[amsat-bb] To Flip or Not to Flip

Erich Eichmann erich.eichmann at t-online.de
Sat Jun 28 12:57:03 UTC 2014

Hi Dan,
SatPC32 handles the  flip mode as follows:
If flip mode is activated It  checks whether the satellite crosses the 
user's meridian during the pass,  either in the North or in the South, 
depending on the setting of the rotor end  positions in menu "Rotor 
Setup" (N or S).  The check is made  when it starts tracking the 
satellite at the beginning of the   pass or during the pass (but not,  
if the satellite had crossed  the meridian already).

The DDE interface (which  can be used also by other  DDE client 
programs) outputs the real azimuth and elevation positions,  not the 
valures converted for flip mode. SatPC332 supports the Pro.Sis.Tel  
controller. So, it can steer that controller directly, also in flip mode.

With azimuth rotors with a range of 450 degr. or more the 450 degr. 
modus also avoids the full turn during a pass if the the satellite 
crosses the rotor end positions. This mode  is in many cases 
mechanically easier to realize than flip mode.

ISS: If the latitude of your location is  > 52 degr.  the azimuth 
direction can only be between 90 and 270 degr.  So, with your rotor no 
flip mode will be necessary.

73s, Erich, DK1TB

Am 27.06.2014 17:27, schrieb Daniel Cussen:
> To  Flip or Not to Flip
> Ok, my setup has flip capability. It also has azimuth of 1.5 turns
> (540 degrees),
> So flip is not essential for end stops as the rotator neither stops at
> North nor South
> The rotator controller software only works in WiSPDDE but this can use
> many different tracking software types.
> Currently using Orbitron. Orbitron only outputs Elevation 0-90 and Az 0-360
> The WiSPDDE rotator driver has been modified to automatically flip if
> elevation goes above 70 degrees and starts to drop again. As soon as
> it starts to drop Elevation, Azimuth value has 180 degrees added and
> Elevation is now suddenly >90
> The software has the option to enable or disable flip on each pass.
> What I need to know is
> 1) What is the best way to predict if I should flip or instead just
> move the azimuth without flipping?
> 2) Is there any software to automatically decide if Flip is best, and
> output Elevation values >180 to WiSPDDE during the middle of a pass?
> For Example worst case would be a satellite coming from due west (270)
> heading east (90).
> I this case it would be best to flip antenna, otherwise azimuth would
> need to rotate 180 degrees suddenly during a pass.
> In another case, ISS coming from south west across to south and then
> south east, but with elevation approaching 85 degrees. In this case it
> would be best to not flip, but our current software flips once the box
> is ticked and if the elevation rises above 70 degrees.
> At the moment it is not possible to do this in WiSPDDE as it does not
> know where the ISS is going to be at the end of the pass as that info
> is not sent over the DDE interface.
> Specific System Setup
> The system will be used to track the ISS for 2.4Ghz HAMTV downlink.
> The beamwidth of dish is 4 to 8 degrees, but signal is very strong at
> high elevations.
> Video is used live so continous accurate tracking is needed
> The azimuth can be any value 0-540 degrees (1.5 turns). Currently the
> software can do 2 things.
> 1) Not flip but instead move to an azimuth position where flip is not
> essential, but sometimes the azimuth is too slow to get to the new
> position.
> 2) Flip the dish, but on some passes it would be better to not flip
> the dish, if say elevation went to 73 elevation but azimuth could cope
> with tracking.
> The decision is currently a tick box. Orbitron only outputs 0-90
> Elevation so WiSPDDE is not being told by Orbitron to flip, the
> decision is not based on the pass prediction.
> I believe some of these problems may be solved with SatPC32 but we
> would possibly need to modify our custom driver to just accept these
> values.
> If using SatPC32 would it solve all these issues? Can it decide to
> flip or not flip based on azimuth speed and pass prediction in the
> middle of a pass?
> Does SatPC32 only ever flip at the start of a pass and never in the
> middle of a pass?
> Will it pick the best option for every pass and output values via DDE
> to WiSPDDE?
> The rotator WiSPDDE is specifically written for this task,
> It is a modified version specially modified by Amasat Itallia.
> The rotator we are using is prosistel Azimuth and Elevation rotator.
> This is quite new and so a specific driver was written.
> The azimuth can achieve 1.5 turns (540 degrees) and Elevation 180. The
> manufacturer only specifies Az 360 and Elev 90 but we have special
> modified hardware and software to allow movement above normal range.
> We have been using Orbitron up to now as it allows sun tracking which
> is handy for dish calibration,
> In reality the setup may not be used too often for school contacts and
> we could perform a manual pre-test or simulation to see if flip is
> best.
> Another option is to just not use passes for school contacts that
> require flip or that will result in a signal loss in the middle of a
> pass.
> What I would like to happen is the software to calculate which option
> is best, to flip on the fly or not to flip
> The decision would be based on the speed of the motors and which mode
> is fastest to keep a signal locked.
> For example
> Time in seconds 1 	AZ 260 El 45
> Time in seconds 2	Az 90 El 80
> Assuming both Elevation and Azimuth can move a 5 degrees per second
> Difference without Flip
> Az 170	El 35 Max Time to correct position 34 seconds
> Difference with Flip
> AZ 10	El 50 Max time to correct position 10 seconds
> So is there any program that does this and can output to WiSPDDE?
> Dan EI9FHB
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