[AMRadio] Source Broadcast Xmtrs

Sat Jun 11 21:09:06 EDT 2011

Commercial AM transmitters have a frequency response to 15 kilohertz 
there are a handful that have an audio response to 50 kilohertz. The new 
digital systems require at least a 30 kilohertz audio response.

On 6/11/11 7:58 PM, Bob Macklin wrote:
> 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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