jimg wrote:

i don't thjink i've ever heard anything goofier. you cannot improve on
the s/s at the receiver input without altering the antenna. given a
reasonable impedance match from the receiver to the antenna, that's
it. and it's not hopeless, it's just what it is. if there were no
atmosphereic noise or propogation effects, swl would be kind boring.

as far as your receiver, most receivers noise floors are so far below
the antenna s/n that there is no improvemnt in your dxing capability
there...and why playing with your antenna can make such a diff.

btw, there are ways to improve the performance dramatically, but
wideband amps are not the answer..whereas very narrow band rf amps
are...especially if they're LN2 cooled along with the antenna
pre-amp...but then you don't have enough money for this scheme.

now the kiwa design like other LNA's is very basic and uses a shunt
feebback two transistor approach. other use cascoded mos devices
(called dual gate by non-engineers)..all are very low noise designs
and give moderate gain/ in the case of kiwa, you get 10dB gain and a
reasonable NF (noise figure) (p.s. your cell phone gets better) ...
but 10dB is practically nothing (you got a 10dB rf attenuator on your
rcvr?) and usually will not change an overall sinpo from 2 to 3.

20dB is better, but if noise at the antenna dominates, the snr remains
the same.

having an rf lab with about $2M of equip to play with, i built a nice
little preamp with built in programmable rlc bandpass filtering....and
even then there is little appreciable improvement (on an old r1000) on
"real" sigs buried in noise...

some mornings though, when the background noise is low, the preamp
boosts weak sigs to a more audible level. non-linear adaptive LMS
noise cancellation does the rest...

if you dont have an rf front end worth a damn, it might help...and a
bcb hp filter might too....but in general, you paid enuf money
for a more than adequate rf front end...the rest is the sunspot cycle,
your propogation conditions, your patience and tenacity...


jimg phdee


I don't think I've *ever* connected an antenna to any receiver without
hearing an increase in noise. Is the goal of improving the S/N ratio
really that hopeless? I've heard great things about the Kiwa
preamp....it that all just hot air or does it really live up to its
claims? Are you guys speaking from experience with the Kiwa unit?

Steve

jimg
Oregon
USA