At 11:27 AM 5/10/2003 -0400, you wrote:
W8JI said:
>If you don't tightly "beam" your receiver through very strong signals to get
>to the DX (and live in a location with very low noise) you probably don't
>need anything beyond a normal "cleaned up" FT1000 or any other reasonably
>good radio. A regular good properly working radio would put most systems to
>the point where the other guy's transmitters are the problem even when
>living in a congested RF area like the USA or Europe.
VK6VZ replied:
Hi Tom
Agree with you totally that the place where a topbander needs to place most
of their effort in improving their antenna system - which is what I do.
Also agree with your comments about the FT1000 or any reasonably good radio.
What interests me particularly about devices like the KK7P dsp (or the
SDR-1000) is their ability to provide a competitive receiver/transceiver
that is very cheap and compact.
On the secondhand market, an FT1000 is now worth pretty much what it
originally cost and a new FT1000MP costs several thousand dollars. Earlier
this year, a friend modified a junker R-4C for me with cheap Mini-Circuits
mixers, MAV-11 ics and a Sherwood 600Hz 1st filter and for a few hundred
dollars outlay (including the actual R4C) I now have a radio that seems
superior to the MP for 160 CW.
In this kind of scenario, to me, lays the fun (and challenge) of amateur
radio.
>W8JI:
>Those of us without large receiving arrays in lower amateur population
>regions could almost get away with a Knight-Kit Star Roamer technology
>receiver with a Time-Wave DSP and do 99.9% of what the best possible system
>would do.
VK6VZ:
Absolutely. That is why an I am interested in a direct conversion phasing
transceiver for 160m only with a really good high dynamic range mixer, dsp
back end and a PA/linear made of $3 switch-mode PSU FETs and very light to
take on DXpeditions. This is fun to make, a challenge, costs a couple of
hundred dollars and can replace an FT1000 and an Alpa linear (or similar) -
say $10,000 worth - for a topband-only station (with a decent antenna, of
course).
In this kind of scenario, for me, lays the fun (and challenge) of amateur
radio.
>W8JI:
>By the way, none of the data or measurements I have been able to find
>indicate these software-based radios are as good overall as what we have
>now. 40dB TOI is absolutely meaningless unless we know a whole lot more. An
>absolute piece of receiving-junk could have 40dB TOI.
>
>As for BW. Ringing is a direct function of bandwidth, the shape of the
>bandwidth slope, and varying group delay times through the system as
>frequency is changed. As W4ZV pointed out, we can't possibly use 20Hz or
>even 100Hz BW with "brick wall" skirts for normal CW. The filter MUST pass
>all sidebands generated by the rise and fall time, or it extends the rise
>and fall!!!
>
>We have to pass the significant sidebands, or the signal "rings". The
>spacing of the sidebands is dictated by the rise time and fall time. This
>would also apply to any noise pulses going through the filter. Narrower
>selectivity lengthens the duration of noise pulses...even if it is a
>software filter....and makes noise "ring". The more it rings, the more noise
>sounds like CW.
VK6VZ:
I recently listened to my friend's SDR-1000 alongside an FT1000MP and to my
shock (and disbelief!) on CW, found myself preferring the SDR-1000. The
25 - 50Hz filtering didn't ring to my ears on 15 to 20wpm CW - as others on
this reflector have also experienced. I believe the evidence of my ears,
as this is all that really matter when I operate... Guess the performance
of the SDR-1000 filtering is one of those things you have to hear to believe.
Once again, in this kind of scenario, to me, lays the fun (and challenge)
of amateur radio.
It is a game of heart as well as head (for me anyway).
Vy 73
Steve, VK6VZ
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