[Premium-Rx] Clean LOs

[Carcia, Francis A HS]

I use a homebrew combiner with a 1/2 inch core that has good isolation.
I also use 6 dB pads on each port. I find there is a problem trusting
numbers
above plus 25 if the generator power gets to close to zero dBM out from the
generators. My combiner with pads on each port has a loss close to 20 dB 
So I'm pushing it. I suppose a couple good buffer amplifiers would help
isolate the two generators. I also don't use the locking function. fc

-----Original Message-----
From: Clemens Paul [mailto:cpaul at gmx.net]
Sent: Saturday, February 12, 2005 5:09 AM
To: Brian D. Comer
Cc: premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] Clean LOs


Hi,

The HP8640B is extremely sensitive to variations in load impedance
also with respect to intermodulation.
Reflected signals up to 60 dB down cause internal intermodulation.
Therefore it's not possible to measure receiver IP3's of more than say
+25dBm
even with the best combiners (tunable, with ~60dB return loss) with a
pair of HP8640B.

73
Clemens
DL4RAJ

 
> The 8640 has fairly low phase noise but is not the best especially if
> the load impedance is varied and the output division ratio is not very
> large.
> 
> 73 Brian
> 
> KF6C/G3ZVC


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