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
Torroids
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 www.torroids.info, parts available from 'kit parts'.
Saturday, 25 February 2012
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.
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.
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.
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.
VFO
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)
MIXER
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.
VFO
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)
MIXER
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.
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:
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
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:
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:
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.
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.
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