YO3BN - Portable End Fed Antenna

Posted at - 7th Jun 2017

Portable End Fed Antenna - Part 3

I tested again this type of antenna, this time without any success. This is very sad because this time I was on the top of the mountain and nobody answered to my calls. On reception it seemed to be unusually quiet, indicating some subtle problems despite its perfect match to 50 ohm impedance.

First Test

Time: 18:00 - 20:00 PM
Date: 1st Jun 2017
Altitude: approx. 150m above sea level
Locator: KN45DE

Unfortunately, for this test I forgot the fishpole, thus the antenna was installed by randomly hooking it into some threes around. The antenna was connected to the ground using a metal rod, the impedance was correctly matched, but I was unable to hear my CW signals to Greece WebSDR. After about two hours of calling, two hams answered to my calls reporting very very weak signal (YO3AAJ/P and YO3CMY). I thought that bad report was due low height of the antenna.

Second Test

Time: 13:00 - 15:00 PM
Date: 2nd Jun 2017
Altitude: 467m above sea level
Locator: KN45DE

This time I set up a nice and strong antenna on the top of the mountain, perfectly matched to 50 ohms. During mountain climbing I met two amateur radio operators, YO3SRP and YO3EME which helped me to install the antenna. After two hours of calling, I got no answer on 80m. Then I made several QSOs on 2m, meanwhile I agreed with another ham located at 100+ Km away to do some tests on 80m, I heard him very loud an clear on 3710 KHz, but unfortunately he didn't heard me. Also, my CW signals didn't reach the Greece WebSDR, the noise floor was unusually very low, therefore all these issues indicating me that the antenna have some problems.

Conclusions

On 6th Jun 2017 I've done some tests at my base QTH with my 10m long wire antenna on 3705KHz and I was able to hear my CW signals on Greece WebSDR at 18:30 PM. So this crappy antenna severely outperforms my end fed placed on the top of the mountain, which shouldn't be correct. Despite of perfect match of the end fed antenna it seemed that does not work properly, actually does not radiate all power. So, I'll do an ultimate test some day between this type of antenna and a center fed dipole in order to choose the right one for my portable applications.

Update - 23th December 2018

I remember the only thing changed before going on the top of the mountain here was the configuration of the tuner, from transformer configuration to L-match configuration. So, for L-match I used the same ferrite core for the coil, 43 material. Later, I realised that some ferrite cores should not be used for high power inductors. Therefore, my antenna here didn't worked as expected because of the ferrite core. I tested this issue at home and the ferrite in the inductor turned red hot after 5 minutes of 50W CW in 3.7MHz. As a rule of thumb, the high perm cores like 43/52/61 materials should be used only for transformers while iron powder cores for inductors only.

73 de YO3BN