[ARC5] BC sets and others.

[Richard Knoppow]

----- Original Message ----- 
From: "Geoff" <geoffrey at jeremy.mv.com>
To: "Rob Atkinson" <ranchorobbo at gmail.com>; "Robert Eleazer" 
<releazer at earthlink.net>
Cc: "ARC-5 List" <arc5 at mailman.qth.net>
Sent: Tuesday, January 21, 2014 5:48 PM
Subject: Re: [ARC5] BC sets and others.


> With 10 kc "channels" in place since before 1940 there 
> hasnt been 20 kc in over 70 years.
>
> Carl
>
     Not quite true, while the BCB is devided into 10Khz 
channels the assignments of stations with adjacent signals 
was always done to provide a much wider effective channel. 
Even in metropolitan areas stations were seldom if ever 
assigned closer than about 30 khz from an adjacent station. 
Typical broadcast transmitters had specs of around 12 khz 
but this was limited primarily by the difficulty of going 
higher due to costs of modulation transformers, etc. In any 
case the high noise on the MW band makes really wide band 
transmission almost useless. The reason current receivers 
have rather narrow bands is at least partly to reduced 
interference from the digital signals so many stations now 
transmit. Some broadcasters, reportedly Clear Channel, have 
limited audio response of their stations to 5khz.
    The only limit in the old days was the telephone lines 
used for network transmission. These were mostly Clas-B 
lines that cut off at 5khz and distortion due to the phone 
lines was very appearant even on relatively short runs. 
Class-A lines, which provided at least 10khz were available 
but _very_ expensive.  These were used mostly for studio to 
transmitter links. A good "dry" line, i.e., one without 
repeaters in it could be pushed to 15 khz by driving it with 
a low impedance source (around 30 ohms) and careful 
equalization.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com