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Radio Direction Finding Forum - Discussions regarding direction finding and transmitter location

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Old 10-23-2016, 8:41 PM
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Red face Need Help finding Lost Transmitter

Hi Everyone,

This is John in Noblesville. My wife has one of those La Crosse clocks that gives the outside temperature. It uses a little transmitter that mounts on the outside of the house. Somehow that transmitter has fallen from its mount and has disappeared, but yet it is still transmitting the outside temp and will until the battery dies.

I have searched several times where I though it might have fallen but have been unable to locate it. By "searched" I mean manually digging through the ivy below where it was mounted.

I wonder if some kind soul could find it with a direction-finding receiver? It transmits on 433.92 mHz. I have no equipment that would work for this.

Thanks in advance for any help or suggestions!

John
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Old 10-24-2016, 7:12 AM
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Do you own a police scanner or know someone that does? They could enter that frequency into the scanner and find it without the need for any direction finding equipment due to it being so low powered in nature.

Shawn
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Old 10-24-2016, 7:28 AM
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One of the old handheld Radio Shack frequency counters might work also
Radio Shack 22-306, LCD Frequency Counter, 1MHz - 1.3GHz
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Old 10-24-2016, 7:31 AM
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A Baofeng UV-5R or other cheap handheld with a VFO would work as well.
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Old 10-24-2016, 8:02 PM
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Track the temperature versus time of day. See when the tmperature falls when the sun becomes shaded and search that line.
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Old 10-24-2016, 8:36 PM
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RFI that is a good free idea.
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Old 10-24-2016, 9:51 PM
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Default another idea

metal detector...
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Old 10-25-2016, 1:24 PM
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I don't think these transmitters transmit continuously so searching using an RF tracking might be tedious. The metal detector may be the best bet.
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Old 10-25-2016, 1:49 PM
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Cool Lost Transmitter

Guys, thanks to all of you for your interesting and creative suggestions! As it happens I do have on old Realistic PRo-2006 scanner that might do the job. All I have to do is figure out how to set the frequency, and I'll be good to go.
I have tried a metal detector because I thought for sure that would be the answer. But there is so much construction trash up around our house that the detector was sounding almost constantly.
RFI's suggestion is worth pursuing although I have searched the area pretty thoroughly. The transmitter I'm seeking is pretty small and there is a lot of ivy with a lot of intertwined roots so it's difficult to get into it to see the ground.
Then too, how much would a replacement cost if I just said the heck with it and bought one? Surely not more than ten bucks or so. But on the other hand, where's the fun in that?!
I have another outside thermometer transmitter in another location so I can test the Realistic scanner to see if it will actually get a signal from that transmitter. And yes, I did disable that one to be sure what my wife's thermometer wasn't coming from it.

Thanks again!

John K9JGS
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Old 10-25-2016, 1:53 PM
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They only transmit periodically and then with a burst. Might not be long enough to detect with a scanner or other radio. I agree the metal detector might be the best bet. I also like RFI's suggestion about time of day, sun-shade line.
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Old 10-25-2016, 7:04 PM
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Quote:
Originally Posted by KR3LC View Post
They only transmit periodically and then with a burst. Might not be long enough to detect with a scanner or other radio. I agree the metal detector might be the best bet. I also like RFI's suggestion about time of day, sun-shade line.
I actually have one of those thermometers. They transmit very sporadically, it would be very difficult to capture on a receiver to DF. I had to replace it once due to battery leakage. It took some searching but I found one cheaply from a vendor.

You could try dropping a similar object from where yours fell and try to determine the trajectory! On the other hand, the mail man might have found it and placed it somewhere like a window sill thinking he was helping you.
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Last edited by RFI-EMI-GUY; 10-25-2016 at 7:08 PM..
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Old 10-26-2016, 1:22 PM
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Give a neighbor's child a $5 reward for finding it, or $1 for their effort if they are unable to.
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Old 10-26-2016, 2:09 PM
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Quote:
Originally Posted by KR3LC View Post
They only transmit periodically and then with a burst. Might not be long enough to detect with a scanner or other radio. I agree the metal detector might be the best bet. I also like RFI's suggestion about time of day, sun-shade line.
Indeed, the transmission is just a quick burst and trying to locate by the signal is doomed.
Usual frequency is around 433-435 MHz.

By the way US *made* car key fobs are around 315 MHz (my Toyota one is but it is US made) while European are around 433.92 MHz. Those and 433-435 MHz have a lot of burst in a lot or areas best seen on an SDR waterfall display.
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Old 10-28-2016, 9:57 AM
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Default Lost Thermometer Transmitter

So I got the scanner programmed to the correct frequency. I hear three or four different burst signals, so I think that means I'm picking up my lost one and several of the neighbors. The signals are roughly every ten seconds. One is louder than the others so I suspect that one is mine.

Next move is to take the scanner outside on the end of an extension cord and fish around to see if I can detect a difference in intensity of the signal.

Unfortunately that loudest signal occurs only about every 60 seconds so this is going to take a while!
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Old 10-29-2016, 10:30 AM
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John, depending on the ivy placement, it may not have even reached the ground. It might be snagged higher up than you've been looking. I don't know how heavy the transmitters are, but if they're light-weight, the wind that caught it might have caused it to fall at an angle, and depending on how high it was, it could be something like 10 feet away from the base. And it could have bounced or tumbled beneath something when it fell.

If you know the exact transmit interval, you can be ready for the signal. But without a signal meter and a directional antenna, you might be wasting your time.

Try removing the scanner antenna completely and see if you can pick up the signal. Adjust the squelch lower if you don't hear it. Then move the scanner and try again. Keep moving it until you are able to turn the squelch to a higher position; this would indicate you're getting closer. Repeat until you locate the transmitter, hopefully not by stepping on it and breaking it. lol

Maybe drop in to the local ham club meeting and see if there's anyone willing to help you with your "fox hunt".

Good luck!
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Old 10-29-2016, 5:02 PM
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Unhappy Lost Transmitter

Well, I gave it my best shot with the scanner set to the freq (433.92), tried adjusting the squelch and volume to screen out the other extraneous signals, but it was impossible. I did clear out a larger patch of the ivy but to no avail.
There is one nice loud signal that shows up roughly every 60 seconds, and now I'm wondering if it is perhaps coming from a neighbor's house. If so, I'm quite willing to piggyback on it!
So the plan now is to let it go and forget it. If the signal eventually disappears I'll see about getting a replacement from LaCrosse.
Thanks to everyone for your good ideas! You guys are great creative thinkers and I did at least learn some things from you.

John K9JGS
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Old 12-22-2016, 7:40 AM
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When all else fails....

http://www.lacrossetechnology.com/sensor-finder/

The temperature transmitter for my La Crosse clock costs $20 on eBay and*Amazon.

And yes, corrosion is also a problem on my transmitter. When the*temperature goes blank, I often find that cleaning the terminals brings it back to life.
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Old 12-22-2016, 7:41 AM
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When all else fails....

http://www.lacrossetechnology.com/sensor-finder/

The temperature transmitter for my La Crosse clock costs $20 on eBay and Amazon.

And yes, corrosion is also a problem on my transmitter. When the temperature goes blank, I often find that cleaning the terminals brings it back to life.
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Old 12-22-2016, 2:51 PM
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The newer low mercury Duracell batteries leak like crazy and damage stuff. I even removed two batteries to protect an instrument and the batteries both leaked, the corrosion damaged a table top weeks later. Needless to say, I have made about $300 in claims to Duracell in past couple years, not for the furniture however. I should have. I cannot recommend Duracell or their ProCell batteries any longer. I used to buy them religously. Even the 9 Volt cells leak. These are all premature failures well before the expiration date.
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Old 12-22-2016, 3:20 PM
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Quote:
Originally Posted by RFI-EMI-GUY View Post
The newer low mercury Duracell batteries leak like crazy and damage stuff. I even removed two batteries to protect an instrument and the batteries both leaked, the corrosion damaged a table top weeks later. Needless to say, I have made about $300 in claims to Duracell in past couple years, not for the furniture however. I should have. I cannot recommend Duracell or their ProCell batteries any longer. I used to buy them religously. Even the 9 Volt cells leak. These are all premature failures well before the expiration date.
YIKES....

TKS for the info.
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