[Test-Equipment] FS: Heath IM4180 FM deviation meter

[wolfbob]

Deviation can be measured several ways. The most popular 
method is with a discriminator that is calibrated. Once the 
discriminator is calibrated a true RMS AC voltmeter can 
measure the deviation of the demodulated signal. To 
calibrate the discriminator/voltmeter it is common to use 
the well known carrier null method. For a sinewave frequency 
modulation at a specific audio frequency, the modulating 
amplitude can be raised from zero until the RF carrier is 
nulled. This is a specific defined and mathematically 
calculated (using Bessel Functions) value of modulation 
index which is a combination of modulating frequency and 
deviation. Specific numbers and equations can be found on 
the net.

WBob, WB6JPI


----- Original Message ----- 
From: "Brooke Clarke" <brooke at pacific.net>
To: "Discussion of Electronic Test Equipment" 
<test-equipment at mailman.qth.net>
Sent: Monday, April 21, 2008 6:32 PM
Subject: Re: [Test-Equipment] FS: Heath IM4180 FM deviation 
meter


> Hi George:
>
> Another FM radio test is SINAD or "SIgnal Noise And 
> Distortion" how to make that measurement is on my web 
> page: http://www.prc68.com/I/MTE.shtml#Test
> I haven't come up with a simple way to measure deviation, 
> but maybe someone here has?
>
> Have Fun,
>
> Brooke Clarke, N6GCE
> http://www.prc68.com/P/Prod.html  Products I make and sell
> http://www.prc68.com/Alpha.shtml  All my web pages listed 
> based on html name
> http://www.PRC68.com
> http://www.precisionclock.com
> http://www.prc68.com/I/WebCam2.shtml 24/7 
> Sky-Weather-Astronomy Web Cam
>
> kc7hkp at comcast.net wrote:
>> Hi Dick
>> What is FM Deviation ?
>> I have not heard this word before in ham radio .
>> Sorry to bother you
>> George
>>
>> --
>> KC7HKP George Yazzolino 14801 NE 20th Circle Vancouver, 
>> Wa. USA ,98684 Grid CN-85 kc7hkp at arrl.net
>>
>> -------------- Original message -------------- 
>> From: "Dick KF4NS" <kf4nsradio at verizon.net>
>>>This test equipment measures peak transmitter FM 
>>>deviation 25-1000MHZ from ham, broadcast, or any FM 
>>>transmitter in the freq range. 50 ohm BNC input jack for 
>>>direct or antenna connection. Has demodulated audio 
>>>output and scope jacks. There are four ranges, 2KHZ to 
>>>75KHZ. Operates from internal batteries or 10-15VDC 
>>>external power supply of 200ma or greater.
>>>Just completed alignment, calibration and was tested. 
>>>Works great. Excellent except for a scratch on top left 
>>>front. One special caveat; the internal meter movement is 
>>>defective and has been replaced by an external metal 
>>>encased 4 x 4 1/2in. (much easier to read too) fully 
>>>compatable meter with CAD designed scale, accurate to 
>>>Heath specs.
>>>Asking $65 plus shipping. Original manual. Pic available.
>>>73, Dick KF4NS St Petersburg, FL 33714 USA Keep The Glow!
>>>
>>>______________________________________________________________ 
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>>
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