[AMRadio] AM Transmitter Advice??


George KB2Z Thermionic_Emission at earthlink.net
Fri Feb 17 08:00:59 EST 2006


Thats poppycock. Everyone knows if you reduce the output filtering, and 
use an all band, coax fed, off-center Windom it will be possible to 
transmit multi-band. If you have a 5 bands off the radiator that would, 
effectively, give you 150% efficiency. 5 bands x 30% =  150%. Think of 
the possibilities. Now who of then experts would dare say, "Theres no 
free lunch". The numbers dont lie.

Brian Carling wrote:
> I bet you a BC610 will out-peg a DX100 any day!
> Don't care what the numbers say...
>
> Grin!
>
> That 12AX7 linear amplifier sounds like more of a FUN project 
> than a useful station accessory! Just WAIT until the experts 
> start telling you it can't be done, you will only get 30% 
> efficiency and all that jazz! LOL.
>
> 73 de AF4K, Bry
>
> On 17 Feb 2006 at 4:29, Jim Candela wrote:
>
>   
>> Hi All,
>>
>>    I recently had a conversation with a ham in San
>> Antonio (forgot his call), and he told me that he
>> built a unique linear amplifier for his central
>> electronics 10a, and for tubes he chose 3 type 12AX7
>> in parallel grounded grid. He said he could run 30
>> watts input (300v @ 100ma) with no problems, and about
>> 20 watts out. I find it odd though that a 10a can do
>> 10 watts with a single 6AG7, and 20 watts is only a
>> 3db boost. 
>>
>> To my way of thinking, a linear amp needs to boost
>> your power at least 6 db (~1 'S' unit) to be worth the
>> trouble. For us AM'ers, going from 100 watts to 375
>> watts carrier does not meet the 6 db boost criteria,
>> and that explains why a good antenna on a DX-100 is
>> better than a average antenna on a Globe King 500.
>>
>> Still, as I once posted last year, a dual 304TL
>> grounded grid linear seems to fit the bill as a 6 db
>> 'brick' capable of 400 watts AM carrier output with
>> 100 watts AM input, or said another way it takes 400
>> watts PEP and boosts it to 1600 watts PEP. There was
>> an old W6SAI construction project about this (single
>> 304tl GG amp), and I recall that the setup in class C
>> could run 1 kw dc input with over 1 kw rf output
>> because of the low gain, and massive amount of
>> feedthrough power from the exciter that finds it's way
>> to the output. This was a way around the FCC power
>> rules of the day.
>>
>> Regards,
>> Jim
>> WD5JKO
>>
>> --- Donald Chester <k4kyv at hotmail.com> wrote:
>>
>>     
>>>> Assuming one is going to build a linear, and so
>>>>         
>>> putting aside other issues
>>>       
>>>> such as linear vs plate modulation, why do you
>>>>         
>>> think it makes a difference
>>>       
>>>> what tube is used? Are you referring to running a
>>>>         
>>> linear at greater than
>>>       
>>>> legal limit?.
>>>>         
>>> Well, go ahead and try building a legal limit linear
>>> that runs a pair of 
>>> 807's in the final.
>>>
>>>
>>>       
>> _______________________________________________________________
>>     
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>>>
>>>
>>>
>>>       
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>
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