JT9-1 and Strong adjacent signal Interferance
- I have been experimenting with Joe's (KT1JT) excellent WSJT-X program, Whilst on Monitor with Tol set to 500, Any strong JT9 or RTTY signal can block/ blackot out the whole passband. Leaving you with a black Wide Graph with one strong signal. This is especially troublesome here in the UK. The whole concept of Joe' Prog is to decode signals at -20DBor less. Stations running even 5W on the Continental Europe are generating upto 5 sidebands each side, Taking up most of the WSJT passband and blocking me out. I could reduce the Wide Graph pass band which is OK if TXing, But if you wish to do general Monitoring it can become annoying. I have experimented with Spectran and Virtual Audio Cable and found that using these in combination, I can Block out some annoying adjacent signals and leave the rest of the passband through to Monitor by using either Band pass or band reject on Spectran (Or passthu, and appropriate settings on the Spactran filters, I have reached a satisfactory level of control.
The Spectran Input is my USB sound card
Spectran output is Line 1 Virtual audio Cable
WSJT-x Input is Line1 (VAC)
WSJT-x output is My USB sound card
Audio Repeater (VAC) input is Line 1 VAC
Audio Repeater (VAC) output are My PC speakers on Monitor.
If you have a particularly strong signal giving blackout to the rest of the Wide graph pass band I engage DSP on my FT-897, start of with the filters set to 1000 High Pass and 2130 Low pass. The with of the Wide Graph Pass band. Set the passband in Spactran to 50- 75 Hz over the offending signal, engage band reject, and hey presto offending signal is gone, and the rest of passband visible. Of course alternatively I could have purchased a SDR, to front end WSJT-x to do the filtering of offensive signals, but this was FREE and more fun.
Virtual Audio cable = http://software.muzychenko.net/eng/
Spectran = http://www.weaksignals.com/
Whilst writing this I had an Italian Station come up who was S9 with me on JT9 with me he was working the USA, but blocking out the rest of the wide Graph, I used the Band reject in Spectran to cut him out, so that I could monitor the rest. Worked him later and sent him this
I hope it helps,
Kind regards ROGer (G8HLH)