Monday, September 10, 2007

A 475-metre Dud

I wanted to replace the current 175-metre "Eastern North America" beverage with a longer one with the same bearing. I needed to make it a backlobe beverage because of a nearby seafront but since these antennas are bi-directional I thought that wouldn't matter.

Erecting it was an ordeal... through difficult terrain. But after many hours outdoor I had managed to get a very straight, no-sagging beverage. Time for testing. The "old" beverage was up so with the help of my two SDR-IQs I could make direct comparisons.

Well, the new one did bring increased signal levels on North American carriers. 4-6dB, which is not bad, but I had hoped for more. However, signals from the other end just about exploded with 15 to 25dB higher levels! So, instead of an improvement I got a 10 to 20dB worse SNR!! One notable example is my North America indicator station NRK Longyearbyen, Svalbard 1485. On the old antenna I had a strong, clean signal. On the new one the signal was stronger, but audio was distorted from several interfering stations.

Sooo.... longer is not always better.

1 comment:

TK said...

Hi Bjarne; I have had same results. Maybe we should consider real bi-directional two-wire beverages. Certainly I am looking forward into test of these next spring/summer before the DXseason 08-09.
73 tk
BTW tested briefly my East BOG of 300 mtrs at 40 degr. (can not lay it down for longer period until my neighbour has finished all the agri jobs before winter!). Indeed a low noise and beautifull signals from Asia ...