QS1-R vs SDR-14 vs Perseus -- Direct Sampling HF Receivers

Tom Azlin N4ZPT n4zpt at cox.net
Sun Jan 24 14:42:41 CST 2010

Hi Mike,

Yes, interesting differences. Did you see

I looked at the Perseus at Dayton last year but in the end chose to buy
a QS1R as a building block for learning. And if the other boards do come
along then it may be a nice full receiver as you say. To complement my
HPSDR. In the meantime a nice back end especially if I can use my GPS
stabilized oscillator as an input to the QS1R and downconverters.

73, Tom n4zpt

On 1/24/2010 2:10 PM, Mike O'Dell wrote:
> thinking hard about how far i wish to put my foot
> into the SDR pot, I've been doing a lot of reading,
> trying to distinguish data from opinion from venom.
> i'm recording them here to elicit commentary from
> the knowledgeable chaps around the table.
> if one is willing to spend a grand on an SDR receiver,
> that puts one in the realm of the "direct sampling" receivers.
> after comparing these three at some length (reading a lot
> of extremely animated conversations, esp on the E-K3 list,
> of all places), the Perseus appears to have the edge if
> what you want is a full-up *receiver in a tin*. The SDR-14
> seems also to be "dedicated receiver" but a bit more
> bare-bones (or purist, depending on your religion).
> However, if one is looking for a receiver which can be the basis
> of a *platform*, then the QS1-R appears to have the edge
> as it was clearly designed as such, and new companion
> boards are coming along.
> It should be noted that the Mercury receiver card and the
> RX section of the Hermes one-board xceiver from the "OpenHPSDR"
> project are essentially identical to the QS-1R.
> As for sampling performance and BW (sans undersampling),
> the QS1-R samples at 125MS/s and goes to 55MHz (hello 6M!)
> the Perseus samples at 80MS/s and goes to 30MHz (limited by preselector)
> and the SDR-14 samples at 67MS/s and goes to 33MHz
> the QS1-R and the Perseus have a much
> newer A/D part than the SDR-14.
> That's one of the huge paradoxes in the
> electronics biz - the guy who starts 6 months
> after you has a big advantage because he usually
> has better parts to pick from. The cellular radio
> base station business is driving the evolution
> of digital RF hardware really hard. The LTE/WiMAX
> MIMO air interfaces assume massive digital
> processing.
> the other possible advantage the QS-1R and Perseus
> have over the SDR-14 is that all of the DDC
> processing (Quadrature NCO + Mixers + Digital Filters)
> is done in an FPGA while the SDR-14 uses
> a fine, off-the-shelf DDC from ADI. The QS-1R
> has a very large FPGA while the Perseus seems
> to have been cost-optimized (not a bad thing!).
> the net result, though, is that in line with
> being a platform, the QS-1R has lots of room for
> further expansion of the digital processing.
> (one option being explored is a true multi-channel
> receiver).
> In all 3 cases, the raw A/D samples
> are available, as are the I/Q signals from the
> DDC.
> so my take is that if one were to take the plunge
> for a "big bite" direct-sampling receiver intended
> to be the basis for AMRAD-style geekery-hackery, the
> Quicksilver QS-1R is the best of 3 quality alternatives.
> again, this is my digestion of the current state of things
> and the whole point of posting this is to have my
> understanding improved by facts known to others.
>     cheers,
>     -mo

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