[hpsdr] hOw AbOuT a PiNG?

[Gerd Loch]

Ahti and Marco,

thanks for the info.
Up to now I do not know anything about TINA software.
I will try to find information on it.

I mainly wondered if you are using buffers between the switches and the
OPA1632.

I also have some general questions on the QSD and hope to get your help:

1. which criterias lead to the choice of the sampling capacitors (here 5n,
with SDR1000 15n ...) or what happens if you use a much smaller and a much
higher value?

2. which influence has the timing of the switching pulses (overlap, gap,
delay ...)


73 Gerd, DJ8AY




-----Original Message-----
From: Ahti Aintila [mailto:oh2rz.sdr at gmail.com] 
Sent: Tuesday, April 17, 2007 2:34 PM
To: g.loch at nt-electronics.de; Marco IK1ODO
Cc: hpsdr at hpsdr.org
Subject: Re: [hpsdr] hOw AbOuT a PiNG?


On 17/04/07, Gerd Loch <g.loch at nt-electronics.de> wrote:
> ***** High Performance Software Defined Radio Discussion List ***** in 
> relation to which schematic are the results of the QSD? 73 Gerd, DJ8AY

Gerd,
I have only the TINA simulation diagram (small enough for an attachment), if
you mean the excellent measurement results of Marco,
IK1ODO:
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
--
If you have the TINA software installed, I can send you the TSC-file.

Marco has the original circuit diagram, but he is still working with some
impedance matching details of that, so better wait for the
final(?) results from him.

73, Ahti OH2RZ

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