GU4YOX - 160/80M Receiving Antennas
The Beverages
The low bands, namely 80 and 160 Metres have always fascinated me and one of the key problems that I have experienced on these bands is the ability to receive weak signals under noisy conditions. This is generally due to a combination of electrical man made noise or simply atmospheric noise that is so prevalent on the low bands. However, there are antennas, particularly for receiving that can help to overcome these issues to an extent that makes it possible to “pull out” the weak ones and make those all important contacts.
The first antenna that I used for receiving on 80 and 160M I built in 1998 and is a Beverage or “Wave Antenna” as it was originally called. This antenna developed by Harold Beverage is relatively simple to construct and easy to install. The receiving element does need to be at least two wavelengths long to be a reasonable performer. I have only been able to install a single wavelength on 80M and I use the same lengths on 160M (ie a quarter wave) and have found it very beneficial for me. So what does the Beverage installation at GU4YOX consist of? Basically, I have a good take off to the North West only being about 10 - 160M wavelengths from the Atlantic Ocean, so I decided to try and run my Beverage so that it runs towards the 300 degree direction. This tends to be a good direction for the majority of US stations and luckily, this is the direction of land at the end of my garden plot. The farmer neighbour that lives at the back of where we live allows me to run my antenna along the boundary of the property.
I use a 9:1 trifilar wound impedance matching transformer on a toroid former at the feed end of the Beverage and this transforms the 450 ohm, typical antenna impedance, suitably to match the 50 ohm coax feeder back to the shack. The Beverage antenna wire is suspended at around 2 metres high by garden canes along its length and the last 10 metres is sloped to ground where it terminates with a 500 ohm resistance before being connected to earth by a 1 metre long copper earth stake. I also use a South Beverage for winter work which is again the same sort of length but mounted along a hedgerow. This is generally taken down in the spring so that the hedge can be maintained properly.
Below are some photographs of the Beverage antenna installation.
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Shielded Loop for 160M
As mentioned earlier I've had high noise levels on 160M for years, with 9+20 being usual. The source of noise is unknown but I think it is just an electrically noisy location on topband. Being close to the Atlantic Ocean, on the west coast of Guernsey it is largely a rural area with some small horticultural growing businesses nearby. About 4 years ago, the Beverage antennas to the south and west have enabled me to work many new countries on 160M. I specifically recall in October 2004 being called by KH6AT and KH6ZM for new countries and States for me. This is a difficult shot from Western Europe and I really was shocked to have made the contacts. The volume was very high and the noise just bearable on the Beverage antennas. I use a Yaesu FT1000MP Mk V and a VL1000 Amplifier usually, and my transmit antenna is an Inverted L. This can be anywhere between 45' and 86' high, dependant on weather conditions. There is around 4500' of ground radials connected to the base of the antenna assembly.
I have read with great interest many articles and heard several stories regarding loops and I thought I would try my own out as an extra string to my bow for CQWW 160M in January 2006. Well, I finished it in time and it worked a treat for me with good results. I managed to log 963 QSO's of which over 300+ were with US stations (Thanks!). So how is a loop like this constructed ? Let me explain how I built mine for simplicity and solid construction.
Firstly, I was given some ex-GSM antenna coax LDF5-50 This is a heliax antenna type coax of 50 ohm impedance and it is solid in construction. Its loss characteristics are excellent and it is not that difficult to obtain a short length to make a loop like the one I describe. I used a 20' length in total and formed it into a circle, taking care not to get the shape un-circular. The diameter is just over 6' when the loop is closed. The loop was measured exactly for its centre point and at the top of the loop a 1" section cut out of the outer conductor only.
The loop of coax was then secured to a timber 2" x 2" cross frame assembly and clipped with plastic cable clips (available from your electrical wholesaler or horticultural stockist). I screwed the clips using stainless steel screws as the salt air in Guernsey can corrode galvanised components easily. The bottom of the loop is comprised of a 6" x 6" galvanised box which can accommodate a pre-amplifier in the future if required. I used some 28-42 mm plastic weather sealing glands to stop the rain getting in. Across the two inner cores of the coax is around 1000pf of capacitance at setting value. I used two 300-1000pf trimmer capacitors in parallel and tuning was carried out later. The outer sheaths are connected together and to the coax back to the Rx. The inner core is also connected to the inner of the coax back to the Rx as can be seen in the photos below.
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When your loop has been constructed and you are ready to tune the loop, I found it easier to take a very long 2 core cable out plugged into the headphones whilst tuning the loop for a peak "noise" in the middle of the day. You could also use hand held or GSM phones if you have "Free" minutes on a couple of mobiles! Anyway, it will tune for maximum noise and that is where to finally leave the setting. I used 50 ohm coax back to the shack and I did not have any broadcast interference problems with the loop. I select the Rx button on the Mk V and select between Beverages and the Loop. The loop is by far the quietest and the signal levels only drop around 20dB. I showed my friend and great DXer Mike GU4EON and he could not believe the difference from the Inv-L. I also mounted a rotator on the ground post and it did not seem to make any noticeable difference except for reducing noise. Noise was loudest end firing and this tended to be towards the house area. I left it perpendicular to the house end firing to the US and EU.
Here is a recording of a QSO being received on the loop during the 2006 CQWW 160 contest with KV0Q in Colorado, received on the loop at 0430 in the morning:
KV0Q QSO (Nearly 2MB)
There is nothing original here in the loop design, it just works for me .
Good Luck with your Loop!
Bob
GU4YOX
