[AMRadio] Broadcast Processors

Tue Jun 14 18:06:11 EDT 2011

CCA was one of those 'you get what you pay for boxes'. I had to take 
care of an AM10000 and it is far from my favorite TX. I can not think of 
many transmitters that were screamers before the PDM and other digital 
modulation schemes came along. Continental came close but only at 50 KW.

On 6/14/11 5:47 PM, Dennis Gilliam wrote:
> Not so much hassle when not being forced to positive peak a lot.  Especially
> below 100Hz
>
> A basic design flaw with that tube lineup and the associated circuitry,
> apparently, as the same characteristics played out with that CCA.
>
> I think the 4CX5000 didn't have sufficient drive relative to screen swing,
> or maybe 'cause the RF driver wasn't modded any.
>
> The end game was to make it holler loudly and damn the torpedoes.  If it
> caused problems, it didn't matter until the bills came due.
>
> Ron Jones forgot more about spanking an AM box to the fullest than all of us
> will ever know.  RIP, Ron.
>
> 73DG
>
> On Tue, Jun 14, 2011 at 2:08 PM, W2XJ<w2xj at nyc.rr.com>  wrote:
>
>> Those transmitters did not go near DC. The low end response would be
>> limited before it got near the high powered stuff.
>>
>> On 6/14/11 4:59 PM, Bernie Doran wrote:
>>> interesting!  Just does not seem logical. The mod transformer would
>> probably
>>> go down to 30 cy or less and probably the audio low cut off was not much
>>> below that.   my Gates COG also has cathode follower drivers, a great way
>> to
>>> drive class BE.   Wonder if there was some component( with all that
>>> processing)  that was near DC and ended up as dissipation. That should
>> have
>>> been obvious from color
>>> ----- Original Message -----
>>> From: "Dennis Gilliam"<dennisgilliam at gmail.com>
>>> To: "Discussion of AM Radio in the Amateur Service"
>>> <amradio at mailman.qth.net>
>>> Sent: Tuesday, June 14, 2011 1:47 PM
>>> Subject: Re: [AMRadio] Broadcast Processors
>>>
>>>
>>>> Ron and I looked this over carefully.  No airflow problems, and the mod
>>>> trans was OK, a oil-filled Electro job.  The duty cycle was tough, with
>>>> the
>>>> mod current meters just never moving off max except total silence.
>>>> Positive
>>>> peaks were around 120%.  The compression ratio was really high, and the
>>>> program density and bottom end correction was right on the edge of
>>>> negative
>>>> overmod.  This TX even used the iron-free 'transparent' cathode-follower
>>>> mod
>>>> driver setup.
>>>>
>>>> Some combinations of parts called transmitters are not meant to
>>>> have asymmetrical positive peak ability.
>>>>
>>>> Years later I saw the same characteristics on a CCA 5kW.  It had the
>> same
>>>> tube compliment, 2X4-1000 modding a single 4CX5,000.  It couldn't handle
>>>> +peaks without tripping the OL relays.  They tried previouly, and had to
>>>> buy
>>>> all new mod iron.
>>>>
>>>> 73DG
>>>>
>>>> On Tue, Jun 14, 2011 at 10:30 AM, Bernie Doran<
>>>> qedconsultants at embarqmail.com>   wrote:
>>>>
>>>>> curious about what killed the 4-1000s, did they have propper airflow
>> and
>>>>> normal plate current?  AB2 can develope 3800 w of audio at 6kv  that
>>>>> should
>>>>> be a good match for 5 kw out.
>>>>> did you ever ask Eimac about this?
>>>>> From: "Dennis Gilliam"<dennisgilliam at gmail.com>
>>>>> To: "Discussion of AM Radio in the Amateur Service"
>>>>> <amradio at mailman.qth.net>
>>>>> Sent: Tuesday, June 14, 2011 1:04 PM
>>>>> Subject: Re: [AMRadio] Broadcast Processors
>>>>>
>>>>>
>>>>>> A short story about an AM transmitter:
>>>>>>
>>>>>> Years ago I was CE for KZZP-AM in Mesa, AZ.  The station had a Bauer
>>>>>> 5kW,
>>>>>> and management wanted it to be 'louder'.
>>>>>>
>>>>>> Replacing the old, single-band limiter, I installed a CRL set of three
>>>>>> units
>>>>>> (AGC, EQ, and limiter), the usual setup.
>>>>>>
>>>>>> Wow, what a difference that made!  It still didn't please the program
>>>>>> director, so I got Ron Jones (the owner of Circuit Research Labs) to
>>>>>> come
>>>>>> out and take a look.  He said 'This transmitter has the worst bottom
>>>>>> end
>>>>>> tilt I've ever seen'.
>>>>>>
>>>>>> He went back and cooked up an experimental box we installed the next
>>>>> week,
>>>>>> and boy, did it sound really good&   loud.  Lots of mod plate glow,
>> BTW.
>>>>>    A
>>>>>> week later, the 4-000 modulators were flat.  I didn't think that was
>>>>>> too
>>>>>> bad, as they had been in service for some time.
>>>>>>
>>>>>> I put in a new set, things were good again.  Boy, those Eimacs were
>>>>> really
>>>>>> working for a living, I thought.
>>>>>>
>>>>>> Two weeks later, they looked like old coffee pots, brown from ion
>> burns
>>>>>> and
>>>>>> totally without emission--again.  I mentioned this to the PD, and that
>>>>>> this
>>>>>> will cost some $.  He said, 'Don't worry about it, we are going to
>> make
>>>>>> a
>>>>>> bundle!'
>>>>>>
>>>>>> New tubes were ordered up, and in went my last spares.  The same drill
>>>>>> went
>>>>>> down, those tubes died in two weeks.  More tubes installed.  More
>> great
>>>>>> glow....
>>>>>>
>>>>>> Then the office manager asked me about the invoices she was getting
>>>>>> from
>>>>>> Richardson Electronics for all those 4-1000's.  I told her the story.
>>>>>    She
>>>>>> went to the boss, and that started a loud argument between her and the
>>>>>> PD
>>>>>> about the $$ out vs. the $$ in.
>>>>>>
>>>>>> The big boss found for her, and the 'magic box' from CRL was retired
>>>>>> and
>>>>>> mod
>>>>>> tubes went back to lasting about a year or so.
>>>>>>
>>>>>> The lesson of TANSTAAFL applied to transmitters.
>>>>>>
>>>>>> 73DG
>>>>>>
>>>>>> On Tue, Jun 14, 2011 at 7:45 AM, Jim Tonne<Tonne at comcast.net>   wrote:
>>>>>>
>>>>>>> Regarding commercial broadcast processors for ham use.
>>>>>>>
>>>>>>>> The transmitter "Frequency response must be less than
>>>>>>>> 3dB down at 0.15Hz, and less than 0.1dB down at 9.5 kHz."
>>>>>>> That figure of 0.15 Hz may sound odd and arbitrary but is
>>>>>>> based on a direct-coupled modulator (i.e., flat down to DC)
>>>>>>> with a one-second time-constant on an input blocking
>>>>>>> capacitor and resistor.
>>>>>>>
>>>>>>> That figure of 0.15 Hz is sometimes specified in the contract
>>>>>>> between the manufacturer and the purchaser.
>>>>>>>
>>>>>>> Another way the low end is sometimes specified is that if
>>>>>>> the transmitter is modulated with a 50 Hz square wave that
>>>>>>> the tilt on the resultant modulation is to be less than 2%.
>>>>>>>
>>>>>>> Why this "nonsense" you may ask.   It is because the
>>>>>>> commercial broadcast processors  generally deliver an
>>>>>>> output waveform that is somewhat clipped, although it
>>>>>>> may be clipped only on transients.   For them to control
>>>>>>> the modulation requires that the following audlio stages
>>>>>>> (the modulator) have such a flat response.
>>>>>>>
>>>>>>> Another area that is of concern in the transmitters is the
>>>>>>> insistence by the purchaser that the response be flat on
>>>>>>> the high end and yet have no overshoot on a 2 kHz
>>>>>>> squarewave.   Can't do that and when the manufacturer
>>>>>>> sits down with the purchaser and explains the math,
>>>>>>> the purchaser comes away enlightened and happy.
>>>>>>>
>>>>>>> - Jim Tonne   used to design BIG PWM rigs at CEC
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ______________________________________________________________
>>>>>>> Our Main Website: http://www.amfone.net
>>>>>>> AMRadio mailing list
>>>>>>> Searchable Archives:
>>>>> http://www.mail-archive.com/[email protected]/
>>>>>>> List Rules (must read!): http://w5ami.net/amradiofaq.html
>>>>>>> List Home: http://mailman.qth.net/mailman/listinfo/amradio
>>>>>>> Post: AMRadio at mailman.qth.net
>>>>>>> To unsubscribe, send an email to amradio-request at mailman.qth.netwith
>>>>>>> the word unsubscribe in the message body.
>>>>>>>
>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>>
>>>>>> ______________________________________________________________
>>>>>> Our Main Website: http://www.amfone.net
>>>>>> AMRadio mailing list
>>>>>> Searchable Archives:
>>>>> http://www.mail-archive.com/[email protected]/
>>>>>> List Rules (must read!): http://w5ami.net/amradiofaq.html
>>>>>> List Home: http://mailman.qth.net/mailman/listinfo/amradio
>>>>>> Post: AMRadio at mailman.qth.net
>>>>>> To unsubscribe, send an email to amradio-request at mailman.qth.net with
>>>>>> the word unsubscribe in the message body.
>>>>>>
>>>>>> This list hosted by: http://www.qsl.net
>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>> ______________________________________________________________
>>>>> Our Main Website: http://www.amfone.net
>>>>> AMRadio mailing list
>>>>> Searchable Archives:
>> http://www.mail-archive.com/[email protected]/
>>>>> List Rules (must read!): http://w5ami.net/amradiofaq.html
>>>>> List Home: http://mailman.qth.net/mailman/listinfo/amradio
>>>>> Post: AMRadio at mailman.qth.net
>>>>> To unsubscribe, send an email to amradio-request at mailman.qth.net with
>>>>> the word unsubscribe in the message body.
>>>>>
>>>>> This list hosted by: http://www.qsl.net
>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>
>>>> ______________________________________________________________
>>>> Our Main Website: http://www.amfone.net
>>>> AMRadio mailing list
>>>> Searchable Archives:
>> http://www.mail-archive.com/[email protected]/
>>>> List Rules (must read!): http://w5ami.net/amradiofaq.html
>>>> List Home: http://mailman.qth.net/mailman/listinfo/amradio
>>>> Post: AMRadio at mailman.qth.net
>>>> To unsubscribe, send an email to amradio-request at mailman.qth.net with
>>>> the word unsubscribe in the message body.
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>> ______________________________________________________________
>>> Our Main Website: http://www.amfone.net
>>> AMRadio mailing list
>>> Searchable Archives:
>> http://www.mail-archive.com/[email protected]/
>>> List Rules (must read!): http://w5ami.net/amradiofaq.html
>>> List Home: http://mailman.qth.net/mailman/listinfo/amradio
>>> Post: AMRadio at mailman.qth.net
>>> To unsubscribe, send an email to amradio-request at mailman.qth.net with
>>> the word unsubscribe in the message body.
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>> ______________________________________________________________
>> Our Main Website: http://www.amfone.net
>> AMRadio mailing list
>> Searchable Archives: http://www.mail-archive.com/[email protected]/
>> List Rules (must read!): http://w5ami.net/amradiofaq.html
>> List Home: http://mailman.qth.net/mailman/listinfo/amradio
>> Post: AMRadio at mailman.qth.net
>> To unsubscribe, send an email to amradio-request at mailman.qth.net with
>> the word unsubscribe in the message body.
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Our Main Website: http://www.amfone.net
> AMRadio mailing list
> Searchable Archives: http://www.mail-archive.com/[email protected]/
> List Rules (must read!): http://w5ami.net/amradiofaq.html
> List Home: http://mailman.qth.net/mailman/listinfo/amradio
> Post: AMRadio at mailman.qth.net
> To unsubscribe, send an email to amradio-request at mailman.qth.net with
> the word unsubscribe in the message body.
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>