The thoughts, observations and adventures of a software engineer and licensed amateur radio operator call sign M0NRD (previously 2E0NRD and M6GTG) with an interest in all things radio related.
Listening to the scanner this morning I heard the distinctive APT 'chiming' sound as one of the NOAA polar orbiting weather satellites was making a pass. It has been a while since I have done any APT decoding, so decided to capture some of the passes of NOAA-18 and NOAA-19 this afternoon.
The first two passes of both satellites were North to South around 20-30 degrees elevation, this image was the best of the them, the UK is in the upper left.
NOAA-19 11:32 UTC 21-OCT-2012
The following passes were much higher, almost overhead, there was some interference on this NOAA-18 pass due to pagers and I got disorientated whilst hand holding 2-meter YAGI, hence the lost of signal near the top of the image.
NOAA-18 14:02 UTC 21-OCT-2012
However the NOAA-19 pass before it was much better. What is noticable is the bands of darkening, caused by nearby buildings and some large trees shielding the satellite from my the line of sight position.
NOAA-19 11:12 UTC 21-OCT-2012
All images were decoded realtime using the SDR-Radio program, received by the FUNCube Dongle connected to the InnovAntennas Yagi.
Not feeling too well at the moment, have a suspected inner ear infection which is causing dizziness and nausea, so taking it easy today.
I switched on my scanner this morning and decided to peruse the CB channels, it is something I haven't done very often as usually there is nothing to receive and is problematic since my scanners cannot exactly tune to the UK frequencies accurately.
What I did find were a lot of suspected 'Eastern European' transmissions on the CEPT/EU band in FM and AM mode. I also came across lots of activity on the "Super Bowl" Channel 6 (27.025 MHz AM). Apparently the popular channel for "skip shooters" using high powered amplifiers and indeed copied a few 1kW transatlantic transmissions. There were also a lot of SSB transmissions about but the PRO2006 scanner I have doesn't have side band capabilities.
I have thought many times about getting hold of a cheap CB, or one of those popular 10m/11m amateur rigs just to get some practice in operating a transmitter before getting around to taking my foundation test. Especially as OFCOM have announced they intend to finally harmonise with the EU on the use of AM and SSB next year. http://www.southgatearc.org/news/october2012/ofcom_ecc_decision_on_am_ssb_cb_apparatus.htm
Had an excellent FITSAT-1 pass last night, successfully received nearly three full frames of CW telemetry.
The image above (from the heavens-above.com prediction site) shows a similar pass and illustrates the reception window which is just less than 8 minutes. Each frame of telemetry takes around 2.5 minutes to receive, so I was extremely happy with the results.
Again I recorded the pass using SDR-Radio and played back the doppler corrected IQ file later decoding with the MRP40 program, hear is a small video demonstrating the decoding process.
and this was the resulting telemetry data when run through the analyser program (see previous post).
---------------------------------------
FITSAT-1 NIWAKA Downlink CW Code
---------------------------------------
Input Data------------------
S1 :f00501bb
S2 :88db0101
S3 :02000102
S4 :1e20201f
S5 :1a12aae7
-------S1------
S-mater of 437MHz RX :4.69[V]
Total Voltage of Solar cells :0.1[V]
Total Current of Solar Cells :0[mA]
Voltage of single cell battery :3.65[V]
-------S2------
Current of single cell battery :1054.69[mA]
Voltage of 3 series battery :12.83[V]
Current of 3 series battery :0[mA]
Voltage of 2.5V reference :0.02[V]
-------S3------
Voltage of Solar cell + X :0.07[V]
Voltage of Solar cell + Y :0[V]
Voltage of Solar cell - X :0.04[V]
Voltage of Solar cell - Y :0.07[V]
-------S4------
Temperature of 3 series battery :2.73[℃]
Temperature of single cell battery :6.25[℃]
Temperature of +Z side :6.25[℃]
Temperature of –Z side :4.49[℃]
-------S5------
S-meter of 1.2GHz RX :0.46[V]
------Timestamp-----
14day 3hour 49min 59sec
I have also uploaded a better recording of the audio.
Earlier today I posted about my latest attempts at receiving the FITSAT-1 Cubesat, the reception hadn't proved too difficult however actually decoding the morse code was proving difficult!
Having another go with the MRP40 decode software and replaying a recorded IQ wave file from yesterday I successfully decoded 80% of a full telemetry frame!
I also found this interesting pdf file detailing the construction of FITSAT-1 and discovered the 437MHz transmitter is only 100mW. So we have a flying metal cube measuring just 10cm x 10cm x 10cm travelling at approximately 4.5 miles/sec roughly 270 miles above the earth, transmitting with just a fifth of the power of one of those PMR446 hand held walkie talkies that in my experience struggle to maintain a contact over a few hundred meters! Isn't technology wonderful?
FITSAT-1, TechEdSat and F-1 Cubesats after leaving the ISS
Anyhow this was the telemetry frame, as decoded using a PC program developed by one of the students on the FITSAT team.
Input Data------------------
S1 :f01601ba
S2 :8dbd8181
S3 :20001820
S4 :1e202020
S5 :*
-------S1------
S-mater of 437MHz RX :4.69[V]
Total Voltage of Solar cells :0.43[V]
Total Current of Solar Cells :0[mA]
Voltage of single cell battery :3.63[V]
-------S2------
Current of single cell battery :93.75[mA]
Voltage of 3 series battery :11.07[V]
Current of 3 series battery :0[mA]
Voltage of 2.5V reference :2.52[V]
-------S3------
Voltage of Solar cell + X :1.13[V]
Voltage of Solar cell + Y :0[V]
Voltage of Solar cell - X :0.84[V]
Voltage of Solar cell - Y :1.13[V]
-------S4------
Temperature of 3 series battery :2.73[℃]
Temperature of single cell battery :6.25[℃]
Temperature of +Z side :6.25[℃]
Temperature of –Z side :6.25[℃]
-------S5------
S-meter of 1.2GHz RX :No Data
Timestamp :No Data
It was dry and a lovely clear sky last night and I had several opportunities to receive the latest Cubesats.
I made some sight modification to the tripod mounting of the small 70cm Yagi antenna I am using, repositioning the clamp allowed me to secure my Android smart phone behind it. Then by using the Satellite-AR app I was able to hopefully point and track more accurately.
As you can see from this close up, it is quite a useful tool. Selecting the Cubesat catagory in the application, shows the procession of the cluster one after the other. The Cubesats have now spaced sufficiently to allow reception of WE-WISH which is just dropping out of sight as FITSAT-1 is starting its pass.
One thing I hadn't counted on last night was the very high elevation and I struggled to turn and tilt the tripod quickly enough whilst still viewing the screen on the phone, this will hopefully improve with practice!
Previously to the tripod I hand held the antennas but the drawback with that method was not being able to check and make adjustments on the computer, the tripod at least allows me to maintain reception.
I again received WE-WISH but the signal was too weak and short lived for any reasonable attempt at decoding the SSTV image. FITSAT-1 was however much better, getting relatively clear signals from the CW telemetry beacon, however I have been struggling to actually decode the messages, however after some research I tried the MRP40 Morse Code Decoder program, which appears to be excellent and as you can see from the screenshot below successfully decoded some of the telemetry messages.
Definitely got the bit between my teeth now, will try to get a full telemetry frame this evening, weather permitting!
The recently released Cubesats were due to pass with high elevation late last evening, so the new antenna was mounted out in the garden on a tripod and the FUNCube Dongle connected to the trusty laptop in the shack.
The Cubesats FITSAT-1, WE-WISH and TechEdSat are now supported by the Satellite-AR application on my android phone allowing me a reasonable chance at tracking them.
According to the tracking data the WE-WISH Cubesat is ahead of FITSAT-1 on the orbit, so my first attempt was to capture some of the Infra-Red SSTV imagery it is sending back, I did managed to receive the signal as you can see on the waveform below, you will also see SDR-Radio was preforming doppler correction very well indicated by the slanted central IQ spur and local 'carrier' in the middle of the transmission (was playing back a captured IQ wavefile) Sadly the WE-WISH signal wasn't strong enough and didn't last long enough for any meaningful decode, but I was able to confirm that instead of being at 437.505MHz it is nearer 437.514MHz as was reported on AMSAT-UK
WE-WISH Downlink Transmission, received in UK 16-OCT-2012 19:32UTC
I was very happy to have received this as the WE-WISH downlink transmitter is reported to be only 100mW! As the signal disappeared I quickly switched to the latter stages of the FITSAT-1 pass and got some nice clear bursts of the CW beacon.
FITSAT-1 Downlink Transmission, received in UK 16-OCT-2012
Tonight there are two other nice high elevation passes of the Cubesat cluster, so hopefully will get out to have another attempt.
I noted that it has been running hot again, the heat sink port on the side has been getting seriously warm so if I do attempt another re-flow of the GPU (if that is the fault) I will have to look at improving the cooling. I am thinking I might drill some holes through the bottom casing to allow more air in and might fit an override switch on the fan since it seems to only come on when very very warm.
What is doubly annoying is that over the weekend I managed to receive what I believe are the FITSAT-1 and TechEdSat Cubesats. My earlier attempts last week were only partially successful and the one time I did manage to get really good signals I forgot to set it to record the IQ file.
Over the weekend I was away from home, visiting the in-laws. I had taken a scanner, my FUNCube Dongle and laptop. I appropriated an indoor TV aerial and surprisingly managing to get some clearly audible signals, despite major issues with pager breakthrough and interference caused by the aerials wideband amplifier.
As soon I manage to get the laptop working, or recover the IQ files from its hard drive I will post the results.
It is a sad time here at the moment as my Father-in-law passed away at the weekend following a long illness. Obviously the priority at the moment is dealing with the aftermath and supporting the wife and family.
However I have managed a few hours to myself this evening to make an attempt at receiving the newly launched CubeSats. This news item has some amazing pictures of the satellites as they were released from the ISS
A full technical breakdown of the new satellites and frequencies can be found here. At the present time signals have been received from WE-WISH, TechEdSat and FITSAT-1 and NanoRack/F1 appears to be silent. I did get some of the FITSAT-1 CW beacon using the antenna in the loft the other night, but was a bit scratchy and didn't manage any reasonable decode. I was using the orbit information of the ISS, but the satellites are now a few minutes in front of the ISS and new TLEs have been issued by Celestrack (1998-067CN-CS)
As it happens the 2012 National Hamfest took place a few weekends ago, and I purchased a small 70cm Yagi antenna, known as a ZL-Special. I am hoping this will give me some decent results as the satellites are mostly in the 437Mhz range.
On Wednesday, September 19, 2012 at 7:13 UTC, i.e. 9:13 CEST, students of Complex of Technical Schools, Kolo, Poland established ARISS contact with astronaut Akihiko Hoshide KE5DNI onboard the International Space Station. Astronaut Aki Hoshide operated with the ISS callsign OR4ISS. This was a direct contact performed by amateur radio station SP3PGZ, located in the school.
Kolo is a 650 years old, small city located in the central region of Poland. Zespol Szkol Technicznych (Complex of Technical Schools, abr. ZST) in Kolo is a modern, dynamic and constantly developing school with more than 60 years tradition, with a well-qualified staff. The school is one of the largest secondary schools in the region. Currently they teach more than 1000 students between 16 and 20 years old.
Local School Amateur Radio Club SP3PGZ was established in 1976 and since then it has been active on many amateur radio bands. The main goals of the club are: promoting shortwave radio communication as a hobby for young people, cooperation in organizing local events and taking part in competitions. Now they established the ARISS school contact.
The contact took place at Centre of Information in the school, where an audience of about 30 visitors and media participated to the ARISS event. Before the contact, host of the event Dr. Armand Budzianowski and students Konrad Kustosik and Mateusz Karulak presented visitors and media information about ARISS and about the students’ preparation to this contact with the ISS via Ham Radio.
At 7:13 UTC, contact was established with OR4ISS by SP3PGZ station. Mr. Greg Walichnowski SP3CSD, the radio contact operator, exchanged welcome greetings with astronaut Akihiko Hoshide KE5DNI. Using the VHF radio in the Service Module, Aki answered 18 questions from the students. To close the contact, students dedicated this event to the memory of all those brave men and women like Yuri Gagarin, Neil Armstrong or Sally Ride and to all ISS crew members who are striving to fulfil humanity’s dream of conquering the universe.
I myself successfully managed to capture a fair portion of the downlink myself. The Polish ARISS organisation have just posted a full video of the contact. (We won't mention that they appeared to lose contact before the dedication at the end, as it was a nice touch)
Hopefully yesterday saw the conclusion to the saga of my broken laptop.
Two weeks ago I had an attempt at reviving a sickly HP/Compaq 6735S a model which is notorious for GPU problems. Specifically the GPU BGA contacts break due to thermal stresses and shoddy manufacturing.
I had stripped the laptop down and using a IR rework station attempted to reflow the contacts with limited success. It survived one power up and then died again.
Like Robbie Burn's famous spider I was not going to give up that easily so I stripped it down again and this time remembering the 7 Ps adage I didn't cut any corners.
The picture above shows the motherboard after I removed it the first time, you can clearly see the GPU in the top right. Notice first the pathetic thermal bonding? Also you can see around all four corners of the chip what appears to be red cement.
Initially I was unsure of whether to remove this and indeed it appeared to be tough and nigh on impossible to remove so fearing possible collateral damage I left the cement in place and heated the GPU on the IR rework station attempting to reflow the joints.
This I believe was the mistake as this bonding would have prevent the chip from floating on the reflowed solder pads. So this time I did remove the cement as you can see below. I found heating the cement did make it malleable, the problem being how to heat it without damaging any of the surrounding components?
In the end I used a precision hot-air gun (which they also have at work) on a low-medium heat setting on a very low 'blow' setting. Using this and a couple of wooden toothpicks I was able to remove the vast majority of the red gunk!
Once removed I applied a small amount of flux around the chip, working it under the device and then used the IR rework station but on a much higher setting than before to ensure the solder properly melted.
To my pleasant surprise the reassembled laptop booted and it has been successfully been powered down and rebooted several more times since.
While not the prettiest of laptops, or indeed in the best condition it does at least have Windows 7 Professional on it and a nice big hard drive and 4GB of memory so should prove more than capable for my experiments - assuming she carries on working, and she does get a little warm!
Ever since I got my FUNCube Dongle Pro last Christmas it has been the main focus of my radio experimentation. I have used it on a number of computers including some quite old not very powerful machines and with different software applications primarily the SDR-Radio and HDSDR suites.
It was a little fiddly to initially set up but I have been impressed with its performance, it has opened my eyes and ears to what is out there on VHF and UHF, much more than I could ever monitor using my scanner receivers. Have a look at my previous postings.
Being SDR, with all decoding being done in software, it is effectively capable of all modes capable with the added advantage of having a variable bandwidth which is useful for data modes.
I have decoded images broadcast from orbit, received transmissions relayed via satellite and even bounced off the surface of the moon! As well as listening to all manner of terrestrial broadcasts.
In a word it is BRILLIANT.
It has its faults, or should I say limitations. It would be nice to have more of the spectrum available at one time and the front end filtering and rejection is troublesome at times. However this is more than made up for by its versatility and performance and it often out preforms my PRO2006 on the same antenna.
On the various forums and social networks it irks me to see people complaining about its performance but then they are usually the same people who go out and purchase a sub £20 RTL2832U based USB FM/DAB/DTV receiver dongle from eBay to use as a SDR and then complain they cannot get it to work or that its performance is lacking. But then that seems to quite common at the moment, everyone expects to just plug it in and it to just work with the minimum of understanding, involvement or experimentation but I digress.
Unfortunately Elonics the suppliers of the tuner chip in the FUNCube Dongle PRO are currently in liquidation and so they have struggled to produce any more units since July this year. This has potentially serious implications for the whole FUNCube educational project as there is no earth based component. Therefore the FUNCube team have instigated a redesign of the receiver and in doing so have increased its functionality and addressed some of the issues. This is the FUNCube Dongle PRO+
The new FUNcube Dongle Pro+ offers the following features and enhancements:
Full coverage of all amateur bands from 136kHz through HF, 6m, 2m,
4m, 2m, 1.25m, 70cm, 33cm, 23cm (150kHz-240MHz and 420MHz-1.9GHz,
70kHz-150kHz coverage through your software’s NCO offset)
0.5ppm TCXO
192kHz sampling rate
Eleven discrete front end filters
Super sharp SAW filters on 2m and 70cm
It is expected mid October 2012 and you can register your interest here
The official release of the FUNcube Dongle PRO+ was made during a presentation given to the AMSAT-UKInternational Space Colloquium 2012 on Saturday September 15. You can view the presentation by following these steps:
- Go to http://www.batc.tv/
- Click on "Film Archive"
- Select "AMSAT 2012" in Category box and click on Select Category
- Select "02 - FUNcube PRO-PLUS" in Stream box and click on Select Stream
I spoke too soon I finally got hold of some thermal paste and reassembled the laptop. Everything looked fine it powered up and had installed all the latest windows and software updates it had missed during it's illness.
I closed the lid when I'd finished then when I opened the lid to use it again and it won't power up! Flashes the cap lock LED five times to indicate the same fault!
Piece of s.....
I did manage to get a decent capture of the ISS downlink during the ARISS School Contact on Wednesday morning before I had to leave for work. It was a bit cold standing out with the antenna but was worth it.
Seems to be lots of ARISS activity at the moment. There have been a number of school contacts over the last few weeks that have had downlink transmission from the International Space Station receivable over the UK and Europe. Tomorrow morning (September 19th) there is another one, but it is unlikely I will be able to have a proper attempt at receiving it.
However these are the last two downlink transmissions I managed to receive.
Last Saturday saw a huge tropospheric lift on VHF and UHF. The amateur bands
were apparently buzzing with activity and scanner enthusiasts were reporting lots of new signals.
Unfortunately I wasn't at home so missed most of the action.
However I did manage to have a Sunday to tinker to my hearts content, I will post up some details of what I got up to when I have more time. I did get an excellent capture of the ISS downlink for the ARISS school contact and did some experiments with receiving some UHF Satcom stuff.
One thing I finally got around to doing was removing the motherboard from a sick laptop. It is a HP/Compaq laptop and suddenly died one evening. It would no longer boot and flashing a diagnostic code on one of the LEDs. The code was "GENERAL SYSTEM BOARD FAILURE". The laptop is quite nice and was going to form a key component of the shack and so I was determined to repair it if necessary.
I did some googling and it seems the model in question is prone to failure of the GPU, or more specifically failure of the contacts between the GPU and motherboardl. This is a common fault now in many devices especially those with components that run hot (Xbox/PS3 etc)
It is thought that the temperature and thermal stresses involved cause one or more of the contacts to break. On inspection of the heat sink over the GPU and CPU I was shocked at the poor mounting and application of thermal pads/paste which undoubtedly made the problem worse.
The suspected faulty GPU is mounted using a ball grid array, where the contacts are under the component the problem with this is you cannot easily repair or replace the contact without specialist equipment. What is required is to reflow the solder joints, heating up the component sufficient so the solder underneath melts reforming the contact.
Several methods of 'homebrew' repair are available using heat guns, blow lamps or placing the board in a hot oven but due to the delicate nature of the board and risk to surrounding components aren't recommended.
As luck would have it I had access to a Infra-red rework station, this device has a high intensity infra-red lamp which heats the component and a heat pad underneath to pre-heat the circuit board. The advantage of this is there is no risk of movement to the components during the process and the temperature can be accurately controlled.
Well I had a go, and can report the motherboard is now working or at least now boots up. I just now have to replace the thermal bonding under the heat sink to hopefully prevent it happening again and then the small matter of putting it all back together!
Not much to report, but have had a few decent monitoring sessions with the FUNCube Dongle.
A couple of ISS ARISS School Contacts took place over Europe during the last couple of weeks, with another taking place on Sunday morning. I was in work during the passes but managed to remotely log in to my computer to do some 'unattended' SDR-Radio recordings.
Late last night there was a bit of a lift on VHF and managed to receive the GB3VHF 144MHz Beacon which while it may not seem very news worthy is given there is a huge hill in the way when you look towards Kent! I have received it before using the Yagi in an horizontal polarization. But last nights reception was via the discone in the loft, which was a first. Love the JT65B tones, very musical.
Earlier last night was also quite amusing when I stumbled across the Hucknall Rolls-Royce Amateur Radio Club who were trying to run an Amateur Radio Direction Finding Fox-hunt but were being completely blotted out by another, seemingly deaf, local operator pumping out 100W, though he did turn it down to 10W eventually.
Again it has been a very busy month since my last post, but I did manage to get a few days to finally start sorting out my workshop/shack.
Just before the horrendous winter of 2010 struck I had purchased a 16' x 10' wooden workshop, in fact you can see it in the picture below the day after it was erected complete with a coating of snow! The workshop was subdivided into two separate sections a smaller 6' x 10' area with it's own door for storage of garden paraphernalia and the remaining 10' x 10' section was intended to be a 'man cave' where I could keep my junk, set up a small workspace and experiment to my heart's content without an accountability. The intention was to free up a small bedroom in the house and remove some of the accumulated junk from the loft!
Well for the past 18 months despite my best intentions the workshop had become nothing but yet another store room! The first task was to empty the workshop and sort out the rubbish, almost immediately I became rather dispirited as it seemed a huge task, however after several temper tantrums, a beer or two and some ruthless decisions followed by several trips to the local tip I had got rid of a large portion of the contents.The remaining good stuff including tools, screws, nails and other items were sorted roughly into boxes to be properly organised at a later date.
I had already run an armoured electrical cable supply into the workshop but no internal wiring. The distribution/RCD unit, cabling, sockets, switches and lighting were still sitting in the screwfix box. Several hours of hard work in the sweltering heat and I had it wired it up with some decent lighting and power sockets. I also took the opportunity to install some
proper thick moisture resistant chipboard tongue and groove flooring to strengthen the existing floor and
that has been covered in some vinyl flooring for ease of cleaning.
I had always intended to line out the workshop with plywood and insulate it but I had a change of heart, mostly due to cost but also for aesthetic reasons since it has a lovely rustic wooden feel inside with roof beams and the tongue and groove panelling, I will probably regret the decision in the winter, but given the fact that everything stored in it has survived two harsh winters with no signs of damp I have left it alone for now.
I have furnished it with some unwanted items including a nice sturdy table, chest of draws and some old book shelves and have gradually been moving my junk into the workshop. I am now in the process of sorting out some more shelving and a soldering station and workbench so I can finally start tinkering again!
I have also installed a wireless access point configured using WDS to connect to the main house WLAN and that seems to be reasonably fast and reliable and have an old PC which gives me access to the Internet and my music library I can listen to without being told to turn it down!
I should add the whole shed/workshop are protected by a proper security alarm with PIR and door contact sensors.
Seems the holiday in early June broke the blogging momentum and unfortunately work commitments since and the stresses involved as a major project nears deployment have sapped my time and energy, so not had much to post.
Family commitments too have also eaten into my spare time not leaving me time or inclination to experiment.
The FUNCube Dongle and the Ultra-cheap RTL-SDR have been unplugged for several weeks and I am ashamed to say most of my evenings have been sent slumped in front of the TV often nodding off to sleep rather than tinkering away.
That is not to say I have been completely idle! I have spent the last couple of weeks with a Cross Country Wireless SDR4+ receiver courtesy of my younger brother. For a while I have toyed with purchasing one after seeing them at last years Hamfest and have read some decent reviews.
The SDR4+ is a HF Software Defined Radio covering 0.85 - 30MHz, the full specifications can be found on their website.
My brother shares a similar interest in radio, probably as he was forced to share a room with me when we were younger and I would subject him to listening to all sorts of strange signals late into the night! Well he decided to purchase one several weeks ago, but was frustrated when it didn't seem to work. On one of visits to see my Mother I took a cursory look and couldn't make it work either. To cut a long story short while he went away on holiday I borrowed the unit away to see if I could figure it out.
I strung up a long random-length wire antenna in the loft and have managed to get some decent results on some bands, but interestingly very little on others, probably due to the lack of an ATU. But I have received lots of broadcast AM, some DRM (but not actually decoded) and buckets loads of Amateur transmissions, LSB/USB voice and Morse, RTTY and PSK31 from Europe, and decoded some HF-FAX. Sadly the SDR4+ will soon be off back to it's rightful owner, but has certainly wetted my appetite.
I have also refurbished my Realistic PRO2022 scanner, as I posted back in 2010 this was my very first scanner and sadly was looking a little bit worse for years of wear. It is still functional, especially for listening to airband but the displays electro-luminescence back light had faded and it was looking a little grubby.
I had already replaced the backlight on my PRO2006, but this was a lot easier due to the display being easily accessible with the simple removal of the front panel, and the EL panel being on flying leads rather than soldered on to a PCB.
I found a cheap supplier of a suitable EL panel on Ebay and quickly had the new one cut to size and fitted, giving a lovely new blue display.
The next thing was to clean the grime and grease that was encrusted on the case and knobs, using a small amount of Clit-Bang degreaser and being very careful soon had the case looking almost as good as new!
Just spent the last week in Cumbria and the Lake District on holiday, for part of the time we were camped near the village of Skelton around 5 miles north west of Penrith. Skelton is famous for it's huge transmitter site. The primary function is shortwave broadcasting, but it also supposed to be the site of a VLF array used for communication with submarines.
While out finding some geocaches I managed to take a few photos of the impressive antenna arrays.
One major limitation of both the FUNCube Dongle and the RTL-SDR based receivers is the poor front end filtering.
Connecting a wide band antenna such as a discone to the input often results in a spectrum full of noise which swamps the target signal.
In most cases the noise is actually a result of out of band high-power transmissions such as FM and TV broadcast stations and pagers which overload the receiver and get mixed in to the tuned signal. The effects can be mitigated to a degree by turning down the gain of the receiver but at the expense of sensitivity to the signal you are wanting to receive.
The FUNCube Dongle in my experience seems especially susceptible to the effects of FM broadcast signals when trying to monitor the 2-Meter amateur band. I'm not sure if the current weather conditions were the cause but yesterday evening it seemed the breakthrough was especially bad. So I decided to experiment with a simple coax 'notch' filter.
There are two approaches to filtering, one is to use a band-pass filter which passes frequencies within a certain range and rejects (attenuates) frequencies outside that range. The other is to use a band-stop filter that passes most frequencies unaltered, but attenuates those in a specific range to very low levels. A notch filter is a band-stop filter with a narrow stop band.
As it happens you can make an effective filter using ordinary coaxial cable which will generate a sharp, deep notch which can be used to attenuate the unwanted signal.
A coax stub notch filter can be made if you connect the antenna to the receiver using a T-connector then attach a piece of coax of the appropriate length (the stub) to the remaining connector.
I happen to have a fair bit of 10Base2 Thin-Ethernet cabling (RG-58U) and connectors which were repatriated from a previous employer over a decade ago. The network cards they used came supplied with lovely long high quality 10m patch leads with moulded BNC connectors and a T-Connector and terminator! Even back then the 10Base2 was completely redundant as the network infrastructure used Cat-5 cabling.
So I dug out one of the T-Connectors and a BNC connector and set to work, connecting the antenna and receiver was simple, all I needed was to construct the coax stub.
To calculate the length of the stub you must first calculate the wave length of the desired 'notch frequency' for the FM band a good central notch frequency is around 100MHz.
The wave length is found by dividing the speed of light (which is around 300,000km/sec in free space) by frequency
So for a 100MHz signal the wave length is 300/100 = 3 meters.
However the speed of the radio wave in a coax is affected by the material it is made of, this is called the velocity factor. For most solid polyethylene coax (e.g RG-58) this is 66% (a handy table can be found here)
So multiplying 3 x 0.66 = 1.98 meters
The coax stub is 1/4 of this wavelength = 1.98 x 0.25 = 0.495 (49.5 cm)
So cutting a piece of coax of that length, connecting it to the T-Connector and leaving the other end open completes the filter. The filter will have maximum attenuation at 100MHz (assuming the coax is cut accurately) and the attenuation will fall off away from this 'notch frequency' (Note the filter will also notch at 300MHz, 500MHz and so on)
Interestingly it seems my RTL based SDR receiver is more affected by pager breakthrough, so I plan to make an alternative stub, adjusting the calculation to use 153MHz as the notch frequency to reduce this. It is possible to add more than one filter at a time using multiple T-Connectors and alternative higher performance designs for coax notch and band-pass filters can be found with a quick Google search.
I made a quick video showing the effectiveness of this simple filter which took about 10 minutes to make!
Not had much radio time since Saturday due to family duties but did managed to find time to edit down some of the audio from the 144MHz SSB Amateur Radio Contest I received.
The first part of the audio was from the FUNCube Dongle, the latter part from the Ultra cheap NewSky DVB-T stick running the RTL-SDR driver.
Both were received using the loft mounted discone antenna which I believe is vertically polarised and so wasn't optimal since SSB is broadcast using horizontal polarization. Even so I was quite impressed with what I did receive with such humble equipment.The stations calling in the audio were G0VHF (morse and voice), M0KWP, M0BAA, 2E0KWM and G4SIV
Please note the corruption that can be heard toward the end of audio appears to be an artifact of the sound editor and/or the transcoding used by soundcloud as it wasn't in the original audio.
As it's the weekend I have managed to experiment with my new SDR device. I have sorted out an adapter so I can connect it to the loft discone and it has been pulling in some very nice clear signals. I have had to do some tweaking especially of the usb transfer buffer size to get some decent audio out of it. I have also had to learn how to use the HDSDR program which I haven't used much before favouring the SDR-Radio one with the FUNCube Dongle.
One thing that caught me out is that when I last used HDSDR with the FUNCube I had to swap the I and Q signals and I don't need to with the Newsky Tv28t so initially I was very confused as it all seem arse about face! Duh! But now actually growing to quite like it as having a much wider spectrum to see is very nice.
By a pleasant coincidence yesterday saw the start of the RSGB 144MHz May Contest so lots of SSB transmissions to tune in to. The FUNCube definitely has the edge when it comes to quality of audio and sensitivity and being able to tune down the gain helps in preventing out of band signal overloading the front end. With the Newsky device I've had to have the gain right up most of the time, but I suspect there is still more optimising to do.
Just a small video showing some of the SSB Contest signals on the spectrum. Don't you just love the masses of noise? Really must do something about that damn router!
I've also got to discover how to calibrate the Newsky as it shows quite a bit off frequency, I understand I need to discover the actual crystal clock frequency and can feed that into the EXT-IO plugin.
As suspected the problem was indeed the computer. I rushed home at lunchtime and in less than 10 minutes I had installed the software on my main PC and it sprang to life just like the video promised.
I only had a short time to try it out, but picked up some FM stations, pager signals and the RAF Waddington ATIS which should have been on 291.675MHz but the frequency on the HDSDR screen was way off.
It does appear to be a little deaf but I hadn't got a decent antenna connected so I won't conclusively say that yet as I've got to make up an adapter this evening so I can connect the loft antenna on. Also the EXT-IO interface has a gain control that I didn't alter from the default.
Well that was quick! The USB Receiver with the RTL2832 receiver I ordered it on Tuesday afternoon and arrived yesterday (Thursday) morning (from Jersey based retailer Cosycave via ebay) so was eager to try it out last night.
Fired up the old laptop and went off to http://www.rtlsdr.com/ and the getting started section to download the drivers and software and everything seemed to be going well. Following the instructions the device appeared to be correctly detected and the appropriate drivers installed, but then it went pear shaped.
HDSDR would open, the EXT-IO window would appear and attach to the device but as soon as I tried to tune the stick or start receiving various errors would appear and nothing worked... I tried a number of different option settings but still no luck!
Feeling a bit disappointed I put it down while I watched some TV and tried again later. I uninstalled everything and went through the process again but still ended up with the same errors.
I decided to rule out a defective receiver so I uninstalled everything again and installed the manufacturers supplied software.
The drivers and something called BlaseHDTV installed without a hitch. I connected the little supplied antenna to the receiver and set off scanning for TV and radio stations. It didn't complain but found nothing! By now it was well past midnight so I went off to bed in a huff.
This morning I connected the receiver to the roof aerial and it did find TV channels from the two local transmitters Waltham (60% signal strength and 100% quality) and Belmont (low signal strength and quality) but when I tried to watch anything I just got random coloured blocks and random noise. Interestingly it didn't find anything using the DAB or FM radio applications.
So is the receiver defective? Unlikely as it did go away and find TV channels.
The culprit is almost certainly the computer. Being an untrusting soul when it comes to software 'off the internet' I didn't want to try any of this out on my main computers in case it messed anything up. However the laptop is an old Sony Vaio with a Pentium 4-M processor and only 512MB of RAM and can be prone to sluggish behaviour, especially when trashing the hard drive. Saying that it will happily run SDR-Radio with the FUNCube Dongle.
Checking back over the specifications of the receiver it clearly states on the packaging that it requires a USB2.0 port... mmmm the old laptop only has USB1.1! Unfortunately I have grown accustomed to ignoring the pop-up balloon which appears I plug something in...
The looks like the most likely reason for the problems, not enough bandwidth - which would certainly explain the DTV issues. So I will have to try it on another PC...
Over the last few months various forums and websites I visit have been buzzing with conversations about the RTL-SDR project (e.g Hackaday)
The idea is to take a cheap USB FM/DAB/DTV receiver (for less than £20) that contains a Realtek RTL2832U chipset and an appropriate tuner chip (such as the Elonics E4000) then by using new custom drivers you get yourself a SDR-Radio with a frequency range of around 64 –
1700 MHz
Sound familiar? Yes it is similar to the FUNCube Dongle.
There are a couple of limitations, unlike the FCD the device doesn't have a pre-amplifier so sensitivity might be limited. The IQ sampling is only in 8 bits so the dynamic range will be limited, but because the device doesn't use a USB Soundcard interface like the FCD to pass the IQ samples to the PC the sample rate can be much higher (theoretically 3.2 MS/s) which allows potential decoding of wideband signals which the FCD cannot do.
Over the last few week I have seen a few Youtube videos and read of peoples experiments so my curiosity was piqued and decided to get one to have a go.
There in lies the problem, since news of this hit the internet demand for suitable devices has rocketed and dealers are cashing in and prices have risen and stocks are low. Also as not every USB FM/DAB/DTV receiver has a suitable chipset it is very easy to buy one that won't actually work. There is a list of known working devices here and yesterday while browsing ebay I found a dealer claiming to be selling the Newsky TV28T for around £16 including postage so thought what the hell!
Should be arriving in the next few days so I will keep you posted!
Before I go I should point out that on some forums and discussion groups I visit that some are under the illusion that they are getting a high quality wide band receiver for peanuts and then have complained because they have got a unsupported device or don't understand how the software works. I am under no illusions it will undoubtedly be fiddly, unreliable and inaccurate but it should be FUN!
If nothing else I will have a way of listening to DAB and watching DTV on my PC, which is hopefully better than my last purchase (which I should really dig out and check what chipset it has!)
With today's modern mobile and wifi networks pagers might seem terribly old fashioned. But pagers are still in use today in places where mobile phones typically cannot reach and also in places where the operation of the radio transmitters contained in mobile phones is problematic or prohibited.
Whilst many of the national networks have closed down some are still going and some locations such as large hospitals have their own systems and are still popular with birdwatchers in Britain and Ireland with companies Rare Bird Alert and Birdnet Information offering news of rare birds sent to pagers that they sell.
Decoding pager messages using a PC involves some software and a receiver usually with a discriminator tap and using the sound card and/or a data-slicer. The most popular software is the PDW suite.
I decided to use the FUNCube Dongle to attempt some decoding as being able to keep everything digital within the PC rather than having audio leads from a scanner plugged into the soundcard meant no problems with audio circuitry messing up the signal. Also the ability to alter the bandwidth should mean I could get some excellent decoding - and I did, both the higher speed and more problematic FLEX and the easier POCSAG protocols.
With the total washout at the weekend with very heavy rain on Sunday I was able to spend a decent amount of time monitoring. I recently brought a dry-cell adapter for the Alinco DJ-X10 receiver (EDH-16) allowing me to power it using normal AA Ni-MH batteries as the rechargeable battery pack it came with doesn't hold its charge any more.
So as the rain hammered on the window I decided to decode some SSTV images on the amateur bands. I connected up the discone and the computer tuned to 14.230Mhz USB and fired up MMSSTV. Some of the better decoded images I've got over the last couple of days are included below.
I did have an attempt at decoding some digital SSTV using EasyPAL but despite some strong signals couldn't quite get a full sync, but I think that was down to the conditions and the relatively poor rejection of the DJ-X10. With no ATU the out of band signals and nearby signals from what I suspect are high power operators were just too much for it, as the following sound file demonstrates.
