1997 VK MICROWAVE DX-PEDITION
The surge in
activity over the last 2 years on all microwave amateur bands
from 2 GHz through to 24 GHz has inspired several amateurs to
plan and then execute a "hit & run" DX expedition
across 4 states to either set "new" or where possible -
extend the existing VK Distance records. The principle aim of
this exercise was to promote even greater interest in these under
utilised bands of spectrum. The participants were myself Alan
Devlin - VK3XPD from Melbourne (the author of this article),
Russell Lemke - VK3ZQB from Port Fairy, David Minchin - VK5KK
from Adelaide, Trevor Niven - VK5NC and Colin Hutchesson - VK5DK,
both from Mt Gambier and Les Janes - VK1BUC from Chisholm ACT.
Our collective achievements can be best summarised as follows. Over a 3 week period from late July to mid August 1997 with little or no assistance from "weather enhancement"-
- 12 new VK Distance Records were set
- 7 existing VK Distance Records were extended.
Several of these records were actually "set or extended" on more than one occasion.
VK DX Records old & new.
An extract of the current VK
Distance Records as provided by the WIA FTAC Chairman - John
Martin, VK3KWA revealed the following distance record data. Note
: All distances are in kilometres, a hyphen (-) has been used to
indicate an existing distance record that was deemed unlikely to
be extended during this expedition, and finally, the figures in
brackets (nnn) indicate our "new" record.
Most of the established Distance Records were considered by the group to be readily extendible without the benefit of "enhanced" propagation (i.e "lift" as a result of prevailing weather conditions) however, there were still some lingering doubts with what was achievable for several of the longer distances. These concerns were later vindicated in the field with relatively poor signal strength reports being recorded for several contacts.
The Lead-up to the Expedition.
Three weeks prior to the actual departure date for our expedition, it was decided to organise a "get together" to arrange a final shakedown of all the equipment.
This meeting also ensured that all the necessary gear would actually fit into the cars ! Colin & Trevor drove from Mt Gambier to Portland, I drove from Melbourne to Moonlight Heads (West of Cape Otway) and Russell simply trotted out to the local foreshore at Port Fairy. As expected, signal reports from Moonlight Heads over these relatively short, "line of sight" water paths of 95 & 145 Km were excellent. A few minor hiccups with several transverters were discovered but these were quickly resolved later back in the "shack.
Having tested the gear & confirmed it would actually all fit in the cars, it was now a simple matter of waiting for our respective departure dates to arrive.
But one week prior to my departure while working at home I broke a bone in my left wrist. This resulted in the usual Xray's & a plaster cast and some concerns about my ability to participate.
Fortunately the fracture was not "displaced" so I decided I would be able to continue albeit with some discomfort.
In 1994 a Experiment conducted in the Brisbane area by VK4AZK, VK4ZHL and VK3ZQB, concluded that a microwave duct existed close to the coast over water and that it could be easily measured from standard meteorological data.At that time wide band 3cm equipment was used to communicate over paths of 100km, through what was believed to be a propagation medium similar to advection. This type of propagation is produced when heat from the sun causes evaporation of water into a cool moist air layer close to the waters surface, overlapped with warm dry air. Providing that air movement is minimal, a refractive duct will be formed .
The formation of
such a duct is illustrated in fig 1. The intensity of the duct is
the product of the air pressure, temperature and humidity. The
later two quantities having the greatest effect.
It was found in 1994 that communication over the horizon was only possible when the refractive level was in the order of 340 - 370 N and the humidity was around 70 - 90%. The presence of a high pressure cell, cumulus cloud and a temperature range of 18 - 24 deg C are a requirement to sustain a advective duct.
The conditions around Moreton Bay and the sunshine coast were conducive to produce such a duct on most days, and we hoped that the available advective propagation measured in the 1994 experiment, could be useful in our attempts to extend the VK4 records. Similar ducts were highly unlikely for the VK8 and VK1 attempts and for that part of the expedition, brute force or "line of sight" paths would prevail.
The increased performance of our narrow band equipment over the previously used wide band FM transceivers, would give us an advantage to work greater distances with similar propagation.
If the duct were to be more intense, then significant distances would be possible.
As the figures indicated in the graph Fig 4 show, the level of refractivity experienced was no greater than that found in 1994. A more detailed analysis of this chart is discussed later in this article.
The Expedition begins................
VK8 ...... Northern Territory
By Alan VK3XPD
26th - Trevor and Colin departed Mt Gambier for Toowoomba in
separate cars early at 0630 hrs. Trevor started his expedition
with an absolute boot load of "brownie points" because
he was taking both his wife and Mother in Law up to Toowoomba to
stay with relatives.
My part in the expedition also began early on the Saturday but I headed West to meet up with David in Adelaide for our trip to VK8. The Mt William 2m Repeater VK3RWZ was used to arrange morning tea at Ararat with Trevor & Colin who then continued north towards Qld.
Approaching Adelaide at 1600 hrs, I used the Crafers Repeater - VK5RAD for liaison and directions to David's QTH in Salisbury.
Sunday July 27th - During a visit to David's shack, I discovered the benefits of ATV. This transmission mode was used to excellent effect between David's father Keith - VK5AKM and Dallas - VK5WA to visually demonstrate various aspects of the hobby. Later we visited the rooms of the Elizabeth Amateur Radio Club - VK5LZ in a disused 45 mtr high water tower - a magnificent site for Amateur Radio with panoramic views in all directions !
Monday July 28th - David and I departed Adelaide in separate cars at 0830 hrs and headed for Marla Bore, 140 Km south of the NT Border - more than 1100 kms away. During our journey we chatted continuously on 2 metres FM to relieve the monotony.
We finally arrived 11 hours later and after some discussions about who "doesn't" snore, we agreed that a Twin Share Motel room was appropriate. Following tea and some discussions on suitable vantage points with a couple of "well oiled" local experts, we both retired for the night. It seemed however only a matter of seconds after David's head hit the pillow that he began to snore loudly. Unable to get to sleep - I moved out to the car.
Tuesday July 29th - David in his Commodore, followed a "road worker" east down the Oodnadatta Track some 30 kms to a vantage point that could quote "see for 200 miles". As David found to his dismay - this site near "Welbourn station" was somewhat disappointing and erroneous in it's description. After a few map readings, the location at VK5KK's end was found to be only 20 km in the desired direction, with dirt at least as high as the vantage point. The only redeeming feature of the site was a 30 ft tower which had of all things, a solar powered UHF repeater on it. I headed North on the Stuart Highway to Mt Cavenagh, 10 kms inside the NT border - a decision again based on the advice from the previous night.
this "mountain" turned out to be a pile of very large
rocks about 50 metres above the local surroundings with no
suitable access. I returned to a high point alongside the Stuart
Highway and established a poor 2m SSB liaison link with David
some 170 kms away to the south east.
The next problem to present itself was the traffic on the highway. It was so busy at that time of the morning with cars, caravans, trucks, road-trains & tourist coaches that it became impossible with the road noise to even consider setting up. I packed up and headed across country in the Futura wagon to a "high" vantage point some 5 kms to the East. From here on a rocky outcrop about 25 metres higher than my surroundings - 2m, 25 watts SSB into a 5 element yagi was still poor with heavy QSB but signals peaked at times to 5-3. Since there were no other high vantage points around there was little choice but to try for the QSO's from here.
Our first band was 10 GHz at 1155 EST. Signal reports were 5-1/5-2 with heavy QSB. Next was 5 GHz with significantly better reports of 5-3 both ways. Our 3 GHz contact resulted in 5-1 & 4-1 reports - again with QSB. The 2 GHz contact at 1325 hrs EST was the most difficult to complete. Signal reports here were 4-1 both ways. David actually climbed the UHF repeater tower and we completed the 2 GHz contact with the dish and transverter in one hand, while holding onto the tower with the other!
The overall lack of system gain (dish gain) as the frequency decreases and yet still using the same sized dish & similar RF output power as that used on the higher frequencies, contributed to these poor results.
Next band was 1.3 GHz. Again, due to a lack of antenna gain at my end, no signals were heard at either end. Refer to the section titled "Equipment used" for a more detailed description of our RF hardware. The final band tried was 70 cm at 1345 EST. I only had FM capability but signals both ways were fully quietening with some slow QSB - averaging S3 to S7 but peaking even higher at times. The 24 GHz band was not attempted simply because the distance was excessive for the wide band gear (FM) we had - so we both packed up & moved closer together in order to complete the remaining 1.3 GHz & 24 GHz QSO's.
As the daylight was running out fast and we still had a long drive back to our scheduled overnight stop at Cadney Park Road-house in SA, I set up 1.3 GHz at the Marryat Creek Fibre Optic Repeater station, 33 km inside SA and completed a 41 km FM contact to David who had set himself up on a "rise about 8 km inside the NT border. Signal reports without pre-amps were S3 both ways with some QSB.
We then tried 24 GHz over the same distance unsuccessfully. I moved closer to a distance of about 15 km but still no success. Eventually, I drove to David's site in NT to verify the functionality of our gear & then drove about 5 km back into SA and we completed a successful albeit short 5.9 km contact with signals "full quietening".
The lack of success experienced on these earlier attempts was attributable entirely to non line of sight paths. It was simply not possible to access a high vantage point that had clear uninterrupted views from inside the NT border over these larger distances to a similar point inside SA.
Having successfully established 7 new Distance Records in VK8 we headed for Cadney Park Road-house some 240 kms to the south arriving at 2030 hrs EST.
Wednesday, July 30th- Next morning after hearty breakfast we continued on to Port Augusta some 700 kms further south, but not before we checked out the impressive 6m mesh dish. This was amongst 8 other dishes ranging in size from 2 metres to 4 metres in diameter, that was set-up as part of a business enterprise that sold TVRO systems from this site. Later, at 1630 hrs EST we arrived at Port Augusta and after a brief "comfort" stop and some food we went our separate ways - David returning to Adelaide and I continued on towards Broken Hill some 400 kms away to the east.
On to VK4 .. Queensland
While David and I were in VK8, Russell, Trevor and Colin headed for VK4. Russell, VK3ZQB arrived in Brisbane on the 25th July a few days prior to Colin,VK5DK and Trevor VK5NC with the object of collecting weather data for the area to build up a profile of propagation conditions. This would later be used to gauge the effects on microwave behaviour in the tropics.
Monday, 28th July - Trevor and Colin went to Mt Mowbullan in the Bunya Range to work VK3ZQB at Mt Mee near Brisbane, a distance of 119 km.
This was a shake-down run to test their gear after the long trip up from down South, being rattled around in their cars.
The path was also interesting as it was entirely over land with some large hills obstructing the shot line. It was far enough away from the coast that the advection that was prevalent along the coast, was unlikely to effect propagation between them. A similar path in the South would at most times be pretty easy, but we were unsure if there would be sufficient tropospheric ducting to assist the signal over the horizon. As it turned out a path did exist and A one way contact on 10 GHz was worked with S5 signals and 5GHz with S9. No contact was made on 3GHz, and later a fault was found in the equipment and repaired.
Tuesday 29th July - A second attempt was made the next day from a high spot near Toowoomba to a high spot near Melaney. This path was clearer than the previous spot from Mt Mee to Mt Mowbullan although it was still "an over the horizon path".Signals on 10GHz were S9, a one way contact only, 5GHz were S9 and 3GHz were detectable but not good enough to work SSB. The later being due to the lower overall gain of the equipment compared to the 10GHz and 5GHz gear. The 10 GHz contact was a worry, as this was the second attempt to communicate and both times Colin could not be heard by Russell. After some time checking and re-checking our transverters, we discovered a new microwave phenomenom later named the "DK" factor. It was discovered that Colin's IF rig off-set switch had been bumped on; So he was transmitting 5 MHz down the spectrum.
The average refractivity for 28th/29th were 335 and 331 respectively. This did not account for the lift over the path and in fact the refractivity over the path was probably much less than the days average.Spot measurements for the 28th were 343 at 0830 hrs taken at Redcliffe near the coast, 320 at 1230 hrs taken at Mt Mee and 344 at 1530 hrs taken at Redcliffe. This indicated that the refractive index was much greater near the coast where the influence of the sun on water increased the refractivity, while the drier air over the land path was less able to bend the signal over the horizon. Interestingly a front had moved through on the 27th with thunderstorms and rain ahead of the front. On the morning of the 28th, stations from Moree in NSW were accessing the Toowoomba repeater, indicating the presence of a tropospheric duct.
illustrates the cross section of a front and it demonstrates that
along the length of the front, exists the mechanism by which a
duct can be sustained.
Either the frontal duct or tropospheric lift associated with the front would have been the most likely reason for the lift that we experienced on both of these days.
Thursday July 31st - I awoke at 0730 EST to a very heavy frost after a chilly night in the car on a roadside reserve 100 kms east of Broken Hill. Late that afternoon, I arrived at Dubbo for a pre-arranged meeting with Kerry Banke - N6IZW. Kerry works for the US based company Qualcomm - the source of the surplus 14/12 GHz satellite link hardware which is then modified for use on 10 GHz. (To date, some 40 units have been imported into Australia by the author from the US supplier Chuck Houghton - WB6IGP.) Kerry is involved with Marconi in the commissioning of the next generation of cellular phone system based on satellite technology from Globalstar. This system is similar in concept to Motorola's Iridium proposal where 66 satellites are placed in Low Earth Orbits (LEO's) and large dishes called Main Earth Stations "acquire" an orbiting satellite as it rises from one horizon and tracks it until it disappears over the other horizon 180 degrees away.The MES dish then re-position itself back to the other horizon, ready to acquire the next LEO satellite.
The Globalstar system will use Uplink & Downlink frequencies of 1.6/2.6 GHz for vehicular comms & 5.8 GHz for intersatellite comms, Telemetry & Control functions. Having completed the "tour", I then headed for an overnight stop at Narrabri.
Friday August 1st - after another early start I continued the journey towards Toowoomba . Using the "Mt Lofty" Repeater - VK4RDD for liaison, I arrived at the "Nasty Cough's" temporary headquarters just after lunch. The elapsed time was 6 days and I had already travelled over 6000 kms. The rest of the day was spent discussing the VK8 results & planning the next phase of the expedition in VK4 with Trevor & Colin at the Toowoomba QTH, with Russell in Redcliffe directing proceedings through "VK4RDD".
Saturday August 2nd - Trevor and Colin packed all their gear into Colin's Camry & we both headed for Brisbane and the QTH of John Lehmann - VK4AZK in Everton Hills. Later that day we organised a "shakedown" run of all the gear. Trevor & Colin drove north to the Caloundra foreshore while Russell and myself drove south across the Gateway bridge to Wellington Point. As expected the signal reports on all bands from 1 GHz through to 10 GHz over this relatively short water path of 80 kms were "rock solid". Interestingly, we found on 10 GHz that the dishes could be pointed in absolutely any direction and signals were still heard - even when a dish was turned 180 degrees away. Additionally, our 80 km QSO on 3.4 GHz was actually a new record as none had been claimed previously. For the next few days it was decided that Colin & Trevor would form one team staying at John's QTH while Russell & I would form the other team based at Redcliffe.
Sunday August 3rd - After a late start, Trevor and Colin headed north to Perigian Beach water tower, a little south of Noosa Heads while Russell & myself drove south to a vacant block of land with excellent panoramic views northwards at a point 1 km inland from Point Danger, near Coolangatta, still inside the QLD border - a distance of 187 km. Inquisitive "locals" told us this block recently sold for $1.2M so we referred to this site as our "million $ block" !
New records were set for 10 GHz at 1325 hrs EST with signal reports of 5-2/5-4, 5 GHz at 1330 hrs EST and 5-6/5-4, 3 GHz at 1341 hrs with signal reports of 5-1 both ways. We were unsuccessful with 2 GHz but Russell & I did hear Col & Trevor at 41, but they heard nothing of us. At 1445 hrs EST, we again repeated the 10 GHz QSO but this time I connected up a TWTA (Travelling Wave Tube Amplifier) to a small 240 volt generator. The TWTA delivers some 18 watts at 10 GHz with less than one milliwatt drive. Signal reports from Trevor and Colin were only 5 & 2 - TOO LOUD that is !! We have found from previous experience that these higher power levels (nearly 20 times or 13 dB more than our normal configuration) certainly makes a big difference in signal strength - particularly when trying to operate in marginal conditions.
Refractivity recorded for the day averaged 338 which is not particularly high, a fact that was indicated by the signal strengths that we experienced. Fig 3 indicates the spot refractivity measurements for the day and it can be seen that the value varies considerably through the day. We noticed that with the increase in refractivity toward the end of the day, signal strengths on 3cm improved. Further attempts at communication on 2GHz proved unsuccessful and it was agreed that the path was not good enough to extend the distance any further.
We had prepared to camp the night and continue stretching the distance the next day, but the forecast did not promise better conditions and so we returned to Brisbane. As it turned out the next day did produce a marginal increase in refractivity, but we had decided to watch and see while we concentrated on operating 24 GHz over short line of sight paths. The final results for the day were 3 new distance records for 3, 5 & 10 GHz in VK4 although these were to be repeatedly broken over the next few days.
Monday August 4th -Trevor and Colin set up the 24GHz transceiver at Scarborough Beach, a suburb of Redcliffe, and Russell and I set up at Pebble Beach near Bribie Island. This was a line of sight path over water of 11.4 km and full quieting signals were heard setting a first for VK4.
Russell and I then moved to Mt Mee where a line of sight path existed but contact was not possible. It seemed that there was a problem with one of the 24GHz transceivers as Trevor and Colin could hear the signal from Mt Mee, but unfortunately is was only one way. 10GHz was used as a sighter for the 24GHz sets and it made the problem of accurately pointing the 24GHz dish easy.
Tuesday August 5th - We were concerned at the poor performance of both 24 GHz & 2 GHz so spent the early part of the day checking out and optimising both systems. Later Trevor & Colin returned to Scarborough with 24 GHz and we drove north to an excellent vantage point in Ocean View. A successful FM QSO over 30 kms was made with full quietening signals recorded. This distance is now the current VK4 record.
Wednesday August 6th - another lazy day with myself & Russell investigating some potential inland sites north of Noosa Heads hopefully to assist in achieving even greater distances on the last remaining day of the expedition in VK4.
We had decided that tomorrow would be spent attempting to extend our current records in an incremental fashion. Trevor & Colin would go north and sit and wait while Russell and myself would head south stopping at selected vantage points and setting up our gear at progressively greater distances until we either ran out of propagation or reached Byron Bay, NSW.
Thursday August 7th - an early start for us all with Trevor and Colin travelling north to the "hill" we had found the previous day near Mt Cooroy, 10 km north east of Perigian Beach. Russell and I again returned to our "million $ block" at Coolangatta. After an initial signal check on 10 GHz (and a new VK4 distance record of 195 km it was decided that Trevor & Colin would later "pull up stumps" and relocate to the known Perigian Beach water tower site.
Unfortunately, their compass
bearing to us at Coolangatta from this new "hill" was
directly in line with another hill which had a Telecom tower
& other signal attenuating foliage on it. While they waited
at the "hill", Russell & I packed up and headed 15
km further South into NSW to a site near Terranora. From here we
extended our previous VK4 distance records for 10, 5 & 3 GHz
to 205.6km Signal reports were 5-3, 5-5, 4-1 respectively. These
QSO's also extended the existing VK2 records for 3 &5 GHz -
again only temporarily.
While Trevor and Colin relocated to the Perigian Beach water tower site, we drove further South to the "Look-out" at Brunswick Heads. On arriving at this site we found it to be somewhat disappointing. Although very high, our compass bearing to Perigian Beach was through a fairly tall mountain range south east of Murwillumbah. We had a successful QSO on 5 GHz but signals were very weak with some QSB.
As Cape Byron was only 25 or so kms away on a peninsula jutting out to the east, we again packed up and re-established ourselves on a verge near the Lighthouse at Cape Byron. The compass bearing to Perigian Beach was now predominantly over a water path - a distance of 246.4 kms.
Our first QSO was on 10 GHz at 1521 EST. Signal reports were 5-1. Then 5 GHz followed at 1531 EST with the signal reports of 5-1. Interestingly, I found after this 5 GHz QSO was completed that it had been made using the 3 GHz Feedhorn in lieu of the 5 GHz. As expected, when I replaced it with the correct feedhorn, an immediate improvement of several "S points" was noticed. The next QSO on 3 GHz at 1558 EST was somewhat difficult with the poor signal reports of 4-1 both ways with QSB. The 2 GHz QSO was unsuccessful with no signals heard at either end.
Finally at 1615 EST, Colin & Trevor packed up leaving us to complete a 24 GHz contact in NSW. Russell remained at Cape Byron while I travelled back to the Brunswick Heads Look-out. We completed our 24 GHz QSO at 1709 hrs EST. The signal reports were S9, a full quietening signal over an entire water path of 15.5km.
Comparing the refractive level measured on the 7th August to that which was measured on the 3rd, it can be seen that there there has been a significant increase in the level on the 7th, which is confirmed by the improved results on all of the microwave bands that we tried. Unfortunately the averaged level of refractivity measured on the 7th was still under what we regarded as a minimum level for "super ducting", and therefore the radio horizon was not much greater than would normally be present. It is our experience that had there been some" lift" in the form of ducting type propagation, we would have had more success. It is probable that the 8th August would have yielded even better result, but as the graph shows, the refractive level crashed quickly indicating the importance of timing.
Our achievements for the day were the establishment of new VK2 & VK4 distance records of 246.4 km for 10 GHz, 5 GHz & 3 GHz. We also extended the current VK2 record for 24 GHz to 15.5kms.
Summary of weather conditions in VK4
Unlike tropospheric propagation where the duct is elevated and can only be appreciated by plotting the data from radiosonde soundings, advection occurs close to the ground and can be calculated from ground level measurements.
Ideally calculation of the refractive gradient of the duct would be preferred, and if greater than -157N/km, then the duct could be termed super refractive.
However we have found that a simple ground level calculation can also predict the presence of a duct, although to what degree of accuracy, has not been confirmed.
Fig 4 is a graph of daily
averaged refractivity calculated from general meteorological data
such as, barometric pressure, wet bulb temperature and dry bulb
temperature. A nomogram was used to plot these quantities and
calculate the ground level refractive index. Shown against the
1997 data are levels calculated from the 1994 expedition weather
The effects of fronts on refractivity can be clearly seen as a sudden rise in the refractive index followed by a equally sudden drop in level.
The refractive level measured on the 7th August was marginally better than the 3rd August, a factor reflected in the distances we were able to work, indicating the ability of ground level measurements to predict the presence of propagation.
It can also be seen in the graph that generally the index remained below 340 with occasion peaks above 340, associated with storm fronts. This is indifferent to the 1994 data where the plots above 340 were the consequence of hot humid weather and not due to storm fronts. The relevance of the comparison is that when the refractive index was above 340 N units in 1994, microwave communication was greatly enhanced; In this exercise that prominent improvement was not noticed. Admittedly the equipment used in the two exercises was vastly different as was the distance worked, but it still indicates that the refractive index measured is relevant to the enhancement experienced, although there are other factors of the weather not included in the calculation that have a profound effect on propagation prediction.
Other indicators such as
humidity, calm air, high temperature and the presence of cumulus
cloud, aid in the prediction of ducting. The presence of cumulus
cloud on this expedition only became apparent as a front
approached, culminating in the development of cumulonimbus storm
cells as the front passed over.
The refractive index for any given day varied dramatically through-out the day and the plot for the 3rd August, depicted in fig 3, is typical. This was due to the rise in temperature as the day progressed and the changes in humidity, cloud cover and wind.
The climate was unusually dry for a sub tropics region with humidity averaging about 65% , peaking at times to 90% and dropping as low as 34%. The unseasonable dry cold climate that prevailed throughout this exercise,e was the most likely reason for the " less than expected" results. If the conditions similar to the 1994 exercise were present I am sure that we would have been able to communicate on microwave frequencies over distances far greater than we realized.
Similar propagation experiments have been conducted in the Gulf of Mexico and the Mediterranean Sea, where microwave signals have been transmitted hundreds of kilometres through ducts just above the waters surface.
There is much more work to be done in the tropics analysing weather data for propagation purposed and experimenting with microwave behaviour in the ducts produced.
On to VK1 .. Australian Capitol Territory
Friday August 1st - we re-packed our respective cars and prepared to travel south for the last & final phase of the DX expedition. Trevor returned with Colin to Toowoomba and attempted to restore his depleted bag of "brownie points" before heading to Canberra on the following Tuesday. Russell would stay on in Brisbane for another week before heading home to Port Fairy. I travelled via Sydney and stayed a few days with Alan & Kay Avery - VK2AXA & VK2DKZ. Alan has similar microwave interests to us and is already active on 10 GHz and expects to be up on 5 GHz very soon.
Wednesday August 6th - Trevor, Colin and I arrived in Canberra just after midday. Accommodation was found for Trevor's family but then any remaining "brownie points" he had in reserve, dissipated immediately, when it was decided we would use the last few hours of daylight to try for a 24 GHz QSO.
We visited the Mt Ainslie Look-out, ACT to check on a few potential sites, finally settling on a site to the south called Mt Sugarloaf adjacent to Pemberton Hill in NSW. At 1536 hrs EST we completed our QSO and established a new VK1 distance record of 16.5 km over this line of sight path. This also extended our previous VK2 record for this band.
Thursday August 7th - With the assistance of Les Janes - VK1BUC and some previous legwork conducted by my resident brother in law, we decided that our next series of QSO's would be attempted from Mt Stromlo, south towards Cooma. Trevor & Colin drove to the Mt Stromlo site while Les & myself drove south through the valley to a site called Bald Hill on the Numeralla road east of Cooma a path of 108 km.
Our first QSO on 10 GHz at 1115
EST resulted in signal reports of 55 both ways with slow QSB. The
5.7 GHz contact was excellent with 5-7 & 5-4 reports at 1125
EST. The 3 GHz QSO was almost identical with 5-5 & 5-6 at
1135 hrs EST.
Our final QSO at this site was 2 GHz with the somewhat disappointing reports of 5-2 & 5-1. This poor performance was again attributable a lack of system gain in both transverters.
Our final attempts to extend 24 GHz were ultimately unsuccessful. Finding the high spots were not a problem - gaining access was with many access roads padlocked or through Private property.
We did achieve a "one way" contact over a 55 km path but a problem in the other unit denied us a "two way" contact so yesterday's QSO of 16.5 km was unable to be extended.
These last 4 relatively short QSO's over a 108 km path set 4 new VK1 distance records and brought to an end a very successful DX expedition which resulted in 12 new Distance records and extensions to 7 existing records in 4 states over a 3 week period.
24 GHz - A pair of wide band FM Gunnplexers producing 40 milliwatts feeding a 400 mm dish fitted with a dipole feed.
10 GHz - Two types of transverter were used. The first was the Qualcomm system comprising of 12/14 GHz hardware modified back to 10 GHz and the second system was a purpose built design by DB6NT.
Each unit has a separate external oscillator chain giving +10 dBm at around 2500 Mhz which is then quadrupled in the main transverter to produce the oscillator injection necessary for either a 2m or 70cm IF.
Both units drive a 1 watt linear which then feeds typically a 600 mm dish with either a Dipole or Penny Feed system. The ERP approaches 2 kilowatts.
5 GHz - All systems were based on the DB6NT design which is a scaled up version of the design used on 10 GHz. Again, external oscillators are multiplied up to 5616 Mhz for oscillator injection to suit a 2m IF. The base transverter produces in the order of 250 mW which then couples to an external GaAS FET linear producing up to 6 watts. RF is fed to the 600 mm dish via either a Dipole or Cylindrical Horn feed system. The ERP is greater than 1 kilowatt.
3 GHz - This system is identical in design as that used for 5 & 10 GHz but again, scaled up with about 4 watts of RF power available. RF is feed to the 600 mm dish via a Cylindrical Horn feed. The ERP approaches 1 kilowatt.
2 GHz - There were 2 different systems used. The first was a complete "no tune" design based on an article originally presented in QST magazine. The other was an older style unit from the UK based company - LMW. Both systems use a 2m IF & produce about 4 watts from a pair of Mitsubishi GaAs FETs. Once again, 600 mm dishes are used and the ERP is about 500 watts.
1 GHz - One unit was a "no tune" design originally from QST with a 10 watt linear feeding a 40 element Loop Yagi and the other was simply an ICOM 1271A, all Mode transceiver feeding 10 watts to a "double quad" Bowtie style antenna. The maximum ERP available is about 250 watts.
70 cm - An ICOM X2A Hand-held developing 5 watts fed a 4 element Yagi at one end and IC24AT feeding an 22 element Yagi at the other. The maximum ERP was about 100 watts.
All systems radiate a Horizontally Polarised signal.
Thanks to Trevor Colin David Russell, Alan and Les who's combined effort has made this exercise possible. Also those who offered hospitality, accommodation and support during our travels through 6 states. We appreciate their contribution to the exercise and thank them for their effort.
Having read the article - it is hoped there may be other amateurs out there who also wish to become involved in the wonderful world "microwave" activity. If so, then simply contact any one of those listed above - QTHR.
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