I used AMIDON BN73-202 binocular cores for the transformer (2T/6T) which actually not only the best performer regarding the common mode suppression (as braid breaker) but the easiest to wind as well.
It is highlighted in many sources that it is important to use inner insulating tubes via the holes to avoid any enamel harm. After I wounded it I think as there is no that much vibration for the wire to stretch to each other to damage the insulating cover it might be left out. However just in case the tube was used which actually made the last turns really difficult to pull through. Probably a thinner wall size might have helped in this. Of course if you use plastic insulated wire this obviously will not be an issue… ;-)
I wanted to assess the ground conductivity therefore a set of 4 termination resistor values were prepared. It is well described in the LBDX how to calculate the surge impedance values in connection with the ground connectivity types.
I had 400, 450, 500 and 550 Ohm versions just to be prepared from poor to good grounds. The material of the resistor selection was a real headache. It is recommended to use composition type resistors but this is what not really available in Eu for reasonable shipping price. So decided to use 4x 2W metal film version in parallel which expectedly gives enough tolerance to survive the contests. As the antenna is LoS ~80m away from the transmitting antenna + the winter is not a thunderbolt season this should not be a problem.
I think my transformer was not perfectly wound as the measurement results gave a range of 1:9.7 to 1:9.9 ratio depending the termination value while this should be rather 1:9.
Used 2.4 long bamboo poles with electric fence insulators. Luckily most of the poles’ narrow end was small enough to drive the insulator directly with tight connection. Had few poles I needed to glue with hot plastic to reach the sufficient rigidity. Was no issues with the open insulator side (the wire remained inside) however the system was up for a long weekend only. The separation between the poles was 20m which made almost flat antenna wire (0.8mm CuZ) with average tension applied. Both ends of the Beverage have 15m long sloping sections to the feed/termination points.
The ground system at the feeding side consisted 3x 1.2m long (d=20mm) copper tube while drove 2x similar to the termination end. Considering that the best termination resistance falls between 500 and 550 Ohm I assume the ground resistance is less then 100 Ohm which is pretty good ground.
Just making sure that the common mode currents are out of the feeding system a coax shield (75m RG58) grounding applied ~5m away from the feed point. The rod is similar to the other ones used.
I picked the 550 Ohm version to use but after re-thought the whole I should have used the 500 Ohm version as with this value has the smallest SWR variation in the measured spectrum. However had no issue during the reception I could hear very well.
The termination value selection was the most funniest part in all. As the weather was pretty moderate (compared to this year’s winter which has not been similar in 20 years) the soil was very muddy and dirty therefore very deep as well. It took almost 20 minutes to walk one way the 268m (880ft) with at least 5kg ballast packed on per foot.
My Father was the designated volunteer who will swap the terminations while I’m engineering the miniVNA measurements. After we finished I forgot the specify that the winner value should be left in the socket as permanent for the antenna. No need to say he brought it back and showing them proudly with big smile did not lose them during the muddy walk. See, how important can be the exact task description and communication? :-D