Saturday, 28 February 2015

Interesting loop tests with 1:1 baluns on 160m

After reading some advice on a radioamateur forum regarding the use of a "short" loop like I have on 160m I tried a 1:1 balun between the ladderline and tuner instead of the built in 1:4 balun. I can't tune my loop on 160m unfortenately, it could be the Palstar AT1KM differential T-tuner has not enough capacity. The story goes that the R of the loop is lower as 50 Ohm and if you use a 1:4 balun R would be even 4 times less which is the cause of difficult to no tune. Another story goes that a 1:1 balun between the transceiver and the loop should supress interference, noise or whatever. Time to test the truth!

The Palstar is able to act as a endfed tuner by removing a bridge to the 1:4 balun inside. I tested it with only one end of the loop connected it didn't make much difference against my short vertical fed by coax and a autotuner at the feedpoint although the noise was 1 S-unit stronger. I use the vertical as reference for the tests I made.

I first connected a Diamond BU-50 1:1 balun to the ladderline and tuner. It immidiatly occured to me that tuning on 160m and 80m was easy but 40-10 got difficult. I then made a transmission on JT65 on 160m and was received but not with that good signals. I tuned in on some SSB stations from Italy and switched over to my vertical. The difference was astonishing, the vertical receive was at least 4 S-units better. And I was able to hear other stations that could not be heard on the loop. The balun is ok, nothing wrong with it. So this was not a great succes, the only advantage was that I could tune the loop!

Now, I don't have a lot of noise on 160m. But with the pre-amp of the Icom-706 on I can produce a S6 noise signal. Time to test the noise reducing story. This time I used a homemade balun with 50 Ohm semi rigid coax cable on a 4C65 ferrit core. You can see it on the picture. I connected it between the tuner and the radio. To keep a long story short, I cannot hear or see any difference! The noise was S6 with or without the balun. I then switched to the loop acting as a endfed and have S7 noise, again tested it with and without the balun and it did not make any difference.

What is my conclusion? Or what did I learn? Well, I can get the loop working on 160m with the tuner and a 1:1 balun but not with a 1:4 balun. Strange as others with similair loops can, though I doubt the effectivity of those antennas. My too short vertical is defenitely doing a lot better. Besides that, standard antenna theory never works here, for some reason it is always different from what others experience. I learned that when building a endfed and several other antennas. What I learned is that the advice given by others is not always working, actually I knew that already.

I have a great time in the CQ 160m SSB right now. Just worked HV0A from the Vatican with.....the loop fed as a endfed.

8 comments:

  1. Hallo Bas, mooi experiment. 160 meter is een leuke band. En Vaticaanstad is meteen iets bijzonders. 73 Paul

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    1. Hallo Paul, ja Vaticaanstad op 160m hoor je niet elke dag. 160m is leuk, maar je hebt er wel een flinke antenne voor nodig om echt te kunnen DXen.

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  2. Ook maar een Smatch bouwen Bas. Ben er zeer tevreden over. Past alles aan.
    Gefeliciteerd met HV0A.

    Peter

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    1. Hallo Peter, ja aanpassen wil prima met een 1:1 balun maar houd geen signaal over. Zou zo een S-match wel eens willen proberen. Kan ik die van jou niet een keer lenen om te testen? 73, Bas

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  3. Hallo Bas, Zo te lezen ben je lekker met de antennes aan het experimenteren. Zoals je zelf al beaamt, je leert er een hoop van. En inderdaad, de praktijk blijkt altijd anders te zijn dan de theorie. En dat is nou het leuke aan dat experimenteren. Je krijgt vertrouwen in je eigen ervaringen.
    En HV0A hoor je ook niet iedere dag, proficiat! Was het een ATNO?
    73 Hans, PE1BVQ

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    1. Hallo Hans, ik heb er vorig jaar ook al eens mee geëxperimenteerd. Maar niet met een andere balun. Er was iemand op het zendamateur forum die er stellig van overtuigd was dat een 1:1 balun veel beter zou werken. Nou, bij mij niet dus. HV0A is een leuke maar geen ATNO. Maar wel een nieuwe op 160m. 73, Bas

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  4. No, I never found a balun reduces noise, either. Better just to forget short loops and build an inverted L with elevated radials, even if the vertical section is 'only' 8-10m high. Just avoid half-wave wire lengths, and enjoy low band DX! A good environment helps, but that is often overlooked by the 'experts', too!

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  5. Hello John, I would like to experiment with a inverted-L. And will do that probabely when I got the antenna mast in the garden again. At this moment it's tnkering around with some wires and the possebilities I have. 73 Bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas