So both numbers will be bogus. S meters do not give accurate numbers in DB.
You will only have better than worse than results with no standard as a
reference.
-----Original Message-----
From: m.ford [mailto:k1ern@direcway.com]
Sent: Thursday, September 22, 2005 1:43 PM
To: R.Measures
Cc: amps@contesting.com
Subject: Re: [Amps] 4CX1500B
Ok, so we are using the same meter for both measurements
and at the same level of meter deflection. The actual measurement
is taken from the step attennuator therefore the quality of the S meter
has no bearing on the measurement unless it is sticking.
Mike k1ern
----- Original Message -----
From: "R.Measures" <r@somis.org>
To: "GGLL" <nagato@arnet.com.ar>
Cc: "AMPS" <amps@contesting.com>
Sent: Thursday, September 22, 2005 1:23 PM
Subject: Re: [Amps] 4CX1500B
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..
>>> _______________________________________________
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