[FCARC] Fwd: [repeater-builder] New test equipment from Masters Communications - a FM deviation meter.

[Adam T. Cately]

For anyone that is interested . . .



-------- Forwarded Message --------
Subject: 	[repeater-builder] New test equipment from Masters 
Communications - a FM deviation meter.
Resent-Date: 	Wed, 24 Dec 2025 12:00:44 -0800
Resent-From: 	kuggie at kuggie.com
Date: 	Wed, 24 Dec 2025 15:00:41 -0500
From: 	Kevin Custer <kuggie at kuggie.com>
Reply-To: 	repeater-builder at groups.io
To: 	Repeater Builder <repeater-builder at groups.io>



Masters Communications announces the availability of new test equipment 
for amateur radio communications - a FM deviation meter.

Several years ago I set out to make an affordable communications service 
monitor, but that task as a complete unit never transpired.  Since then, 
some aspects of a service monitor have been made available in the way of 
cheap Asian test equipment. There are FM signal generators, spectrum 
analyzers with tracking generators, VNA's, and other things that easily 
fit the ham or hobbyist's budget.  While this stuff isn't laboratory 
grade - it's better than not having anything.  This inexpensive 
equipment is great for testing FM receivers, but there is a current lack 
of equipment to test FM transmitters.  What does a ham do to *quickly, 
easily and accurately* measure deviation on a FM transmitter, set up a 
repeater controller, or make measurements on a link transmitter or 
adjust an ASL node?  There's got to be a better way..

Sure, there some inexpensive are ways to do it - but none are easy to do 
/ use, and may require a computer and complicated software. Plus - you 
might not have access to a modulating frequency of the right value to do 
Bessel Function for your required deviation. Case in point - VARA FM 
Wide.  VARA FM creates a 1500 Hz tone when you press the "Tune" button.  
This frequency results in a first Bessel null at 3.6kHz deviation.  
That's pretty far removed from the optimal value of 2.2 - 2.5kHz 
deviation for VARA FM Wide.  A real deviation meter can easily read the 
deviation of a FM transmitter - even though the tone(s) produced by 
software doesn't work well with Bessel nulls.  None of this type of 
testing shows distortion which is evident when you hit the limiter.  
There's got to be a better way...

What about the Heathkit IM-4180, AEA DM-1, and MFJ-224?  They are long 
gone.  I've owned all of these, and they were kludgy.  The Heathkit and 
MFJ are tuned with a VFO knob, were rather unstable and difficult (at 
best) to use.  The MFJ only covered 2M.  The AEA was crystal controlled 
- so it was limited in frequency coverage and only had a very granular 
display.  None of them were very sensitive, nothing like a real service 
monitor.  There's got to be a better way....

Here's a *better way:*

The FMDM-150M Deviation Meter 
<https://www.masterscommunications.com/products/fmdm/fmdm-150m.html> is 
fully explained on our website.  If you are interested - check it out 
when you have the time.

Comments and questions welcomed....

Kevin Custer
Masters Communications
Palm Coast FL
USA

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