Scanning option with graphical display

DL5YDJ
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Scanning option with graphical display

Post by DL5YDJ » Fri Jul 03, 2020 4:44 pm

Hi everyone,

the GD77 has already different scan options. What about if you can see on the display on which frequency is a signal for a range of 500Khz or 1MHz?
Each horizontal dot of the graphical display of the GD77 is showing a frequency channel. If a signal on a channal is detected the vertical dots will show how strong the signal is.
This is a scan option of the latest Yaesu handheld FT-1/2/3 series. It is very helpful to show on one view on which frequency is a signal and how strong this signal is. With the Yaesu you can scan a range of 1MHZ with 12,5Khz step to see signals.
Capability of graphical display and CPU should be good enough to handle such kind of scanning.

What do you think about it?

73 DL5YDJ

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IU4LEG
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Re: Scanning option with graphical display

Post by IU4LEG » Tue Jul 07, 2020 1:53 pm

good idea... I like it so much

sfoto
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Re: Scanning option with graphical display

Post by sfoto » Mon Jul 20, 2020 6:40 am

definitely a nice option to have, but im afraid that FT's CPU and rx unit are far more powerful and capable than limited hw of 77's

VK3KYY
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Re: Scanning option with graphical display

Post by VK3KYY » Mon Jul 20, 2020 7:18 am

I don't think there are any technical limitations, apart from perhaps RAM memory to store the RSSI values.

There would definitely be enough RAM to store at least 1000 RSSI values (i.e the RSSI for 1000 scanned frequencies)

The limitation is the time it would take for someone to write this function.

sfoto
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Re: Scanning option with graphical display

Post by sfoto » Mon Jul 20, 2020 10:02 am

VK3KYY wrote:
Mon Jul 20, 2020 7:18 am
I don't think there are any technical limitations, apart from perhaps RAM memory to store the RSSI values.

There would definitely be enough RAM to store at least 1000 RSSI values (i.e the RSSI for 1000 scanned frequencies)

The limitation is the time it would take for someone to write this function.
what about time it takes to scan the band? i guess most of readings would be outdated by the time it finishes even 1MHz wide

VK3KYY
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Re: Scanning option with graphical display

Post by VK3KYY » Mon Jul 20, 2020 11:37 am

Around 50mS per frequency step.

As the minimum bandwidth of the FM chip is 12.5kHz, then there is no point in scanning using 2.5kHz steps, if you are just looking for a signal.

So assuming you scan at 6.25kHz steps, which is 2 x the minimum resolution, then the scanning speed per Mhz would be

1 / 0.00625 * 0.05 = 8 seconds per MHz.

If you scanned with 25kHz steps, using 25kHz bandwidth, the speed would increase to 2 Seconds per Mhz.

I think we tried decreasing the hold time, on each frequency when scanning to 25mS or less, but the scanning was not reliable, because of fluctuations in signal level, however perhaps for a purely graphical display then perhaps it would be possible to decrease the hold time and still be able to determine the approximate RSSI.

DL5YDJ
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Re: Scanning option with graphical display

Post by DL5YDJ » Sat Jul 25, 2020 2:27 pm

With he Yaesu FT-1D it takes about 3 to 4 seconds to scan 101 frequency steps. I think it would not be a blame for the GD77 if it takes 5 seconds to scan 1 MHz with 12,5Khz step. In other words... to get in about 5 seconds a bandscope view of a 1 MHz range it would be great.

VK3KYY
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Re: Scanning option with graphical display

Post by VK3KYY » Sat Jul 25, 2020 11:52 pm

I think that we can probably scan about 1Mhz per second using 25kHz steps.

However, I'm not sure how this function would work.
When you start scanning would the screen update immediately show the graphical display.
How would the scan limits be set etc etc

Someone would need to write a full specification including graphical mock-up's, to explain how this feature would work.

Zl1XE
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Re: Scanning option with graphical display

Post by Zl1XE » Sun Aug 02, 2020 8:36 am

Here is a proposal as a straw man for discussion and improvement.

Proposal 1: Minimal code.
Screen mockups: (Digital and Analog modes)
Image
Holding UP key down initiates mode (as currently)
Holding Down key down exits mode (as currently)

If in Analog mode then:
Display Start and End frequencies and allow data entry (as currently).
- numeric entry starts filling up start frequency then stop frequency.
Holding UP key down(2sec) initiates the scan (as currently).
Feedback while scanning is the VFO id and frequency (as currently) and a line representing RSSI (new).
- The line stretches full width (256 pixels) and is 1 char high. It is above the frequency value.
- As the scan progresses a vertical full height black line moves across screen from L to R.
- This scanning line leaves behind a vertical bar representing the scaled RSSI of each scanned channel.
- The channels are grouped/spread across into 256 bins.
- These values are not stored. The display can represent the data and is lost on exiting.
- The scan repeats (currently stops at end).
- The scan stops if the DOWN key is held down(2sec) and holds on the frequency when the button was initially pressed (as currently).
- This exits Scan mode and the user can use single UP/DOWN keypresses to nudge onto the exact frequency.
Additional Possibility:
- The LEFT/RIGHT keys could be used to jump back and forward while scanning. This means the problem of overshooting a channel with a late keypress is avoided by pressing LEFT, waiting for eth visual indicator (or sound) to reach your exit frequency, and then a long press to exit. I assume (say) 100kHz as a stepsize ?
Note that currently L/R adjust squelch. So maybe use Function L/R to jump.

If in Digital mode then:
- Current behaviour is to scan the Channels in the current Zone.
- Add a line as in Analog which behaves the same way but uses the channels instead.
- E.g. if 16 channels in Zone then map the 16 channels to the 256 pixels (16 pixels per bin).
- If the Zone is "All channels" or the number of channels in a zone exceeds 256, then group them into 256 bins.
- UI is same as for Analog.
- I don't know how it works currently with Talkgroups and TS1, 2 when on the same frequency. I assume it just scans the channels in the Zone as they are defined for that Zone ?

Proposal 2: Much more code.
I had the idea of having a scan list setup in the CPS, uploading that and selecting from the list (using L/R buttons) when entering scan mode instead of entering frequencies directly. This for Analog. Not sure how to improve Digital over scanning a Zone.
As this requires more work i have not yet detailed it. But it seems that a pre-made list of useful ranges of frequencies to scan is more useful than entering a manual range every time. YMMV.
Last edited by Zl1XE on Mon Aug 03, 2020 5:13 am, edited 1 time in total.

DL5YDJ
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Joined: Fri Jul 03, 2020 2:34 pm

Re: Scanning option with graphical display

Post by DL5YDJ » Sun Aug 02, 2020 11:42 pm

Some ideas and proposal from my side based on ZL1XE proposal.

On your second screen mockup I am missing an arrow to show which column in the bar graph is the VFO frequency. I would install the arrow in the middle of the bar graph so that the VFO would be the center frequency of the plot.


Key usage

- up and down key short
does change the frequency step 12,5khz, 25khz.....for scanning (this should be shown anywhere in the display)

- left and right arrow key
press left arrow key short decreases VFO frequency one step. Step size is definded by the up down key
press right arrow key short increases VFO frequency one step.
press left arrow key long start scanning from high frequency to low frequency
press right arrow key long start scanning from low frequency to high frequency

- If you have got a scanning plot on the display:
with the left and right key you can move the arrow, which is the VFO frequency, to a column where a signal is indicated. This should be an easy way to find strong signals in an unknown region.

Please let me know if you have problems to understand.

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