This is the second post in a three part series regarding the late May field weekend of the Thornbury and South Gloucestershire Amateur Radio Club (TSGARC).
The trouble with camping during May is it gets light early! Setup had been a long and busy day but the birds knew nothing of our endeavours and were chirping their happy, annoying song at first light. John (M3EQQ), despite slumming it at the house, was up just as early as the birds and made sure everyone was awake also 😉 To his credit he woke people with a cuppa but it was clear there was to be no sleepy lie-in… Mind you, it was going to be a busy day as there was food, rotor cable and plugs to purchase not to mention the completion of tasks outstanding from the previous day, delayed due to the extended time working upon the trailer tower.
Generally speaking the noise floor at field/portable sites is very low so you can hear almost everything, but making yourself heard is harder. For this event I wanted to make the club heard. I’d heard many good stories and good signals from stations around the world using hex beams, so I purchased a Hexbeam from Anthony (MW0JZE). This was fed with 400w from an Ameritron AL-811XCE amplifier. The result was fantastic, not only could we hear the DX but we could also work it 🙂
A large part of Saturday morning was spent assembling the hex. Yes, it took a while as I was careful to assemble it correctly and as per the YouTube video instructions. The antenna does not come with instructions which is a nuisance but the video instructions are excellent – just accessing them from a remote field is a little challenging… Next time, however, assembly will be much quicker.
After the hex was on the tower, John (M3EQQ) and I went to get the much needed food and cable to replace the damaged rotor control cable. The little castle town of Berkeley has some good shops so food was not a problem, but cable needed a drive further afield. Fortunately there is a branch of Attwoolls not far away and they were able to supply 30m of cable and new connectors. On our return it was clear the other members had been equally busy as we now had a full sized vertical 80m loop and a Beverage receive only antenna for the 80m band. Both the 80m loop and Beverage were connected to Rob’s (G4RNK) Kenwood TS-2000.
The Beverage was the creation of John (M0HFH) who had read much about its ability to overcome noise on the lower frequency bands; the field weekend gave the ideal opportunity to try a 1.2λ, 80m Beverage. Researching the many methods of construction John (M0HFH) came across some old papers published by the BBC research team at Crowley. This gave in-sight into the height of the antenna from the ground and some surprising information, higher is not always better!
The Beverage in various designs has been around since inventor Harold H. Beverage developed the antenna design based on designs used by Edmond Bruce at the Otter Cliffs US Transatlantic listening station in 1919. The antenna used during our field weekend was the simplest form of this design and consisted of a 9:1 home-made balun feeding a long wire (120m galvanised steel electric fence wire) terminated at its far end with a non-inductive resistor into a copper earth stake with 4 x 15m radials. A similar ground plane earth system was set up at the feed end to be the earth point for the coax feeding the radio. The antenna was set at 1.5m above the ground.
We attempted to match the Beverage terminating resistor to the earth system using a method adopted by W8JI which involved measuring the range (not the value) of SWR indicated on an MFJ-259 antenna analyser sweeping a frequency range from 1.8HHz to 7MHz and varying the termination resistor until the variation in SWR was minimised. Kyle (M6KBP) recorded the values of SWR in the form of a table whilst John (M0HFH) varied the terminating resistance using a switched resistance box; communications from one end of the Beverage to the other by 2m handheld. We settled for a termination resistance of 640 Ohms after some discussion of the results.
Listening to weak signals on the lower frequency bands, in particular 160m, 80m, 40m, the Beverage revealed a substantial reduction in background noise and an increased signal to noise ratio as compared to the TSGARC vertical with radials.
Rob (G4RNK) was responsible for the 80m loop. It was made from hard drawn, PVC coated, copper wire about 265ft in length. Its matching stub was made from 75 Ohm coaxial cable a quarter wavelength long, (66%). This matching stub was then connected to 50 Ohm coax which ran back to the TS-2000 transceiver in the radio tent. With a view to working stations to the East (Europe) and the West (USA and beyond!), the loop was orientated to face East/West with its nulls to the North and South. The feed point of the loop was 1ft above ground, the top of the antenna was at 30ft, suspended between to masts, so the mean height of the loop was 15ft for 80 the 80m band. This sort of antenna can be tuned for use on other bands with a transmatch antenna tuner.
The hexbeam replaced the 2m beam on the trailer tower as at 12kgs it needed a strong support. The tower will support something much heavier but the other masts would have been overloaded. It was raised to about 13m above ground where it pretty much remained for the rest of the weekend. Feeding the hex was an Icom IC-7200 and the aforementioned amplifier. The system worked faultlessly and some nice contacts were made, my personal favourite being Tokyo. Lots of contacts were made by myself and the mic was shared with John (M3EQQ) and Kyle (M6KBP). This gave John and Kyle the opportunity to see a capable station in operation and to talk with stations further afield.
Around 20:00hrs GMT about S3 of pulse type interference was observed from the West, this continued till we shutdown just after midnight. Interestingly the interference seemed to start around 14MHz and spread across all higher parts of the spectrum up to 50MHz. Higher frequencies were not checked. The interference was not observed on lower frequency bands – nothing was heard on 3.7MHz using the 80m loop. Swinging the hex to the East also greatly reduced the interference. In the adjacent field on the Western side there is a large overhead power line, but we understood this was not in operation… If the interference was emanating from the power line I would have expected it to hear it on 80m. A mystery, but there was speculation that it may be some farm machinery in the big shed located to the West.
Sunday morning dawned with another early call, cuppa and breakfast from John (M3EQQ). The remaining 10m masts were erected. With these we now had an impressive selection of antenna’s and the site looked great in the sunshine. In total there was the 12m trailer tower, 2 x 10m masts supporting the Tonna 2m and 6m antennas plus 2 x 12/10m masts supporting the 80m loop. With this selection of antennas it was a shame that we didn’t have more radio’s and operators. However, Rex (G4RAE) made use of the 5-element, 6m Yagi making several Morse contacts.
HF propagation was superb, strong phone contacts were had with Aruba on 20m, 17m and 15m, St. Helena and numerous other stations in the USA. It was clear that the hex, amplifier combination was delivering good performance. Band conditions remained excellent till shutdown soon after midnight. The mic was again shared with John and Kyle allowing them to make some excellent contacts. The interference noted the previous evening was not present till a similar time when it returned with exactly the same characteristics.
Shirley, John’s (M0HFH) partner, lent the club her wood burning fire. Its an excellent piece of kit that burns wood exceptionally well and provides lots of surface area on which to cook. So late in the afternoon, John (M3EQQ) started to barbecue chicken and sausages. Whilst we ate the food a friend of Rob’s (G4RNK) arrived with his quadcopter. The quadcopter had a small camera attached and despite it being a little windy good photo’s of the site were captured.
Monday was very different, the HF bands appeared to be in good shape for a few hours in the early morning when we had some great contacts, but soon after deteriorated leaving signals either well down on preceding days or non-existent. Andrew (G0RVM) took the opportunity to run an antenna workshop with Kyle (M6KBP). The workshop started with the basic principles of the dipole then progressed to calculating its size, construction and finally adjustments for resonance and on-air testing. The dipole was made for the 17m band and it clearly worked when compared with the hex. Another Foundation class member, Derek (M6xxx) got involved, helping Kyle with the physical construction of the dipole.
Nighttime arrived and conditions appeared to improve greatly. Again many contacts were made culminating with an excellent conversation between Kyle (M6KBP) and Ray (N4LEM) using his Collins HF-80.
Andrew G0RVM, John M0HFH and Rob G4RNK
