5 transformer on the output.

Sunday, 12 February 2012

Greece, I'm here and feeling for them

What can I say? I am in Greece for a 6 week vacation. I am in Crete, a proud but rather poor island. Dependant almost entirely on summer tourism.

IMG 1698 1699
Rethimnon Old Harbour

On the TV there are pictures and pictures of violent riots in Athens, with people attacking the police while the politicians continue to debate the EU bail out deal in the parliament behind them.

But what are the issues I am hearing here?

First they realise they have been sold down the river by corrupt politicians for many years, which resulted in accepting massive loans from banks, and inflows of capital grants from the EU, mostly spent on quite unnecessary projects just to let local businesses cream off profits. You can see the half finished public works everywhere…roads going nowhere, marinas with no services…

Many Greeks believe this corruption continues among politicians, they believe they have not yet accepted that it is all over.

Second they object to being treated in the way they are, for two reasons. The crisis grew over 10-20 years, the EU knew about it for sure, but they continued to pour money in. Next there is no recognition of the very great differences in culture and economic approach between Germany, who is driving the bail out actions, and the Greeks. Most Greeks are honest, they work hard, they just want to lead their lives.

So what do I see as the solution?

If the EU wanted Greece inside the euro then it must accept the consequences, not just let Greece get into trouble then drive impossible solutions. If the euro is a common currency, there has to be common share of ups and downs. But there clearly has not been. Even France knows this as their balance of payments is (€39bn) while Germany's is €98bn! Imagine how much worse it is for Greece. The German economy is driven by exporting, sure they are good at making things, but their domestic consumption is restrained in favour of dominating other counties with their exports. They have to accept a better balance.

So the solution is more equity.

And second it is not a short term shock that Greece needs, it is long term cooperation. The euro group has to make special arrangements to control the financial markets (not the other way round) so that over 20 years Greece and all the others can harmonise.

And lastly I must mention the banks, the real cause of the problem, can anyone tell me why the banks loaned so much money to Greece? I know that they misjudged the ability to get their money back, thinking that Greece was in the euro and giving interest rates the same as Germany… but they should have known better! So now they too have to give back, and accept the 70% hair-cut that is under negotiation. A poor, foolish investment is a poor, foolish investment, and that is what they have made, no matter how they try to dress it up...

Idea for a low power amateur radio amp

As I said below I am taking an interest in low power amateur radio. To this end I have been looking at SDR Transceivers, and at a low power amplifier for 7MHz operation.

Here is the schematic:

Amp schematic The input is a unbalanced to balance balun with 1:1 ratio, loaded by the 56R resistor. The amplifier uses a pair of IFR510 MOSFETs, whose bias is set by the 1K variable. The output stage power is through a balanced transformer/RFC design, and is transferred to the output by a transformer, The MOSFETs need a load of 19R when the Vcc = 13.8V and the power is 10W So the transformer ratio n = sqrt(Rout/RL) or sqrt(50/19), or 1:1.6.

The primary also must have a reactance of > 4 x 19R at 7MHz, so the inductance must > 1.7uH. The output ferrite is chosen to be a Binocular design with Al = 385nH, so for >1.7uH we need n = sqrt(L x 1000/AL) or sqrt(1.7x1000/385) = 2t, so the secondary must be 3t to give a ratio (1:1.5) near the required 1:1.6.

The output passes through a low pass filter to remove harmonics. Seems simple, but will it work?

Critical Parts List

Input transformer: 10t:10t, #24 wire, Farnell torroid 180009 (type 61, TN22/14/7mm, AL = 125)

RFC: 10t:10t, #22 wire, Farnell torroid 180009 (type 61, TN22/14/7mm, Al = 125)

Output transformer: 2t:3t, #20 wire, Fair-Rite Binocular Ferrite BN-61-202, Al = 385

LPF: 1.3uH, 3t, #20 wire, Farnell torrid 180008 (type 61 TN13/7/5.4mm, Al = 125) MOSFETs: IRF510, part number 844-IRF510PBF from Mouser Electronics

Drawing the strings together

LAW - 300 politicians

300 is about the majority for passing legislation that affects us all. Including legislation about copyright and the internet.

In UK a bill "Digital Economy Act" very much influenced by global media conglomerates, was rushed through parliament without adequate debate. It needs to be rescinded and re-thoughtout completely. It is the thin edge of the wedge to control the wonderful, open, free, global, new communication tool we have, the internet.

But that really is not the major issue, which is the total revision of copyright to fit into today's global world. An issue which politicians are not facing up to.

STUDIOS - 10 conglomerates
These industries are a pain. They have a business model - window release of movies being the worst - which is living in the past. They have no case to answer when they claim that Bit Torrent (the main channels through which films are downloaded) as it has been shown by investigations of the most respected kind that movie sale have not been influenced by pirate downloading.

In fact the studios have the solution to downloading right in their own hands. In a global market place if a major new film is released in USA but not in UK or elsewhere, people are going to want to watch it, and then peaople are going to download it. So if they abandon the window release and provide global legal access to new movies the amount of pirating will go down.

PUBLIC- 2-3 billion people

And then there are us, the people. We are being hit by blunt instruments, devised by interested parties, such things as the USA SOPA bill (now defeated) and the ACTA treaty (to hopefully be voted down by the European Parliament in June, even if the text has been signed by many local governments including UK with no debate).

It is very, very clear that we the people do not want any interference in the freedom to speak over the internet. Of course there are things we should not say, like inducement to terrorism, or child pornography, or things we should not do like copying music or films illegally. But this is no reason to interfere with free speech on the internet.

Last weekend there were demonstrations across Europe, in about 200 cities, against the ACTA treaty. A few reluctant politicians, who now have egg on their faces, are staring to change their ideas and say that perhaps ACTA is not a well thought out and democratic treaty - it is not of course, as it was drafted by a closed committee with strong influence from the media industry, but little or no public consultation. It was agreed behind closed doors, now they want us to vote for it!

CONCLUSION 1 − 2 − 3

Let's discuss and redefine copyright, so that it protects artists and ensures them a proper and due income. See my earlier copyright proposals.

Let's tell the media moguls in no uncertain terms that they have to change. Not supporting an old business model, they have to change, offering global, legal access to works, not building a business model based on 100 year old technology (the 35mm film) and controlling the release of works in windows to maximise their profits, not to the benefit the creators.

Let's make sure we all speak with the same voice, we the people do not want any interference with the open, global network, the internet.

Friday, 10 February 2012

DRM's future

The curse of DRM is still alive and well. Both on movies, HDTV and ebooks.

DRM is an encryption put on a work at its source, which only licensed devices can decode. But this is wrong thinking as it alienates the consumer who cannot do what he wants with the works he buys - for example reading an ebook in any software in on any device he owns, or watching a Movie on his media centre, not on his DVD player.

So what to do?

When I buy a digital work, I could ID myself. This ID can be burnt into the work I buy with a personal encryption key. This would allow any device I own to display the work, provided I give it my personal decryption key. What are the implications? When works are sold they must be personally encoded, this virtually blocks DVDs and HDTV from the scheme as there is no way to personalise a DVD in the shop where you buy it (it maybe could be done in an on-line warehouse buying a unique code on to the disk… But is is very viable as a system for on-line downloading.

Take note that each of us would need a personal digital ID, this has to be issued by a trusted body, just like the SSL certificates for web sites today, or maybe you could simply use your bank smartcard? Forward

This is surely the route that on-line retailers could follow if they insist on continuing with DRM, but remember that the music industry has abandoned any DRM on its tracks, and not found any increase in piracy. In fact their sales have gone up as consumers appreciate the utility of their product. However by uniquely IDing every copy sold, any copies found in the wild can be traced to their purchaser...

In the end DRM is probably self destructive as consumers first have to be trusted not to distribute copies of works - at least not to more than friends and relatives. And DRM is a disincentive to buy when used to limit the use of a product to using it on specific licensed devices (like Blueray DVD, HDTV and ebooks), or to use it to limit the time over which you can view the work (e.g. Apple FairPlay DRM on Movies). As I see it the future has two directions:

1 Works that are sold, with either personal DRM or non at all

2 Streamed products that are viewed once per payment.

3 Radio and TV

How about that? May the great debate go on…

and PS: how about a standard format for each media, AAC/FLAC for Audio, MEG4 for video, EPUB for ebooks. Time to all get in line.

Thursday, 9 February 2012

Updating copyright

Copyright should no longer be a monopoly, just a way of ensuring artists get paid.

My first thoughts are

When a work is released it can be made available on any medium, by others copying it, but rights on every copy must be properly paid for

Only global release allowed, no geographic restrictions

A work need only be paid for once. Then it is owned. e.g. if you see a film in a cinema, you can have a dvd or download for home viewing a second time, without paying again for the rights.

Free ownership of a work in any format.

Personal ownership of works purchased, no restrictions to transfer from one medium to another, copying allowed for personal use. But not for resale

Release cannot be restricted to a single time over any period, to a single channel or specific time or within geographic limits

Max copyright 20 years from date of release

Works purchased may be transferred, moved, to others who pay for them, or as a gift.

Friday, 3 February 2012

Great, the 11th Feb is death to ACTA then!

Great news, the world is getting ready again to reject the imposition of insidious new laws covering the internet and copyright. Law that have been promoted and written by private medai conglomerates, and negotiated in secret, with no input from you and me, and no debates in our parliaments (at least in UK, although the EU did spend a little time on it and rejected its acceptance.)

But the fact remains that this is a bad treaty, impinging on internet freedom which equate to freedom of speech. The text has been finalised and lots of countries have signed up to it!

So let's protest, lets use every tactic we can - like the internet blackout that stopped the USA SOPA proposals.

11th February 2012

The day is 11th February and I daresay we will start to see how we can take part before then. AT least I hope so.

Very clearly put - Europe's future

This is a great, simple analysis of the future of the euro. We seem today, fortunately, to be moving up the scale. I would put us somewhere around "The euro remains the euro" with the ECB starting, cautiously to recognise the need to monetize debts.

Of course the whole thing hitches on the proposals by Germany to have rigorous fiscal rules to prevent future casinos like the uncontrolled debt of Greece, Portugal etc (The PIGS). Once these rules are signed and in place in the laws of every euro country, then this is a step to fiscal harmony and the ECB can take another step towards being the bank of last resort.

But what remains is not such huge debts of sovereign countries (although bad enough in places) but the huge debts of banks - especially the UK.

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