Topband: FT-8 question

W0MU Mike Fatchett w0mu at
Sat Dec 2 16:47:16 EST 2017

Give FT8 a try.  I worked my first EU the other night and then a few 
last night in the contest,  G, F, EA and CT9.  Not much Caribbean or 
Africa on.  I did copy a couple of JA's the other night while the 
antenna was at EU while I slept.

Remote is where many of us will be as we continue to fill up the world 
and cities with noisy electronics.


On 12/2/2017 10:07 AM, Jim Thomson wrote:
> Folks on FT-8 use a 2.5 khz  ssb wide RX  filter.    FT-8 is supposed to be good for 20 db  below the noise floor.
> I assume that means 20 db below the noise floor of the 2.5 khz RX filter ?
> But a 250 hz cw filter would drop the noise floor by 10 db... vs the 2.5 khz wider filter... if CW mode used.
> So  if Im reading this correctly,  FT-8 mode, using a 2.5 khz really only 10 db better than a 250 hz cw filter, using cw mode ?
> If that is the case,  being able to copy signals 10 db  weaker than the noise floor of a  250 hz filter is still nothing to sneeze at.
> The issue I see with FT-8.. on any band is the requirement for a  2.5 khz filter.... and possibly being prone to qrm.
> Right now, my issue is extreme high noise levels on 160m... on a 100 by 130 city lot.    Point a semi directional RX ant in the desired direction.... and its
> also pointed at a noise source.  Seems like I am surrounded by noise on 160m.   Im going to drag out by noise canceller and try some more rx experiments,
> b4 I throw in the towel.    FT-8 might just be an option for folks like myself that are plagued with high levels of noise.   Another possible option might be
> the use of real time  remote RX.   Another possible option might be using my 80m rotary dipole for 160m RX.   As is, its infuriating listening to high noise
> levels on 160m.   If I cant hear on 160m...except for the usual louder stations,  Im not going to even try TX.
> I have tried using a pair of  500 hz filters, and also a pair of 250 hz filters, and also a 125 + 250 combo, in both my MK-V..and also 1000-D.
> The MK-V also has a 240-120-60hz  dsp filter.  The 1000-D has a tunable audio cw filter.   The problem with the narrow xtal filters is...
> with noise levels so high, the noise...  rings out the filters.   The signals coming out of  each filter... get stretched a bit in time duration.
> What Im left with is this mess whereby the desired signals +  noise end up all mashed together.  Typ noise on 160m, using a 2.4 filter
> is S9 to S9 + 10 db.   Right now, Im trying to evaluate if 160m is even worth the effort required.   Are the  rest of you on 5 acres out in the woods ?
> Jim   VE7RF
> _________________
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