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

[Bill Andrews]

Don't mean to disappoint you, but this is not about ham radio.

This is Bill Andrews wife, I noticed your name and wondered if
you were any relation to the Knoppows in Michigan?

I worked for Jerry Knoppow, at a wallpaper store in
Dearborn Michigan, and several others.  His father started
the business. Knoppow's wallcovering was the name.
 Are you any relation to that family?

Just curious.

Corinne Andrews


> [Original Message]
> From: Richard Knoppow <dickburk at ix.netcom.com>
> To: <garyschafer at comcast.net>; Discussion of Electronic Test Equipment
<test-equipment at mailman.qth.net>
> Date: 4/22/2008 7:22:53 PM
> Subject: Re: [Test-Equipment] FS: Heath IM4180 FM deviation meter
>
>
> ----- Original Message ----- 
> From: "Gary Schafer" <garyschafer at comcast.net>
> To: "'Discussion of Electronic Test Equipment'" 
> <test-equipment at mailman.qth.net>
> Sent: Tuesday, April 22, 2008 6:35 PM
> Subject: RE: [Test-Equipment] FS: Heath IM4180 FM deviation 
> meter
>
>
> > If you really want to get into it, high quality AM can be 
> > generated by
> > properly phasing two FM transmitters together.
> >
> > 73
> > Gary  K4FMX
> >
>     There are several patents on transmitters of this type. 
> The system is known generically as "outphasing" and a Google 
> search will find a good deal of information. One of the 
> earliest patents was issued in France to Chireix and the 
> system is often called by that name. It was used in the 
> 1960's for a high power RCA broadcast transmitter called the 
> Ampliphase but it was not very successful in practice. 
> Outphasing modulation is currently used for some microwave 
> transmitters.
>
>     There is a good deal of technical information about FM 
> on the web and I wrote off list to Charles with some 
> suggestions. Again, a Google search will find both simple 
> and quite advanced treatuses on it. FM seems simple but is 
> really not very intutive. Really understanding it requires 
> some math and aspirins.
>     BTW, in theory FM sidebands extend infinitely, however, 
> the further they are from the center frequency the smaller 
> the amplitude so, beyond a certain limit, they are not 
> significant.
>     A system of narrow band FM was used in the first Ampex 
> video recorders. Its worth looking up because it violated 
> the theory of the time indicating that the theory was wrong.
>
>     All modulation can be generated by combining amplitude 
> and what is sometimes called quadrature modulation. 
> Quadrature modulation is a mathemetical concept and does not 
> exist physically however, it is a component of the analysis 
> of any type of modulation.
>
>     Sometime around the 1960s a fellow named Kahn wrote a 
> number of articles touting a system he had developed for 
> using AM transmitters for SSB by splitting the original 
> signal into AM and FM components. The AM component went into 
> the audio input and the FM component was used for RF drive. 
> When everything is balanced right the AM transmitter acts 
> like a high efficiency linear amplifer. I have not done a 
> patent search but I suspect his patents will show up on a 
> Google Patents search. I believe the military used Kahn 
> adaptors for some applications.
>
>     I've used the Bessel null method of setting FM deviation 
> on satellite uplink transmitters many times. It isn't 
> difficult but requires a good narrow band detector of some 
> sort (a spectrum analyser is ideal) and an accurate 
> knowledge of the audio frequency used for modulation.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk at ix.netcom.com 
>
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