RE: [linrad] users_extra

[Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxx>]

Hi Bob,


> Can you set the Delta 44 scale as you can on the Windows Driver?
Yes, you can switch to another console with Alt F1,F2... and run
ossmix. Then you can switch back to Linrad with Alt and the appropriate
function key. (I have a script to set gain with ossmix)

> If so, you might try changing it from +4 dBu scale to the -10dBv
> scale on the input.  I find that it is impossible for me to yse
> the +4dBu scale on output ever.
> 
> If this can be done on the fly, then you would have at least one
> easy setting to change between strong signals (+4dBu) to weak signal
> (-10dBv).
The WSE converters are designed to run with Delta44 in "+4dB" mode.
Increasing the A/D gain is not improving much. The RXHFA unit has
a switchable attenuator at the antenna input and a RF stage. You
can set the sensitivity in 5 dB steps over a 25 dB range on the fly
from within Linrad.

The idea is to do the same on 144, but the attenuator and/or switchable
RF amplifier have to be external to the RX144.

The switchable attenuator/RF amplifier should not be required under
normal circumstances. Only if you have a station within the passband 
that is more than about 145 dB/Hz above the noise floor you will
need it. If your tower-mounted 144MHz preamplifier lifts the noise 
floor by 25 dB (to squeeze out the last 0.01 dB of system noise figure), 
the dynamic range will still be good enough in most locations, but 
with such high preamp gain a switchable attenuator would be a sensible 
precaution. 

73

Leif / SM5BSZ



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