Re: Phase or frequency modulation?

Liz Tuddenham wrote:

Don wrote:

Liz Tuddenham wrote:

Ralph Mowery wrote:

liz@poppyrecords.invalid.invalid says...

Has my Icom been designed for a market where phase modulation is the
norm or is there another explantion?

>
Frequency and phase modulation should come out of a transmitter almost
identical.  As they start off different in the first stage of the
transmitter the audio frequency going into the modulastor stage must be
modified so the end results is the same for FM and PM.

>
Yes - but it would appear that PM is the de-facto standard for
commercially-built 'amateur' 2-metre transceivers despite all the
literature calling it FM.

>
Yes, your sentiment seems "on the money."
>
This thread apparently advanced from an IC-706 to a DIY receiver. If
your schematic indeed pertains to your DIY receiver - excellent work
showcased in an excellent thread! (It taught me a few things, thank
you.)

>
It is based on an idea that has been in the back of my mind for many
years.  The change from an exchange-powered to a mains-dependent
telephone service in the UK was the final factor that made me decide
that I neded an alternative communications system.  I thought that,
while I was making one, it might be a good idea if it was EMP-proof, so
I decided it would have no semiconductors.  It has turned into an
interesting project.
>

For what it's worth, the IC-706 probably uses the 75 micro-second pre-
emphasis standard prevalent in the Americas and Japan. Meanwhile,
Europe favors a 50 micro-second standard.

>
Those are the standards for wide-band broadcast FM, but they are outside
the range of permitted modulating frequencies for narrow-band amateur
work.  The time constant for the Icom appears to be around 2000
microseconds.
>

Although Phase Modulation is popular in Asia:
>
    <https://pmc.ncbi.nlm.nih.gov/articles/PMC11501851/>
>
it's doubtful the IC-706 was developed for an Asian market.

>
Apparently it was.  There is a Japanese version with a slightly
different specification from the European one.    You may have hit upon
the real explanation, I haven't checked to see if mine is a Japanese one
which has been sold in the UK by accident.

Dave Platt's "it's not a bug it's a feature" also makes a lot of sense.
I got on the wrong track in regards to standards after an attempt to
de-cipher repeater builder's cryptic warning about "Just watch the
pre-emphasis and de-emphasis!"

    IC-706 ... This is the HF radio that also does 6 meters.
    When coupled to a high-end repeater controller that
    understands what a HF remote base is (like an NHRC-10,
    an Arcom RC210 or similar capability controller) this
    makes a dandy HF remote base. Just watch the pre-emphasis
    and de-emphasis! ...

  IC-706MKII ... This is the later 706 HF radio that also
  does 6 meters and 2 meters. The same firmware bug that
  affects the CTCSS frequency applies; use the same
  procedure.

  <https://www.repeater-builder.com/icom/icom-index.html>

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.