In these first days of August, while here we go fast towards autumn, I started installing the first two RX antennas for the low bands:
- Active loop
- Reference Vertical
The first one I installed was the vertical proposed by PA5WM and recommended to me by IZ3BSU.
I had already assembled it but I still had to position and tune it.
Having used a 300-61 toroid instead of the 160-61 I had to revise the number of turns.
To the box I connected 6.2m of 1mmq electrical wire, to the GDN 5 radials 4m long and a piece of 40cm 8mmq wire that connects to a 1m long 22mm diameter copper GND rod.
The antenna has been calibrated on site with VNA and at the moment it has an impedance of 329 Ohm which I cannot lower without the aid of an adaptation resistor.
The meter says it needs R=99Ohm so I ordered 9W non-inductive 100Ohm resistors from Mauser Electronics, I wait for them to arrive and I will continue with the fine calibration.
I did not take antenna readings at the station as conditions change considerably after the switch box and the connection of all the other antennas.
The cable that arrives in the station from the switching Box is buried at a depth of 20cm and the shield is connected to the ground by gnd rods every 5m.
At the first reception test the antenna has a reception of about 30dB attenuated compared to the 110m long wire, remember that the antenna is monoband, calibrated at 1.838kHz with a reduced bandwidth, already in 80m the antenna is completely not working.
The signals at a first test are, although very attenuated (I have not mounted any preamplifier after the 1: 1 isolation toroid), much cleaner than long wire but I have not had many opportunities to test it.
Calibrated and connected the vertical I installed the loop. Cross Country Wireless supplies it with a 3m long wire but clearly you can do it again at will using the preamplifier, the bias-T and the supplied power supply.
My choice went to a loop of 8m total circumference, square, 2m each side …. made with copper-plated steel files used in the military for the connection of the remote control to the explosives triggers .. extremely resistant to traction, very light and brown, therefore camouflaged among the trees.
Now I just have to wait for the order made to Mauser to arrive, which also includes the termination resistances for the beverages and the bogs … and then complete the calibration even if I do not expect any better tangible in reception.
The upper side is fixed between two trees by means of a Kevlar rope from 2mm to 7m from the ground, the side at the base is therefore 5m from the ground.
The antenna did not present any functional problems except that the 12V 2A power supply sold by C.C.W. as “super filtered and stabilized” it provides a voltage of 12.06Vdc which drops to 11.9Vdc at the connector output.
This voltage under load (powering the preamp) drops to 9.9V .. which makes me think, even if it seems strange, that either the 2A of the power supply is not really 2A or that the preamp absorbs more .. I will do further tests in the next days to find out.