Techniques SOTA

VERTICAL SPIRALATA FOR THE 80 METERS

Here a useful realization for those who MHz does not decide of the space necessary to spread a dipole for the 3,5.

The band of the 80 meters is lend well in fact to the vertical polarization in the DX, and varies expressing with fishing rods and spins hung to trees several had already given good turns out to you in QRP CW in the slid years.  

Hour with decreasing of the propagation in HF and it wants to make connections also in SSB the evening, has made me to rispolverare this plan already described with some incongruenza in Italian books and Americans, therefore more better to pass the practical one in order to verify formulas and theories, and to remove the doubt to make “rubberizes loaded HF”.

The spiralata antenna is a risonante circuit in series, obtained wrapping a beautiful little advanced coil to the 1/2 wave on sopporto insulator and with to the base an agreement condenser, its efficiency is advanced to the vertical normal school having an inductance distributed on all the length, the passing band is advanced, and the earth system is 2 simple stakes of mass drowns to you in the land without to spread radial in my case, but suggested if you have space.

To the top a cruise like obtained capacitivo hat is placed knitting 4 brass batons to the thread of the coil.

The support of the antenna is the tubes in plastic diameter used 10 cm for the grondaie and acquires you to the Castorama, the total length of the vertical one is of 6 mt., with 3 tubes from 2 meters glue to you with glue for PVC.

The spaziatura of the coil is not uniform, in order to increase in fact to the rendering part with wide spaced coils 10 cm in order to tighten itself while they knows itself towards the hat until to 5 cm of spaziatura.

Us 2 persons want in order to wrap the thread and every coil has been glue with glue to warmth before raising all in vertical. This operation is facilitated from the base in wood with 2 hinges in iron from 10 milimeter of diameter, that they concur of ribaltare the system and rendering the assemblage operations comfortable, in 2 hours of job is ready.

Data of the version 3,6 MHz:

Thread electrical worker from 1,5 covered milimeter = Mt. 42

Tube long support mt. 6 diameter 10 cm

Winding approximately 130 coils on 5,5 mt

Condenser to the base: 560 pF

In my case I have obtained 120 very Khz of band passing within 1,5 of R.O.S with perfect centraggio (1: 1) to 3.600 MHz, the other vertical loaded traditional ones gives 40 KHz when it goes well… to have a distributed inductance is favorable!

Adding or removing 100 pF in parallel with a shunter it is possible to move on all band CW and lessened Fonia without problems of R.O.S in antenna.

The batons of the capacitivo hat are long 50 cm and the obtained value is gone around on the 25 pF, in any case going in QRP with 10 maximum watt is right a fineness, applying instead 100 watt turns out indispensable in order to avoid the effect crown.

In rain presence the sliding of frequency modest, once is finished the antenna suggests therefore to paint it, in order to better isolate coils from the atmospheric agents. You will notice from the photos that some coil has been moved, are necessary 2 points of glue to warmth for every coil ....... but that day was ended! hi

But as ON AIR is behaved?

In reception it is optimal with the better rendering on low angles, is normal therefore to listen to + fort the Europe North to 9+ 40 respect to one Italian station more neighbor.

In transmission it turns out to you are encouraging inasmuch as I go in QRP with 10 watt and the antenna introduces of the losses as all the systems raccorciati regarding vertical the fourth wave that would turn out 20,50 meters very!

The relationships receipts are 5/7, 5/9 real ones in QRP.

In my case being to level of the Prato I have not used pulling, on the roof better to put at least 4 in nylon for emergency.

73 de ik2nbu Arnaldo