Saturday, September 17, 2011

QDFA vs. 310-degree Beverage - A Skywave Comparison

The results I reported a few days ago regarding the QDFA's good F/B ratio vs. the 310-degree beverage was for groundwave reception. Now DX-ers are more interested in skywaves than groundwaves, so tonight I set up a test to find out. Although there were a couple of unexpected results (Pori, Finland 963 stronger on the QDFA than the beverage for instance), the general picture is that the QDFA has 5 to 10 dB weaker signals from the back than the beverage, while it has 9-12 dB stronger signals than the 310 beverage from the front. Admittedly though, only NRK Svalbard 1485 and the NDB "BV" 399 were on the "right end" so the results should be treated with some caution. Add to this picture that the netSDR which was running the QDFA is 2-3 dB less sensitive than the Perseus, which ran the 310 beverage. Switching antennas confirmed this. The QDFA had an extra 10 dB of gain in front of it, a Kiwa preamplifier.


Anonymous said...

Dear Bjarne, A few years ago you sent a letter to NHK Kochi Japan. I work as an English teacher in Kochi and my student (an NHK engineer) brought the letter in to show me. He was so pleased to have received your letter and gave me a copy. I'm afraid I am rather late in getting in touch! anyhow, i hope you are still enjoying your hobby and listening to Radio Japan! I have never visited your country but intend to one day.
All the best, an English teacher in Kochi, Japan

Bjarne Mjelde said...

Hi! Yes I do remember the response from NHK Kochi! It is always a pleasure to receive AM stations from Japan, and I appreciate all the friendly responses I have received from station personnel over the years.