To answer my own question. The dB reduction in gain that I observed was a voltage ratio. Phil's simulation show more on the order of 6 dB decrease in gain between the four switch and two switch QSD circuit. The two don't agree properly so something is wrong.
I will be repeating the measurement in a few days with a v5.0 and will post what I see.
73,
Tony KB9YIG
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----- Original Message -----
From: "Tony Parks" <raparks@...>
To: <softrock40@...>
Sent: Wednesday, October 26, 2005 2:56 PM
Subject: Re: [softrock40] QSD Models
Interesting graphs Phil. Your results are similar to what Phil, VK6APH, has
reported recently. My observations with a stock v4.0 SoftRock vs. a two
switch SoftRock showed a 3dB difference between the two units as indicated
by the dBm reading on the PowerSDR panadaptor. Not sure, but I think the dB
scale on the SDR is actually indicating signal power. If that is the case
then my observations and your simulation are not too different since 3dB
ratio in power is a 6dB ratio in voltage.
How are you establishing zero dB in your simulation?
Thanks and 73,
Tony KB9YIG
----- Original Message -----
From: "Phil Covington" <p.covington@...>
To: <softrock40@...>
Sent: Wednesday, October 26, 2005 1:04 PM
Subject: [softrock40] QSD Models
Hi all,
I've placed some results of simulation of a two switch and four switch
QSD circuit on my blog at:
Check it out if you are interested in the QSD circuits.
73 de Phil N8VB
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