[Amps] Operational Input Impedance

[Joe Subich, W4TV]

microHAM SMORF and N8LP LP-100A will provide calibrated R+/-jX for
this application. SMORF will allow "calibrating out" a known distance
of standard cables.  Either unit has a remote sensor unit that can
be connected to the input jack of the amplifier under test with a
simple double female connector (essentially zero length line).

73,

    ... Joe, W4TV


On 12/23/2017 3:10 PM, John Lyles wrote:
> I have done it with these methods: One is to find or build an operating 
> impedance bridge. A Delta Electronics OIB2 is the module that was made 
> for HF range up to 1 kW. It will read inline impedance under power.
> Another is to use an external dual directional coupler, rated for few 
> hundred watts and down to HF range. Werlatone makes such a device. You 
> might find something from Narda or Microlab/FXR surplus, not sure they 
> will go that low. Then calibrate it into the test using a vector network 
> analyzer. It has to have ext A/B/R inputs for this to work.
> There are other ways, these are the most direct, and unfortunately 
> costly ways. But they will give you the exact input complex Z of an 
> amplifier under power.
> 73
> John
> K5PRO
> 
> 
>> Date: Fri, 22 Dec 2017 14:11:13 -0700
>> From: Steve London <n2icarrl at gmail.com>
>> To: amps at contesting.com
>> Subject: [Amps] Operational Input Impedance
> 
>>
>> So, this begs the question: What is the actual input impedance during
>> operation ? How would one go about measuring it with something like an
>> antenna analyzer or VNA ?
> 
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