RE: [linrad] RE: Hardware

[leif.asbrink@xxxxxxxxxxxxxxxx>]

Hi All,

Jim WB9UWA wrote:

> I would suggest to you that the demands on dynamic range 
> are very stiff for Linrad. 
I do not like to see it expressed like this.
The dynamic range demands depend on your RF environment an
on what you want to achieve.

Look at the Jan/Feb issue of QEX.

Linrad as such does not have any demands at all. It will
accept any digital data stream that your Linux sound system
is capable of supplying from your hardware.

> It would be real easy to build something that works poorly.
Hmmm, It IS really easy to build something with excellent
performance in a quiet location. You just need a low power
(15 milliwatt) CW transmitter for 144MHz to feed into the
LO port of two TUF-1 mixers in parallel. Connect the IF ports 
to channels 1 and 2 of the souncard. Connect a 0.25wl cable
between the two RF ports and feed the signal from your preamp
to one of the RF ports. Nothing else! It does really work and 
you will get full EME sensitivity if the preamplifier has
sufficient gain. The problem is (of course) that the dynamic
range is poor.

BUT if you do not need the dynamic range, anything better 
is a waste of money!

> If you can imagine a ham neighbor only 
> a few miles away keying a clean carrier INSIDE your SSB 
> passband and then
> trying to copy a weak CW signal inside the same SSB passband at 
> the same time, then you 
> get a very general idea of what is needed for a 96 KHZ passband 
> receiver.....
Exactly:)

> Then think of the Time Machine as similar to using a low end CB 
> in a Large active city.
I think the Time Machine is better than that, but still it
is probably not adequate in really demanding situations.

73

Leif / SM5BSZ



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