## Re: [aprsisce] Re: Crop Circles? NOT!

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• ... Ok, so if I calculate the non-reception (0 S-units) range the same as a signal strength of 1, I ll get close enough? ... Yes, that s why it s an inverse.
Message 1 of 22 , Oct 2, 2012
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On 10/2/2012 4:58 PM, James Ewen wrote:
> Yup, I remember the conversation... a signal strength of 9 would yield
> the smallest circle since the signal strength indicates close
> proximity. A signal strength of 1 would yield a large circle due to
> the possibly large distance to the unknown transmitter source. A
> non-reception report should equate to at least the same distance as a
> signal strength of 1.

Ok, so if I calculate the non-reception (0 S-units) range the same as a
signal strength of 1, I'll get close enough?

> The basic concept should be that the coverage area shown should show
> reception out to the edge of the receiver sensitivity, and as the
> signal strength increases, the coverage area show shrinks. The higher
> the signal level, the smaller the circle.

Yes, that's why it's an inverse.

> The routines used to generate PHG circles should be pretty similar to
> the DFS reports.
>
> PHG uses Output Power, HAAT, Antenna Gain and Directivity to create a circle.
>
> DFS uses Input Signal Level, HAAT, Antenna Gain, Directivity to create a circle.

Yes, the only difference in the calculation is where the power/s-units
go. One is power divided by 10 and the other is 10 divided by S units
which is why zero s-units is totally not a good idea.

PHG uses:

> Info->PHG.range =
> sqrt(2*Info->PHG.height*sqrt((Info->PHG.power/10.0)*(g/2)));

DFS uses (ignore the PHG, they share a data structure):

> Info->PHG.range =
> sqrt(2*Info->PHG.height*sqrt((10.0/Info->PHG.sunits)*(g/2)));
> Info->PHG.range *= 0.85; /* Present fudge factor */

In both cases, g = pow(10,((double)Info->PHG.gain)/10);

> If you assume an RX sensitivity of about -120 dBm for maximum
> reception circle size, and then downsize from there as the signal
> strength increases, you should be good... simple, huh? 8)

I'm a software engineer, not an RF engineer. If I use 1 for the s-units
in the range calculation for a non-reception (zero) report, I'll be
good, right? A simple "yes" or "no" (and a note to that effect in the
Wiki) would be appreciated.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
• ... Well, a directional DF report is not the same as a DFS report. I understand your point though, you are assuming that when one points at a specific
Message 2 of 22 , Oct 2, 2012
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On Tue, Oct 2, 2012 at 3:15 PM, Lynn W Deffenbaugh (Mr) <kj4erj@...> wrote:

>> I was using the right-click|lat/long|New DF here menu item...
>
> DF is not the same as DFS.

Well, a directional DF report is not the same as a DFS report. I
understand your point though, you are assuming that when one points at
a specific location, that they are going to enter BRG/NRQ information.
Stay with me though...

>> When you create a "New DF Here", what information is placed in the
>> comment? Is it just random, or is there some method to the madness? It
>> looks like New DF Here assumes a DF bearing, and not a DFS report.
>
> Yes, that is the case. And the range and bearing from the center of the
> map (with the assumption that's likely to be ME) to where you said "New
> DF HERE" is what is pre-populated into the range and bearing, hence
> giving you the initial comment.

That's not what I am seeing happen though.

In the right click menu, you can choose New DF @ Center, and the
bearing/range pre-populated in the comment will be pointing at the
location that you clicked on the map, and set to the distance closest
to the range circle for the zoom level you are using. ie the bearing
inherits the bearing from center TO the location clicked, and distance
based on your map zoom (As per Bob's conceptualization).

When I click on a location on the map and select new DF here, I don't
yet see a correlation as to the values in BRG/NRQ. I thought you might
have pointed back towards the center of the crosshairs, but that's not
it.

>> If
>> it's just random noise, leave it blank and then the DF and DFS buttons
>> would be available. It is very nice to have the object name and icon
>> auto-populated.
>
> Nope, not random noise, but an interpretation of center vs HERE for DF
> objects.

I'll keep poking to see if I can find that correlation.

>> That populates the comment, and thus makes the DFS button unavailable.
>> If you do the same sequence but select Create Object Here, you get the
>> DF and DFS buttons, but the object name/icon aren't auto-populated.
>
> What would you propose the name/icon be for a generic "Create Object
> HERE"? There's no indication that you're doing anything special so no
> matter what I pick, I'm as likely to be wrong as right.

Nope, leave Create Object Here as it is... I'm looking for a way to be
able to right click on the map and be able to create either a DF or
DFS object.

I think the easiest solution would be to utilize the Create New DF
Here dialog to do this. From what I see, I have to click on the DF
button to adjust the BRG and NRQ data to get it pointed where I want.
If the comment was left empty, and the user had the DF and DFS buttons
available, you'd be good to go.

>> I'm refreshing my knowledge of the DF reports portion of the program,
>> and adding information to the Wiki on DF reports.
>
> I'm glad you remotely remember how it works, because me, being a
> non-hunter of foxes, have no clue. I'm just the coder here!

I'm digging through the grey matter to remember... As I play with it,
it's coming back. And as an added bonus, I'm creating documentation in
the wiki this time! That means that the next time I have to try and
remember I can look it up...

This is just making me realize just how long it has been since I have
Exercise...

We should see if we can get you out from behind that Mountain Dew
occasionally... 8)

I keep being amazed at how much functionality there is in
APRSISCE/32... we have an amazing program available here! I only use a
fraction of what is available.

--
James
VE6SRV
• ... Using an S-Units value of 1 for a non-reception report would be better than what we have now. In reality, the non-reception area should be bigger than the
Message 3 of 22 , Oct 2, 2012
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On Tue, Oct 2, 2012 at 3:21 PM, Lynn W Deffenbaugh (Mr) <kj4erj@...> wrote:

>> A non-reception report should equate to at least the same distance as a
>> signal strength of 1.
>
> Ok, so if I calculate the non-reception (0 S-units) range the same as a
> signal strength of 1, I'll get close enough?

>> The routines used to generate PHG circles should be pretty similar to
>> the DFS reports.
>>
>> PHG uses Output Power, HAAT, Antenna Gain and Directivity to create a circle.
>>
>> DFS uses Input Signal Level, HAAT, Antenna Gain, Directivity to create a circle.
>
> Yes, the only difference in the calculation is where the power/s-units
> go. One is power divided by 10 and the other is 10 divided by S units
> which is why zero s-units is totally not a good idea.

> I'm a software engineer, not an RF engineer. If I use 1 for the s-units
> in the range calculation for a non-reception (zero) report, I'll be
> good, right? A simple "yes" or "no" (and a note to that effect in the
> Wiki) would be appreciated.

Using an S-Units value of 1 for a non-reception report would be better
than what we have now. In reality, the non-reception area should be
bigger than the S1 reception area, but making them the same is close
enough.

What about splitting the difference between S1 and S0? S0.5 or such?
Just a thought...

To keep you happy though...

YES.

--
James
VE6SRV

PS You missed a good chance at a meme from way back with this:

> I'm a software engineer, not an RF engineer.

It should have been "Dammit Jim, I'm a doctor, not an RF engineer!"
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