[TVARC] WJST-X: Just How Much Bandwidth is Being Decoded?

Sun Jul 1 07:54:28 EDT 2018

I think there’s a checkbox on the Advanced screen which should take care of that.

Pete, K2PS

From: Earle D Hancock [mailto:earleiphone at gmail.com] 
Sent: Sunday, July 1, 2018 7:52 AM
To: Pete Stafford
Cc: Anthony Hackenberg; tvarc at mailman.qth.net
Subject: Re: [TVARC] WJST-X: Just How Much Bandwidth is Being Decoded?

Ahhhh, I have a headache. 

E

On Jul 1, 2018, at 6:38 AM, K2PS Pete Stafford <psk2ps at gmail.com> wrote:

Hi Tony,

Glad you figured out how to change the bandwidth.  Took me a bit of digging as well.

The only differences between your current setup and mine is that I use USB-D2 mode, and I set Split Operation to Fake It.  I can’t tell you what these settings really mean, but they seem to work, at least in the Default Configuration.  Needless to say, I haven’t successfully worked KH1 on the Hound config, so can’t comment on that.

Good luck!

73, Pete, K2PS

From:  <mailto:tvarc-bounces at mailman.qth.net> tvarc-bounces at mailman.qth.net [ <mailto:tvarc-bounces at mailman.qth.net> mailto:tvarc-bounces at mailman.qth.net] On Behalf Of Anthony Hackenberg
Sent: Sunday, July 1, 2018 4:42 AM
To: TVARC  <mailto:MailList at QSL.net> MailList at QSL.net
Subject: [TVARC] WJST-X: Just How Much Bandwidth is Being Decoded?

Hi Members of TVARC's Maillist (especially those interested in FT8 via WJST-X,

My basic question is just how much bandwidth (range of frequencies) is actually being decoded by the WSJT-X software and what determines it?  Is it the entire waterfall's window width (range of frequencies)? OR, is it more complicated, and really depends on your rig's "bandwidth" (filter) setting?  

ONLY read on if you want my overly detailed description of my amateurish experiments to try and determine an answer, which at best, IMHO, is inconclusive.  Hopefully, one or more readers of this posting will have the real (& right) answer.

My inconclusive experiments appear to say WJST-X's decoding range really depends primarily on your rig's bandwidth (filter) setting and not on the waterfall window's width.  However, since my knowledge and experience with the software and it's underlying technology is extremely superficial, I cannot categorically say my experiments proved anything.

Here's what I've observed watching the waterfall display and tweaking my rig's bandwidth settings. When using WJST-X software with my ICOM IC-7610 rig, this software takes control of my rig.  It puts both of my rig's 2 independent receivers into "USB-D1" mode & into "Split" frequency operation. So, pursuant to the Baker Island DXpedition's band plan for 17 meters, the "RX" one is set to a dial frequency of 18.095.00 MHz; while the "TX" one is set slightly less at 18.094.50 MHz.  However, the software also selected the "standard" filter ("FIL2") for both receivers and on my rig this selected filter's bandwidth is ONLY 500 Hz!  On WJST-X's waterfall display (width set to display a frequency range of about 4 KHz), I only noticed signals (red/pink/yellow cascading) in a narrow 500 Hz part of the waterfall display.  In normal (not FT8 DXpedition mode), I never really paid attention because in normal mode, your transmitted signal is going to be relatively close your receive frequency (the other guy/gal's transmit frequency).  However, in FT8 DXpedition mode, they are VERY fall apart (the FOX is below 1000 Hz & the HOUNDS are above 1000 Hz).  My (hound) TX frequency (red bracket-like symbol) on the waterfall display fell clearly inside this narrow 500 Hz range; but my RX frequency (green bracket-like symbol) where I was listening for the fox (his/her transmit frequency) was down near 300 Hz (clearly way outside that 500 Hz range).  Thus, there was a much larger span between these 2 frequencies compared to when you're operating in normal (not FT8 DXpedition) mode. As a consequence ONLY 1 frequency (my hound TX frequency @ the waterfall's red bracket symbol) was within the rig's pass band (bandwidth); while the RX frequency (@ the waterfall's green bracket symbol), where I was trying to hear the fox, fell way OUTSIDE that 500 Hz rig bandwidth.  I believe (but cannot prove) that WJST-X was only decoding signals that fell within this narrow 500 Hz rig bandwidth (passband).

So, now the question of just what determines how much frequency range is WJST-X really decoding and what does it depend on becomes REALLY important.  The only thing I was seeing in the waterfall that looked like "real" signals was an intense band of red/yellow cascading waterfall but this ONLY appeared within that narrow 500 Hz bandwidth.  Nothing that looked like signals appeared anywhere else on the waterfall display.

By trial & error, I finally discovered how to adjust the bandwidth settings on my rig.  FYI, on the ICON 7610, you depress & briefly HOLD the "Filter" button (near the top right side under the "Twin PBT" knob) until the bandwidth setting display pops-up on the bottom half of the rig's main screen. I selected "BW" on this display and then "FIL1" (which was originally set to 1.2 KHz).  I used the main tuning knob to increase it from 1.2 to 3.6 KHz (my rig would not let me go above 3.6).  So, now my SPLIT operation, was configured like this on the rig:

   [Receiver side]   SPLIT      TX [Transmit side]

   VFO USB-D1 FIL1              VFO USB-D1 FIL2

   18.095.00 (MHx)              18.094.50 (MHz)

So, now the first independent receiver in my rig is using the revised "FIL1" bandwidth setting of 3.6 KHz; while the second independent receiver (TX frequency setting) stays with the "FIL2" setting of only 500 Hz. This made a HUGE difference in what I viewed on the waterfall display.  Now, cascading colors (hopefully signifying real signals that WJST-X was now decoding, were in evidence across much more of the waterfalls 4 KHz range (width).  Now, some apparent decoding was happening in the 300 to 1000 Hz range where the fox's transmitted signal should be.

I have to thank Pete/K2PS for putting a brief but tantalizing hint in his excellent summary of how to configure the WJST-X software in FT8 DCpediton mode. Here's his hint that clued me into doing this investigation:

"Expand your bandwidth to up to 4000Hz if you can. That will let you get into a portion of the band where you’ll have more chance of finding an open spot from which to call him [the fox], since many folks [hounds] won’t be looking up that high – but they [fox] will."

So, again, I pose the question: what determines how much bandwidth WSJT-X is decoding across?

73,

Tony/K4QR

P.S. Sorry about the length of this posting.  It's a case where a picture, or video, would have truly been worth a "thousand or more words" but although I have some photos & movies of parts of my experimentation, I did not want to attach them to this posting.  So, I had to paint a picture with way TOO many words.

-- 

Anthony W. Hackenberg
Email:  <mailto:anthony.w.hackenberg at gmail.com> anthony.w.hackenberg at gmail.com

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