Tuesday, 25 June 2013

Mountain Radio Challenge


Mountain Radio Challenge, or MRC, is an annual CB Radio event held on the last Saturday in November each year. It is when a group on enthusiasts head out to different mountain tops to set up for the day, or weekend, and try to pass a series of messages along the line via ground wave signals between stations up to 150km's apart. Last year there were 10 stations, and I was set up on Mt Arapiles in Western Victoria as station MRC 4.

I used a Uniden Grant LT 40 channel am/ssb, with a 1/2 wave vertical antenna mounted on a telescopic mast with a short run of RG58 coax. Power was by two 12v batteries, one for the radio and one for the small inverter to run my laptop. Portable solar panels helped keep the batteries topped up.

It is a lot of fun, and a good excuse to set up in the field. Plenty of skip contacts also before the official start time of 2pm, although contacting MRC stations either side is a must before hand to ensure there are no  surprises, resulting in the message not getting through once the event starts. Any one interested can go the the web site and contact Tony to get involved. Had stations across several states in the past.
Mick 361

Thursday, 20 June 2013

Plane Plotter...My new toy.

                    HF condx have been absolutely appalling recently, so i've kept myself busy in the VHF/UHF parts of the spectrum, particularly ACARS and ADSB. I have been testing 3 ACARS specific decoders to use with my RTL-SDR (i have several programs that do it, but not to the fullest degree).
                    These programs were: ACARSD, KG-ACARS and Plane Plotter. ACARSD is a nice looking bit of software that presents images of the aircraft that are decoded as well as plotting these on a map, which the user must supply and calibrate (a frustrating experience if ever there was one!!). But i persisted and was rewarded with quite a good program....when it decoded. This is the only issue i had with ACARSD....it tended not to be as sensitive when compared against my benchmark software (MultiPSK, Sorcerer and PDW) and it was missing aircraft with very good signals. The user interface and setup are highly configurable and the price is right at zero,nada,zitch.
                    KG-ACARS is also free. However i had 2 main issues. 1) The GUI is in Japanese and fairly minimalist. There is an English instruction document within the download that is fairly good but also is a little ambiguous. I found this to be trickier to set up than the ACARSD map! 2) As the software is intended for use in Japan, we are warned that it may not decode ACARS TX from other international aircraft. A real shame in my books, because i thought this was a very nice program.
                    So we come to COAA's Plane Plotter. I had the free trial of this for a while until i had something to compare it to. I have to say that i LOVE this comprehensive, easy to set up and use, detailed, never skip a beat decoder! AT 25 Euros ($35 AUD) this delivers a lot of bang for your bucks. You don't get the pretty images of aircraft, oh no....this is a decoder for those who like straight forward data and modes. You get all of what the other 3 offer plus much more (but you still have to build and calibrate your own maps of course, after all...it's character building right?). It handles ADS-B, SBS, BEAST, RTL1090 (plus more) and even downloads satellite images for your area and plots them (satellites) at night. I purchased it 2 days ago and haven't stopped using it yet. I have run it alongside my benchmarks as well as watching flightradar24 to see if it was missing any contacts...nope. Money well spent.
                     In summary, there are many aviation programs out there ranging from free to VERY expensive. With the free ones, you get what you pay for and with the expensive ones....well, they're expensive! Plane Plotter sits nicely in between and is by no means average.
                     Here are just a few of the many available details:

Plotting on my (Googles) calibrated map


aircraft view


Wednesday, 12 June 2013

Project 9: A coax collinear antenna for ADSB

           Another VERY quick antenna project to enable better reception for my ADSB system. I used the method described here: http://www.balarad.net/ by Dusan Balara (thank you!).
           The antenna is simply 8,12 or 16 (i went for 16) 116mm (plus 50mm) sections of coax, with each end of each section stripped allowing 25mm of solid core which is then inserted between the outer jacket and braid of the next, giving it an offset appearance. A small piece of plastic is placed between each of the core sections to avoid shorting. The joins can be taped if you're in a hurry, but i love using heat shrink and it restricts movement better.
16x116mm sections
plastic squares for insulating the cores
keeping the cores insulated
a small section of the completed 2metre long collinear. note the off center appearance.
The finished product (center) , added to my growing farm.
           A 2 metre section of sparkies conduit from bunnings is used to house and protect the collinear, seal the top (i found an old cap from a roll of copper that a plumber left behind), seal the base and up she went.
           This was the fastest of my builds to date (taking just over 45 minutes) and the cheapest. 2 metres of 75ohm RG6 cost $2, 4 metres of conduit ( i will use the other 2 metres on my next project) cost $4. I don't know how much this antenna would cost to buy, but i'm certain it won't be $6!!
           Apparently this antenna is said to have excellent "horizon" qualities, and this is indeed the case. In testing this evening, i am receiving aircraft far earlier and losing them far later than last nights session with the discone.

Sunday, 9 June 2013

Using the RTL 2382U as an Automatic dependent surveillance-broadcast (ADS-B) receiver

          Ive been making good use of my RTL to receive ACARS with ACARSD recently and was looking for something a little more technical. Some googling led me to ADSB# which in turn led me to ADSBScope. Well, i spent 6 frustrating and ultimately fruitless hours of my life trying to get ADSB# to work, no matter what i did, even down to uninstalling the drivers, it just would not work. Then i found RTL1090. What a joy this piece of software is to install and use! RTL1090 is the necessary link between the dongle and ADSBScope, tuning to 1090MHz and providing the data for ADSBScope to plot.
         Both programs are well documented on the net and simple to install. At first i was dubious as to whether the dongle would actually work in the GHz range. Anecdotal evidence says it will, but each dongle seems to have its own intricacies. Fortunately,  the RELWITHDEB zip i downloaded contained a test file that indeed showed it could. (how much more can this great little stick achieve?? actually, i have read that it is possible to modify it to receive below 30MHz!!...but thats for another day).
         The following shots are taken just after i got it running and i have spent a very enjoyable day watching my "RADAR".
RTL 1090


2 aircraft plotting

Wednesday, 5 June 2013

Playing around with SailMail PACTOR 3

Recently there has been some discussion in my UDXF group about the difficulties of decoding SailMail PACTOR 3, so i though i'd give it a shot. Surprisingly, i had no problems . This was decoded on 10474.7kHz using Sorcerer:
PACTOR 3 signal

PACTOR 2 preamble (i assume)

And the decoded PACTOR 3 data