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From: N1BUG <paul@n1bug.com>
Message-ID: <532aacaa-2bfd-24f9-6e9d-c008e467686d@n1bug.com>
Date: Sun, 24 Dec 2017 19:12:30 -0500
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Subject: Re: LF: TXing 2200m WSPR
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I had a thought.

I set the HP 3325B to 10V pk-pk, ran it through the scopematch into 
the dummy load. Scopematch showed exactly the expected voltage and 
indicated 50 ohms, no reactance.

Next I inserted the low pass filter between the scopematch and dummy 
load. There was a slight change indicating R very slightly lower 
than 50 ohms (amplitude of current just a tiny bit greater than 
voltage), voltage lagging current slightly. It wasn't off by much! 
This would seem to be closely in line with Andy's earlier 
calculation of 48.5 -j2.86... slightly lower R, slightly capacitive.

The LPF appears to be a bit better near 141 kHz but again, at 137 
kHz very little impedance transformation according to this test.

I then moved the LPF to the other side of the scopematch (sig gen > 
LPF > scopematch > load) and verified that I see very little 
(unmeasurable) loss through the filter.

Paul N1BUG


On 12/24/2017 06:16 PM, Andy Talbot wrote:
> Yes
> 
> Try anything and try to work out what is happening.  But first of 
> all, he needs to know what power being deliverfed into a 50 ohmsload 
> is seemingly higher than it 'can' be.    The Vdd^2/2/Rl cannot be 
> violated.
> If it appears to be so, then Rl or Vdd or the measurement  has to be 
> wrong.
> 
> I once had to go though a similar 
> try-everything-and-believe-nothing-until-tested process to work out 
> why my 700Watt 137kHz Tx appeared to be more than 100% efficient!
> It turned out my Bird 30dB 1kW attenuator only had 29.4dB 
> attenuation at DC.  And for a 1GHz jobbie, 137kHz is DC.