Circular Polarization - NVIS Turnstile Antenna
with JUMA Turnstile Controller JUMA TC
Update 2021-06-22 OH7SV
(Revision C with external dummy load for QRO power documentation added)

Introduction to Circular Polarization
Thoughts on NVIS circular polarization. Courtesy of Hans PA3ECT
Circular polarisation and propagation. Courtecsy of Jan PA0SIM

Click the pictures to enlarge

My 80m turnstile antenna on map

Turnstile antenna dimensions for 80m (only on dipole shown)
Fine tune the two 90 degrees crossing antennas to a best SWR in the same frequency.

Turnstile antenna setup in the field. Mast 15 m. Guy wires 1mm and 2mm
Kevlar ropes.

Art image in fog by XYL Ulla

Turnstile antenna GND view. 18 meter Spiderbeam shortened to 15 meters.

Fiberglass mast bottom. Note the two coax cables, one for each dipole.
Low loss Ultraflex7 ( equal
lengtht of both of the cables!

Installation team OH7SV, OH7FVG, OH3YP and OH2NLT photographer.
Installation was during the JUMA 10 years celebration at OH7SV remote station.

Antenna construction material

Feeding box. I used 6 mm polycarbonate as a back plate which is
fixed to the fiberglass mast
with 2
8mm stainless steel U-bolts. The box is Multicomp G256 Polycarbonate 80 x 80 x 55 mm.

Two common mode baluns for 80m in the box. 7 turns of RG-316 or RG-142 PTFE coax on
Wurth 742700790
ferrite cores.
Both antennas must be isolated from each other and they must be balanced separately.
Use common mode baluns with 500 ohm or more of common mode impedance.

Type N water proof connectors. Note the water drain
holes on the bottom of the box which
allows condensated water to get out.
All the metal hardware is stainless steel material A4.

JUMA TC Turnstile Controller. It can be used from QRP level to legal power.
You can select between remote control or manual X, Y, LHCP, RHCP antenna.
Remote postion is compatible with Remoterig I/O by interface with standard ethernet cable.
X, Y, LHCP, RHCP can be selected with the two I/O signals. See Remoterig snap-hot

PTT control grounding signal is needed
(3.5mm jack) to swap polarization between transmit and receive states.

Test picture with exact 90 degrees phase difference and equal amplitudes in both of the antenna ports.

JUMA TC Turnstile Controller main board layout.
 The dummy load is implemented with two 100ohm/35W SMD resistors in parallel.
JUMA TC provides SWR 1:1 for whole the band!
Reflected power is dumped into the dummy load.

If you are using QRO power and want to work in the band edges replace the SMD dummy load
with an external 50ohm 250W dummy load. If the antenna SWR is 2:1 the dumped power
is abt 10% and with SWR 3:1 the dumped power is abt 25% of the transmitted power.

Extrenal dummy load connector installed. Remove the SMD resistors R17, R18 and D6
and install a BNC connector for external dummy load.

BNC connector installation tip for an external high power dummy load.
If you make this modification remove the diode D6 because it can't stand more than 50W.
See down the page revision C for external dummy load schematics, layout and BOM.

Close view of the quadrature hybrid coil for 3.7MHz. 13 turns 1mm enamel cu wire in parallel.
iron powder Amidon T-106-6. Other bands are possible with corresponding windings and capacitors.
The coil reactance XL is 2 x 50 ohms and both the capacitor's XC is 100 ohms each for desired frequency.

1.8MHz: Iron powder core Amidon T-130-2 (red), 2x19 turns 1mm cu in parallel. Capacitors C12, C13, C14, C15 430p/1kV each.

Revision B documents with with internal dummy load for 100W
JUMA TC Turnstile Controller Schematics Rev B (PDFf)
JUMA TC Turnstile Controller Layout Rev B (PDF)
JUMA TC Turnstile Controller BOM Rev B (xls)
JUMA TC Turnstile Controller front panel Rev B (PDF)

Revision C
documents with with external dummy load for QRO power
JUMA TC Turnstile Controller Schematics Rev C (PDF)
JUMA TC Turnstile Controller Layout Rev C (PDF)
JUMA TC Turnstile Controller BOM Rev C (xls)
JUMA TC Turnstile Controller front panel Rev C (PDF)

Revision D documents for both internal and external dummy load

JUMA TC (Turnstile Controller) PCB Gerber files are available here

Ionosonde links
Petersburg Russia (off-line)
Juliusruh north Germany
Lycksele Sweden

Sodankylä north Finland

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