Wednesday, 11 December 2013

DVB-T ATV UT100C Getting there: Transmitting video files , getting constellation diagrams



I have had success with transmitting video files, both test and HDMI ones I have captured off my camcorder via a Avermedia DarkCrystal HD Capture Pro PCI-E card. It all works as intended at full frame rate.

The UT100C works well with files, even Full HD. Dongle at 1mW to rabbit's ears antenna, received off main house TV antenna.

There is new software for the UT100C at  https://www.dropbox.com/sh/dvshv74hvjkau3a/uifV9Ve95l

I was using Windows 8 but swapped back to Windows 7. Not sure it makes much difference as there is now a signed Windows 8 driver.

Some receiver screenshots:

The image and channel properties at 16QAM. TV receiver software is ProgDVB. It works, its free, its been around a long time.


The 16QAM constellation diagram from Crazyscan2 with TBS 6220.  (I think this is very neat! All praise crazycat69!)


Re-transmitted at 64QAM as per Australian DVB-T standard.



The band scan showing my strong signal and the FTA stations further up the band. I should do the same with my BladeRF, although it only does about 20 MHz bandwidth..


I am only using a Haswell Pentium, working hard. It locks at full screen. (yes, they do make them and only cost $80!)  Although I will have to use something better.


On the transmitter side, modulation parameters, while TSPlayer is running. It plays files in a loop which is handy for testing.

 

 
 
The dongle is on a i5 Haswell, which does things with ease. The video file transmitting puts very little  load on the CPU as there is no encoding.
 
 
 



Still working on live transmission. I haven't tried audio, even with files, but the latest software is meant to support it.

Any comments welcome on how to get live TX going at full frame rate. Email vk4zxi(at)outlook.com.

Saturday, 7 December 2013

Improvised DVB-T test instrumentation

Improvised DVB-T test instrumentation

My last post was on snooping on DVB-S signals from satellites. I found some useful software to do that, Crazyscan and Blindscan. However, the author of Crazyscan also wrote Crazyscan 2 for DVB-T but needs specific TV hardware:  http://sourceforge.net/p/crazyscan/wiki/Info/

I ordered a TBS 6220 (DVB-T) (~$100) as well a TBS 6925 (DVB-S) (~$300), both pci-e cards, direct from the manufacturerhttp://www.tbsdtv.com/ . With courier delivery, they arrived within a week.

Setting up the TBS 6220 is straight forward and works well as a TV card with DreamTV; mainly to confirm that the device works. I put both cards in and software for both, but things got messy. Removing the TBS-6925 and its software, including auto start programs, fixed everything. I need to walk before I run.

My interest is with Crazyscan2. Setting it up is easy, just putting all the needed files in the same directory.

The result is amazing: a scan over 1 GHz at 1 MHz increments, albeit for DVB-T stations and slow; well seconds! I am used to the BladeRF. But they are two different animals.


The screen shot the VHF/UHF spectrum from my TV antenna aimed at Mt Tamborine. The DVB-T stations can be seen the left side of the shot.

However, clicking in the middle of the peak of a DVB-T signal gives me what I have been chasing, the constellation diagram! It also gives other data for the signal down the bottom of the slot.


The constellation diagram gives an idea of the quality of the signal and any issues with modulation, amplifiers and antenna.

So for about $100 for the card and a modern computer, I finally have a means of checking my DVB-T TX, hopefully the subject of the next post.

Thursday, 28 November 2013

Satellite TV, RX and positioning

Satellite TV, RX and positioning

Playing with satellites TV or radio is not too hard or expensive. I did a fair bit on it a few years ago (C and K band, ~4 GHz and ~12 GHz) and still have some of the gear. I could see my house in Brisbane on Google maps from the big white C band dish, ex Sky. It was a heavy fixed dish, jerry-rigged with a linear-actuator for position control. 

A full new C (and usable on K) band system is around $400 on eBay.   Sometimes they are available for free, migrants and expats used them to get overseas TV. I had one, disassembled, but tossed it when we moved to Gold Coast. Should/may have kept pole, as big steel is expensive.

All satellite TV use a LNB (low noise block) to receive and down convert to a standard IF range of about 1 to 2 GHz for a TV set-top box. The coax is used to carry control signals as tones (diseqc) or DC. The coax is very high performance, but cheap because of the massive use of it.

The big dishes are controlled by linear actuators and a positioner box. I have one set. I last used it to with a remote control to raise and lower a TV, (on big drawer slides) that was in front of a window (acker Heath Robinson(UK), Rube Goldberg(USA), Bruce Petty(AU)) . It worked but wasn’t pretty. Disassembled now. I will try to find photo. Linear actuators are cheap ~$75 and powerful; could be used for lots of weird purposes.


A big dish can be used with any frequency just by changing the receiver/antenna at the focal point. Dishes are only useful for higher frequencies as the receiving antennas get too big.


For lower frequencies, Yagi or similar types, often multiple,  are used.
 

Positioning dishes is fairly easy. One dimension is plug and play, with many receivers having built-in positioner control, or using a separate box. I have a Superjack DG-120+l and control box. I used the box for it with the TV lift.
 
Two dimensions is not much harder, just use two positioners bolted together at 90 degrees, as per the Yaesu G-5500. Any positioner or rotators can be used (see ARRL Antenna Handbook re satellites). With two rotators or linear actuators, quite big dishes or arrays can be controlled. One advantage of satellite antenna is that they can be on the ground, putting them higher may be necessary to clear obstacles.  
 

However, the control is manual with two controllers, again per Yaesu G-5500. Low orbit satellites (like Funcube or weather) are visible for about 15 minutes. It may not be too hard to track them just using signal strength and knowing their trajectory. Finding them as they come over the horizon is probably the difficult bit, but again, their position is known and the positioners can be calibrated.
 

It is "possible" to track satellites automatically, I suppose, but I have not seen a reasonably priced system. There may be some for the Yaesu G-5000, given that it is a standard piece of amateur hardware. A Raspberry-Pi or similar could do it, the actuators all give position feedback (reed-switch pulses as minimum) but the program would be fairly equipment dependent.
 
I may be able to track satellites on 2m or 70 cm. I am currently building a tilting mast (literally: yacht) and a 2 m vertical and a 70 cm crossed pair antenna. The antenna will be on a horizontal fibreglass pipe I had made ~$80, as a "T", with a rotator below. I could put a second pole-mount rotator on the fibreglass pipe to give vertical rotation. With the two rotators, I could point an antenna anywhere in the sky. It would be easy to make the 70 cm circular polarization with phasing. Then I could TX and RX! Could do same with 2m if make crossed too.


Some of the receivers (and SDR satellite programs, such as BlindScan and CrazyScan), have positioner control via diseqc, but one dimension.
 

Changing a TV channel with the remote can include moving the dish automatically; pretty neat really. Very common in Europe and Asia.
 

Given that most amateur TV is DVB-S, I might check some of this anyway, as I want to be able to receive the picture (via box or card), as well as the signal (using BladeRF) from Brisbane. I have got an old Foxtel K band dish on the roof and a 1200 mm dish in the back shed.
 

 
Awesome spook card, it has a pass-through for rtl-sdr or BladeRF SDR. Using Crazyscan/Blindscan and BladeRF with SDR-Console (or what-ever for spectrum analysis) just sounded too cool…  Little Pentium system might get used for something other than print server and scanner.
 

With a dish, at best, I can only use the 1200 dish with a positioner on existing Foxtel mount. I don't have space for a C band dish again. Not that there is much on C band now, most is on K.
 
Might drag out old Dream 800 set top box and see what still works. Dream box has pass through, so I might be able to get satellite spectrum; a first IF tap again! Bizarre if it works.
 
To be continued...

 

Saturday, 9 November 2013

BladeRF on Haswell i5 running Windows 8 with SDR-Console at 935 MHz 20 MHz bandwidth

BladeRF on Haswell i5 running Windows 8 with SDR-Console at 935 MHz 20 MHz bandwidth

Screen shot of BladeRF running on Windows 8 with i5 Haswell processor.



The BladeRF windows installer uses an unsigned driver. With the extra security of Windows 8 it will not normally even give you the option of installing unsigned drivers, Windows 7 does. However Windows 8 has a special restart where the unsigned driver block can be disabled. I think I described it in earlier blogs.

Using the earlier beta of SDR-console V2 per earlier blogs, the bandwidth is 20 MHz rather than 30. I think the narrower bandwidth is more appropriate re Nyquist, about half the 38.5 MHz bandwidth of the BladeRF. At 20 MHz, the CPU is barely busy at about 4 % versus 10 times that of screen shots at 30 MHz in earlier blogs. Simon Brown, the author of SDR-Console said in his Yahoo forum that the FFT runs at 30 MHz too. Dropping the bandwidth to 20 MHz seems to calm everything down.

   Screen shot of BladeRF running on Windows 8 with i5 Haswell CPU showing CPU load



My computer uses an ITX motherboard but is capable of running a (cheap) 27" 4K monitor (same LCD panel as Apple, Dell etc.) through its Displayport using Intel integrated graphics, while it is doing all of this. It gets a bit warm, but is in a tiny case. A HDMI camera input PCIe uses the one expansion slot. 4K monitors are very good for a number of reasons, but I will discuss that in another post.

Screen shot of BladeRF running on Windows 8 with i5 Haswell CPU showing system components and temperatures.


Screen shot of BladeRF running on Windows 8 with i5 Haswell CPU showing detailed core parameters


Summary: BladeRF runs on Windows 8 using SDR-Console at 20 MHz bandwidth with no issues.

The whole point: BladeRF receiving DVB-T test transmission from VK4ZXI 1mW at 2 m from UT-100C DVB-T usb TX

BladeRF receiving DVB-T test transmission from VK4ZXI 1mW at 2 m from UT-100C DVB-T usb TX

Well, it works. UT-100C USB DVB-T TX transmission from my laptop being received by BladeRF on 70 cm channel.

Not a bad signal with few spurious. Amplifiers will have low pass filter.




Now to do the amplifiers and antenna.

Friday, 8 November 2013

BladeRF with SDR-Console- Sceenshots (draft)

BladeRF with SDR-Console- Sceenshots (draft)

Just a quick post of some screen shots of the brilliant BladeRF running on the equally impressive SDR-Console by Simon Brown to show cababilities of both and the noy-surprising heavy load on an i5 2500K processor.

Free to air TV channel, 7 MHz wide with BladeRF running 30 MHz bandwidth




Same signal but one edge with 150 kHz bandwidth to show detail



 
 
Machine performance with 30 MHz bandwidth, CPU @ 67 C and fan whizzing. Ran like this for 20 hours, so all quite stable.

 

 
 
CPU load with some interesting signals. Reported stuttering is probably not a fast enough CPU. 30 MHz at 12 bit resolution would push anything.


 
 
Plan to try it on Windows 8 machine. Reported problems may be due to Windows  8 not accepting (or telling you) unsigned drivers. Such can be loaded in special restart mode.

Thursday, 7 November 2013

It lives! BladeRF SDR on Windows using SDR Console V2: 30 MHz bandwidth, 300-3.8GHz



Summary of BladeRF SDR TRX

BladeRF is a high performance SDR transceiver made by a small start-up company, Nuand http://www.nuand.com/bladeRF.

Currently only mainboard is available for US$420, with a HF/VHF transverter due late November to give coverage down to 10 MHz. For receive only, an up-converter for RTL-SDR dongles could be used to go lower.

Technical Specifications:

•Fully bus-powered USB 3.0 SuperSpeed Software Defined Radio

•Portable, handheld form factor: 5" by 3.5"

•Extensible gold plated RF SMA connectors

•300MHz - 3.8GHz RF frequency range

•Independent RX/TX 12-bit 40MSPS quadrature sampling:  LMS6002D is a field programmable RF  transceiver http://www.limemicro.com/products/LMS6002D.php
 
 

•Capable of achieving full-duplex 28MHz channels

•16-bit DAC factory calibrated 38.4MHz +/-1ppm VCTCXO

•On-board 200MHz ARM9 SOC with 512KB embedded SRAM (JTAG port available)

•On-board 15KLE or 115KLE Altera Cyclone 4 E FPGA (JTAG port available)

•2x2 MIMO configurable with SMB cable, expandable up to 4x4

•Modular expansion board design for adding GPIO, Ethernet, and 1PPS sync signal and expanding frequency range, and power limits

•DC power jack for running headless

•Highly efficient, low noise power architecture

•Stable Linux, Windows, Mac and GNURadio software support

•Hardware capable of operating as a spectrum analyser, vector signal analyser, and vector signal generator

Being a start-up, much of the software is still being developed, but some is available to make an awesome SDR receiver cum spectrum analyser.

Why?

While I was interested in them as an SDR, my immediate need was for a spectrum analyser for my DVB-T project covered in an earlier post.

I am trying to amplify the 1 mW DTV-T output on the 70 cm channel from the UT-100C modulator dongle. I have three amplifiers, trying to get about 5 W or so, to transmit.

Progress

Bottom line of BladeRF: it works as specified.
 

 




A commercial TV signal at ~635 MHz with 30 MHz bandwidth on USB3 Windows 7.

My Sandy Bridge i5 CPU is running at 37% and its fan is wizzing. Bloody amazing!
Imagine if it could be demodulated on the computer as well. I think there are 5 TV channels 7 MHz band.

I had to use the TV antenna with its masthead amplifier. My discone was a waste, too low and we are in a shadow area for free to air TV.

How

I initially tried to get it working on a Windows 8, but ended up getting it going on a clean Windows 7 i5 Sandy Bridge machine, first using USB2, then with no drama on USB3.

Per the Nuand blog entry, http://www.nuand.com/blog/platform-support-update/, the stand-alone Windows installer (http://nuand.com/downloads/bladerf_win_installer.exe) works. It puts everything into the Program Files (x86) directory. The installer includes firmware and the FPGA image (.rbf files). The main program to manage the BladeRF is “bladeRF” (in start list).

Run BladeRF from Start menu to get command window. Check you can talk to device. Load FGGA image and LEDs on board should start flickering. That’s all! Then to SDR software.

 Updated .rbf files can be substituted as they become available. The FPGA image must be loaded each time the device is turned on or reset, not sure why, but no big deal at this stage. 

As such, there is no need to go through the rather complex process of compiling everything to do the install as detailed in the wiki: https://github.com/Nuand/bladeRF/wiki/Getting-Started%3A-Windows. The description of the process is useful if you wanted to change any of the source code.

Windows SDR software: SDR-console V2 beta

The only Windows software I can find that supports bladeRF is SDR-console V2 beta. The current beta doesn’t but I managed to get an earlier version of SDR-console that was designed to work with bladeRF: Build 2.1 Beta 1545, see http://www.ham-radio.ch/kits/sdr-radio.com/2.1/ for all versions. Setup SDR as per any other.

Bandwidth list “only” goes to 5 MHz, but maximum gives 30 MHz (maximum can be set in radio definition). V2 “only” goes to 1 GHz, not sure if setting or otherwise. At the moment, not a problem, but it would be good to go to 23 cm band as UT-1000C can go that far.

Windows 8

As for Windows 8, not sure what the problem is. Main one is non-signed driver, which can be overcome with special start-up mode for Windows 8 (not a criticism, I can see why they do it) It may be a Windows 8 issue, as that is one of the listed issues for the device. It may also be a change in the firmware that is incompatible with the current V2 .dlls (the latest beta lists bladeRF but can’t find it). Will try again in next few days.

I am happy

While everything is still a bit hairy, I am happy.

I have a spectrum analyser for my DVB-T project. Now I can set up the amplifiers without clipping/splatter etc.


Everything else is a bonus. I can only encourage others to buy one of these devices and start experimenting. The company is a start-up and needs all the support it can get for a fantastic device.
 


SDRs at the first IF of IC-7410 TRX as a panadator: More detail

Note: I take no responsibility for any attempts at doing what is described here. I am not an expert with these radios and am following my own interpretation of how this is done. It is shared on the basis of the philosophy of amateur radio.

The main advantage of a 1st IF tap is avoiding the problem of sharing one antenna with a RTX and SDR; not simple.
As mentioned in an earlier post, I have installed a tap into the 1st IF of my IC-7410. The tap is made into the TRX’s first IF (64,455 kHz), above the roofing filters (the key to a good RX). The ICOM even have a socketed test point to do it (some hesitation playing inside a new $2000 TRX! Much reading of circuit diagrams). With the plug (hard to get but only $1.50 and are used on all main brands of RTX), isolation amplifier- http://www.cliftonlaboratories.com/z10000_buffer_amp.htm (gives details of how it is done), preferably through a bandpass filter (obtained but not installed) then to Funcube. I have it running, but not permanently installed.
 
 
A SDR at the first IF is really neat. It can be used as a panadator for the RX, although the SDRs display gets a bit woozy as I tune. However, you can see a large section of the band with the SDR and all the little signals that are swamped just using audio. The SDR can be used indepentently as a rx and tune within the first IF; basically using all the good front end of the RTX that the SDR doesn’t have.
The address for the 1st IF isolation amplifier I used is http://www.cliftonlaboratories.com/z10000_buffer_amp.htm. It gives details for fitting the amplifier for other TRX including FT-1000MP. When purchasing, You need to specify the gain of the amplifier, usually unity, as the signal should be fairly strong once it gets to the first IF. Delivery from the USA to Australia can take 3 weeks, ask how much extra for faster delivery.
Another way is at http://www.w1ghz.org/small_proj/small_proj.htm, about halfway down. It includes a filter to remove the local oscillator, and a further article that uses an opto-isolator to turn the SDR off during transmit. I had been looking for this site as I wanted to add both the filter and switch, having bought the parts to do it. The Mini-Circuits parts are available on special order from http://www.minikits.com.au/, as are many other interesting bits; he makes up patch cables to order too. There is another article on 1st IF taps that uses an in-line Mini-Circuits filter, which is easier to do, but I haven’t been able to find it.
The cheapest SDR to cover the 1st IF is just a RTLSDR dongle from ebay. You can get them on eBay for less than $20. Try to get one from an Australian store, otherwise you will be waiting weeks for delivery. I could only find one this morning: http://www.ebay.com.au/itm/USB-Digital-TV-Radio-for-PC-DVB-T-DAB-FM-SDR-Receiver-Dongle-RTL2832U-/331059172700?pt=AU_Components&hash=item4d14aa155c. Just search eBay for “RTL2832”.
These dongles go down to about 60 MHz, just enough for the 1st IF.
The other one you can use is a Funcube Pro+, but they are from the UK and more expensive, ~AU$200 although are plug and play. I use one of them.
For software there is SDR Console, HDSDR, SDR#, and CuteSDR among others. There is a site devoted to RTLSDRs that cover all of these and more: http://www.rtl-sdr.com/.
For a panadapter, SDR# is probably enough. See http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/. Use the latest version of zadig: http://zadig.akeo.ie/. If using Windows 8, as I do, there is a special start-up mode for installing non-signed drivers. Windows 7 just gives a warning.
It can be tricky getting the RTL dongles driver and associated files installed.

Added 9 Jan 2014

I have snipped parts of the block and circuit diagrams to make it clearer where the 1st IF tap is and how it seems a reasonably safe place to put it.

However, a word of caution to others wanting to modify different TRX for a panadapter. The IC-7410 is a very different design to other radios as much of the circuits for Rx and Tx are not shared. The best place for a panadapter is before the roofing filters if they are used. Unlike older superhet designs, the 7410 generates SSB modulation in the DSP, not through a sharp skirt filter (typically 9 MHz or 455 kHz). As such, taking an IF tap near the main SSB filter of a conventional TRX is very different as the RX and TX paths are shared, unlike what is done in the 7410.

 The tapping point is most clear in the circuit diagram of the 1st Rx mixer and the last Tx mixer, as they are clearly separate, plus there is a test connector to plug into. There is possibly no need to switch the isolating amplifier out when in Tx, but the bandpass filter could still help remove the local oscillator, but it should be minimal as a balanced mixer is used. It may be possible to just run coax out of the TRX and have the isolating amplifier outside.


Similarly, the tapping point can be seen approximately in the block diagram that clearly shows the different Rx and Tx paths. The green path is Rx.


It has been useful to re-visit the 1st IF tap on the IC-7410 to reassure myself that it seems a safe place to do it.

Further, re-reading the Rx and Tx design descriptions and circuits makes it clearer that the IC-7410 is a hybrid software-defined radio (SDR). All the Rx and Tx is done in the firmware programmable digital signal processor (DSP). The analogue parts are mixers, amplifiers and band-pass filters etc. The main signal filtering is done in the DSP as is the modulation/demodulation. Most SDRs could do with the bandpass filtering of the 7410.

Coming back to one of the points of a 1st IF tap is the difficulty of using a SDR and a TRX sharing a single antenna. Reading the circuit diagram, it should be possible to find a tap point where the Rx is separated from the Tx. With that, the SDR and TRX could safely share the same antenna with a splitter and 3 db loss of signal. A job for another day... Comments are welcomed.
 

Saturday, 26 October 2013

Software Defined Radio- SDR




Software Defined Radio (SDR), mainly receivers are what really got me back into amateur radio earlier this year, after a 40 year absence.
 
I had a brief revisit to radio 10 years ago, when I was medically retired, but was disappointed that so little seemed to have changed.

So I went and played (when I was able) with computers, audio, video, home cinema and satellite TV (and sport cars) instead. But once I had done about all I could do there, I was after something new.

Then I re-discovered radio starting with the TV dongle software defined radio, rtlsdr.

While I am still annoyed that mainstream transceivers (that I could afford; or justify) are still little changed, SDRs really are a hoot; you can see what is out there- lots of really weird stuff and no dial twirling hoping to find anything of interest.

I started with the TV dongles; they are not to be dismissed lightly, a couple of MHz bandwidth, 60 MHz-1200GHz range, all for $20. I bought a discone antenna and put it up as high as I could with a piece of pipe ~5m. Still interesting looking at FM, TV and all manner of odd things on VHF/UHF; still much to be done there. See http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/. It is an excellent blog now;. 

Added an up-converter and started using them on HF (I have a “Ham it up” and another simpler one. Silicon Chip magazine has been doing a series on SDRs over the past few months).

Minikits in SA do very sharp bandpass filter kits for the amateur bands, my first go at surface-mount components; not easy but it works. In Helensvale they do not seem to make a big difference. There does not seem to be much interference (other than what I generate with a couple of computers and wireless network).
 
I had bought a secondhand multiband vertical ten years earlier, so I put that up and could get onto the amateur bands; mainly 40 and 20m. That was a real buzz; finally being able to easily see what was on the band (all at once) and to quickly tune a signal, even if they paused, as they still showed up in the SDRs waterfall.

The SDR software is as important as the hardware. I tried everything I could find. Of all of them, SDR-Console is my favorite, although V2 is still in beta, with features being added all the time. http://v2.sdr-radio.com/. HDR# is a simple one, but fairly easy to get going. See http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/ for lots more discussion. (The rtl-sdr dongles are cheap to get going, but the drivers can be a problem, first finding the ones you need. Second, if you are running Windows 8, it won’t let you use un-signed drivers. It can be done by restarting in a special mode, but it is a bit involved. That is not a criticism of W8, I recommend it.)

Another good one is HDSDR  http://www.hdsdr.de/. It is a more mature version and can do CAT control of transceivers.

I had an old Yaesu TRX but thought I would get a new “state of the art” one, eventually settling on an Icom IC-7410. I can control it using an SDR with HDSDR via USB CAT, which was pretty neat fun.

I decided I should get a better, but not too expensive, SDR than a TV dongle and bought an AFEDI-Net  US$250  http://www.afedri-sdr.com/. Network-based, nearly 2 MHz bandwidth, DC to 30Mhz. They are very good, especially with SDR-Console; which has just added CAT-control to V2, but I haven’t tried it yet.

I also have a  FUNcube Dongle Pro+ http://www.funcubedongle.com/  ~£150. DC – 1900 GHz, but only 192 kHz bandwidth (the original amateur SDRs were sound-card based with 192 kHz as a maximum). The bandwidth is not a limitation on HF, but annoying on VHF and up.

I have never been much of an operator, mainly tinkering, even when I had my first station (VK2ZXI) while at high school, 2m simplex at Echuca/Moama on the Murray River. But, eventually I wanted to transmit. Not so simple with a TRX and a separate receiver.

I bought a special antenna switch, ELAD ASW-1 ANTENNA SWITCHBOX RX-TX http://ecom.eladit.com/epages/990298944.sf/en_GB/?ObjectPath=/Shops/990298944/Products/%22ELAD%20ASW-1%22. The switch lets me use the TRX transmitter and the SDR, but not the TRX receiver. It works well, especially using CAT control.

But never being happy, I wanted to be able to use the Icom’s receiver as well, as it is supposed to be one of the best. I imported a special RTX/RX antenna switch from the UK, but have yet to set it up. One problem is that the SDRs must be protected (antenna input grounded) before the TX starts; not a simple problem, although I think I am a bit paranoid as the ICOM takes a while to switch from RX to TX. I have a sequencer from Minikits that will get around the problem, but again haven’t got it going yet.

Another way around the antenna sharing is to tap into the TRX’s first IF (64,455 kHz), above the roofing filters (the key to a good RX). I have made a start with that, ICOM even have a socketed test point to do it (some hesitation playing inside a new $2000 TRX! Much reading of circuit diagrams). With the plug (hard to get but only $1.50 and are used on all main brands of RTX), isolation amplifier  http://www.cliftonlaboratories.com/z10000_buffer_amp.htm (gives details of how it is done), preferably through a bandpass filter (obtained but not installed) then to Funcube. I have it running, but not permanently installed.

A SDR at the first IF is really neat. It can be used as a panadator for the RX, although the SDRs display gets a bit woozy as I tune. However, you can see a large section of the band with the SDR and all the little signals that are swamped just using audio. The SDR can be used indepentently as a rx and tune within the first IF; basically using all the good front end of the RTX that the SDR doesn’t have.
 
My SDR activities are on hold at the moment while I try and concentrate on getting decent antennas and tiltable mast (off a yacht) working.
 
Concrete has been poured and the mast is assembled and works. Initially had the end siting on a  saw horse while the concrete set, but my wife hit her head on it. So I put it on a step ladder; now I hit my head on it. I must tilt it up and out of the way.
 

 

Low-cost Amateur Digital Television- DVB-T ATV using UT-100C transmitter USB dongle




I am setting up a DVB-T tx on the atv channel on 70 cm. I am using a UT-100c USB dongle http://www.hides.com.tw/product_eng.html http://www.idealez.com/hides/product-detail/en_US/69859. It is only US$169 and produces 1 mW of DVB-T output. The software is at https://drive.google.com/folderview?id=0BzoVnSl8XNdQMmZPbDhEczA2RjA&usp=sharing. There are some pdfs of the device and how the software works.
 
To use the dongle, only the windows driver and PC2TV are needed. With PC2TV, only the video works at the moment. PC2TV takes a deal of setting up but will work with a PC/laptop webcam. 

Only the UT-100C dongle is needed to start. Some ordinary domestic DVB-T receivers can be used. The DVB-T channels in Australia are 7 MHz wide, the same as free to air TV.

As such, the standard Australian DVB-TV settings can be used. At 1 mW, it is possible to xmit on a free commercial channel and tune a TV to it, without causing any dramas. However, to work on the 70 cm channel, a TV dongle or set top box that can tune outside the normal free to air channels is needed. The cheapest and simplest way is to use a DVB-T receiver dongle (~$20)on the same PC as the xmitter; sounds bizarre but works. It is necessary to edit the channel parameters for the dongle, but that is relatively easy. 

The other person, I know of, using these TX dongles reports at http://www.oe7forum.at/viewtopic.php?f=7&t=410. It is German, but he has photos and web links. His work is also on the British ATV forum http://www.batc.org.uk/forum/viewtopic.php?f=15&t=3158 and http://forums.radioreference.com/amateur-radio-equipment/269047-dvb-t-70cm-23cm-2-3mhz-bw.html.

The Europeans are limited to a 2 MHz bandwidth, whereas we can use up to 7 MHz, hence their need for narrow bandwidth receivers (that are available from Hides). I bought the low bandwidth receiver ($80) but haven't used it.

In terms of other amateur DVB ATV activities:  

There is a long-running DVB ATV amateur project DATVexpress, a collaboration between amateurs in the USA and UK.  http://g4guo.blogspot.com.au/ http://datv-express.com/ (see technical articles for some of the background of DVB) http://www.w6ze.org/ (DTV section).

There are ATV groups in Brisbane  http://members.optusnet.com.au/~cardenrj/ and Melbourne http://www.vk3rtv.com/index.html. Both good for information.

Both have ATV repeaters. My aim is to access the Brisbane Repeater.

Currently I am trying to do (too many things at once):

1) Increase the power output, via a couple of Minikits amplifiers http://www.minikits.com.au/ . They are very good source of kits and bits. Also RF Shop   http://www.rfshop.com.au/. I have a Chinese generic 70 cm 50 W amplifier as the final. Although I was hooking them all up last night and found the Chinese amp has some weird thread on its UHF connectors. I pulled it to bits and can replace them with N connectors easily (I think). With TV, the amplifies can only run at about 10 % of their rated power. 

2) Setting up a better camera than a webam. I have changed from my laptop to my main station computer so I could install a HDMI camera input card (also does other analogue video inputs), an Avermedia DarkCrystal HD Capture Pro PCIE Card C027 ($100) from local Umart http://www.umart.com.au/newindex2.phtml?bid=4 .

I am using a cheap Canon camcorder HFR406 ($209) from JB Hi Fi. Somewhat surprisingly it worked quite easily, I think because I can use standard digital video ie 1080i or 720p in the PC2TV software. (Video formats drive me nuts).

3) Build a tilt-up mast, rotator and 2 m and 70 cm antenna. I am still setting up the basics of my station. Current status is mast is ready to tilt up, I have been waiting for concrete to set from a week ago. I have assembled all the bits to make the antenna (not simple to get). The design is per the ARRL Antenna book and uses insulated elements. It has been hard to source "top-hat" or stepped nylon washers and "push-nuts" for the insulated elements.

4) Playing around with studio software, to be able to have overlays (call sign) and switch between camera(s) and recordings. See http://www.vidblaster.com/. It has a virtual camera that can be the input to PC2TV. It is a commercial product but there are freeware ones around. They are mainly designed to stream to a network or record for YouTube, rather than direct to a TV xmitter.

5) Trying to get some basic test gear going. I have an interest in Software Defined Radio. I can use an RTL dongle SDR as a spectrum analyzer, but currently have limited bandwidth (3 MHz, whereas I need 8+). I am chasing some cheap Chinese gear that will give me spectrum and constellation plots. I need the test gear to monitor my amplifiers to start with, to avoid clipping/overload etc.

 

Thursday, 29 August 2013

Hi all.

The purpose of this blog is to share some of my activities and ideas on amateur radio and related areas, including home theatre.

Currently, my main radio interests are Software-Defined Radios (SDR), smart/active antenna and computers in radio in general; more on that later.

First, my journey around radio, electronics and computers; my path to my current interests.

My interested in electronics and audio started in my early teens, playing with valve radios and loud speakers. However, the main kick-start was when my father, Wattie Wollin, bought me the September 1969 issue of electronics Australia. Dad was interested in radio and gave me some books on "wireless" dating from the mid-1930s when he was a lad. While very capable, his isolation from education, the 1930s depression and WWII lead him into a meat industry trade at 13 and away from radio.

I first became interested in amateur radio when at Echuca High School in the early 1970s and obtained my limited certificate and first call sign, VK2ZXI; 2 because I lived in Moama in New South Wales, across the Murray River from Echuca. I used to ride my bike interstate to school!

I worked closely with George Loft, VK3AGM, learning a lot about radio, along with bee-keeping, general engineering (fitting and turning, welding etc.), truck mechanics and life in general. George was a bee-keeper, like his father, but one of the most intelligent people I have ever met. George designed and built radios including digital gear, built his own metal lathe and designed and built specialist bee-keeping equipment. George did buy an FT-101 about when they first came out; I still remember it sitting between the two of us in the truck while moving bees at night.

My only radio was a converted taxi radio on 2m simplex; all valve plus one transistor in the receiver pre-amp; I still have it. I helped George build a 40 foot tower with a hand-driven rotator for me. I used a string around the gear and a piece of elastic on the wall of my shack to give a linear direction indicator. I built a 10 or so element Yagi to go on top; it all worked wonderfully well, reliably working within a 50-odd mile radius. (I use imperial units here deliberately as metric didn't officially start in Australia until the mid-1970s).




I initially wanted to study communications engineering at university, but at the last moment changed to agricultural engineering at the University of Melbourne, not wanting to make my hobby my job; a decision I have never regretted. I did agricultural engineering, together with some of the electrical engineering subjects to third year.

I drifted out of amateur radio while at university, living away from home (my station) and not interested in, or able to afford, commercially-built radios.

I started work with the State Rivers and Water Supply Commission in 1978, by chance, in their research unit. I developed an interest in computing, something that was of little interest while at university; developing a simulation of the Murray River and the effects of salinity interventions. Simultaneously, I started using instrumentation to measure ground water and soil permeability. So, in the end, I combined my interest in electronics with my job.

An interest in research lead me a year later to the Horticultural Research Institute, Knoxfield, in Melbourne's outer suburbs to a greenfield job in engineering in post-harvest horticulture. Again, computers and instrumentation was the focus, with a program for the economic optimization of export packaging and transport of fruit (Burroughs mainframe), and a computer simulation and controller for controlled-atmosphere fruit storage (Data General Nova and a CP-M micro-computer). I completed a Masters degree at Melbourne across the agricultural and electrical engineering departments (on the storage-controller and simulation), and a Graduate Diploma in Digital Computers (analogue computers were still around then) at RMIT.

Enough for now, to be continued...