It also depends on if the receiving station is using reception preamplifiers - and the other station not.

Icom 7300
Signal link usb
win10
radio works on Fldigi and Digilink
with soundcard setting used for wsjt x
73
Ed W8EO

You are competely right, Bill, though I didn’t believe that at first.

 

Listened now to a local station on FT8 with constant signal, and switched in my station’s preamp-1: WSJT-X recorded same dB report.

 

I switched in my station’s preamp-2: WSJT-X recorded same dB report.

 

I switched in my external LNA (Low Noise Amplifier) GaAsFET RX preamplifier: WSJT-X recorded same dB report.

 

So I learned something today, Bill, after this experiment!

 

73 from Tom (LA4LN / LN1V)

 

 

Sendt fra E-post for Windows 10

 

Fra: Bill Somerville
Sendt: søndag 12. april 2020 kl. 14.05
Til: WSJTX@groups.io
Emne: Re: [WSJTX] Question about SNR reports

 

Tom,

 

it shouldn't so long as the pre-amp has lower noise than the band noise, and if is hasn't there's not much point to it.

 

73
Bill
G4WJS.

 

On 12/04/2020 12:56, Tom V. Segalstad wrote:

It also depends on if the receiving station is using reception preamplifiers - and the other station not.

73 from Tom (LA4LN / LN1V)

Sendt fra Outlook Mobile

 

From: WSJTX@groups.io <WSJTX@groups.io> on behalf of Bill Somerville <g4wjs@...>
Sent: Sunday, April 12, 2020 12:36:53 PM
To: WSJTX@groups.io <WSJTX@groups.io>
Subject: Re: [WSJTX] Question about SNR reports

 

On 12/04/2020 01:48, M Lu wrote:

I saw a chat awhile back that if the report you received was *stronger* that the report you sent to the other station, then there was something meaningful about that.  But I can’t recall.  I am seeing that happen occasionally on 80 meters with my inverted L and 100 watts from EU stations.

 

Mark Lunday, WD4ELG

Hi Mark,

there are many ways to form signal strength reports, each has limitations.

1) S-meter, these are roughly relative to absolute received signal strength but do not account for noise contributions,

2) absolute logarithmic signal power, usually in dBm, which are accurate measurements of received signal strength but are only meaningful alongside details of the aerial system used, or if used for comparative measurements,

3) signal to noise ratio, which accurately measure the power of a received signal relative to the received noise power, so are an accurate measure of signal readability,

4) signal to noise+interference ratio, similar to SNR (3) but accounts for interfering co-channel interference as part of the noise power. Note this is not necessarily relevant with narrow band modes like FT8/FT4 where advanced filtering eliminates the impact of interfering signals.

WSJT-X uses (3) SNR with the noise power estimated across a 2500 Hz bandwidth. It attempts to find the true noise power without contribution from interfering signals, although this is not easy to do accurately.

So to answer your question, SNR reports are often not reciprocal because of various factors. One station may have a more or less radiated power, another station may have a higher or lower noise level, yet another may be using a narrower than 2500 Hz bandwidth receiver that distorts the SNR measurement. None of this is exact science, the numbers are at best estimates. We feel that SNR is the most useful way of recording signal strengths.

BTW the next release of WSJT-X has an improved noise measurement algorithm for FT8/FT4 that measures the noise floor far better in the presence of strong signals. This means that SNR figures with large positive values will be given for the strongest signals, rather than the current situation where they tend to saturate at about the +20 dB range making their value falsely low.

73
Bill
G4WJS..

--
Tom (LA4LN)

 

 

--
Tom (LA4LN)

Of course, you probably have to take the info down, and then go to the US site, Amazon.com

Neil, KN3ILZ

Bob,

he's given you the link to the cables at Amazon, all you have to do is click on the link.

Neil, KN3ILZ

On 4/12/2020 10:32 AM, Bob McGraw - K4TAX wrote:

Please share where you obtained these and any other model/ spec information.  Many of us could take advantage of this information.

Bob, K4TAX

On Apr 12, 2020, at 9:28 AM, John <jonie41@...> wrote:

You could also only use cables that have chokes on them.

These are what I use, no problems in my shack.

https://www.amazon.ca/Hi-Speed-Cable-Ferrite-Chokes-3-Ft/dp/B008VOPCGY/ref=sr_1_1?crid=XE1SX7A7UMVB&keywords=tripp+lite+usb+2.0+hi-speed+a%2Fb+cable+with+ferrite+chokes&qid=1586701608&sprefix=usb+cables+a+to+b+with+choke%2Caps%2C178&sr=8-1

John

VE3KKQ

---------- Original Message ----------

From: Bill Somerville <g4wjs@...>

Date: April 12, 2020 at 10:03 AM

On 12/04/2020 14:22, Ed Oxer, W8EO wrote:

What is this? This message appears randomly. I have read all the info

on the Web about this and am no further ahead in addressing this.

Sometimes the app works well but at other times this message appears

even when the app is working. Sometimes the message shuts

down the radio. After alot of "horsing" around I can fix this problem

but with no degree of consistency. In advance thanks for any help.

Hi Ed,

the most likely cause is RFI disrupting the USB connection between your

rig and PC. Try using a different aerial, dummy load, or reduced power

and see if that eliminates the issue.

73

Bill

G4WJS.

W0MN EN34rb 44.08226 N 92.51265 W

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