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.

73

After waiting a while I have decided to take the plunge and purchase a ALA330S magnetic loop antenna for running as the main antenna for Perseus.

Currently I have a 35mtr inverted L up about 40ft at the end and 35ft at the 'L' to the ground then into a RF system MLB. This works very well but the layout of the QTH and the location of the shack means that from time to time in the upper HF bands my own QRM was audible. Perseus makes it very easy to spot rises in the noise level across bands, my Plasma TV (a well known brand) causes all kinds of spikes in 24 MHz when running. So with this in mind a search of the sites with reviews of the ALA330S was conducted and credit card in hand off I went to purchase one!

On arrival the antenna could not be more compact, you get an aluminium loop about 1.1mtrs and the mounting box at the base of the loop if you could say a loop has an up or down; along with a control box (12v power injector I assume) and being in the UK a 240v PSU and short fly lead. By default the loop comes with BNC connectors so that’s +1 for the loop as the Perseus has a BNC input - no need to change the BNC or put an adaptor on the input lead.

For testing I mounted the loop on the shack window sill (which is about 30ft up) in a loft conversion where the 2nd sprogg has now forced me to move into! With this in mind that *everything* I have is on in this room I began to do some testing. The first results were mind blowing and I mean it. I could null 909Khz BBC Radio 5 to remove the side splatter to hear 900Khz and 918Khz! Something the inverted L never allows - I have decent signal levels off the wire and 909Khz is very strong. The loop was amazing!

So I moved lower in frequency to try a couple of tests. First RTE on 252 KHz was found and peaked - then a rotation of the loop to null RTE and leave the other station audible. I was soon hooked on my new found "antenna" power and checked the lower frequencies and found the same effect. I could null from around 80 KHz upwards. This meant that the beacons and Navtex on 490 KHz and 518 KHz could be peaked or a stronger station nulled to allow the signal or signals underneath to be heard. This was very very good on 518 KHz!

As listeners are aware Navtex broadcasts tend to transmit over each other which would not be an issue to the ship(s) that were in local range to the station as they would only hear that one - however DXers have a bit more of an antenna and as a result the weaker stations tend to compete at the same time and normally result in no decoded text. The loop allowed me to null signals so that copy was 100% from the wanted station! LF DXers remember the ALA330S has lower gain at LF and MF than the 1530 or 1530S! So this loop was not even designed to work this low in frequency this well!

Moving to HF you see the 330Ss gain begin to show as Perseus reminds you in bands with high levels of signals by lighting the ADC clip light. Now that is something I saw from time to time on the inverted L but never like this. Anywhere about 4Mhz and I was greeted by the clipping LED and had to employ the attenuator - note only 10db was needed - but it was needed.

Going beyond the 10Mhz region of short wave and the nulling of the loop beings to drop away. You notice a very slight change in signal that's all nothing like LW, MW and the Tropical bands. But at 17Mhz I am lucky? that a PLT device is just audible - this can be nulled out; so maybe the local QRM can be but on signals coming from far off the effect is lost. I am not sure, but I can say it does well very well at HF should you have a signal that is local and causing as PLTs do some QRM.

As the bands have not been very busy of late I cannot say how well the loop performs on an opening but Sunday yielded some DX on 28Mhz which the inverted L could not hear at all - they were lost in the noise - whereas the ALA330S could.

So is it worth £220 YES, and would I buy another or recommend one YES!

As an idea of its performance; below is an image (taken just now) of the true level of signals that it provides.