A tale of two baluns

When looking at running a random wire of any length the question of if to use a balun or not always comes up. Since they appeared in the early 90’s people have raved that feeding a random wire with a balun and coax is much better than bringing the feed line into the house where the QRM is much higher. Remembering back in the 90’s when there was not that many noisy plasma TVs or switched mode laptop PSUs or even the dreaded PLT using a random wire and bringing it into the shack via the window frame never seemed an issue. Fast forward to 2009 and with all the noise generated in a modern shack means that a coax fed antenna does have many advantages.  I am not going to enter into the variable resistance of random wires across HF and is 4:1 better than 9:1 – there are many sites on Google that cover this subject with much greater flair in technical depth that I could ever hope to.

Going back 15 years I was at a rally where the RF systems HF balun was for sale – and after reading some “spin” about the product and then seeing that in the very noisy hall signals were in fact not so masked by noise as at other stands where the antennas were directly fed into the radio. This stand was using a balun and a direct feed side by side where you could switch between them. Most interesting to me at the time! I had my first HOKA Code30 and a PC and a very nice (at the time) 17” screen – all which generated a larger amount of QRM than I really wanted. Enter the RF systems balun. A quick £40.00 later and I was the owner of a very small round item that would cure my shack noise on HF, wonderful!

A quick change in antenna layout at the QTH meant now my 40meter wire was fed with the balun and at the time some pretty decent double screened RG58. Quick tests showed that it was better, and yes the noises that splattered about HF were in fact gone! Well worth that hard earned £40.00. And has ever since then worked very well from QTH to QTH my trusty balun has always fed the random wire into the shack. 

This brings about today’s thinking - is my RF systems balun the best there is? Are there better baluns? Could I change it and notice a difference? Well they are some very good questions I asked myself! And you too should be asking yourself! Could my balun be good but could it be better?

A Google for baluns and peoples comments led me to have a look at the Wellbrook UMB. Now these are just a little more money than the RF systems balun but and it is a big but. I am so impressed with my Wellbrook ALA330S that I was already convinced that if they can make a loop that good surely they could make a better balun?

A quick search on eBay and volia! I was the proud owner of a Wellbrook UMB. Comparing the two physically the RF systems balun has an SO239 one end and a twisty on pole/stud the other end for the antenna, the UMB has a BNC (ugggh) coax connector and two twisty pole/studs for earth and the antenna.

Swapping the first balun out for the other was easy, I already had an earth running up to the body of the SO239 on the RF systems balun which was unwound from the coax and then connected to one pole of the UMB and the antenna swapped over to the other connector. The coax was terminated with a PL259 and not wishing to unsolder this I used a SO239 to BNC adaptor – I know not ideal but it was a test ok!

Before the change over I took three screenshots from Perseus with a spread of signals around LF and MF which I always find are a good test. I’ve added the screenshots in order which are before and after. Have a look and see what you think. I’ll do some more tests later on with the HF bands when there are actually some signals to test against. QRM wise I am pretty lucky that a quick sweep of HF shows they are more or less identical in the reduction of the local noises I have here.

Medium wave 1.6Mhz spread RF systems balun. (fullsize in the gallery)

Medium wave 1.6Mhz spread Wellbrook balun. (fullsize in the gallery)

If you check the qallery you'll see the rest of the screenshots taken this morning.

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