v. 20200606

Order Nrs
for
Conrad

61mm mix #61 ferrite ring core : Fair-Rite  5961003801 .  or FT240-61.
===>> Do NOT use any other ferrite mix ! <<===

     Both pri. and sec. are each wound with :
Two AWG12 PTFE silver plated wires. 
Use for primairy winding 2 different colors to be sure it is correctly wound with both wires IN PARALLEL..
Use for secondary winding 2 different OTHER colors  to be sure it is correctly wound with both wires IN PARALLEL..See photo.
Wind and connect two wires in parallel.. DO NOT TWIST.
This wire is very slippery. Fix with tywraps.

Fix winding ends in place with black tywraps.   See photo.
==> Wind all turns very tight against the ring core body <<==
==> Wind the secondary turns in-between the primary turns <<==  See photo 

If no PTFE wire is avaialable, you can use easier to handle :
2x2,5 mm² speaker twin lead 5mm wide or DC power cord 6,3mm wide.

     Winding data :
Pri0-Pri9 : 9 turns, two silver plated PTFE wires wound and connected in parallel (40m).
S0-S3      : 3 turns, two silver plated PTFE wires wound between primary turns and
                    connected in parallel.
S1            : Secondary tap after 1 turn from start (80m).
See the topsilk of the PCB and the photo for how close to wind and how to solder.

1231500

Aliexpress.com

Ferrite ring core ==>> Fair-Rite 2631801202 (28/19/14mm) ==>> MIX #31 <<==
(or Ferroxcube => mix 3S4 <= core type TX29/19/15-3S4,  ).

DO NOT use any other ferrite mix !

2 m Coax RG316 (or RG174) suitable up to 400W.

602710

(Conrad).

Use as much as possible capacitors in parallel. For instance :
-  Silver MICA and/or
-  Low inductance polyester film  WIMA FKP2 630Vdc and/or
-  Ceramic NP0 (zero temperature coefficient).

Use as much as possible the same values in parallel, to divide the total RF current equally over all paralleled Cs. Check that all C s can handle the RFvoltage and RF current at working frequency.

I total =  26 A @ 80m, 9,7 A @ 40m in sec. winding, and 2,9A in pri. winding.
Umax over series tuning Cs is 220VpRF. Use : 630Vdc capacitors. 

You have to determine the optimal total capacitor value yourselves. See "Construction".
See these capacitor values below (meaured at the new PCB) as a guide.
C80 in total 6400pF or 9x 680pF + 270pF
C40 in total   890pF or 8x 100pF + 89pF

          IMPORTANT : 
The two output wires between PCB and loop are made of one piece of 6,3mm wide and 20cm long DC cord. The length is critical !! and influences C40 and C80 values.
Determain values for C40 and C80 with the definitive length of 20cm of antenna connection DC cable !! To be able to feed  wires through the two cord grips at the top of the box, and to connect to the loop feedpoint, do split the 20cm long 6.3mm DC cord for as short as possible length. Keep wires paralleled, as this also influences the values of C40 and C80 !! 

          Determining values the of C40 and C80 : 
Easiest done using a GOOD NanoVNA V2Plus4   => Sold at  www.tindie.com the original vendor.
REM : all other named NanoVNA on NanoVNA.com are not original but 
(bad) cheap copies of old designs.

For measuring C40 and C80 with NanoVNA V2Plus4, use low inductance resistors as dummy loads :
Use for 80m a load of 0,555 Ohm or 18x 10 Ohm 0,25W resistors in parallel.
Use for 40m a  load of 5,5 Ohm or 4x 22 Ohm 0,25W resistors in parallel. 
KEEP RESISTOR WIRE ENDS SHORT !!
SOLDER THE ANTENNA OUTPUT WIRES DIRECTLY ONTO THE RESISTOR BODIES,

For 10 min 100W power endurance test :
Induction free 0.6 ohm RF resistor 100W for 80m test.
Induction free 5.6 ohm RF resistor 100W for 40m test.
On cooling profile 0.6 K/W..

Wima, FairRite : Mouser.com.

Silver mica :
tonefactory.nl