A Low Noise Receiving Antenna

Written by Garry Schumacher VA7AJJ / VA7NV

A couple of years back, I purchased a Wellbrook loop antenna.  They are extremely pricey but, maybe not so much, as I am finding out, that is if you want to enjoy Ham radio as best you can.

Here, at my location in Colwood BC, I had been using an inverted L as my main antenna, backed up by a 43 foot vertical for the higher bands (at the time of writing this article). Both antennas have worked well for me but with band conditions the way they are, my biggest problems have been to hear incoming signals rather than to worry about being heard by other stations.

Some background:  When I moved to this location, (2004) it felt like I was in Ham operators heaven.  All power lines in my area are underground and there was so little noise, this location seemed to be the holy grail for ham radio.  Fast forward to the year 2020 and that is no longer the case.  If I listen on my inverted L antenna, the noise is so strong that it registers a solid S-9 most every night. That means, any signal I want to hear clearly must exceed that strength or it is lost in the hash of the interference. No fun, believe me!

I tried all the usual stuff in an endeavour to find the source of that interference and eventually was able to diminish the strength of the noise by 2 S-units.  Not great, but nevertheless huge in terms of being able to copy desired signals. As we shifted into summer, I again noted a steady increase in the ambient noise until it finally reached the level where it had previously been. Talk about a bummer.

What do you do?  I started researching ways to address that issue.  One of the things that kept coming up was to use an active loop as a receiving antenna and to transmit on my inverted L. Obviously no amount of noise is going to have much effect on my signal when I transmit so all I had to do was solve the receiving issue.  If I could, all would be golden.  Right?  Enter the MLA_30+, a receiving loop made in China.  I found dozens of reviews of this antenna on Youtube. Based on those reviews, I purchased one through Amazon.ca, knowing that if I had any issues with it, Amazon would back me up.

At $65 for that loop, I would say it looks to be overpriced once you get the package but after it had been connected and working I had to admit, it did make a huge improvement over having to listen on the Inverted L. My listening enjoyment had just jumped up a notch. The usual S-9 noise level on 80 meters was reduced to S – 4 or 5 or thereabouts. Then it rained. The loop quit working and no amount of cajoling could get it to work.  Ahh!

Now my dilemma was do I continue with the far less costly antenna, in other words, buy another and hope it would work for a longer period of time or explore alternatives. I knew there were several other companies that were selling active receiving loops but all of them were much more costly than the Chinese made loop.

Being the naturally cheap Ham op, I opted to try building a receiving loop with a pre-amp purchased from Amazon. Sadly that too turned out to be a failure. Performance lacked what I hoped for quite dramatically.

Finally I decided to spend the money and buy one of the Wellbrook loops from Great Britain. I had it in my head that their loop amplifier was the best.  Four hundred or so dollars later, I found my Wellbrook loop on my doorstep.  You might think I would have rushed to get it assembled and tested but that did not happen for the next few days as I had other projects to finish.  Finally I managed to get around to it and connected it to my SDR receiver.  It worked, though initially I had some doubts, it was so quiet.  Yes I could tell it was working but the question remained, how well?

The dreaded band noise, when listening on the loop was ever so much lower.  This I found encouraging and determined to find the optimal location in my yard to set the antenna.  I eventually settled on a spot away from my house and my neighbours and any other possible interference generating locations.  Now, when I listened on the 80 meter band, the signal meter in my radio indicated a noise floor of 2 – 3, S-units. Could it actually be correct.  Had I really managed to drop the received noise from S-9 down to less than S-3? I had to test it out on some “known” signals at a time when I could compare it to another of my antennas.

I pieced together the items I needed to connect to my Icom 7300. It is equipped with an accessory that allows me to receive on one antenna while having the ability to transmit on a alternate antenna.

The Wellbrook loop was put into service.  It seemed like nothing short of a miracle when I switched the transceiver on and saw the S meter hovering between 2 and 3 S-units of noise while noting that the signals I was listening to were bouncing to a strength of 7, 8 or even S-9. I describe it as unbelievable!  Fantastic!  Worth every penny!  Time has shown me that a received signal will be down by about 2 – 3 S-units (12 – 18 db) on the loop as opposed to listening on the inverted L.

But, and it’s a huge but, I can hear a signal that only shows up at 2 – 3, S-units on the strength meter (IC-7300) whereas I would never have known that station was even there prior to getting this loop.  Since then, I have managed to get the MLA-30 working, with a larger diameter, more substantial loop which provides increased gain and I have to say it does a respectable job, however when compared to the Wellbrook loop, it is no contest.  On 80 Meters, the MLA-30 receives with a noise floor of S4 – S5 (on my SDRplay receiver) whereas the Wellbrook loop shows a constant noise floor of around S-3 on my IC-7300.

That suggests to me that the MLA-30 is a reasonable antenna for anyone’s needs but the Wellbrook loop is just that slight amount better and when it comes down to which will I listen with primarily I expect it is going to be the Wellbrook loop.

UPDATE:

The Wellbrook amplifier quit working just after the warrantee period expired.  Rather than spend the $300 or so that they wanted for a replacement amplifier, I opted to just continue with the Chinese made loop.  I also learned, when I switched it to use with my IC-7300 that the noise floor was better than what I previously had thought.  Before when I listened on the Chinese loop, as a comparison I had it connected to a separate receiver (SDRplay) and simply assumed that the meter reading would be virtually the same, but obviously that wasn’t the case.