[AMRadio] AMRadio Digest, Vol 96, Issue 29
Poli, Louis (US SSA)
louis.poli at baesystems.com
Tue Jan 24 11:26:56 EST 2012
Rick;
The difference in efficiencies has to do with the amount of average time the amplifier is drawing plate current (working and putting out power) and the time it is off/idle.
This topic is not light reading, but a good understanding can be obtained from the ARRL Handbooks, especially those of the 1950's.
Also, a search on the net on the topic of the Class A, B, C amplifiers, their relationship to linearity, and as applied to CW, AM, and SSB.
All this might give you the background you are interested in.
Also an understanding of why and how you tune, especially for a big amplifier, for the linearity you need, is very necessary anyway.
Regards,
Louis N3OL
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Today's Topics:
1. Re: Ongoing Quest: Legal Limit AM Amp (Bernie Doran)
2. Legal limit (rbethman)
3. Re: Ongoing Quest: Legal Limit AM Amp (WB5OXQ at grandecom.net)
4. Re: Ongoing Quest: Legal Limit AM Amp (Rick Poole)
5. Re: Ongoing Quest: Legal Limit AM Amp (Rick Poole)
6. Re: Legal limit (Ross Stenberg)
7. Re: Ongoing Quest: Legal Limit AM Amp (Ross Stenberg)
8. Re: Ongoing Quest: Legal Limit AM Amp (Warren Elly)
----------------------------------------------------------------------
Message: 1
Date: Tue, 24 Jan 2012 09:47:04 -0500
From: "Bernie Doran" <qedconsultants at embarqmail.com>
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
To: "Discussion of AM Radio in the Amateur Service"
<amradio at mailman.qth.net>
Message-ID: <18979DAE858F4F789D375799DB559217 at computerPC>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
nowhere does it say a 375W carrier
----- Original Message -----
From: "Warren Elly" <w1gud4 at gmail.com>
To: "Discussion of AM Radio in the Amateur Service"
<amradio at mailman.qth.net>
Sent: Tuesday, January 24, 2012 8:45 AM
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
> Me thinks the gentleman needs something less than a dx-100...
> You're not going to see much difference between a barefoot 100 and 375
> watt carrier allowed by FCC
>
> 73, Warren
> W1GUD
>
> On Jan 23, 2012, at 11:07 PM, Rick Poole wrote:
>
>>
>> Looking for a good design for a legal limit amplifier for my DX-100
>> (looks like I'll be homebrewing it).
>>
>> I've pretty much narrowed down the choice to a linear amp capable of
>> 375 watts carrier output or 1500 watts PEP output at 100 percent
>> modulation, vs a Class C amp with high level modulator driven from
>> the DX-100's audio output.
>> .
>> I was thinking about a pair of 3-500's in Class B push-pull.
>>
>> Everybody keeps telling me that I'll get maybe 30 percent efficiency
>> at best during dead carrier times. At 100 percent modulation and
>> class B I should get 60 percent at worst. I really, Really don't
>> understand that at all... seems like if I can get 60 percent at 1500
>> watts PEP I should be able to get 60 percent at 375 watts dead
>> carrier. But, I'm accepting it for the moment, and anyway, I digress...
>>
>> 375 watts unmodulated carrier output at 30 percent efficiency means
>> 1250 watts input, or 875 watts dissipation or 437.5 watts per tube.
>>
>> 1500 watts PEP at 60 percent efficiency means 2500 watts peak input
>> or 1000 watts dissipation, 500 watts per tube peak.
>>
>> So it seems to me like a pair of 3-500's should be able to cut it,
>> especially if I give them plenty of air.
>>
>> I want to stick with glass tubes because I'm planning to put them
>> behind a window so I can "feel the glow" during operation. Anyway,
>> it'll impress the living crap out of the XYL :-). Hence, the
>> ceramics have been ruled out for now.
>>
>> So, a few questions...
>>
>> 1. Will a pair of 3-500's in Class B push pull really handle the
>> load with no problem, assuming adequate air?
>>
>> 2. This may be a rookie question, but google hasn't given me a clear
>> answer... is there such a thing as class B push pull grounded grid?
>>
>> 3. There are some commercial class AB pair-of-3-500 amps (e.g.
>> SB-220, TL-922) that are limited in what they can do by the power
>> supply. So, I plan to make sure the power supply can easily handle
>> the load. Any suggestions on the best places to get power
>> transformers that are up to the job? So far I haven't found one
>> under about $600.
>>
>> 4. I'm actually not that certain that I'm competent to design
>> something like this from scratch. Any plans available on the net
>> that I can use for a starting point?
>>
>> 5. Current tentative plans call for the power supply to be separate
>> from the RF deck, and they may be separated by as much as 6 feet
>> (there are compelling reasons for that that go way beyond the scope
>> of this post). Is that practical? Where is a good source for high
>> voltage (3500 VDC) cable and connectors?
>>
>> 6. As noted above, I plan to put the tubes behind a window so I can
>> see them. Is there a glass that can be used for the window that will
>> maintain shielding?
>>
>> Thanks...
>>
>> Rick WA1RKT
>> Londonderry, NH
>> Catch me on 14.300 MHz Intercon / MMSN most days
>>
>> ______________________________________________________________
>> Our Main Website: http://www.amfone.net
>> AMRadio mailing list
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>
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------------------------------
Message: 2
Date: Tue, 24 Jan 2012 10:07:37 -0500
From: rbethman <rbethman at comcast.net>
Subject: [AMRadio] Legal limit
To: AM Radio List <amradio at mailman.qth.net>
Message-ID: <4F1EC939.3050208 at comcast.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I seems that this is one of those perpetual discussions.
The ONLY specified number is the 1500W PEP.
Don Chester, and numerous others have demonstrated the mathematics
behind it all.
The reality is when the math is looked at, a carrier of 375W, modulated
at 100%, gives us the SPECIFIED end result of 1500W PEP.
If you have a carrier of 200W, and modulate it at 100%, you get LESS
than 1500W PEP.
Why are we going round in circles again?
Bob - N0DGN
------------------------------
Message: 3
Date: Tue, 24 Jan 2012 09:09:30 -0600
From: WB5OXQ at grandecom.net
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
To: Discussion of AM Radio in the Amateur Service
<amradio at mailman.qth.net>
Message-ID: <20120124090930.17660mfi4ai2uwfe at webmail.grandecom.net>
Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
format="flowed"
I had a 3-500 pair amp and it did not do 375 carrier without the
plates getting very hot even with lots of air. My current amp with 4
572b tubes does better on am but the power supply transformer hums
pretty loudly on voice peaks but does not seem to overheat.
Quoting Bernie Doran <qedconsultants at embarqmail.com>:
> nowhere does it say a 375W carrier
> ----- Original Message -----
> From: "Warren Elly" <w1gud4 at gmail.com>
> To: "Discussion of AM Radio in the Amateur Service"
> <amradio at mailman.qth.net>
> Sent: Tuesday, January 24, 2012 8:45 AM
> Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
>
>
>> Me thinks the gentleman needs something less than a dx-100...
>> You're not going to see much difference between a barefoot 100 and 375
>> watt carrier allowed by FCC
>>
>> 73, Warren
>> W1GUD
>>
>> On Jan 23, 2012, at 11:07 PM, Rick Poole wrote:
>>
>>>
>>> Looking for a good design for a legal limit amplifier for my DX-100
>>> (looks like I'll be homebrewing it).
>>>
>>> I've pretty much narrowed down the choice to a linear amp capable of
>>> 375 watts carrier output or 1500 watts PEP output at 100 percent
>>> modulation, vs a Class C amp with high level modulator driven from
>>> the DX-100's audio output.
>>> .
>>> I was thinking about a pair of 3-500's in Class B push-pull.
>>>
>>> Everybody keeps telling me that I'll get maybe 30 percent efficiency
>>> at best during dead carrier times. At 100 percent modulation and
>>> class B I should get 60 percent at worst. I really, Really don't
>>> understand that at all... seems like if I can get 60 percent at 1500
>>> watts PEP I should be able to get 60 percent at 375 watts dead
>>> carrier. But, I'm accepting it for the moment, and anyway, I digress...
>>>
>>> 375 watts unmodulated carrier output at 30 percent efficiency means
>>> 1250 watts input, or 875 watts dissipation or 437.5 watts per tube.
>>>
>>> 1500 watts PEP at 60 percent efficiency means 2500 watts peak input
>>> or 1000 watts dissipation, 500 watts per tube peak.
>>>
>>> So it seems to me like a pair of 3-500's should be able to cut it,
>>> especially if I give them plenty of air.
>>>
>>> I want to stick with glass tubes because I'm planning to put them
>>> behind a window so I can "feel the glow" during operation. Anyway,
>>> it'll impress the living crap out of the XYL :-). Hence, the
>>> ceramics have been ruled out for now.
>>>
>>> So, a few questions...
>>>
>>> 1. Will a pair of 3-500's in Class B push pull really handle the
>>> load with no problem, assuming adequate air?
>>>
>>> 2. This may be a rookie question, but google hasn't given me a clear
>>> answer... is there such a thing as class B push pull grounded grid?
>>>
>>> 3. There are some commercial class AB pair-of-3-500 amps (e.g.
>>> SB-220, TL-922) that are limited in what they can do by the power
>>> supply. So, I plan to make sure the power supply can easily handle
>>> the load. Any suggestions on the best places to get power
>>> transformers that are up to the job? So far I haven't found one
>>> under about $600.
>>>
>>> 4. I'm actually not that certain that I'm competent to design
>>> something like this from scratch. Any plans available on the net
>>> that I can use for a starting point?
>>>
>>> 5. Current tentative plans call for the power supply to be separate
>>> from the RF deck, and they may be separated by as much as 6 feet
>>> (there are compelling reasons for that that go way beyond the scope
>>> of this post). Is that practical? Where is a good source for high
>>> voltage (3500 VDC) cable and connectors?
>>>
>>> 6. As noted above, I plan to put the tubes behind a window so I can
>>> see them. Is there a glass that can be used for the window that will
>>> maintain shielding?
>>>
>>> Thanks...
>>>
>>> Rick WA1RKT
>>> Londonderry, NH
>>> Catch me on 14.300 MHz Intercon / MMSN most days
>>>
>>> ______________________________________________________________
>>> 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
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>> 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
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>
------------------------------
Message: 4
Date: Tue, 24 Jan 2012 09:25:22 -0500
From: Rick Poole <wa1rkt at arrl.net>
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
To: amradio at mailman.qth.net
Message-ID: <6.2.5.6.2.20120124085408.04806360 at rkt-tech.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed
Just a few thoughts to start the day...
1. I know that the difference between a DX-100 and the legal limit
is about 1 "S" unit. But, an "S" unit is an "S" unit. I have seen
plenty of times, although on SSB, where an "S" unit made the
difference between, say, phone-patch quality (for running traffic for
boats at sea) and not. Not that I'm going to be running phone
patches on AM, just using that as an example.
2. QSL on the part about using the best antenna... plan is to do
that and THEN add power. Current antennas are a 160-meter inverted V
at 60 feet with open-wire feeders, and a half wave coax-fed
off-center-fed dipole at 35 feet. They both work pretty well, but
the plan is to get both of those up higher, in the spring.
3. I considered using a commercial pair-of-3-500's amp like the
SB-220 or TL-922, but the ones I've looked at appear to be too
power-supply limited to get true legal limit especially on AM. I
have a TL-922A and get 1200 watts PEP out of it at best, on
SSB. Yes, I know that there is no measurable difference between 1200
and 1500 but per (1) above, if I can't get at least X4 amplification
(1 "S" unit) then it's not worth doing. Anyway, nothing I can buy
for less than around a thousand bucks is likely to be very happy
running on AM for very long. Now, a Chippewa... :-)
4. I don't "have to ask for a schematic to build one of the simplest
pieces of ham gear" but it has been more than 40 years since the last
time I home-brewed a high-power amp (or much of anything else, for
that matter), so if an article was available on the web that
describes a reasonable design AND perhaps offered suggestions on
where to get the necessary parts, that would be very helpful.
5. I'm acutely aware of the dangers of high voltage. I'm currently
restoring a 30L-1 including rebuilding its power supply, and I'm
comfortable that I know what I'm doing and will still be here when it's done.
Rick WA1RKT
------------------------------
Message: 5
Date: Tue, 24 Jan 2012 10:29:09 -0500
From: Rick Poole <wa1rkt at arrl.net>
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
To: amradio at mailman.qth.net
Message-ID: <6.2.5.6.2.20120124102305.0480f868 at rkt-tech.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 10:09 AM 1/24/2012, WB5OXQ at grandecom.net wrote:
>>>>>
>I had a 3-500 pair amp and it did not do 375 carrier without the
>plates getting very hot even with lots of air. My current amp with 4
>572b tubes does better on am but the power supply transformer hums
>pretty loudly on voice peaks but does not seem to overheat.
<<<<<
Good morning, James.
How's that even possible?
572B's are rated at from 120 to 160 watts dissipation each, depending
on whom you want to believe. Times 4 = 640 watts absolute maximum
and in most cases, less than 500. 2x3-500 = nominally 1000 watts
dissipation. So how is it possible to drive 4x572B harder than 2x3-500?
Rick WA1RKT
------------------------------
Message: 6
Date: Tue, 24 Jan 2012 09:29:16 -0600
From: "Ross Stenberg" <k9cox at charter.net>
Subject: Re: [AMRadio] Legal limit
To: "AM Radio List" <amradio at mailman.qth.net>
Message-ID: <779133E2079F46199B876992F0F866E4 at RossFlexSDR>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
It is 6 of one and half a dozen of the other :^)
>>>I seems that this is one of those perpetual discussions.
The ONLY specified number is the 1500W PEP.
Don Chester, and numerous others have demonstrated the mathematics
behind it all.
The reality is when the math is looked at, a carrier of 375W, modulated
at 100%, gives us the SPECIFIED end result of 1500W PEP.
If you have a carrier of 200W, and modulate it at 100%, you get LESS
than 1500W PEP.
Why are we going round in circles again?
------------------------------
Message: 7
Date: Tue, 24 Jan 2012 09:31:37 -0600
From: "Ross Stenberg" <k9cox at charter.net>
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
To: "Discussion of AM Radio in the Amateur Service"
<amradio at mailman.qth.net>
Message-ID: <024C2734D76B4076B2F809152BAF5AF2 at RossFlexSDR>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Oops
>>>Happy Tuesday--
Still raining out there? GLOOMY Here but dry so far. Gonna get colder
again.... geez.. make up your mind, Mr.Weather!!!!
------------------------------
Message: 8
Date: Tue, 24 Jan 2012 10:39:37 -0500
From: Warren Elly <w1gud4 at gmail.com>
Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
To: Discussion of AM Radio in the Amateur Service
<amradio at mailman.qth.net>
Message-ID: <6DFB6143-5AE7-4742-B8D7-D39CC1DF93FF at gmail.com>
Content-Type: text/plain; charset=us-ascii
It's the math Bernie
1500 pep at 100 percent is 375 watts
And no it doesn't say 375 it says 1500 pep
On Jan 24, 2012, at 9:47 AM, "Bernie Doran" <qedconsultants at embarqmail.com> wrote:
> nowhere does it say a 375W carrier
> ----- Original Message -----
> From: "Warren Elly" <w1gud4 at gmail.com>
> To: "Discussion of AM Radio in the Amateur Service"
> <amradio at mailman.qth.net>
> Sent: Tuesday, January 24, 2012 8:45 AM
> Subject: Re: [AMRadio] Ongoing Quest: Legal Limit AM Amp
>
>
>> Me thinks the gentleman needs something less than a dx-100...
>> You're not going to see much difference between a barefoot 100 and 375
>> watt carrier allowed by FCC
>>
>> 73, Warren
>> W1GUD
>>
>> On Jan 23, 2012, at 11:07 PM, Rick Poole wrote:
>>
>>>
>>> Looking for a good design for a legal limit amplifier for my DX-100
>>> (looks like I'll be homebrewing it).
>>>
>>> I've pretty much narrowed down the choice to a linear amp capable of
>>> 375 watts carrier output or 1500 watts PEP output at 100 percent
>>> modulation, vs a Class C amp with high level modulator driven from
>>> the DX-100's audio output.
>>> .
>>> I was thinking about a pair of 3-500's in Class B push-pull.
>>>
>>> Everybody keeps telling me that I'll get maybe 30 percent efficiency
>>> at best during dead carrier times. At 100 percent modulation and
>>> class B I should get 60 percent at worst. I really, Really don't
>>> understand that at all... seems like if I can get 60 percent at 1500
>>> watts PEP I should be able to get 60 percent at 375 watts dead
>>> carrier. But, I'm accepting it for the moment, and anyway, I digress...
>>>
>>> 375 watts unmodulated carrier output at 30 percent efficiency means
>>> 1250 watts input, or 875 watts dissipation or 437.5 watts per tube.
>>>
>>> 1500 watts PEP at 60 percent efficiency means 2500 watts peak input
>>> or 1000 watts dissipation, 500 watts per tube peak.
>>>
>>> So it seems to me like a pair of 3-500's should be able to cut it,
>>> especially if I give them plenty of air.
>>>
>>> I want to stick with glass tubes because I'm planning to put them
>>> behind a window so I can "feel the glow" during operation. Anyway,
>>> it'll impress the living crap out of the XYL :-). Hence, the
>>> ceramics have been ruled out for now.
>>>
>>> So, a few questions...
>>>
>>> 1. Will a pair of 3-500's in Class B push pull really handle the
>>> load with no problem, assuming adequate air?
>>>
>>> 2. This may be a rookie question, but google hasn't given me a clear
>>> answer... is there such a thing as class B push pull grounded grid?
>>>
>>> 3. There are some commercial class AB pair-of-3-500 amps (e.g.
>>> SB-220, TL-922) that are limited in what they can do by the power
>>> supply. So, I plan to make sure the power supply can easily handle
>>> the load. Any suggestions on the best places to get power
>>> transformers that are up to the job? So far I haven't found one
>>> under about $600.
>>>
>>> 4. I'm actually not that certain that I'm competent to design
>>> something like this from scratch. Any plans available on the net
>>> that I can use for a starting point?
>>>
>>> 5. Current tentative plans call for the power supply to be separate
>>> from the RF deck, and they may be separated by as much as 6 feet
>>> (there are compelling reasons for that that go way beyond the scope
>>> of this post). Is that practical? Where is a good source for high
>>> voltage (3500 VDC) cable and connectors?
>>>
>>> 6. As noted above, I plan to put the tubes behind a window so I can
>>> see them. Is there a glass that can be used for the window that will
>>> maintain shielding?
>>>
>>> Thanks...
>>>
>>> Rick WA1RKT
>>> Londonderry, NH
>>> Catch me on 14.300 MHz Intercon / MMSN most days
>>>
>>> ______________________________________________________________
>>> 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
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>> 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
>
> ______________________________________________________________
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------------------------------
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