[AMRadio] Source Broadcast Xmtrs

Sat Jun 11 21:42:28 EDT 2011

I'm kind of getting into this thread in the middle after Jim Tonne's rebuttal 
which is totally correct, but I'd like to throw this into the fan......... 
Traditionally broadcast transmitters could do 15 kc. with no problem (assuming 
they were worth the metal they were built out of) but when NRSC came along in 
the middle 80's the audio bandwidth was brick walled at 10 kc. then the RF 
envelope was made to be 10 kc as well a couple of years later. With the advent 
(and in my opinion curse) of AM IBOC there is a move to cut the analog bandwidth 
down to 5 kc. FWIW FM IBOC is OK +/- 3dB again in my opine.

That being said, the average home / car AM receiver would be hard pressed 
to pass even 5 kc. 

Bill AD5OL

________________________________
From: Bob Macklin <macklinbob at gmail.com>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Sat, June 11, 2011 6:58:53 PM
Subject: Re: [AMRadio] Source Broadcast Xmtrs

Bandwidth for communications quality AM is +/- 3KC. Commercial AM broadcast 
transmitters have more bandwidth than this. Close to +/- 5KC.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Bernie Doran" <qedconsultants at embarqmail.com>
To: <ka4inm at tampabay.rr.com>; "Discussion of AM Radio in the Amateur 
Service" <amradio at mailman.qth.net>
Sent: Saturday, June 11, 2011 4:48 PM
Subject: Re: [AMRadio] Source Broadcast Xmtrs

>" big iron limits the fidelity in ways that a rice box doesn't" what an
> interesting view, rice boxes cut off the lows and also cut off the mid and
> highs  300 to 2100 seems typical, so I guess if the definition of fidelity
> is 300 to 2100 then perhaps the big iron does limit fidelity.  of course 
> now
> someone will chip up and say we can only use 3 kc bandwidth, or that we 
> need
> to conserve bandwidth, does it wear out after a period of time?
> ----- Original Message ----- 
> From: "Ron Youvan" <ka4inm at tampabay.rr.com>
> To: "Discussion of AM Radio in the Amateur Service"
> <amradio at mailman.qth.net>
> Sent: Saturday, June 11, 2011 6:32 PM
> Subject: Re: [AMRadio] Source Broadcast Xmtrs
>
>
>> John Lyles wrote:
>>
>>> Alas, as Don Chester replied, 1 kW and smaller AM tube rigs are getting
>>> scarce. However, small mom-and-pop stations are still there on local
>>> channels in smaller communities, barely hanging on, with tube
>>> transmitters and backups. If you live in such areas, such as I do in
>>> northern New Mexico, recommend getting to know the management, or the
>>> local contract engineers who take care of these. Nowadays, one engineer
>>> could maintain 5-10 stations. Sometimes all the engineers are friendly
>>> enough to invite you to their get-togethers, such as Friday lunch at a
>>> cafe.
>>
>>  As a broadcaster of over 48 years experience I don't understand the
>> fascination with plate
>> modulated AM transmitters.
>>  First I was a HAM wannabee when AM was king and the heterodynes were
>> both hideous and everywhere.
>> Frequently unavoidable on just about every QSO. *
>>  Secondly the "big iron" that everyone covets limits the fidelity in 
>> ways
>> that a rice box followed
>> by a one kW linear amplifier doesn't.
>>  Thirdly, USA HAMS are limited to 375 Watts unmodulated carrier, (1.5 kW
>> P-P) a one kW AM
>> transmitter can produce one thousand Watts of unmodulated carrier.  (so
>> you need to cut it back)
>> * everyone disappeared when SSB took over (what ever that is) as did the
>> heterodynes when I got a BFO
>>  Early commercial and locally built AM transmitters were often a low
>> power modulated transmitter**
>> followed by a linear amplifier
>> ** frequently using Heising modulation
>>
>>  Ron KA4INM  73
>>
>>> I have gotten two of my rigs from the AM forum listings over the years,
>>> and one from a local station that wanted it moved out quickly. They are
>>> now relocating their TX to a new tower, so they called again last
>>> Friday,"help move this thing". A little Harris solid state, an old solid
>>> state MW1 Gates, and a rare and horrible ITA1000. A ham friend is
>>> helping move the transmitter site, hopefully he will get the ITA. The
>>> others will stay in service on BC Band. So by helping them out,
>>> transmitter gets recycled.
>>
>>
>> -- 
>>    Ron  KA4INM - You can't fool me ...
>>                      ... I'm a moron.
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