NO3M

Amateur Radio

2200m Double Loop Receive Antenna

In the quest to approach the elusive 10dB RDF on 2200m, I recently reconfigured the co-planar EWEs (firing east and west respectively) into a anti-phased pair similar to the DHDL receive antenna designed by AA7JV for 160m:

Total length is approx. 356 ft, the top wire is at 50 ft AGL and the bottom wire is 3 ft AGL supported by “T” posts and plastic insulators.  The theoretical pattern compared to a single EWE (gain normalized):

Tests comparing it to a 2-element vertical array with 400ft spacing have been ongoing for over a week, but last night I decided to revert back to a single EWE part way through the evening “session” to gather data to compare the double loop configuration against a single EWE.

The following plot shows the SNR difference between the double loop and 2-el array and later the EWE and 2-el array while receiving N6LF’s FST4W-300A signals (5-minute transmit periods):

The average SNR difference between the double loops and 2-el array is 3.38 dB.  The average difference between the EWE and 2-el array is 2.09 dB.  That’s a 1.29 dB difference in favor of the anti-phased loops vs. the EWE.  However, a more pronounced difference was observed using the experimental station WH2XND’s WSPR-2 signals (2-minute periods):

In this series of data, the average SNR difference between the double loops and 2-el array is 6.75 dB.   The average difference between the EWE and 2-el array is 2.80 dB.   That’s a 3.95 dB difference in favor of the anti-phased loops vs. the EWE.  I tend to trust this data more than the 5-minute cycle as it’s more granular in terms of time and less likely to be subject to inherent averaging of the longer mode.  It also seems to reflect the theoretical increase in SNR (1x – 2x RDF) expected for antennas that differ by approx. 2.2 dB RDF (EWE 7.4 dB RDF,  anti-phased loops / DHDL 9.6 dB RDF).

The DHDL inspired configuration seems to be a worthwhile upgrade from a single EWE on 2200m.  It’s a lot less fussy than externally phasing (coax or twisted pair lines, inversion transformer, additional feedpoint and terminations, etc.) a pair of independent loops.

The astute observer may be wondering, “how is it that a EWE with a lower RDF is outperforming the 2-el array?”  Good question…….

 

630m / 2200m Transmit antenna updates

http://no3m.net/antennas/630m-antennas/

New 630m QSO distance world record set by VK4YB and NO3M

On October 14, 2019, at 1032z, VK4YB and NO3M completed a distance record setting QSO on the 630M band using JT9. This QSO was the culmination of two years of effort around every equinox since September 2017. Hopes were wearing thin as we were moving away from the recent equinox (Sept 23). Even when the path may have been open over the past 3 weeks, either end would be plagued with QRN. While the particular opening that facilitated this QSO was not as comparably strong as others in the past, something special was obviously at play.

The distance is 9307.5 mi (14979.0 km), increasing the previous record distance of 8351.9 mi (13441.0 km) set by VK4YB and K5DNL by almost 1000 mi.

Below is the screenshot provided by VK4YB:

 

(click image to enlarge)
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