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THE MAGIC BAND (50 - 54MHz)
Activities on the 6 metre band

C42 transceiver and inverter power supply.Over the years I keep coming back to this band. First operations were back in 1980 with what was then a popular way to get onto this band an Army surplus C42 low band VHF radios. The contacts around metropolitan Melbourne were a lot fun and the C42 was a great radio to tinker with as it was close to indestructible.  

The photo right is the C42 transceiver and its essential inverter power supply. The frequency coverage of the C42 radio is from 36 to 60 MHz suited to 50 kHz channel-spacing. An internal crystal calibrator and a centre tuning meter enable the frequency  to be set accurately, but the radios were notorious for frequency drift over time. I guess two C42s in contact would happily drift across the band together! The RF power output was about 10 watts, but I believe substantially more power was possible.

After purchasing a second hand Yaesu FT736R in 2000 which had a 6 metre band module I started exploring this band again with both FM and SSB. I was constantly amazed during the summer months of the highly stable interstate contacts I could achieve with a modest 10 Watts on either FM or SSB. This was of course the normal sporadic 'E' propagation that occurs at this time of the year. The 6 metre band is unfortunately a band that has never attracted large numbers of operator, so you could easily imagine how many opening go un-noticed and un-worked.

The six metre band (50-54 MHz) is I have been told by more experience hams is the magic band where almost all types of radio propagation can be experienced. Typical path propagation found on the six metre band are path enhancements due to atmospheric inversion layers, although not as greater effect as on higher frequency bands, ionospheric refraction via the F2 layer at about 200Km in altitude and the mysterious Sporadic Es which are clouds of ionized air at around 100Km in altitude. Other more exotic forms of propagation include path enhancements from the ionized trails left by meteors passing through the upper atmosphere, which for some reason have their greatest effect at around 70 MHz and last but far from least are the ionized polar auroras.

The sun in real time courtesy of SOHO/[instrument] consortiumAll the effects mentioned have a common origin; the sun, pictured left in real time courtesy of SOHO/[instrument] consortium. SOHO is a project of international cooperation between ESA and NASA.

Sporadic E skip (Es)

I had in fact almost dismissed the six metre band as too noisy in the urban environment and requiring a half way descent antenna set up to take advantage of any of the above DX. However I do have some modest capability on the band, that is 10watts FM and SSB (Single Side Band) and a half wave 'J' Pole antenna. And on the 14 of December 2002 I heard a number of sold signals from the south east Queensland being worked on VK3RHF a local repeater. I was surprised to hear an even stronger signal on the input to the repeater, that is a direct path. The repeater was quite busy, so I tuned down to the bottom end of the six metre band and put a call out using Single Side Band. To my surprise I had a sold 5/6 reply from VK4PF located on the Gold Coast. I was even more surprised when he told me that he was using a half wave antenna attached to his house spouting. Openings on the six metre band were in fact as good as advertised!

I have put the contact with VK4PF down to sporadic E propagation. A bit of research has revealed that sporadic E clouds occur about 100km above the ground and need to be at about the half way point between stations. Also the optimum range for contacts via the E layer, are around 1500km and that the minimum distance is not likely to be less than 800km and not more than 2400km for a single hop. Multiple hops are not common and generally required to be across an ocean.

Sporadic E propagation is not un-common on the six metre band but it's not a daily event, so we need to use a bit of science and have a strategy to take advantage of this effect. Firstly most Sporadic E, but certainly not all occurs during the warmer months. It is not a night time phenomena. As mentioned earlier, the range of contacts via Sporadic Es are from a minimum of about 800km to a maximum of about 2400km with the optimum distance being around 1500km. So from a Melbourne perspective the vast majority of the Australian population that is within this range exists from the northern coast of New South Wales to the city of Cairns in Queensland with the optimum distance being around Brisbane and the Gold Coast. There fore we are looking for Sporadic E clouds more or less over or to the north of the Parks / Dubbo area of New South Wales to work into Brisbane and the Gold Coast area.

Monitoring Techniques

My DX plan for the summer of 2003/2004 from my QTH in Melbourne was to monitor various 6-metre band  repeaters and beacons in the northern New South Wales and Queensland area at various times of the day to identify openings and then to establish contacts on FM and SSB voice channels, 52.525MHz FM and 50.110MHz SSB.  

BEACONS REPEATERS
Location Call Sign Frequ Location Call Sign Frequ
Cairns Qld VK4RIK 52.445MHz Bundaberg Qld VK4RBG 53.775MHz
Townsville Qld VK4RTL 50.087MHz Army Peak Qld VK4RGA 53.725MHz
Macay Qld VK4RRG 50.077MHz Sunshine Coast Qld VK4R? 53.700MHz
Longreach Qld VK4RBM 52.345MHz Brisbane Qld VK4RLB 53.725MHz
Nerang Qld VK4RGG 50.058MHz Brisbane Qld VK4RBS 53.950MHz
Brisbane Qld VK4RBR 53.975MHz

Map of Australia indicating the position of various 6mtr band repeaters and beacons within Queensland. Year: 2002

Repeater sites are indicated in BLUE and beacon sites indicated in RED.

 

For more information on the C42 Wireless Set and similar wireless warriors see: http://users.monash.edu.au/~ralphk/

For more information on early UK military communications equipment manuals see: http://www.vmarsmanuals.co.uk/archive/files_index.htm

For more information on early British communications equipment see: http://wftw.nl/b-one-default.html

 

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Page last revised 28 January 2008 
 

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