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RSSI Meter for Video Receiver


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#41 Mr.RC-Cam

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Posted 25 May 2010 - 07:45 PM

This is what I extracted from your text:

Tuner pin 4: Tx-OFF=1.05v Tx-ON=4.26v

As you can see, the transmitter on/off measurements are quite different. So, the pin that you call "pin 4" is RSSI.


For those that have this same Lawmate receiver, the tuner module is a Comtech FM2400RTIM8 or equivalent clone of it.
- Thomas

#42 andrei

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Posted 25 May 2010 - 07:46 PM

Now that is some weird s--t.
I've noticed that the pics i posted were squeezed side to side but this is downright scary.
I tried to edit the post to fix it but no good came out f it.
Here is what i was attempting to post.

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#43 Mr.RC-Cam

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Posted 25 May 2010 - 07:51 PM

The answer is in your neatly published table. Hint: If you need more help identifying the RSSI pin then please see post #41.
- Thomas

#44 andrei

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Posted 25 May 2010 - 07:54 PM

This is what I extracted from your text:

Tuner pin 4: Tx-OFF=1.05v Tx-ON=4.26v

As you can see, the transmitter on/off measurements are quite different. So, the pin that you call "pin 4" is RSSI.


For those that have this same Lawmate receiver, the tuner module is a Comtech FM2400RTIM8 or equivalent clone of it.



Thank you Thomas.
My head is spinning from trying so hard to measure and remeasure all afternoon and solder without dammaging anything in the process.

#45 Mr.RC-Cam

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Posted 25 May 2010 - 08:04 PM

You are welcome; Glad you found the RSSI signal.

Your shared experience will help show how simple it can be to ID the tuner's RSSI pin. Fancy photos, data sheets, and magic are not needed; A voltmeter will quickly point to it.
- Thomas

#46 andrei

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Posted 25 May 2010 - 10:36 PM

Pea nuts.
Done.
I'll post a pic when i have it mounted nice and proper on the Rx.

#47 masam

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Posted 25 May 2010 - 11:26 PM

The postman delivered mine today, :) Wow, that was fast Thomas, considering I'm on the other side of the world!
I havent tested it yet. I'll definitely have pic and feedback once its installed on my spare Fox 1.2/1.3GHz video rx.
Initially I'll be using it to do some video tx antenna(homemade) comparison tests.

Thanks again Thomas.

#48 Kilrah

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Posted 26 May 2010 - 05:57 AM

Got my little box :)

#49 masam

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Posted 27 May 2010 - 08:17 AM

Today I've got mine calibrated and running. Following the instructions, calibrating is fast and easy. Just thought of another use for this RSSI meter (easy visual indication of strongest signal), useful to locate a downed plane with a directional antenna on the video rx, provided the video tx is still transmitting.

As far as installation goes, I think I'll just cover it in heatshrink and velcro it to the rx.

Attached Thumbnails

  • P1010338(1).JPG
  • rssi meter install.JPG

Edited by masam, 29 May 2010 - 12:49 AM.


#50 Devonian

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Posted 27 May 2010 - 10:09 AM

My little parcel arrived in the UK today - thanks Thomas :)

Unfortunatley, my 2 receiver modules are still on back order :angry:

Nigel.

#51 Terry

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Posted 27 May 2010 - 10:56 AM

Got mine too, will update as soon as tested.

Terry

#52 Mr.RC-Cam

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Posted 27 May 2010 - 12:33 PM

It sounds like nearly everyone has received their meters. Please make note of your initial impressions and overall experience with it, then share it all here. I appreciate the feedback.

Thanks for posting the installation photos: Please keep them coming.
- Thomas

#53 mrfliboy

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Posted 28 May 2010 - 08:02 AM

I did a actual field test with it this past monday and was truly impressed on the accuracy. Easily readable and definitely let me know when signal was getting weak. Very quick response.

Hopefully make it to Rat Shack this weekend and find the time to mount it in a project box. Any suggestions for the pushbutton??

I'm thinking long rod to activate or unsolder and mount onto box????

Edited by mrfliboy, 28 May 2010 - 08:05 AM.


#54 Mr.RC-Cam

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Posted 28 May 2010 - 08:59 AM

I did a actual field test with it this past monday and was truly impressed on the accuracy. Easily readable and definitely let me know when signal was getting weak. Very quick response.

Thanks for the field report.

Any suggestions for the pushbutton?? I'm thinking long rod to activate or unsolder and mount onto box????

A typical installation will not need access to the calibration switch after the meter is installed/setup. However, if you want to remotely mount the CAL switch then the board has two solder pads just for that use. These are the two empty pads at the top-left side of the switch and they are labeled J1. The existing switch is left alone and you merely solder the remote push switch to these pads.
- Thomas

#55 mrfliboy

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Posted 28 May 2010 - 09:58 AM

A typical installation will not need access to the calibration switch after the meter is installed/setup. However, if you want to remotely mount the CAL switch then the board has two solder pads just for that use. These are the two empty pads at the top-left side of the switch and they are labeled J1. The existing switch is left alone and you merely solder the remote push switch to these pads.



Sweet!!!!

#56 Terry

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Posted 28 May 2010 - 12:04 PM

What sort of % dose the picture get unwatchable?

Terry

#57 Mr.RC-Cam

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Posted 28 May 2010 - 02:49 PM

What sort of % does the picture get unwatchable?

That depends on the receiver's RSSI characteristics. If I follow the published instructions, my 900Mhz Rx has a very snowy image when it is close to 0%. However, we have ultimate control over the displayed % values simply by gaming the calibration setup.

For example, if you want the display to be 0% at a particular snowy image condition, then use the snowy image during the low signal calibration (instead of turning the Tx off). You can remove the Rx antenna to invite a snowy image at a short test distance, so this is not a hard thing to do indoors at the work bench. Even easier outdoors.

BTW, to see what your image looks like when it is near 0%, just test out the video system with the Rx antenna removed. As you move the Tx away from the crippled Rx you can watch the meter as the image goes bad.That will tell you what to expect with your existing calibration.
- Thomas

#58 andrei

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Posted 28 May 2010 - 09:59 PM

Here is my almost finished ground station with the most recent addition.
I vandalised a dashboard clock in order to get the case.

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#59 mrfliboy

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Posted 31 May 2010 - 06:01 AM

Radio shack project box, pushbutton switch (had laying around), 4-40 allen bolt and nylon lock nut for push button. Velcro dot on back for using with different Rx'ers. Thanks again for a great product.

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  • DSC00165.jpg


#60 Mr.RC-Cam

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Posted 31 May 2010 - 10:28 AM

Great photos, please keep them coming. Also, it would be grand if meter users described how the meter worked for them while out in the field. If you are using it to compare & evaluate antennas, then please report on your experience doing that.
- Thomas