[hpsdr] hOw AbOuT a PiNG?

[Marco IK1ODO -2]

At 04.53 16/04/2007, Ahti wrote:


> > Whatever happened to the ISD Op-Amp thread?
> >
>Eric,
>Thanks for your response. Not much has happened with the ISD. So far
>the impedance match is good, power consumption and component count are
>low but that came at the cost of slightly higher noise figure.
>Especially, I could not reach the excellent dynamic range reported by
>Marco, IK1ODO:
>http://www.spin-it.com/sdr/IK1ODO_SDR1.html
>
>73, Ahti OH2RZ

Hi all,

I'm still working on it, with the aim of improving the behaviour at 50 MHz.
So far I have sensitivities (noise floor in 2.4kHz BW) of around -123 
dBm (50MHz), -127dBm (28MHz), -130dBm (7MHz).
The two-tone dynamic range arrived at 108dB in 14 MHz (quite 
difficult to measure), and the 3rd order IP is +35dBm.

I recently modified the circuit to have 180° conduction angles on the 
switches, as suggested by Ahti. The improvement is small, but 
measurable; however, the input impedance matching is a little worse 
(after having changed all circuit values and rewound four different 
input transformers).

I received an E-MU 1616m just saturday, and will do some more work on 
in in next weeks. I would say that the IQSD is ok, the improvements 
will be marginal now; we need an LO to go with it. AD announced the 
AD9912 - 1 GHz 14 dds with spurious cancellation. Who will be the 
first to try it?

73 - Marco IK1ODO


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