Re: K3 vs HPSDR Mercury
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G’day I have been using an Elecraft
K3 for about a month now, which is the best performing superhetrodyne/analogue
transceiver (with a great DSP back-end) that I have ever used. Once I got
the filtering and DSP adjusted right, in terms of pulling weak signals out of
noise it was clearly better than my previous FT-1000. I also have a working HPSDR
Mercury digital down conversion (DDC) SDR receiver (the Mercury receiver board
plus the Ozy communications interface) which use with the PowerSDR
software. For those not familiar with SDRs, the DDC type effectively convert
radio signals from analog to digital at the antenna socket, using an analog to
digital converter. Mercury has a When it comes to pulling
weak signals out of noise, on the basis of A/B testing that I’ve done, weak
signals almost lost in noise are easier to understand and less tiring to listen
to (more of the latter in a minute) on Mercury than on the K3. I am not an engineer, but a scientific
journalist by profession and a CW and contest operator with some 37 years ‘on
the clock’ as a radio amateur. I have been using SDRs for about three
years (and am the co-author of the SDR column in the Radio Society of Great
Britain’s RadCom with my friend Phil, VK6APH who is an engineer and one
of the main designers of the HPSDR). I clearly have a personal interest in SDR,
but until I started using them was extremely skeptical about their performance. My understanding why the
HPSDR sounds better to me than the K3 (and others who have witnessed the comparative
tests) relates to the crystal filtering that the latter – and other
analogue HF receivers – use. As many on this reflector
will know, when noise pulses/spikes pass through a crystal filter, the phase
response of the filter changes, depending on the noise frequency. However,
when noise pulses/spikes pass through an ADC with a linear response - such as
the LTC2208 that Mercury uses - the phase response stays the same, because the
ADC treats them in a linear manner. What happens in practice is
that on the DDC SDR any ‘noise’ actually sounds mellow and
easy-on-the-ear (!), in a manner that has to be heard to be believed. In
the case of an analogue radio like the K3, it seems that even one stage of
crystal filtering is enough to cause a phase response to noise that eventually
irritates/tires the user (certainly in my case) and makes them want to switch
the radio off. I love using the K3 and find
it an absolutely brilliant radio, but am looking forward to putting together a
HPSDR transceiver to take advantage of the way a DDC SDR receiver deals with
noise. Whether top ten contesters find DDC SDRs to their taste will be
interesting to see, but as a 160m CW DXer with over 220 countries confirmed, as
far as I am concerned they are the way ahead. Incidentally, I think both
the Flex SDR-1000 and FLEX-5000 are QSD-type SDRs, rather than DDCs. Vy 73 Steve Ireland, VK6VZ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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G'Day, Steve.
Am awaiting delivery of my first K3, and am enjoying much and learning much, from these K3 Reflector posts. Fascinating insights here. One of the more recent posts (see below) caught my eye, concerning noise, and the Mercury comparisons. If you're ever so inclined to share the K3 settings that work best for you on CW -- say, the settings used on a noisey evening on the low end of a crowded 40-Meter CW band -- that would be helpful to me as a starting point. Somewhat related to this, I tried several times to get my current cw transmitter to get through the big boys on the low end of 40, to QSO with VK6VZ, but to no avail !! You had one heck of a pile up there a few evenings (mornings) ago. The 100-watts and the long-wire here just doesn't do it for Australia, unless the freq is absolutely clear. 73, thanks for your postings, and look forward to reading more. //Mark, w2or (at) arrl.net. I have been using an Elecraft K3 for about a month now, which is the best performing superhetrodyne/analogue transceiver (with a great DSP back-end) that I have ever used. Once I got the filtering and DSP adjusted right, in terms of pulling weak signals out of noise it was clearly better than my previous FT-1000. I also have a working HPSDR Mercury digital down conversion (DDC) SDR receiver (the Mercury receiver board plus the Ozy communications interface) which use with the PowerSDR software. For those not familiar with SDRs, the DDC type effectively convert radio signals from analog to digital at the antenna socket, using an analog to digital converter . . . . |
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In reply to this post by Steve Ireland
G'Day, Steve.
Am awaiting delivery of a K3, but am learning much from postings here. A more recent post (see below) caught my eye, re noise, and the Mercury comparison. If you're ever so inclined to share the K3 settings that work best for you on CW, noisey evening on the low end of a crowded 40-Meter CW band -- that would be helpful to me as a starting point for finding my own settings. Thanks. Somewhat related to this, have tried several times to QSO you on cw, on 40-m, using existing equipment, but the big boys there predominate. You had one heck of a pile up there several dags ago. If you're ever so inclined, shoot me a note (off the list) as to when you'll be back there again. 73. Thanks for your postings. Look forward to reading more. //Mark, w2or (at) arrl.net. Old Post: I have been using an Elecraft K3 for about a month now, which is the best performing superhetrodyne/analogue transceiver (with a great DSP back-end) that I have ever used. Once I got the filtering and DSP adjusted right, in terms of pulling weak signals out of noise it was clearly better than my previous FT-1000. I also have a working HPSDR Mercury digital down conversion (DDC) SDR receiver (the Mercury receiver board plus the Ozy communications interface) which use with the PowerSDR software. For those not familiar with SDRs, the DDC type effectively convert radio signals from analog to digital at the antenna socket, using an analog to digital converter . . . . |
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