[1000mp] FT-1000 with Heil PR-40

[Adam Farson]

Hi Jim,

Agreed. I also spent many years in the telephone industry. The 250 - 3400 Hz
response masks for standard voice channels were based on the work done by
Fletcher and Munson in the thirties. The characteristics of the human voice
have not had time to undergo any evolutionary change since then.

The 350 Hz - 2.7 kHz AF response mask (at the -6 dB points) in ITU-R M.1173
for J3E emissions in the maritime radio services was derived from the same
source. It is not binding on the amateur radio service, but is an excellent
guideline yielding the best compromise between articulation and best
utilisation of peak-power-limited transmitter output. Some countries do, in
fact, specify a maximum occupied bandwidth of 2.8 or 2.9 kHz for amateur SSB
signals in their national radio regulations.

Transmitting a significant amount of energy below 200 Hz will "rob"
transmitter power, without enhancing articulation at the distant end.

In the light of all this, and in consideration of the fact that the SSB
generator in a modern amateur transceiver limits the occupied bandwidth to 3
kHz or less, there does not seem to be any point in using a microphone which
is flat to 18 kHz. A microphone tailored to the transmitter's AF response
will be much less costly, and may well sound cleaner and more articulate at
the distant end.

http://www.ab4oj.com/icom/ic756pro3/pro3notes.html#mics is written around
the Pro3, but is relevant to any HF-SSB radio system.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: 1000mp-bounces at mailman.qth.net [mailto:1000mp-bounces at mailman.qth.net]
On Behalf Of Jim Smith
Sent: 28 July 2006 01:28
To: All about Yaesu 1000mp
Subject: Re: [1000mp] FT-1000 with Heil PR-40

Depends what you mean by "normal" SSB purposes.

Several decades ago I was a designer of telephone carrier systems.  In one
system I worked on, each channel had a 250 Hz low pass filter and a 3400 Hz
high pass filter at the transmit end.  This system was designed to be "toll
quality" which means that it would satisfy the end to end requirements of
the long distance telephone system.  So, 3150 Hz bandwidth for a
telecommunications channel which sounded "natural". With guard bands, each
channel was allocated a 4 kHz chunk of the spectrum.

There was also a requirement to pass "program material".  i.e.  commercial
AM/FM radio broadcasts.  We had a way of using 2 channels for this.  So a
program channel, including guard bands, was allocated a max of 8 kHz.

It is not obvious to me what normal ham radio SSB purpose would require a
bandwidth almost 6X greater than a good quality international telephone
circuit and 10X greater than the bandwidth I routinely use when trying to
communicate under difficult conditions.

In any event, I would expect that the transmit filters in any ham SSB rig
would have bandwidths far lower than that of the proposed microphone so, if
it costs more than a mic with a more restricted bandwidth, you're spending
money which could be put to a better use.

73, Jim	VE7FO



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