With 0db attenuation, take the S meter reading at the adjacent
frequency, tune to the fundamental frequency, add attenuation as needed
to give the same S-meter reading as before. The # of db of attenuation
is how many db down the total IMD is.
On Sep 22, 2005, at 7:38 AM, GGLL wrote:
> Hello Rich, have my best wishes for you and family to be ok., I (once
> again)
> have a question for you, please see below:
>
> R.Measures escribió:
>> On Sep 21, 2005, at 3:28 PM, robert briggs wrote:
>>
>>
>>> I have received several query's about the Super Cathode Drive method
>>> on my 4CX250 B amplifiers.
>>> The amplifier's take around 100 watts of drive power for 600 watts
>>> output.
>>> When the drive input is correctly matched the Grid ("screen" )
>>> current
>>> is 1 to 3 Ma with the amplifier loaded.Anode voltage 2500 vdc.
>>> Idle current for a pair of tubes is 25 to 30 Ma.
>>> According to Orr in his note's "QST July 1967 IMD 3rd order would be
>>> -46 db 5th order
>>> 49 db.I have no measuring equipment to confirm this.
>>
>>
>> The main tool needed to measure total IMD is a second SSB receiver --
>> preferably one with a double-filter -- tuned c. 4KHz above or below
>> the
>> signal being measured.
>
> Rich, can you briefly describe me how can I do that test?. What am I
> looking
> for at the second receiver?.
>
> Thanks in advance
>
> Best regards
> Guillermo - LU8EYW.
>>
>>
>>> The point I am trying to establish is whether this setup would be
>>> applicable to the 4CX1500B.
>>
>>
>> The 4cx1500B already has low IMD in grid-driven config.
>>
>>
>>> Bob VK3ZL..
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>
>>
>> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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