Can anyone confirm a theory I have heard that fits in with my own
recollection? The theory is that pre-1978 AM transmitters used much
larger bandwidth - often exceeding what was officially allowed - and
the audio quality was far better than AM is today.

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Scott <newsgroups@gefion.myzen.co.uk> wrote:

Can anyone confirm a theory I have heard that fits in with my own recollection? The theory is that pre-1978 AM transmitters used much
larger bandwidth - often exceeding what was officially allowed - and
the audio quality was far better than AM is today.

The Philips Technical Review describes this as common practice in the
late 1930s. I've not read anything to say it was discouraged or
abandoned in later years.


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~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

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In article <ufe8tgtqudu0ph2q1n0slenlum40b2tkg5@4ax.com>,
Scott <newsgroups@gefion.myzen.co.uk> wrote:

Can anyone confirm a theory I have heard that fits in with my own recollection? The theory is that pre-1978 AM transmitters used much
larger bandwidth - often exceeding what was officially allowed - and
the audio quality was far better than AM is today.

I think you have to go well before 1978. Yes, filters were added to the
audio to cut down on having sidebands that went into other's channels. The
BBC did this for the medium wave Light Programme service while I was still commuting to TVC by car. That ended in 1973.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

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Well, I seem to recall it was supposed to be only 10KHz, and often the
limiting factor was the bandwidth of receivers themselves. On the basis that the more the barn door is open the more muck flies in they reduced it to
9Khz I seem to recall. Of course stations like Luxemburg did as I recall transmit up to 12Khz a lot of the time. The problem is that after dark as
most of that stations output was in the dark, you tended to get a lot of
fading and co channel interference and most people could not use the extra bandwidth as their receivers were quite selective. Some of the widest band
ones were the cheap bakelite radios with droppers in the back ac and dc of course and got very hot, but they were simple and we as open as an aircraft hanger most of the time.

Pioneers medium wave tuner amps had a bandwidth widening circuit based on signal strength, which in a quiet electrical en environment were very nice
on Am.

I just wish they had not called the ferrite Rod a loopstick in their instructions.

Brian

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"Scott" <newsgroups@gefion.myzen.co.uk> wrote in message news:ufe8tgtqudu0ph2q1n0slenlum40b2tkg5@4ax.com...

Can anyone confirm a theory I have heard that fits in with my own recollection? The theory is that pre-1978 AM transmitters used much
larger bandwidth - often exceeding what was officially allowed - and
the audio quality was far better than AM is today.

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Yes there was a popular design by Mullard for a transistor IF based on
their components that did widen the bandwidth with signal strength. If you wanted to use this double tuned IF for communication work you had to clip a link on the pcb to disable the function. For what it was worth it did not
work as well as the Pioneer design and tended to let in splatter from
adjacent channels which spuriously opened up the bandwidth which created a weird breathing effect if it was speech on the interfering channel.
Nowadays brick wall filtering on transmitters and bloody Optimod has mad AM and most other radio formats sound terrible. There really is no need for massive primitive compression in my view.
Brian

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"Liz Tuddenham" <liz@poppyrecords.invalid.invalid> wrote in message news:1pl9c06.1qmfu0svgzckN%liz@poppyrecords.invalid.invalid...

Scott <newsgroups@gefion.myzen.co.uk> wrote:

Can anyone confirm a theory I have heard that fits in with my own
recollection? The theory is that pre-1978 AM transmitters used much
larger bandwidth - often exceeding what was officially allowed - and
the audio quality was far better than AM is today.

The Philips Technical Review describes this as common practice in the
late 1930s. I've not read anything to say it was discouraged or
abandoned in later years.

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

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Recently, a fault at a local Premier Radio mw transmitter caused mayhem
around here since it was splattering many khz either side and had spurious ghosts and a very loud second harmonic rather distorted. It was over
modulated too. I did contact offcom and it was feed in a couple of weeks. I know they say God is omnipresent but not on the medium wave band surely?
grin.
Brian

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"charles" <charles@candehope.me.uk> wrote in message news:59a589ece6charles@candehope.me.uk...

In article <ufe8tgtqudu0ph2q1n0slenlum40b2tkg5@4ax.com>,
Scott <newsgroups@gefion.myzen.co.uk> wrote:

Can anyone confirm a theory I have heard that fits in with my own
recollection? The theory is that pre-1978 AM transmitters used much
larger bandwidth - often exceeding what was officially allowed - and
the audio quality was far better than AM is today.

I think you have to go well before 1978. Yes, filters were added to the audio to cut down on having sidebands that went into other's channels. The BBC did this for the medium wave Light Programme service while I was still commuting to TVC by car. That ended in 1973.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

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