what's happening on my scope?

[grueic8600]

hello. tonight on my 8600, i zoomed way out. interesting how everything changes when you do that. side note: i found a pdf of configuring the scope view and it looks pretty great. anyway, i created a quick video of tuning 10khz increments from 5990 to 6000 and the whole scope shifted or rather, tilted and there was a bunch of color where there was not before. i posted the video on a google drive and here is the link to it: 8600 scope change

i mean, when i zoom in it's mostly just black with blue speckles and then some light blue and sometimes yellow or green where people are talking or a station is broadcasting. here, you can see the black/blue speckles on the left and right edges, but when the change from 5990 to 6000 happens, there's a LOT of bright green and yellow where the tilt had happened.

plus i guess i don't understand why the peaks get bigger when you are zoomed way out like this vs. being zoomed in nearer the range of where i am listening. but, i don't know much about the scope!

thanks

 

[majoco]

That looks pretty normal. I don't have an 8600 but I do have a Winradio G33DDC that has three screens which can be configured as either spectrums or waterfalls. One I have set as a spectrum from zero to 30MHz - this gives me a broad overview of the general conditions and which bands are active - I can expand it as required. The second display is centred on the selected frequency and can display up to 2MHz either side - I have this set as a waterfall to spot any intermittant signals and is usually set to 500kHz either side of the centre frequency. The third screen I have set as a spectrum only about 20kHz wide which show the carrier and sidebands of a signal, much like the display you showed but not in colour - this is very handy for notching out an interfering signal or something like that.

So in your case, I think you have set the width of the display too narrow - just looking at the one signal is not very informative - I suggest you set the display to 500kHz wide s you can see a lot more - then pick on a signal and zoom into it for more info. Just keep playing with it, it's a pretty steep learning curve!

 

[grueic8600]

thanks. yeah what's nice is i can "zoom in" or "zoom out" but i was just wondering why everything seemed to tilt or shift when i hit that 5.990mhz to 6.000mhz mark. i think i'm set it +/- 2.5mhz from the center position in this video.

 

[grueic8600]

you know, now that i think about it - i wonder if that's where an internal bandpass filter is?

 

[majoco]

Oh, I see it now! I thought the bright white line in the centre was the carrier of an AM signal! But in fact the green bits are the whole of the 49m broadcast band! I think what's happening is you have a change from one filter to another or something similar on that waterfall. Probably 5.990MHz is the high edge of one low frequency filter and 6.000 is the low edge of the next higher one. The yellow colour on the edge is all noise, you can probably get rid of that by turning the RF gain down, but the blue on the other edge is because that area is now outside the bandpass filter and therefore there is no noise. I can do that on my waterfall by turning the gain up or down.

 

[N7OLQ]

This is normal. The radio has "bands" that I assume correspond to filters. Sensitivity (or at least the display) seems to jump a little when you cross an edge. You can set pre-amp, ATT, IP+, & antenna settings that will apply to just that band. Band edges:
1.60 MHz
2.00 MHz
6.00 MHz
8.00 MHz
11.00 MHz
15.00 MHz
20.00 MHz
22.00 MHz
26.00 MHz
30.00 MHz
1100.00 MHz

The span adjustments seem to change how signal strength (color) is displayed. I assume because the data (max/min and averages) used to do the calculation changes. It is a little disorienting for me still.

 

[grueic8600]

you know it's just amazing to look at that graph. it's literally seeing everything around you well, what the antenna can pick up and then boost. it's fun sometimes to zoom way in to maximum and see how peoples voices are spread-out so to speak. or when i find a real strong AM channel you can see the spike in the middle and smaller spikes on either side of it. it's also so familiar b/c in computer graphics i work with image filters that have different "weights' and they act similarlly to the shapes i see on the spectrum graph - a spike in the middle (which shows the pixel) and then little spikes to the left/right which shows how much the pixels on either side will be affected, then the next two further outside pixels etc...

 

[toad99]

I find that when you change the span, the reference level will change. Also when the span is +/- 2.5 mHz, you might see "ghost" signals that aren't really there. If you try to tune to one of these, they simply vanish.

Another strange behavior is when you tune from 1590 kHz to 1600 kHz, everything below about 1200 kHz just disappears.

 

[kruser]

This is normal. The radio has "bands" that I assume correspond to filters. Sensitivity (or at least the display) seems to jump a little when you cross an edge. You can set pre-amp, ATT, IP+, & antenna settings that will apply to just that band. Band edges:
1.60 MHz
2.00 MHz
6.00 MHz
8.00 MHz
11.00 MHz
15.00 MHz
20.00 MHz
22.00 MHz
26.00 MHz
30.00 MHz
1100.00 MHz

There's another down lower at 0.50 MHz (500 kHz).

 

[grueic8600]

i noticed a couple ghost signal last night. very high up, well, above 25.000mhz and as i approached them they were gone.