Dipping my feet into the Flightaware/PiAware waters

Being with my family is my #1 priority. Having young children means that all of your hobbies will likely get put on a shelf for a while. In my case, my radio hobby had to take a back seat. Learning about parenthood and that insane amount of time it takes to keep children alive meant that there wasn't enough time or mental capacity to do much else, for about 6 years.

After a while, however, you start the get the hang of things.

Last year I had been really feeling like there was something missing in my life, and it was likely RF. After watching lots of friends on Facebook build impressive ADS-B monitoring systems, I decided it was simple enough, cheap enough, to get my toes wet in the hobby waters.

So, a Raspberry Pi, Flightaware Pro stick and filter were purchased, and I was off.

assembled on the test bench

I was shocked that I was actually able to decode some aircraft at 1090MHz with a little whip in my basement. My mind started buzzing with what a resonant antenna mounted outdoors could produce.

Next, an external antenna was procured, but where to mount it? For the time being, it would be in the second floor of my barn, for various reasons why I won't go into here. Having the resonant antenna with a small amount of gain helped me see quite a few more aircraft. This was getting exciting!

Before long, I told my BFF, Jay Tarantino, AB1II, about this setup and I had him hooked after about 2 second of talking to him on Facebook Chat. 

Jay got the same system and put his antenna in his attic. Jay, unlike me, is in a FANTASTIC location to hear aircraft close into KBOS. In fact, he's close enough to hear the ground aircraft. We were both hooked!

Within a few months, I realized that my RF hobby was starting to come back. Jay and I were chatting regularly about radio topics. We were both finding oddball aircraft and flight paths, we were both having a lot of fun. 

But then it started to happen. How can I make my system better? How come Jay can see more stuff than ME? What can I be doing to improve my system?.....down the rabbit hole I went. 

The first thing was to get the antenna out of the attic and into the air. I slowly started to think about how to mount it and started digging through an old pile of antenna masts, mounts and accessories to see what I could put together. I had forgotten about an H-frame I had made years ago that was originally built to mount a pair of M2 eggbeater antennas. I decided that If I was going to do the work to mount one antenna, I may as well mount a few antennas! The first batch of antennas included:

- a Daimond X50 (144/444Mhz)

- a DPD dual air-band antenna (VHF/Mil-Air)

- an old Marine GPS antenna of unknown origin

- a Flightaware 5dbi ADS-B vertical

- an M2 435MHz eggbeater 

Next, find a piece of mast to mount it all on and get it vertical. I had some 2" Aluminum mast from another project, so I was able to cut a piece of and get the whole thing mounted over the course of a weekend. 

The initial RX antenna array

That did the trick! I was able to see quite a bit more ADS-B traffic and as a bonus was able to start listening to ATC using the VHF air-band antenna with a RTL-SDR receiver into a second Raspberry Pi (using rtl_tcp and GQRX). 

There was a problem, however, quite frequently Jay would be seeing traffic down close to me that I wasn't seeing. That was driving me mad, so next I started reading more and started thinking about looking for greater efficiencies. The first step was about understanding the SDR receiver and it's gain settings. By default, the Flightaware Pro stick and PiAware are configured to use hardware automatic gain control (AGC). This is probably fine for most, but if you have any noise or out of band signals nearby, it will cause your receiver to miss a lot. I started working with the gain settings, but wasn't finding much in the way of consistent results. 

My next detour was to look at filtering and pre-amplification. The Pro stick claims to have a LNA built into the device, but how decent of an LNA? Low noise, to me, should be something in the vicinity of 0.5db nf. I wasn't sure what the spec was on the Pro stick, so I started looking online. There were many to choose from, I ended up trying one I found on Ebay from a Canadian company called GPIO labs. a GPIO labs bandpass filter was also procured. The issue I noticed with these devices was that they came as pre-assembled circuit boards not in enclosures. When I received the boards in the mail I noticed they were very fragile and as I would soon discover, not particularly well soldered (at least the SMA connectors). 

Meanwhile, I had also come across a mini-circuits bandpass filter that was appropriate for the 1090MHz signals I was monitoring, and was physically much studier than the GPIO labs filter. I also happened to have a small aluminum box with holes just the right size for SMA connectors with enough room for the filter and pre-amp. A few bits of UT-141 coax with SMA connectors from the junk box and voila!

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GPIO labs ADS-B 5v pre-amp, Mini-Circuits VBFZ-1065-S+ bandpass filter

At the same time, I decided to try swapping out a different receiver. I went with a Nooelec NESDR SMArt. I was concerned that having an external LNA into the oboard LNA of the Pro stick might just end up being more gain that would be useful, and besides, we're talking $25 per receiver! The receiver ends up being one of the cheaper components of the system. That, in fact, is a new paradigm that I can get behind. 

The new receiver, pr e-amp and band-pass filter all show improvements, each time getting me a little more signal to decode, but we're not quite done yet. It was time to replace the cheap Flightaware 5dbi antenna with something a bit more substantial and a little more gain. I ended up with the DPD Productions 9dbi vertical for ADS-B. That.....is what I needed. 

Now, finally, I'm able to track aircraft much further out on the edges and I'm suddenly seeing a ton more close-in aircraft as well. I'm now finding consistent results when adjusting the receiver gain under dump1090, with my gain currently set at 27. 

This was a really fun project that took me from "mildly interested in getting back into an rf project" to "I now can't stop thinking about all things RF". 

There are MANY more projects now in various states of planning. Next up, GNSS monitoring on a global scale and a side benefit, a stratum 1 time source. 

73

de N1JFU

The RX array with the new DPD 9dbi ADS-B antenna far right

A new project is born

In 2011 I bought a new Elecraft K3 HF/6m rig. I had a great time using it on 6m last year during the Sporadic E season. Over the course of the last year I started thinking about interfacing transverters for 2m and above to the K3. I noticed that Elecraft sold an external switching box that would allow me to control an IF relay for switching the transverters per-band. The issue with using this box (KRC-2) is that you end up having to sacrifice the ability to switch external relays for the HF bands. I thought it would be interesting to to see if I could use 1 HF radio for all bands, 160m-10GHz.

More to come...

Yaesu Vertex FTL-7011 information

(This post is really for the archive, for anyone searching for info on the FTL-7011 FTL-2011 and FTL-1011)

Recently I dug up an old FTL-7011 UHF commercial radio to use with a ClearCom Radio interface box. This allows the UHF handhelds we use on productions shoots to talk to the production intercom. Anyone on the Intercom system just needs to hit the call button to key the external radio.

I started looking for information on the pinout of the microphone jack and found a forum posting that ended up being false information. I think I know how it happened. There is a schematic floating around the internet for an FTL-2011. One of the main board connectors had 8 pins, and looked to be like RJ-45 mic pinout. It wasn't, that was just a main board connector. Here is what I found:

Pin 8 is the hook indicator line, attached to the metal mic hook.
Pin 6 is 5v
Pin 5 is the Mic+
Pin 4 is the Mic-
Pin 3 is 9v, presumably for the pre-amp circuit for the desk mic (it wasn't connected on my hand mic)

Pins 6 and 4 need to be shorted to PTT.

For power adjustments I found that the schematic was also wrong for the FTL-7011. The low power adjustment ended up being VR2002 and the high power adjustment was VR2003.

I set low to 5w and high to 10w. The radio measured a max of 21W, but it's old and most likely abused.

Hot Amplifier

With my recent experimentation with the WSJT protocols on 2m, I've run into a new problem. The FSK441 protocol is effectively 100% duty cycle while it's transmitting, and with the sequencing it's 30 seconds of transmit, 30 second of receive. This has the side effect of creating a very warm amplifier, to say the least. I'm currently using an old RF Concepts amp, 45 watts in/170 watts out.

To reduce the chances of melting your amplifier, it's recommended that you drive the amp at reduced power. That past week I've dropped my input power to about 20watts PEP. Even at that rate, the heat sink on the amp was very warm to the touch. I figured the easiest solution to solve this problem would be to put some fans on top of the heat sink to try and draw away the heat, create some constant airflow.

I went down to the work shop and rummaged through some old junk boxes and pulled out 3 working 12v fans that were pulled from an old PC (it occasionally pays to be a pack rat). So, now I just needed a mounting method. Over the course of the week I had time to think about it, and after a trip to the hardware store I came up with an overly complicated mounting bracket that would hold the fans down to the amp. I'm not sure where the quote came from, but i've always subscribed to the thought "Anything worth doing, is worth OVER-doing!".

I found I had some small aluminium strips that I had purchased at the local home center, it seemed to be the right material for the job, but I didn't quite have enough of it, so off to the store I went. Luckily for me they recently built a big box home center 2.0 miles from my house. Said company now extracts money out of me on a weekly basis.

So, with crude measurements, a few whacks of a hammer, some drilling and I have a basic bracket. I simply tied the lead wires together and crimped them into an Anderson Power-Pole connector, which is the standard low-voltage connector in my shop.

The three fans together draw about 350ma at13.8v. Ideally I'd like to find a small circuit that would detect the amp keying and would turn the fans on for a set period of time. Normal voice operations doesn't really require it, but extra thermal protection never hurts. For WSJT modes having the timer be longer than the typical sequence would effectively keep the fans on constantly, which is a good thing.

The whole assembly is currently sitting snugly on top of the amp, but it's not permanently attached. I think I can get away with not having to drill any holes into the heat sink since it's fairly tight.

Now, the dangerous thoughts are running through my mind. Since I've greatly increased the thermal dissipation, how much harder can I run my amp? Could I run at full power?

I don't currently have the ability to measure the surface of the heat sink, but I'm guessing I could probably run closer to 30w input, maybe 130w output. I think it might be time to look for an inexpensive IR thermal sensor, like I saw at show-n-tell at the last NEWS group meeting. I'm guessing Harbor Freight probably has something that will do the trick.

Work has begun on my new (to me) Elecraft K2

A number of years back I purchased a partially-built Elecraft K2 kit from a co-worker who lost interest in building it about 1/3 of the way into it. I had always planned on using it as an IF rig to drive VHF/UHF/Microwave transverters, since it's very well suited for the purpose.

Well, the kit sat on the shelf for years and gathered lots of dust. Oddly enough, a few years later the co-worker was re-invigorated in his interest, bought and built a new K2 kit! A few weeks back I completely tore apart my workbench and got it finally configured the way I wanted it, with all the test gear powered up and in the right position. I had previously only been able to power up two devices at a time which made it difficult to build anything.

Feeling like I could fix anything, I found a little bit of motivation and dug up the K2 kit. Several layers of dust later and I was into it! When my co-worker had first started building the kit, it was the first major electronics project he had taken on which resulted in a few problems that needed to be worked out. Simple things, like missing soldering a ping on an 8 pin DIP, etc. Simple, but will stop you dead in your tracks if you can figure out why it's not working! At this point the rig is working on 40m CW, and I'm starting the next build phase.

I get the feeling that I'll need to re-visit 40m in the future, I think it's suffering from a lack of sensitivity, but I feel the need to march forward. I figure at the rate that I'm moving (slow) it will take me a couple of weeks to complete. I still also need to build and install the SSB module and I also plan on picking up a KIO2 module.

I hate PL-259 connectors!

I was down in the shop tonight re-arranging feed lines so I could route the upstairs 2m radio to the bigger 2m beam (I have a 12el and a 6el up) to the 175W brick amplifier. During the shift I came to realize this RF Concepts amp had SO-239 connectors (female PL-259). GRRR! Why does the radio industry insist on using these crappy connectors!

Just then I remembered that last October at NEAR-Fest I had picked up (2) N-female chassis connectors for the express purpose of replacing the amplifier connectors. So, I opened up the amp and was relieved to find that it would be an easy job replacing them. I now have 2 fewer crappy connectors in my world. Here are some snapshots of the excursion:

Here is the first connector installed, the second one was a snap. The whole process took 15 minutes max. Now I'm motivated to go around to all my radios and see how easily they can be replaced!