K5ESW said:
"The difference in the FT8 reported SNR and how most hams think of SNR
seems explained well by Jim, KC5RUO.
http://www.arrl.org/forum/topics/view/1957
https://tapr.org/pdf/DCC2018-KC5RUO-TheReal-FT8-JT65-JT9=SNR.pdf
Thanks Paul. I had read one of those articles before. I didn't find
Jerry,
The difference in the FT8 reported SNR and how most hams think of SNR
seems explained well by Jim, KC5RUO.
http://www.arrl.org/forum/topics/view/1957
https://tapr.org/pdf/DCC2018-KC5RUO-TheReal-FT8-JT65-JT9=SNR.pdf
He says for FT8, the noise bandwidth that impacts FT8 software´s
abili
alf of K4SAV
Sent: Thursday, August 1, 2019 5:09:55 PM
To: topband@contesting.com
Subject: Re: Topband: FT-8 performance
I'm not sure how FT-8 calculates the reported S/N number. I found very
little information on the subject and what I did find was not easily
understandable. What I
On 8/1/2019 1:27 PM, James Wolf wrote:
I think there is some misunderstanding of bandwidth using FT-8.
The power limited Shannon limit I posted about today is
independent of equivalent noise bandwidth
The equivalent noise bandwidth of an FT8 detected tone is only 6.25 Hz. So
-26 dB
I'm not sure how FT-8 calculates the reported S/N number. I found very
little information on the subject and what I did find was not easily
understandable. What I did was an experiment in which I was able to get
close to the same number being reported. According to what I have read
about FT-8
If anybody's interested in trying my version of the python FT8 decoder with
a more sensible SNR
implementation just go here: https://github.com/mcogoni/weakmon
I modified the code to look for the lowest power bin within the input
bandwidth and each
individual signal is compared to this.
To obtain b
I think there is some misunderstanding of bandwidth using FT-8.
A single FT8 "signal" occupies somewhere just a hair more than 50 Hz.
However, that is not the number to use for calculating the equivalent noise
bandwidth. FT8 is made up of 8 tones, only one of which is on at any time.
Each tone
It is instructive to calculate the Shannon
maximum theoretical data rate (power limited case)
(refer to wikipedia page for Shannon-Hartley theorem).
If S/N ratio (BW=2,500 Hz) = -24 dB,
then S/N ratio (BW=1Hz) = -24 + 10 log 2,500 = -24 +34
= +10 dB. 10 dB converted to a dimensionless ratio is 10
Do either JT9 or FT8 *really* need a wide SSB filter? What happens if we
use a good narrow CW filter instead?
73, Mike
www.w0btu.com
On Thu, Aug 1, 2019, 2:03 PM K4SAV wrote:
> W0BTU directed a question to me about JT-9. I have never tested JT-9 so
> I don't have any information to supply on t
W0BTU directed a question to me about JT-9. I have never tested JT-9 so
I don't have any information to supply on that subject.
The S/N number supplied by FT-8 was only a curiosity to me because I
could see a huge disparity between what was being reported versus what I
was observing on my rec
You might want to listen to this TAPR presentation on Noise and Noise
calculations.
https://youtu.be/xXXj1Ko4ZXg
I found it pretty interesting.
Mike va3mw
On Thu, Aug 1, 2019 at 2:12 PM uy0zg wrote:
> Is the main problem here in efficiency?
>
> The main thing here - the signal is not heard b
Is the main problem here in efficiency?
The main thing here - the signal is not heard by a person!
---
Nick, UY0ZG
http://www.topband.in.ua
Tim Shoppa 2019-08-01 20:40:
The "work signals way down in the noise you could never work otherwise"
myth, is just part of the myth that FT8 is an effect
We went thorugh a similar discussion here a year ago about the "cooked" S/N
statistics. Or at least they are cooked in a way that no CW operator would
cook them, by considering a bandwidth 50 times wider than the FT8 signal.
On a quiet WARC FT8 band (no interfering carriers) signals that are -18dB
Good morning
Do we know if the SNR is calculated over the RF passband filter width, or
is is calculated over AF filter bandwidth in the WSJTx engine, which it
knows? There is a big difference.
Mike va3mw
On Thu, Aug 1, 2019 at 11:09 AM Marco Cogoni wrote:
> Hi,
>
> I agree with Jerry. I spen
Very interesting. How does JT9 compare, especially in regards to the noise
floor issue that Mark raised?
73, Mike
www.w0btu.com
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
I meant Jerry, not Mark. Sorry.
On Thu, Aug 1, 2019, 10:15 AM Mike Waters wrote:
> Very interesting. How does JT9 compare, especially in regards to the noise
> floor issue that Mark raised?
>
> 73, Mike
> www.w0btu.com
>
_
Searchable Archives: http://www.contesting.com/_topband -
Hi,
I agree with Jerry. I spent a few weeks trying to use FT8 to obtain
antenna radiation patterns and I discovered how the SNR is computed:
it's totally flawed. Basically WSJTX computes the number in two steps:
the first one estimates how strong the adjacent frequency bins are with
respect t
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