Digital Tests on NB Transponder

Quote from G3WDG

I did some further tests here just now and was getting FT8 decodes reliably down to -20dB. This seems to be about the threshold for successful decoding here.

This is about 10dB below what I can see on the BATC WebSDR waterfall. SIgnals decoding at -10dB are just visible.

Charlie, I did some tests too, but with JT65A (this mode is selected automatically in WSJT-X dev-1.7) and same results: -20 is the limit , and corresponds to ca. 1 mW (0 dBm) output power in a 60cm wide offset dish indoors.

Perhaps we should try it together some time?

G3WDG I know, but I remember having issues installing 1.9 , but will try tomorrow

This morning I made a nice JT65C and FT8 qso with PA3FYM. This worked ok. I discovered a 25Hz jitter on my lnb showing in the spectrum. That why JT65a is difficult. But modes with wider spacing of the tones are ok.

Can agree to label 10489.610MHz as FT8 frequency?

73 Rob PE1ITR

I also received multiple decodes in FT8. The decode of the main signal and of the jitter artefacts.

Yes, .610 ('dial frequency') is a good choice. I already entered this in the WSJT-X bandplan for JT65 modes.

.615 ('dial frequency') may be a choice for FT8 ?

According to the transponder "band plan", the Narrow Band digital mode runs from .600 - .620. We can best place FT8 on the edge such as .600 dail freq or .617 dail freq. The rest is then free with .610 as the center of digital mode activity for JT65c or whatever mode. OK?

G3WDG I upgraded to v2.0.1 after I discovered that I couldn't get decodes from Rob pe1itr ; -)

pe1itr Everything is fine for me, as long as I know where to find what. There are more modes, like JT9, WSPR, etc.

OK .600 it'll be for FT8. Fine with me.

Is there a chat for the narrow transponder like the wideband one ? I can connect to the irc channel but I don't see messages from others that are also connected.

Thank you

ON7KGK Go to the Goonhilly websdr and type your credentials in the window below the waterfall. It's a web based interface and works for (almost) everybody (?)

Ok Agreed. I set:

FT8 = .600 "Dail Freq"

Other NB MGM = .610 spreading upwards

Not me. But I will be qrv in one hour or so with FT8 on .600 (Dail Freq).

Hi Rob,

nice to meet you in FT8.

Here 100mW, 85cm duoband feed. Sigs abt. 20db over noice. Maybe 1mW could be enough

73

Mike

Mike tnx qso. Here is a screenshot of the last part of our qso. GW8OGI called me also.

DH5MK A few days ago I did some tests (with an 'old version' of WSJT-X (1.7-dev) )
with JT65A and had decodes on the Goonhilly websdr about -19 / -20 using between 1 - 3 mW (couldn't measure it accurately with the standard directional coupler) output with an indoor 60cm dish. Rob pe1itr and Charlie G3WDG suggested upgrading to WSJT-X 2.x and with JT65C (larger tone spacing) it works flawlessly, also with FT8. Curious what the lowest EIRP might be : -)