Antenna comparisons

Antenna comparisons:

End-fed Half-Wave versus Loop

Using FT-8 Log Data

Otto J. Arnoscht, N4UZZ

Three radio amateurs provided their FT-8 log listings for 07/29/18 005430 on 20m for comparison of antenna performance. Station A (N4UZZ) has a 350 foot rectangular loop at 27 feet. Station B (KJ6MTJ) has an end-fed half-wave antenna (EFHW from mounted north-south at 6 feet above ground on a wooden fence. Station C (KS4TAC) has the same EFHW antenna running from a 6-ft high position near the house sloping upwards into a tree about 35 feet high. About 20 feet of the 130-ft wire extends over the tree and descends downwards on the other side of the treetop. The slope points towards the southwest.

Between the three stations, 27 stations were decoded. An arbitrary signal value of -30db was assigned to any stations that were not decoded. The data from the FT-8 log are provided in tabular form and graphic form on Page 2.

The average signal reports for the three stations were:

Station A: -14.59 (350 ft loop at 27 feet)

Station B: -13.63 (EFHW on 6-ft fence)

Station C: -14.30 (EFHW sloping to 35 ft)

Five stations were not decoded by Station A that were decoded by Station B. Of these five, three were also not decoded by Station C. One dx station in Portugal was decoded by Station A and not Station B or Station C. One dx station in European Russia was decoded by Station B but not by Station A or C. Stations A, B, and C failed to decode 6, 6, and 7 stations respectively that were decoded by one or both of the other stations.

There were a total of 27 received stations. In comparison to Station A with the loop, Station B with the end-fed on a fence received 13 stations stronger; 5 stations about the same; and 9 stations weaker than Station A. In comparison to Station A, Station C received 6 stations stronger; 14 stations about the same; and 7 stations weaker.

The averages reported above were influenced by the arbitrary assignment of a signal report of -30db for stations not decoded. This appeared as a reasonable value to assign since stations with signals below

-24db are unlikely to be decoded. (It should be noted that the db values given here are WSJT-X signal-to-noise ratios and are not related to antenna gain values.)

Overall, the results are that the EFHW antenna strung along a fence at 6 foot height above ground winds up with the best performance on this comparison. It beats out a 350-ft loop at 27-ft height, and beats the other EFHW that is sloping up to a tree about 35 feet up. The overall perspective is that all three antennas performed very close to each other. With FT-8, there is a bit of a random factor in which stations are decoded or not decoded at any specific time period, and in this comparison stations that failed to decode a signal were punished in their scores.

This test underscores the idea that no special antenna structure is needed to work dx and that even a wire strung along a fence can be quite competitive. This should serve as a strong encouragement to amateurs who want to explore hf but do not have the means for expensive antenna installations.

Table 1

WSJT-X signal reports for 27 stations logged

Additional columns are subtractions of SNR values for the purpose of comparison between the antennas.

Below: Chart 1

Graphic presentation of table data. Each three-color cluster of columns represents one signal. The columns present the SNR of the received signals. Blue columns are N4UZZ, orange is KJ6MTJ, and gray is KS4TAC. Numbers correspond to line position in the table.