How common is 8.33 kHz channel spacing on the US?

[alcahuete]

Well you may be correct. I heard several United flights on 126.325 last night that were, as it appears using the 8.33 channels, how do I know? The voices were "fuzzy" until I changed from the 25 kHz to 8.33 kHz spacing. Then they were clear as a bell. Southwestern and American were clear on the 25 kHz spacing. I even recorded a video illustrating the difference. I live about 100 miles from the Ogallala RCAG site, of course I can't hear it here. It's one of the Denver sector sites.

8.33 is a step size. If you are tuned to 126.325, that is a standard 25 kHz spacing. 8.33 would be something like 126.330. Judging by your location, you're listening to ZDV (Denver Center) Sector 09, which has a RCAG in Nebraska. ZDV is absolutely 100% using 25 kHz spacing. If you're hearing something else, the problem is on your end.

 

[KC0QNB]

8.33 is a step size. If you are tuned to 126.325, that is a standard 25 kHz spacing. 8.33 would be something like 126.330. Judging by your location, you're listening to ZDV (Denver Center) Sector 09, which has a RCAG in Nebraska. ZDV is absolutely 100% using 25 kHz spacing. If you're hearing something else, the problem is on your end

I take it you didn't watch the video I posted showing me changing the step from 25 to 8.33 and back while an airplane was talking? It is pretty clear how the sound clarity changed.

 

[alcahuete]

I take it you didn't watch the video I posted showing me changing the step from 25 to 8.33 and back while an airplane was talking? It is pretty clear how the sound clarity changed.

I don't need to watch the video. I am intimately familiar with the operations at ZDV. They are 100% using 25 kHz, and the frequency is 100% 126.325. If you are showing something different, something is wrong with your setup, period.

 

[KC0QNB]

I don't need to watch the video. I am intimately familiar with the operations at ZDV. They are 100% using 25 kHz, and the frequency is 100% 126.325. If you are showing something different, something is wrong with your setup, period.

Not surprised by your reply, to be clear I was listening to aircraft talking to ZDV, I can't hear the ground signals from about 100 miles away from the RCAG.

 

[alcahuete]

Not surprised by your reply, to be clear I was listening to aircraft talking to ZDV, I can't hear the ground signals from about 100 miles away from the RCAG.

Whether you're surprised or not, I'm speaking the truth. The airplanes are not going to be using a different frequency than the center. If ZDV is using 126.325, the aircraft are as well. Do you think the planes are going to be using a different frequency?

 

[dem1]

I noted in your video that the signal peak is weaker and broader at 25 KHz than at 8.333 KHz. Switching band steps should have no impact on the signal characteristics, but it does shift the receive frequency slightly off center on the display and away from any DC spike.

If you haven't already done so, try my earlier suggestion of moving the receive frequency away from the center and see what happens. I just did this with an ATIS transmission on 126.550 with center tuning first, and then shifted halfway to the right on the display with free tuning, both using 25 KHz steps (see screenshots). You can hear in this audio clip how much cleaner it sounded when shifted off-center. So maybe your issue is similar. If not, it's one more theory down the drain

 

[KC0QNB]

I have accepted it for what it is, maybe a problem maybe not. Today everything sounds fine.

 

[G7RUX]

When I scan a know freq at 12.5, 6.25 or 25, it parks right there and signal appears within the bandwidth of 10,000 and usually dead on.

View attachment 180522



When I select same freq with 8.33, it shifts up to 118.177 which is 2 khz higher, not dead on, and it comes in fuzzy and unintelligible. .


View attachment 180523

View attachment 180524




What antenna are you using and how far away are these planes your hearing? Asking because I see your gain is maxed out.

Oh, this is an issue I have come across before and it is an issue with rounding errors in the calculations for the loop multipliers. The Malahit suffers greatly with this.

Basically the raster is off for 8.33 kHz steps (obviously the frequencies should align perfectly with the 25 kHz channel centres) and this is an issue which requires a software fix.