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ARDFrx80-7.
Details of coils and crystals.
pa0nhc 20171029

Print this page, and also see "Setup". 

        Construction details and the adjustment of the ferrite antenna are HERE

L102 : two wires twisted, 7 turns, 1mm dia on a Conrad 8x50mm Ui=300 ferrite rod.
Use one pair twisted wires from a  CAT5 network cable. 

Nominal self inductance : 8.0 uH. See "Setup" for one time adjustment of the self inductance.

L101 : 3 turns over the center of the ferrite rod.


        Local oscillator coil L2 : 
Standard Neosid 7.5 x 7.5mm RM2.25 
BV5048 .

          One time adjustment of L2 :
Connect a capacitor of 150 pF 1% with abt. 2cm long legs to pins 1 and 5.
Hold a grid dip meter near/between the capacitor wires.
Find the circuit resonance. 
Adjust the ferrite core WITH A SPECIAL WELL FITTING TOOL for 13.0 MHz resonance.
Fill the hole of the coil with pure bee wax.
Remove the capacitor.
From now on, L2 should NOT be readjusted.
Tuning the oscillator should only be done by C110.


        10,7 MHz IF coils.
L3,6 : 7.5 x 7.5mm RM2.25, Standard Neosid coil BVW5170.

REM : In 2014 a coil type BVW5056 was used. In 2017 it is not available anymore. Now a BVW5170 type coil is used
            But coil BVW5170 has a different connected coil : diagonally. 

For correct coil connections, you first have to make following modification :

For PCB #15 the coil connections of a modified coil BVW5170 should be at the bottom left and top right ==>>
See the bottom copper side of the PCB. 

1. With a felt pen, make marks on the bottom of the coil form near the pins connected to the coil.
2. Temporarily put the coil at the top copper side in place..
3. With a felt pen, make marks on the outside of the copper screening bus, where both coil connections should come. Remove the coil from the PCB.
4. Using a plastic 3mm pen with a flat top, press the complete coil form out of the copper screening bus.
5. Turn the coil form so, that the markings on the coil form coincide with the markings on the copper bus.
6. Push the coil form back into the bus.
7. Cut the middle pin of the row of three, fully back.
8. Put the modified coil into the top copper surface of the PCB, and confirm that the pins which are connected to the coil, are in the holes at the left-bottom and top-right.
9. First solder the grounding pins of the copper bus, while pressing it firmly onto the PCB.
10. After that, solder both coil pins.

CHECK that no short circuits are present, especially near the soldered ground lugs.


Bottom side of PCB #15.

 


        Chokes.
REM: the here used Neosid SD75 type chokes have a higher self inductance at a given Self Resonating Frequency than smaller chokes on ferrite rods.

L7,10,12  -  22uH: standard Neosid radial choke SD75 RM5 (SRF >= 11MHz). Conrad orderNr 535389
Or use vertically placed 7x3mm axial chokes  10uH.

L11  -  68uH : Neosid radial chekel SD75 RM5 (SRF ca. 10MHz). Conrad orderNr 535400
Or use vertically placed 7x3mm axial chokes 22 uH.

L13,14,15,201 :  10uH axial chokes Epcos 7x3mm. Conrad orderNr 501881

        FB2,5,6,7 :
Order at
www.box73.de : "Ferrit-Dämpfungsperlen".  Small ferrite pearl 4x3mm. 

        Crystals.

10.7 MHz crystalfilter F1+2: Order at
www.box73.de : "quartz filter" 10M12B.

    BFO crystal Cr:
Order at www.box73.de : "quartz 10.7MHz HC18U
In order to improve frequency stability, and to prevent 10.7 MHz RF radiation, you should solder the can if the crystal QUIKLY to a special grounding surface near the crystal.