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Dealing with FT8 interference on 20m #FT8 #qrm #lsb #20m

Sholto Fisher
 

This probably has occurred to others but I’ve found that tuning to 14.074 LSB gives me a better shot at hearing digital signals as the FT8 crowd are kept at bay by opposite sideband suppression in my rig.

 

I run an IC-718 with no filters so maybe you guys with your Elecraft, FTDXs and Flex radios don’t need it!

 

You just need to remember to invert your signal in the software. Some modes such as PSK31, Packet, and Feld Hell don’t need it but others like MFSK and Olivia do.

 

73

 

Sholto

K7TMG

 

Sent from Mail for Windows 10

 

M5AKA
 

Sholto, surely what you are suggesting is the same as transmitting on 14.071 using USB so your transmissions don't cause interference to existing activity on 14.074.

I cannot see the point in inverting your sideband?

73 Trevor M5AKA

On Friday, 19 April 2019, 20:33:08 BST, Sholto Fisher <sholto.fisher@...> wrote:


This probably has occurred to others but I’ve found that tuning to 14.074 LSB gives me a better shot at hearing digital signals as the FT8 crowd are kept at bay by opposite sideband suppression in my rig.

 

I run an IC-718 with no filters so maybe you guys with your Elecraft, FTDXs and Flex radios don’t need it!

 

You just need to remember to invert your signal in the software. Some modes such as PSK31, Packet, and Feld Hell don’t need it but others like MFSK and Olivia do.

 

73

 

Sholto

K7TMG

 

Sent from Mail for Windows 10

 

Sholto Fisher
 

Hi Trevor. I find even high audio tone FT8 transmissions cause the agc to pump. I suppose these are stations running full legal power or very close to me.

 

I'm sure with high end receivers this isn't a problem but for my IC-718 with no narrow filtering it seems to help. Also I don’t have to listen to a warbling 3KHz+ signals every 15 seconds

 


From: main@digitalradio.groups.io <main@digitalradio.groups.io> on behalf of AKA via Groups.Io <m5aka@...>
Sent: Saturday, April 20, 2019 5:51:58 AM
To: main@digitalradio.groups.io
Subject: Re: [digitalradio] Dealing with FT8 interference on 20m #20m #ft8 #qrm #lsb
 
Sholto, surely what you are suggesting is the same as transmitting on 14.071 using USB so your transmissions don't cause interference to existing activity on 14.074.

I cannot see the point in inverting your sideband?

73 Trevor M5AKA

On Friday, 19 April 2019, 20:33:08 BST, Sholto Fisher <sholto.fisher@...> wrote:


This probably has occurred to others but I’ve found that tuning to 14.074 LSB gives me a better shot at hearing digital signals as the FT8 crowd are kept at bay by opposite sideband suppression in my rig.

 

I run an IC-718 with no filters so maybe you guys with your Elecraft, FTDXs and Flex radios don’t need it!

 

You just need to remember to invert your signal in the software. Some modes such as PSK31, Packet, and Feld Hell don’t need it but others like MFSK and Olivia do.

 

73

 

Sholto

K7TMG

 

Sent from Mail for Windows 10

 

Graham
 

Most side band filters are  asymmetric,  with  sharp cut to the carrier  frequency  and a lesser slope to the  higher/lower cut  off  frequency ,

Or,  as racal did  with the  ra6790 and move the  oscillators about , whilst using the  3.4k am  symmetrical filter , unless  lsb/usb where  fitted  

Seems of of  over run quite a lot of bandwidth, stark contrast to the  time  Andy and myself spent , scouting clear spots to  run, the then new, opera system,  granted its only 1 or  2 Hz wide , but the  decoder pass  band is a couple  of  hundred Hz  on  most bands  , less on the  lower bands ,  +/- 50 Hz on 136 K 

73-Graham
g0nbd