5500 ROTATORS ( YAESU VERTEX ) AND FODTRACK IF MODIFICATIONS

AZIMUTH SYSTEM

Azimuth voltage

Azimuth voltages between the CU and the FODTRACK interface are too low ( in my case ) : so rotator is turning further as wanted .....
Because of warranty no mods to the CU or the rotator hi. Solution : lowering the 39 K resistor between pin 13 and pin 14 ( U2D ) or ( maybe ) better : replace the 10 K resistor between ground and pin 13 by one with a higher value.

Click on schedule if necessary

Original version	Test version (modified)

Explanation

Because of the non inverted amplifier principle of this circuit ( U2D ) is :

U+ = U- ( U₁₂ = U₁₃ ) =>

Now, simple mathematical manipulations deliver the formulas 1 and 2 above ( R_13-14 and/or R_gr-13 ) hi.
In this case I decided to change the value of the 10 K resistor ( R_gr-13 ) to ca. 14 K : problem solved.

An example ( calculation resistor ) : click here.

Calculation resistor, Dutch : click here.

Azimuth potentiometer

During a system test I measured the values of the potmeter mounted in the azimuth rotator :

Zero ohm was not reachable *( impossible ) when rotator is at the end stop ( MIN, LEFT ), and:

Over the whole range the tolerance is not very good also temperature influences are existing.
The range - value - was much lower than 500 ohm : azimuth potentiometer only 455 ohm.

* In most cases no electronic end stop possible .....

A very simple and easy solution is : adding a zero adjust voltage to the system ! See channel master modifications or click here.

Another solution : changing the mechanical adjustment of the potmeter, it is easy to do. Ofcourse after it taking care when mounting the rotator parts ( markers ) otherwise it will be a disaster.

And a third solution : replacing the potmeter by another type ( metal ) ..... In most cases the pointing accuracy is now better too. If the load is not very heavy the system is working precisely.

Because of the better tolerance I also modified the interface a little bit.
A good tolerance is useful even when selecting a
bigger stepsize ( pointing accuracy ) ! The resulting tolerance can be better now.

Remark : the rotator I received had a 435 degree range, no 450 degree.
If you have the same construction, use it as a 360 degree rotator.

ELEVATION SYSTEM

No problems with the elevation system, 100 % working at once ( FODTRACK 2.5 and 2.6 ).

The fodtrack IF is working very well : compliments to XQ2FOD !

Ofcourse you can use this interface if working with IT ( Instant Track ) combined with : FODDRV ( written by Michael Radwick N8XKZ ), FLIPDRV and ORBITDRV. Do not forget the shift/offset function if necessary ( fine tune position ) .....
The Instant Track version I used : 1.50 A.F.

Apologies because of the bad translations, I did my best, hope you can read it .....

55 73 Leon pc1l@amsat.org

http://www.qsl.net/pa3gje
http://www.qrz.com/database?callsign=pc1l
http://www.qrz.com/database?callsign=pa3gje

NB

Later on I got another 5500 azimuth rotator ( Yaesu Vertex ) but still low potmeter values :

The old one : 435 degree max and 455 ohm.
The new one : 447 degree max and 455 ohm.

Manfred ( XQ2FOD, writer FODTRACK ) calculated some voltages delivered by the control box, the CU, ( 8 pin connector ) : the end position voltages can be between 1.86 and 5.62 volts, adjustable by VR3 and VR4.

Thanks to XQ2FOD ( because of FODTRACK prgr 2.6 and the special BETA version he sent to me ).
Fodtrack gives a lot of fun to many radio amateurs.

More abt Manfred : http://www.qsl.net/xq2fod

PS ( calculation resistor R_gr-13 )

1. Calibration mode fodtrack : set AZ -> 64 => AZ = 90.7 degree ( on screen !). Value 1 ( end stop position north ) used in the fodtrack.cfg file ! Is it impossible reaching a real rotator pointing of 90.7 degree via the adjust possibility ( CU ) : continue reading.

2. Actual voltage U₁₄ ( ~ U₂ ~ U₃ ) will be 1.2 VOLT but ( in this case ) the rotator "turned too far" ( > 90.7 degree ). Because of the low rotator potentiometer value the voltage on pin 6 ( CU, 5500 series ) does not reach 1.2 VOLT at the 90.7 degree rotator point. First, the real rotator pointing has to become 90.7 degree, then, find out the actual, resulting voltage and at last, calculate the new resistor value, see below.

However, before positioning the rotator ( to 90.7 degree ) and measuring the voltage on pin 2 ( U2A ) set adjust potentiometer ( CU ) in the middle position because after replacing the resistor this potentiometer will be in the middle position again if resistor calculation is OK. Now set rotator pointing at AZ = 90.7 degree, use for instance the manual function. Measure the new actual voltage at this 90.7 degree point ( different from 1.2 VOLT, it will be a lower one ) on pin 2 ( U2A ).
In this example the new actual voltage will be 1 VOLT.

3. We knew already : U₁₂ ( ~ U₁₃ ) is 0.25 VOLT
( AZ -> 64 ), see the values Manfred gave ( schedule ).

Now you will find R_gr-13 giving in ( see formula 2 ) : R_13-14, U₁₃ and U₁₄ ( 39 K, 0.25 VOLT and 1 VOLT ). Result : 13 K.

The system tolerance is not changing by replacing the resistor.

PS ( berekening weerstand R_gr-13 )

Indien vanwege afwijkende potmeter waarden de rotor aanwijzing niet goed te krijgen is :

1. Plaats de loper van de betreffende instel potmeter
( CU ) in de middenstand !

2. Breng de rotor zo precies mogelijk op 90.7 graden azimuth, bijvoorbeeld door middel van handbesturing, denk eraan, deze azimuth waarde geldt voor een code 1 eindstop positie ( calibratie mode : azimuth waarde
64 ).

3. Meet nu om U₁₄ te vinden de spanning op pin 6 ( CU, 5500 series ) of pin 2 ( U2A ). U₁₃ is 0.25 VOLT.

4. De nieuwe weerstands waarde is nu bekend : voer de gegevens in formule 2 in ( R in OHM of K, U in V ).

PS ( adjustments )

It is not possible to change or correct the described specific rotator position error in using a shift via the digital offset ( FODDRV ) possibility. Use, for instance, a zero adjust voltage if possible.

LED INDICATOR

Because it is sometimes important to know if the system is working ( hi ) I built a LED indicator, so you know now when the rotator must turn .....

LED indicator, front ( see also above : original version ) and back with the other components

In verband met enige vragen over het direct aansluiten van de LEDS :

Ondanks het feit dat de LEDS makkelijk kunnen worden aangesloten tussen bijvoorbeeld de 5 VOLT lijn en de collectors van de betreffende BC546B's met een voorschakelweerstand en eventueel een diode heb ik hier gebruik gemaakt van een aparte indicator omdat nu ook in de stand MANUAL de LEDS een seintje kunnen geven. Dit geeft aanzienlijk meer informatie ( afgezien nog van wat andere mogelijkheden ).