Real World Measurements of a Multi-Band End Fed Antenna
using a 9:1 Un-Un
Excited as I was to get on the air with my new antenna, I didn’t take record any data regarding its SWR, radiation resistance (RR) and resonant point (X) with my antenna analyzer. Satisfied that the antenna worked by making QRP contacts in the WAE this weekend, I pulled out the analyzer and recorded some data for bands 40 through 10.
SWR should be 1.0 RR should be 50 X should be 0
This is the ideal but is not often the case in real life set ups especially in the field when operating portable!
I found one strange thing on 40 meters. The readings were markedly different if I held the analyzer in my hand or set it on a table by itself. The readings were better if I held the instrument in my hand. Holding the analyzer or setting it down made very little difference on the other bands with 17 Meters the exception, so I didn’t post those here.
MHz SWR RR X
7.030 4.3 104 101 Not touching
7.030 2.4 66 50 Touching
10.116 2.0 27 10
14.062 1.8 30 16
14.280 1.7 39 25
18.085 2.1 35 31 Not Touching
18.085 1.7 35 19 Touching
21.058 1.5 45 21
21.430 2.3 20 3
24.905 4.2 41 75
28.062 2.2 30 30
28.560 2.5 38 42
My antenna wire is 35 feet long and 30 feet above the ground and its orientation is horizontal, (perpendicular to the ground!)
Building the 9:1 UnUn was fun and I was eager to have a multi-band antenna!
This antenna got a lot of bad press among the ‘Antenna Guru’ crowd on E-Ham. They said their (facts) were from computer modeling programs, but there was a lot of opinion written their too and a lot of disparaging remarks toward anyone who would stupid enough to actually use one of these antennas. Their facts and data in no way came close to my real world measurements!
I plan to take this antenna into the field and test it as a sloper, both with the analyzer and on the air. I’ll post the results here.
I hooked up a tuner and took readings on 20 meters. I was able to get the SWR down to 1:1 and the RR to 57 using the tuner which is very close indeed to the ideal. The readings are sensitive to whether I held the analyzer in my hand when looking through a tuner. That bothers me. There seems to be some (not a lot) but some, RFI in the shack here too.
All antennas have trade off’s!