BAT DXing or noise hunting ….

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WA2SQQ:
Some of us have used ultrasonic directional mics for hunting down power line noise. I came across this and decided I’m going to order a few of these. You can use your SDR for both RF and audio noise hunting.

https://youtu.be/-ikeMSn35T0?feature=shared

W1ITT:
That ultrasonic microphone is available from Chinese sellers on Ebay inexpensively, like 10 or less than $10 at one vendor.  It's a different sort of SMD than what I'm used to.  I'm guessing that you use paste and cook it in a toaster oven or under an air soldering iron.  Does anyone have any experience with this particular package.
I have used an SDR-IQ with a run of the mill 30-something khz sensor with limited success.  Without a preamp it was a bit numb but I could hear my fingers rubbing.  The unit listed in the video seems to have an onboard preamp.  It looks as if it would be swell at the focus of a plastic punch bowl to listen to power line insulators.
What's the special magic to dealing with that particular SMD  package?
73 de Norm W1ITT

W1NB:
Norm,

Yes, you use a solder paste which is solder suspended in a flux paste. There are reflow ovens that you can buy but unless you are doing a lot of boards I recommend using a rework heat gun. I purchase my paste from Amazon but you can get it at most electronics supply houses like Mouser or Digikey. Usage is very easy. You simply place a small droplet of paste on each pad to be soldered, set the component, then heat it with the gun until the paste turns into solder. As long as you don’t put too much paste on a pad, the solder will pull into the pads and component tabs and give you good results. The paste works great with just about all SMD components. It will actually align the components on the pad when it’s heated to the activation temperature. Keep the airflow low on your heat gun. Just enough to heat the pads you are soldering. If you’re using it on rework, get some heat resistant tape and use it to cover the surrounding components so you don’t accidentally float them.

Bob, thank you. I’ve been battling power company line noise all winter. This may be just what I need to track it down. With the amplified version shown on the video, I think it can be mounted in one end of a paper towel roll to make it highly directional.

WA2SQQ:
The element featured in the video has a built in preamp. They aren’t expensive. Going to order one or two.

W1ITT:
Scott
I have a rework hot air soldering tool and I'm passable with it on components with insect-style feet that stick out.  This one scares me a bit because the pads are hidden.  I suppose the device must be made to take the heat, so to speak.  At the 10-fer cheap prices on Ebay we could afford to spoil one or two in the learning curve.
I got a cheap plastic punch bowl at the party goods store to use as a parabolic (more or less) dish with the idea of getting some gain as well as directivity..  MFJ sells a unit like this already made up but it costs more money.  I think Rick K1BQT did the design work.  But I think I can do better on the QC that the folks in Starkville.    And besides, this little unit looks to do most of the work for us.
73 de Norm W1ITT

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