5 elementtinen LPDA

[oh5yw]

Sveitsiläinen kaverini Udo on innokas FMDX-kuuntelija ja usein kiipeä jollekin vuorenharjanteelle laitteet mukanaan kuuntelemaan kelejä. Juuri äsken hän saapui kotiinsa kaksiviikkoiselta matkaltaan neljääntoista maahan....
Mukanaan hänellä on antennina kaupallinen italialainen 5 elementtinen logper-antenni.
Se on helppo purkaa ja kasata, vahvistus on tasainen koko bandin ja menee vaikka matkalaukkuun....

Tässä joitain kuvia:












Pyynnöstä hän myös mittasi antennin mitat jos vaikka innostuisi rakentelmaan moisen..

"The boom is constructed of two isolated square tubes, each 14mm thick. They are exactly 89 cm long. Spacing is 10mm.

On the front side (towards transmitter), there is an F-plug for the coax cable (grounding goes to the lower boom tube, inner goes to the upper tube).

On the back side, there is a small coil (without core) soldered between the two tubes: 12 windings of enameled copper wire, 10,2 mm long (0,8mm wire diameter) and 6mm coil inner diameter. Inside the coil is a resistor in parallel to the coil, so it is not possible to measure it (without de-mounting). I can barely see the colors, they are orange-blue-orange-yellow or yellow-orange-blue-orange ("orange" might also be "brown"). I suppose this resistor is for discharging static electricity.

Now to the elements:
Spacing on the booms (from the longest to the shortest element):
1: 3,5 cm from the coil end of booms (longest)
2: 29 cm
3: 51 cm
4: 70 cm
5: 86,5 cm (shortest)

Length of elements:
1: 84,5 cm
2: 72,5 cm
3: 62,3 cm
4: 53.5 cm
5: 45.9 cm

The elements are fixed on the boom by means of squeezed screws (without head = threaded bar) of 8mm diameter which is 2 cm long outside of the element. They go through the boom and the screw nut is fixed on the other side of the boom.

73
Udo, HB9ERD"