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.