V1.3 now has the ability to select either CW-upper sideband or CW-lower sideband in the setup menu. For CW fans, it helps to have an increase in pitch as the slice frequency increases. I take the opposite sideband and set it to the CW pitch frequency. When set this way with wider filter bandwidths, the opposite sideband stays suppressed for really excellent single-signal reception.
Although we've been able to independently adjust the lower and upper filter skirts to null an interfering signal either above or below the operating frequency, now the pitch shift can move in the direction of the operating frequency.
At first, I thought placement would be better in the slice flag, but since the upper and lower skirts are manually set anyway, I see no detriment in leaving it in the setup menu. I have not tried it yet, but hopefully CWU and CWL are captured in the new profiles. Well done!
I agree. I would like to see a setting that automatically pulls in the opposite sideband skirt at or near the CW offset frequency, or something user defined.
In CW, it makes no sense to have perfectly symmetrical skirts at wide bandwidths. We've then lost single-signal ability. Using 600 Hz as an example, then for anything less than 600 Hz, we *would* want equal CW symmetry.
or, am I off in the weeds? 73, w5xz, dan
Not sure how it was in PSDR since the 6700 is my first Flex. In either USB or LSB, there's no need to set the filter below zero. In CW the issue is affected by the offset and we must extend beyond zero. The offset is a function of the selected side-tone frequency.
K5UA's formula is the right one. K5UA's Axiom: "Keep the filter symmetrical on the CW offset until the filter width approaches twice the CW offset, then any additional filter width gets added to the high side of the filter, just like in SSB mode. Vice-versa for LSB CW mode."
As an example of the need to go below the zero point for wide CW filter settings (wide is defined as more than 2x the CW offset), let's select the 3 kHz CW filter in SSDR. Presently the 3K CW is a symmetrical passband at -1500 Hz and +1500 Hz. Now, as proposed by some, let's take the opposite sideband (determined by the new CW-L/CW-U menu feature) and bring it to zero. For CW-U, keep the right side untouched at +1500 Hz, now bring the lower side from -1500 to exactly 0. Now listen. Pretty awful, isn't it. There's no way anyone can listen to that audio passband. If that becomes the default setting, it will generate a lot of complaints. This is not the same as bringing the lower limit to zero in USB or LSB. Hate to mix audio into the discussion, but the audio passband is a function of the DSP passband.
The right way: For the 3 kHz CW filter and a 600 Hz offset chosen in SSDR, 2x the offset is a 1.2K filter. Since half of the 3K filter is 1500 Hz, we have well exceeded the symmetry threshold. For a 600 Hz offset, the symmetry threshold is a 1.2K filter (-600/+600). Since 3K is more than 2x the offset (1.2K), then we keep the offset amount intact on the undesired sideband. That's -600 Hz for CW-U. Since 3K is more than 2x the offset, the additional bandwidth most go to the high side. We end up with -600 Hz and +2400 Hz for a 3K filter. The bandwidth is 3K and single-signal reception is intact. We get exactly what we want from the wider CW filter: (1) the desired wide bandwidth with full passband audio; and (2) single-signal reception.
Probably the best way to understand this is to use my example above and move the filter skirts while listening to a CW QSO. One experiment is worth a thousand words.
it's often relaxing to rag-chew using a wider CW bandwidth to get a feel for what's around you, then narrow-up as needed to fight QRM. True, we can see them now too.
I've had several QSOs where the calling station is outside of my narrow CW bandwidth and missed them only to be asked later why I was ignoring the calls.
CW net control ops use wide CW bandwidths since folks are calling on everything from old crystal boatanchors to SDR transceivers. Incoming frequencies can vary many kHz.
I tend to run with pitch at 700hz and when tuning around use the 800hz BW setting. In my case this is not really an issue. With this type of rig, my first Flex, I tend to point and click. I am getting pretty good and usually click with a few hertz of center passband. As soon as I start the QSO I go to 50 hz unless it is a round table.
When I was NTS for 2RN and handled a lot of CW traffic I ran with a wide BW filter setting so that Stations that QNI would be heard by me even if they were way off QRG.
Personally, I would prefer to keep the filter system just as it is even if I would ever go wide BW and possibly be tuning on the wrong side of the CW signal. If wide I always verify which side I am on by slightly tuning the VFO and see which way the pitch goes. There maybe times when I need to sit on a QRG and be able to hear wide BW on both sides such as listening for a weak DX signal that may not be on QRG.
I think a good solution would be, if it is decided to modify the CW filters to a non-symmetrical state, please allow a menu selection for both methods.
One of the nice features of a SDR System is it is easy to add menu selections for the old method and the proposed new method. That way CW operators who like the present system will not lose out.
By the way Steve and the gang did a great job on the CW fixes. On transmit we are clean on transmit to 100 wpm, CWL works, and the Red LED on the front panel never stays Red during receive. We currently have the best QSK of any rig out there.
Keep up the good work!
73 & 161,