Sunday, November 10, 2019

Testing the 40m super gain antennaproject in the PA-beker national contest

Half of the dipole situated diagonal in
the garden.
Today was the PA-beker dutch national contest. This is a contest on 80m/40m only between Dutch participants. Excellent for testing NVIS (Near Vertical Incidence Skywave) antennas. A project that is one of my favorites has been in my browser favorites for over 10 years now and I always wanted to try this antenna to experience it is really a miracle NVIS antenna. The original antenna was described by W4NVK in 73 Magazine from October 1969. A more modern version can be found here. Basically it is a low dipole on 2,1m above the ground. On the ground there are 3 reflectors about 21m long (dipole+5%) spaced 1,80m from the center. It should have 15dB rejection of unwanted low angle stations and noise. Vertical up forward gain would be 9dB. Well, that's all numbers....we want to hear the difference!

See part of the reflectors to get the idea

So, I built the antenna Saturday afternoon, it is a very simple antenna and it didn't took much time. When testing I immidiatly noticed less noise on the band and signals from nearby (Germany/France) were at least 1 S unit stronger compared to the inverted-V, a good sign!

I started the PA-beker contest on 80m, my inverted-V does well on that band. In the mean time I kept an eye on the MUF (Maximum Usable Frequency) for 40m. Best would be 7,1MHz or higher for 300km range. But unfortunately during the contest the MUF didn't came high enough, it was about 6,5MHz on 300km max. 40m was very, very difficult to make contact on within our small country. However I managed to make a few contacts after all, although I think it is a miracle it was possible with such a low MUF. I tried to record the difference I heard between the inverted-V and the NVIS super gain antenna. After some unsuccessful recordings I finally have one without too much QRM. Listen for yourself...
At the first second you here me switching and notice some difference. At 14-24sec PD0CQ is calling PA3EVY RX with inverted-V, 25-40sec PD0CQ is making the contact with PA3EVY this time RX with the NVIS antenna.

Actually I noticed the difference all the time. All my 40m contacts were made with the NVIS antenna.
So unfortunate I only made 14 QSOs. The last 15 minutes of the contest I spotted all the Dutch stations I heard. I worked everything I could hear (except PD0CQ since I didn't hear him anymore). On 80m there were 74 QSOs including dupes, nice but it didn't have my interest this time...


Thanks for your comment. Bedankt voor je reactie. 73, Bas