DIY Kit for Aircraft Band Monitoring

Aircraft-Band-RadioThere is an interesting kit being sold on eBay designed specifically for aircraft monitoring of 118-136 MHz (meaning it could also cover a number of ACARS frequencies). The receiver is being sold as a DIY kit, a completed kit, or an assembled kit and enclosure. Prices range from ~$16 to $38 plus shipping from Hong Kong. I purchased a kit and enclosure, as building it is part of the fun for me. I will let you know how the construction goes and how the receiver performs after I get the kit together. Delivery time is estimated to be between 2 and 3 weeks, typical of things coming from Hong Kong.

Here is a picture of an assembled board:

swl-aircraft-kit

If anyone has experience with this kit let us know your results!

Robert Gulley, AK3Q, is the author of this post and a regular contributor to the SWLing Post. Robert also blogs at All Things Radio.

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51 thoughts on “DIY Kit for Aircraft Band Monitoring

  1. Dale R. Parfitt

    See my reply of December 3rd regarding narrowing the tuning range.
    I don’t see the advantage of changing D2 and D4 to Ge diodes. While they have a lower Vf, this would simply change the squelch seeting where squelch is broken and on D4, the AM demod is excellent as is.

    Connecting a counter will load the oscillator and change its frequency. You are better off with a calibrated signal generator to check frequency coverage.
    Dale W4OP

    Reply
    1. Russ KK7YP

      Here’s another easy way to fix the wide tuning problem: Change the band spread capacitor (C14) from 27pf to 15pf. Add a 7pf capacitor across L1 (on the solder side of the pc board), and replace R1 (3.3K) with a jumper.

      Turn the tune pot fully clockwise and adjust the brass slug in L1 to receive 136,00 MHz, Turn the tune pot fully counterclockwise and verify receiving 118.00 MHz. If you have access to a frequency counter with a light-loading Hi-Z input, you may wish to verify the local oscillator is operating 10.7 MHz above the received frequency. I have an active probe that runs on a 9V battery that contains a FET input stage followed by an LNA, an MAV11. Placing the probe onto pin 7 of the NE602 allows me to monitor the Local Oscillator without loading it. If you don’t have a rig like this, you may use a calibrated receiver in this range to snoop on the local oscillator.

      Reply
  2. Andrew

    Hi after some troubles my kit live ! 🙂
    My advise change D4/D2 diode for old any type germanium diode .
    Check if C7 C8 C9 are 43 pf ( I get 47 pF
    My rx consuming 32 mA I don know why V1 is warm.
    Problem which I can not solve is wide tunnig range.
    Chceck also all resistor and replace exatly what is on scheme.
    Anybody knows where to buy and how to connect any frequency meter ?
    73′ sp9waz Andrew

    Reply
  3. Dale R. Parfitt

    Here are some voltage measurements that may help others with build issues. My power supply was set at 11.8VDC
    U6 LM386
    Pin1 1.3VDC pin2 0V pin3 0V pin4 0V pin5 6V pin6 11.8 pin7 6V pin8 1.3V

    U3 MC1350
    Pin1 8V pin2 8V pin3 0V pin4 2.5V pin5 1.77V pin6 2.5V pin7 0V pin8 8V

    Note that Pin5 on U3 is the AGC input. No signal will read around 1.77V. As the AGC kicks in the voltage on pin 5 will increase (reducing the gain of the 1350) strong signals will have 4V or more on pin5.

    BTW, 3 of my 4 boards had Minimum Discernable Signal (MDS) of -107 dBm when aligned. One was at -97dBm. After some work, I discovered that the MC1350 was out of spec- even though all pin voltages were OK. I swapped out for a new one on hand and now that RX is also -107dBm.
    Hope this helps,

    Dale W4OP

    Reply
  4. Dale R. Parfitt

    I have built (4) of the receivers now and after alignment, all 4 perform very well. MDS is around -105dBm which while it could be better, most signals are well above that level.
    Currently, CP11 is not used but CP6 is- an error in the paper work. The silk screen is correct.
    R15 is called out in the parts list and pictorial as 4.7K while the schematic shows 10K. Either value will work- it just alters the op amp U4B gain a bit.

    The ceramic filter Y1 does have a faint dot indicating pin 1. It is normally on the right end of the printed side. However, one unit had the dot on the left side. When inserted that way, MDS was poorer by over 10dB. If there is any doubt- socket it and try it both ways. Regardless of the dot- all (4) of mine are correct when the printing is facing the SMD NE602.

    With the supplied varicap, D1, the tuning range is way too wide. From memory, about 110-145MHz. This makes tuning quite critical. This can be lessened by adjusting C14 and R21 value. I changed D1 to a BB409 and R21 to a 1.8K and now tuning is 116-134MHz.
    When tuning L1, be sure to get it set for the aero band, and not the image frequency.
    A calibrated signal generator makes quick work of the alignment.

    GL,
    Dale W4OP

    Reply
  5. Lars Jacobsen

    I have a problem with mine, the transistor 78L08 gets hot and gets pulled into the output voltage, I’ve found out that it’s the MC MC550 IC that creates the problem, as soon as it’s removed, run my 78L08 as it should. Then there might be. be someone who had an idea of what could be wrong?

    Reply
    1. LUBO

      Ahoj Lars, tiež mám tento problém. Už si ho vyriešil ? Mne to stále nefunguje.

      Preklad: Slovensky 🙂
      Hi Lars, I also have this problem. Have you it solved ? To me it still doesn’t work.

      Reply
    2. Dale R. Parfitt

      If U1, 78L08 is getting hot- something is drawing too much current. If the MC1350 was ever installed backwards- it is gone and now needs replacing.
      To check the load on U1, measure the resistance from Z2 to ground. Once the electrolytics charge up, it should measure around 3.5K.
      Current draw when running from 12VDC is 30mA.

      GL,
      Dale W4OP

      Reply
  6. Ambrogio

    I built one of these receiver few days ago. It has a pcb inductors.
    In my opinion it is not a good receiver: it is very hard to tune even using a ten turns potentiometer.
    Sensitivity is not good at all while the selectivity is very bad.
    It has nothing to do with an airband receiver: I do not receive any communication at all. Just some noise produced by the FM station spread all over the tuned band .
    I have a very old receiver that i did built many years ago and it performs much better than this one.
    Regards,
    iw2fvo

    Reply
  7. Steve Pitts

    I just built one and it is completely dead. I don’t see any oscillation on the NE612. Any troubleshooting advice?

    Reply
    1. Dale R. Parfitt

      Hi Steve,
      Did you solve your issue? I also have no oscillator waveform from the NE602/612.
      I can inject a 10.7MHz 400Hz modulated signal into the inout of the MC1350 and hear it on the adio out- but still low lwvel even after peaking T1.
      Dale

      Reply
  8. Fernando

    A mi no me funciona nada , al probar echaba humo del diodo 1n4148, debo haber colocado mal las resistencias y condensadores, no fue una buena experiencia

    Reply
  9. Robert Straub

    I ordered the kit and followed all directions, but instead of a shhhhhhhh static noise it sounds like a record needle being scratched crossways across a record and doesn’t pick up or local Automated Weather Observation System even though it’s close by. I’m not great at soldering yet but hope I can make it work, any similar experience and a fix hopefully?

    Reply
    1. Jay Marcucci

      Sorry, I haven’t checked thios area in a while but I recently successfully completed the 3rd one of these and never came across that issue. I would check and make sure you put the three legged ceramic filter in the correct direction – That’s a possible mistake area. Diode direction could also be an issue. Also check your solder connections and make sure you haven’t bridged any traces.
      What are you using as a power source?
      Regards,
      Jay KC2YSK

      Reply
  10. Raymond C

    Hi Robert,
    Thanks for the reply. Sorry I did not reply earlier but I have been away for a few days gliding. I am using a ground plane antenna built from plans found on the web. It consists of four arms pointing down at 45 degrees and a central wire running straight up, all cut to specific lengths for the frequency band I want to receive. The arms are just steel wire but they seem to work just fine. I don’t know if copper wires would improve the reception or not. Its on a short(2 meter) mast and mounted on top of my shed. I’d say the top is 5 meters off the ground. I bit the bullet and pulled it down the other day and found one of the 45degree arms was loose. After tightening and checking the coax connection the reception is much better with hardly any noise and grounding the antenna doesn’t make any difference to signal strength any more, so I am guessing it was the loose arm that was the problem. I have another question about this little receiver. Is there any way to add a potentiometer in the tuning circuit to give me a finer tuning adjustment? I have quite a few stations almost on top of each other and a way to fine down the tuning would be good. I think I saw something like this on you tube but it was in Russian and I could not understand what he was trying to achieve. Thanks again for your help. Cheers. Ray.

    Reply
  11. Raymond C

    Not sure if this thread is still active but if anyone reads this maybe you can help me. I have been using this kit for a while now and it is working quite well. I have added a tiny type d audio amp and some speakers. I am in Sydney Australia and quite close to the main airport.My problem is that I used to be able to get Bankstown Airport ATIS and even some planes communicating with the tower as well as my gliding club tower at Camden Airport, weak but audible. Camden Airport is about 50km from my home. Lately I am not able to get anything other than the main airport frequencies. The strange thing is that if I connect a ground to the centre conductor of my antenna coax my signal improves markedly. I still have not heard any of the other airports but the locals get much louder and I am able to reduce the volume and much of the noise disappears making it much better to listen to. Does anyone have any idea why grounding the aerial centre conductor improves reception so much?

    Reply
    1. Robert Gulley

      Hi Raymond
      What type of antenna are you using? Usually grounding the center pin attenuates, but in your case it is sending some (probably) local noise to ground. You may have some interference coming in the signal . . . .

      Reply
  12. Peter Howie

    Hi Guys.
    This kit worked well for me. The three legged ceramic filter is problematic. I’ve told the vendor. Looking at the writing in the device, I’ve found the pin 1 is in the left hand side. This goes into the rectangular land on the circuit board. Pins 2 and 3 have circular lands (meaning the shape of the copper surrounding the hole).
    If anyone can help…..my squelch is very noisy, almost deafening to such an extent it is unpleasant to use. Just rotating causes an almighty CLICK in the phones. Is thus just mine or others as well? I will try to out some suppression in there. 73s. Peter. ZL1SX

    Reply
    1. Raymond C

      Sorry I cannot help with troubleshooting problems. Would it be OK to power this set with a 12v motorcycle battery? I have tried various power supplies but the noise makes the set almost unusable.When I use a battery its way better just not sure if 12volts is too much for this set.

      Reply
    2. john

      Peter, my squelch is much the same as yours. But my receiver is so sensitive that household noise keeps the squelch open no matter where I adjust it. If I take the antenna off I can get that huge click. I did find that I had put a 4.7k resistor at r19 instead of 47k, the colors on those Chinese resistors are very hard to read. That helped somewhat. I’m also going to try the aluminum box that is sold as an accessory, to shield the set from all the household noise.
      Mine came with a bad NE612. A new one brought the radio to life. And most of the resistors measured just barely in or slightly out of tolerance. Not high quality. Still, it’s a fun set.
      John KB5AG

      Reply
  13. Romulo Silva

    Hi guys,

    I have bought the kit however I am struggling to troubleshoot my problem as I have no oscilloscope on me.

    Components are properly set, there are not short circuits and when I plug the P2 phone I only hear a really loud noise which seems to be ground missing on RF circuits, however I have no way to check for ground as I also have no multi/voltimeter

    Reply
  14. Robin

    Hlw
    I’m going to make this from scratch.
    so can u tell me the parts Marking of T1, Z1, Z2, D2, D4 and Y1.
    Also the website where i can buy these parts individually.

    Reply
  15. Raymond C

    Thanks Robert. I had a dig around in my shed and found an old whip antenna form one of my old boats. Can’t remember which one it came off but anyway I connected one of those BNC connectors to the end of the coax and plugged it in with the aerial standing in the corner of my shed.Ahhhh the sweet sound of success. Ever so faint I was getting an ATIS station and from the duty runways recognised it as mascot. Now I know for sure that everything is connected right so outside we go. I sat the antenna in the frangipanni tree outside the shed and moved everything else outside. After some tuning I got the Sydney director quite clear. Quickly get the ladder and with some cable ties secured the antenna to the top of the shed and routed the coax inside, just long enough to reach the corner of my bench I had to perch the battery and circuit board on a shelf but the results were much better now. I roughly cut a few plastic standoffs and screwed the board to a piece of 4×2 and started tuning. So far I have got 5 different frequencies. Sydney Approach, Director, Sydney Tower, ATIS and a ground crew which I think may be Qantas ground but not sure. I have learned quite a bit building this little kit firstly about soldering and the importance of flux and the right size solder , temperature etc. And now about how important a good aerial is. Next step is to build a proper antenna. I like the look of one that has four prongs pointing down at 45degrees and one pointing straight up. The rods are made from brass welding rod and the mounting is some kind of coax connector.If anyone is interested I will report on my progress.Thanks to all for the helpful comments so far.Cheers. Ray.

    Reply
  16. Raymond C

    After staring at the circuit diagram and the board I was able to figure out the orientation of all the remaining bits. Happy to add that after I powered it up from a 9volt battery I was able to hear a couple of radio stations at the bottom of the tuning range and a couple of what seemed like data transmissions without a proper aerial. It gives me hope that I at least connected everything properly and that it might work eventually. Now to figure out what kind of aerial I need to make. Thanks for the advice along the way. If anyone has suggestions about aerials or anything else I am happy to hear them.
    Cheers Ray.

    Reply
    1. Robert Gulley Post author

      Ray – Congrats on building the kit!! And it sounds like it is working on the first go – very rewarding!
      There are many antenna options of course, but if you want to keep things inexpensive you could build either a ground plane antenna (like the one pictured on the project web site), or a J-pole antenna. There are numerous plans online for these two designs of course, but you might even have a telescopic whip antenna already that will fit the BNC connector it appears to have.
      Any 2-meter antenna with the proper connector would do pretty well (those are for 144 MHz, so 118-137MHz that is the airband will receive fine. Let us know how things go!! Cheers!

      Reply
  17. Raymond C

    Thanks Jay. I have not installed the diodes yet but I think I get the drift. I have all the caps and resistors done but I am having trouble with one part. Y1 a 10.7mhz crystal. It has three legs and there is a red dot above the left hand leg as I look at it with the writing facing me. I cannot find any indication on which way round this goes.The instruction sheet says”please pay attention to the direction of the pin, 1 on the right foot”. So I am assuming the red dot mark is pin 1 but which way is right? Any help appreciated. Meantime I will continue on with the diodes and transistors. So far I have surprised myself with the progress.

    Reply
  18. Raymond C

    Thanks Jay. I see now the diodes and transistors are listed together in the parts list. It was your drop box pics that gave me the hint about laying everything out on cardboard and tape. That’s a great idea, everything labelled and ready to just pick up as needed. I know diodes and maybe transistors too have to be connected a certain way around so I will do some googling and see if I can figure that out. So I will make a start and see how I go. Anything in particular that might trap a newcomer like me in this build?

    Reply
    1. Jay Marcucci, KC2YSK

      Glad idea helped as for diodes the band on the diode is indicated on the board and you have to match the correct direction as a diode is 1 way. You will also find a picture of diodes in upper right corner of schematic page

      Reply
  19. Raymond C

    Hi, Just Like G Morgan I came upon this site through an internet search. I have also bought this kit and as a total beginner in electronics it looks somewhat daunting to assemble with any prospect of a working circuit at the end. Thanks to all the previous posters on this thread I have assembled all the resistors and ceramics on a piece of cardboard and tape and identified all the parts. I was missing just one 47p ceramic cap which was easily replaced from an old printed circuit I had laying around.At the end of the ID process I had just one transistor unidentified but also one left over. It looked a bit like a resistor only clear with two black bands so I am assuming it is the missing 2AP9 transistor (D2). Would someone be good enough to help me ID this part. Also I have a lot of questions about order of assembly of the board and which components need to be connected in a particular way. Do I start at the edge of the board and work my way across or is there a definite order of operations? Any help would be much appreciated. I am in Sydney Australia by the way and not far from the airport.

    Reply
    1. Jay Marcucci, KC2YSK

      That part is a diode thus the D . Any order is fine. I did the mech parts first then the resistors, caps and transistors at the end, before plugging in the ICs . Built two of them and they worked great.

      Reply
  20. Graham M.

    Thanks for the offers of help and advice. I’ll keep you posted on the result. I’ve got a fire extinguisher handy for the big power up.
    Cheers for now, and happy xmas to all you over the Pond

    Reply
  21. G Morgan

    Hi there folks

    Some searching on the web brought me to this interesting and friendly site. I have bought the above kit (mine already had some of the circuit built).
    Being very keen on airband, VHF and HF, this kit naturally caught my eye. I am a bit spoilt around here in the UK for airband reception and I will be surprised if this item does pick up something reasonably well. I live in hope.
    I have one query which i would be grateful if anyone could answer. The two diodes listed as AS119’s seem to be of differing sizes. Anyone know of any reason for this?
    The only query about this kit (apart from the above) is the bloke building it . . . The soldering is reasonable (no, you can’t have a picture). You may well see smoke from the other side of the pond, when I finally get some power in to it. I’ll report back in due course.
    The kit bought recently was off a guy called Tomtop on Ebay.co.uk, a business seller.
    All the best from the UK, Graham 14/12/15

    Reply
    1. Jay Marcucci, KC2YSK

      I’ve built 2 of these kits, one with the the components already installed and one with the inductor as part of the circuit board. Both work really well, however, neither had diodes that were the same. There were 3 diodes in both units one silicon, easy to figure out, one the typical in48? Diode and then a 3rd with 2 large black bands. Email me if you need more info
      Jay

      Reply
      1. Katie W2LP

        I puzzled over this too, but from looking at the schematic I concluded that:

        D1 is the black silicon diode 1N4001, or similar
        D2 is the glass encased larger diode that has a lower forward voltage drop than standard silicon
        D3 is the smaller glass encased fast switching diode 1N914 or 1N48, or similar

        Reply
        1. Michael Black

          The 602 and 612 are nearly identical, a minor change in specs or temperature of operation. The pinouts are the same. It may even be that one is no longer made, I vaguely remember something like that.

          Michael

          Reply
  22. Jay Marcucci, KC2YSK

    Hey guys, the results are in, the new kit with the tuning circuit works way better than the one with the inductor in the PCI board. Better to tune and a bit more selective. Definitely would recommend this version. Both came with parts list, schematics and board layout. I opted to buy it from BanGood.com as the coils were already wound and installed. But it’s on eBay as well, without the coils pre installed.
    Here’s the link
    http://www.banggood.com/DIY-Aviation-Band-Receiver-Kit-High-Sensitivity-p-990306.html

    Reply
  23. Jay Marcucci, KC2YSK

    I agree, selectivity is not a plus. I am just finishing a second kit, but while layout is nearly identical, the tuning circuit section is different and does NOT have the trace inductors. I’ll report back on this version. Of course , the fun is in the building these. ,but now I’ll have two of these with cases so think I’ll stop at this point .

    Reply
    1. Michael Black

      It looks like an FM broadcast band type filter, even the narrowest are about 150KHz wide. I’ve never seen narrow filters in that type of package.

      I suppose it depends on where you live. Maybe near n airport it’s crowded enough that the receiver is too broad, but probably many see very limited traffic on the aeroband. No sense raising the price for all when most won’t need the better selectivity.

      Though maybe if you’re in a place where you do hear signals on the band, it matters.

      The y used to be common, crystal filters the size of a small crystal, with three leads, for two-way FM, at 10.7MHz. One of those would provide much narrower selectivity, and if the skirt wasn’t great, neither is the existing filter that great. Other gear might supply such filters, I found an old to-way radio in the garbage last year that had three or four. I think I’ve brought home boards from hamfests with such filters, but they may have been at 21.4MHz, which is another (though less common) IF in two way radios.

      Digikey or Mouser used to sell such filters, though they were around ten dollars.

      More cumbersome, there are lots of much bigger 10.7MHz filters for two way radio out there. Those can probably be found cheaper on the used or surplus market. But they won’t fit the board, you’d have to mount it separately, and connect with small pieces of coax.

      Changing filters likely means changing terminating resistors, for best operation.

      Michael

      Reply
  24. Robert Gulley Post author

    Thanks for the link, Katie, and for sharing your experience with the radio. Like you, the fun for me will be in the building – anything else is a bonus in terms of quality. But as a friend of mine likes to say, every radio gives us a unique experience whether by the way it “sounds” or how it receives or tunes or whatever. At least that’s the justification I use for getting more radios !

    Reply
  25. Katie W2LP

    Full info, including the schematic, for this kit can be found here: http://115.28.16.44:81/file/3242.pdf . This is required for assembly becasue the board doesn’t indicate component values on the silkscreen and no documentation came with the one I ordered.

    I found that it was more sensitive than I expected (using discone mounted at 30′) but the selectivity was beyond terrible. Certainly no match even for the rather poor airband receiver in the PL660. Still, kind of a fun kit to build and I was surprised that it worked at all, with the PCB trace inductors.

    Reply
  26. David WB4ONA

    Please post links to your schematics for this thing. If there is no schematic provided, please post hi res photos of the top and bottom of your board (both populated and unpopulated, if-possible). Let’s get some tech back into this Hobby – Please! Thank you & 73’s, David

    P.S., Happy Thanksgiving
    [Yeah, I know Thanksgiving is a “Trigger-Word” for Many these days… Screw- it.]

    Reply
  27. Robert Gulley Post author

    Thanks, Mario – the aircraft band is one of my favorites, along with commercial HF frequencies for voice and data, HFDL. When I saw “kit” and “aircraft monitoring” I was sold!

    Reply
  28. Mario Filippi

    Thanks for the great kit info Bob. The VHF aircraft band is fun to listen to especially those ATIS stations that continually broadcast airport information. Have fun assembling it and let us know how it works.

    Reply
  29. Robert Gulley Post author

    Thanks for the feedback on the unit, Jay – makes me even more excited to get it! It’s funny, no matter how many radios one gets, there is always room for one more!

    Reply
  30. Jay Marcucci, KC@YSK

    I’ve built the version mention above and it works very well when connected to my 5/8 vertical VHF/UHF antenna. I am far away fro the airports yet get quite a bit of traffic. I have pictures of construction throughout the process and into the case if you want copies, I can share the drop box with you. Decent documentation and extra parts – came in handy when a 10 Ohm resistor smoked. I received it in about 7 days from China. Liked it so much , I ordered a second kit that had a slightly different tuning circuit but other wise the exact same design. It’s due in tomorrow

    Reply

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