Re: IQ balance problem with receiver module
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Hi Erik
It wasn't my intention at the time, for the QRP Labs receiver module to be used as an SDR front-end in a system requiring flat 192kHz bandwidth.?
The 600:600 isolation transformers are useful in some instances to reduce ground loop or hum problems. If you want flat wideband gain you can just leave them out (bypass them).
FYI during the development phase, I did carefully evaluate samples of the 600:600 transformers, connected to different load impedances, and measured the responses you can see in the attached graph. As you can see it is quite flat over the range 100Hz to 10kHz, regardless of the load impedance; but beyond 10kHz the available bandwidth becomes more and more sensitive to having exactly the right load impedance. Logically it would also become more sensitive to normal tolerance differences between the transformer used for the I and Q channel, which would make it harder to obtain good I-Q balance across a very wide bandwidth.?
73 Hans G0UPL
On Sun, Apr 29, 2018 at 10:52 PM, <erik@...> wrote: Clear, thanks. Will avoid using the transformers.
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Erik@Home
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