Category Archives: Amateur Radio

9th July 2020- Mt Tumorrama and Tumorrama hill

These two summits are fairly near each other, making them an obvious pair for a dual activation. The higher of the two is Mt Tumorrama and there is a communications installation on the top, consisting of a compound containing a small building, a tower, lots of antennas and at times some spurious signals can be heard on HF bands, most likely to be from inverters for the heating and cooling system.

I drove out to this area via the Brindabella Rd. It is about an hour and a half to Mt Tumorrama from Canberra.

The activity this time was mainly on HF, with a bunch of contacts with VK2/3/4 and ZL1(BYZ) on 80m and 40m CW, finally a 2m FM contact back into Canberra with VK1AD.

Moving on to Tumorrama Hill, I drove around to the western side of the hill and parked as high as I could, on the side of a fire trail. Walking up to hillside through low bushes, the silence of the forest is only punctuated by bird calls. A very pleasant place to be.

The HF gear was set up again and this time it was CW only, on 80 and 40m. No 2m contacts were logged. Again vk2/3/4/5/7, ZL1/2/3.

I drove home on the Brindabella Rd, descending from about 1100m to the Goodradigbee River then climbing back up to “Picadilly Circus” where Brindabella Rd, Mt Franklin Rd and Two Sticks Rd meet, then driving back into Canberra via Uriarra Crossing over the Murrumbidgee River.

Equipment Repairs

Kenwood TR751A – pot replacements

The Kenwood TR751A 25w multimode radio for 144 – 148 MHz is well regarded, with a sensitive receiver and good transmit quality. However the pots installed as dual concentric types for the AF Gain, RF Gain, Squelch and RIT functions have a reputation for failing. The manufacturer has discontinued supplying spare parts for these radios as they are now about 30 years old.

A source of replacements was identified in very similar pots stocked as spares for a Ranger CB radio at R&R Communications in the USA. This source was documented by members of the Yahoo Group for TR751 and TR851. (The group recently moved to

I ordered and received the replacement pots but had not installed them, the job waited on the back burner while I was preoccupied with other matters. With my interest in portable operations on 2m ssb/cw I realised that this radio could provide the additional power I sometimes wanted (additional over the FT817’s 5 watts) and could be a useful part of my portable operations. I am aware that the increase amounts to only 7dB but sometimes that makes the difference when using small antennas you’ve carried up to a summit and reassembled there.

After removing top and bottom covers, knobs and the front panel cover, I removed the two pots, unplugging the cables from their headers on the PCBs mounted on both pots. Desoldering the old pots from the boards was a long winded process and I found that my solder wick was not working as it should. I suspect the solder originally used has a different ratio of tin:lead and therefore needs slightly higher temperature than the 60:40 I usually use. Eventually the pots were off the boards and the new problem was to fit the replacement pots. The spacing between the three pins of the front pot section and the pins of the rear pot was quite different between old and new pots. I decided to put in small extensions for the pins of the rear pot. This was done using wire that was cut from resistors and capacitors after being soldered onto a PCB for a filter kit. Also the switch connections were different, requiring a jumper to be inserted between two pins on the PCB.

Following reassembly, the new pots appeared to protrude from the front panel much further than the originals did. I found this could be largely resolved by installing an extra nut on the control to effectively position the pot further behind the front panel. The pic following shows the result of this adjustment. A minimal amount of threaded shaft protrudes in front of the mounting panel. The limiting factor was the PCB visible here that is pushed against the assembly behind it, in fact I had to wind this pot a little bit forward because I couldn’t return the front panel assembly fully to its correct position without doing that.

Showing the two pots and their PCBs and wiring

Once back together the radio was tested ok and later I used it for a test on SSB from Black Mt, Canberra. I had a quite successful activation on 2m ssb, making contacts into Sydney (about 270 km) and to Nimmitabel (about 100km) using the TR751 and a loop antenna that had been lent to me by Andrew vk1ad. it was mounted on a short fibreglass pole.

During the testing of the radio I was pleased to see that its current drain on receive was 400 mA, which is slightly less than the FT817. On transmit full power it drew almost 6 amps. No problem for the LIFEPO4 battery normally used, which has a 20C rating, meaning it can provide 20 times its AH rating. 4.2 x 20 is 85 amps. the relatively low current drain on receive means this radio is a good option for using on battery powered activations. By comparison the IC706 or FT857 style radio would draw twice that current on receive. On transmit, the bias level of the final amplifier would double that current even before producing any RF. Turning the power level down on the higher power radio to its minimum of say 5 watts does not change that bias current, so running those higher powered radios at low power is very inefficient. It doesn’t matter if you only want 30 minutes of operation, but the same power consumed by the 706 in 30 minutes of reception would run the TR751 for at least double and possibly 4 times the 30 minutes.

Icom IC703 portable HF multimode transceiver

This rig was my primary HF rig for SOTA and parks activations. But it developed a problem in the VFO circuitry, behaving as though the dial was slipping. Turning the dial would normally result in the frequency changing continuously. However the fault was causing the frequency to freeze occasionally. I didn’t mind turning the dial a bit more but I thought that if some of the components in the encoder were faulty, maybe more would be faulty before too long and I should replace it.

I ordered the part from Icom Australia and it turned up after a predicted delay as it had been out of stock. I was told the part is used in multiple other radios including the recently released IC9700. It was reassuring to know the part was still in production.

The vfo encoder is located in the control panel for the radio. It just sends up and down signals back to the main unit. It is based on a set of LEDs and detectors, I assume light dependent resistors, arranged In a circular pattern at regular spacings around a central shaft. A circular disc with a set of holes or windows cut into it at specific positions corresponding to the LEDs allows light to pass through from the LED to the LDR. The vfo tuning direction is deduced from the timing of when light is first detected by each sensor, compared with a twin located slightly more or less than 180 degrees further around the circle. If the sequence of light detection is the sensor at 0 degrees followed by the sensor at 181 degrees, the dial must be turning clockwise so the frequency is required to move up. and vice versa when the dial is turned anti clockwise. Well, that’s how i understand it. The entire assembly is sealed into a small package looking like a potentiometer and has a cable terminated in a small plug.

The control panel for the IC 703 is very similar to that of the 706. I think it’s likely that the 706 front panel looks identical inside and this fix would apply to that radio series too.

The control panel after removing the vfo knob

Top right is the grey RJ series microphone connector, below that and behind the shield plate is the encoder. I unscrewed the nut on the encoder first. The PCB has to be lifted out of the case, a procedure I performed with a lot of care for fear of damaging the board or traces on it. Once the PCB is removed the encoder can be removed and the new one installed in its place. I removed the mike connector to get easier access to the encoder.

The PCB inside the control panel
The encoder with cable

After that I replaced the knob on the encoder shaft but it was loose and i couldn’t see how it was attached. Many knobs on Icom radios have a grub screw inside the knob, covered up by the rubberised section around the knob. Removing the rubber revealed nothing of the sort. Looking for help on the web I found reference to a small spring steel clip inside the knob. There was none inside mine. Then I found it on the workbench where it had fallen out when I originally removed the knob. A bit of careful work with tweezers put it back into the knob and the knob then went back onto the shaft and stayed there.

The spring holding the vfo knob to the shaft

Reassembled, the acid test was to turn it back on. Initially it appeared to be dead. I recalled a reset procedure and tried that without effect. Reading the manual page on the reset I found the correct procedure was to hold the up and down buttons then press power. Following that procedure the rig came alive, to my great relief, and I was able to tune in some broadcast stations using a 50cm piece of wire.

I now have to take the rig out for a field test to confirm it is back to normal.

Bullen Range, vk1/ac-033, 9th May 2020

The walk up to the summit of Bullen Range is a 5km effort, with a few steep sections but mostly reasonably level walking along a fire trail. Access is from Tidbinbilla Road which connects the village of Tharwa with the Tidbinbilla Nature Reserve. Bullen Range is a few km west of the Tuggeranong Town Centre.

Bullen Range is west of the Tuggeranong Town Centre in southern Canberra. AC-033 is the highest point of the range.

The map above shows Tidbinbilla Road and the connection from the suburb of Gordon. The river shown is the Murrumbidgee. Crossing it at Point Hut Crossing and then turning right onto Tidbinbilla Road leads to a parking spot at a gate into the Bullen Range area just east of Paddy’s River.

There are six gates to pass and only one can be unlatched. You need to climb over the rest. The track goes to the west of Barnes Hill, then two right turns lead to an uphill climb to the ridge line. This 5km trip took me about 90 minutes this time.

After arriving onsite and making several quick contacts on 2m FM with locals, the HF antenna went up on the telescopic pole. A felled tree served as an operating table and a wood stump became a seat.

Just as the HF contacts started, the rain started. It had come from the west where my view was obscured by trees. The tarp I usually sit on was hastily set up as a rain shelter.

The radio and other gear was sheltered from the rain by a tarp. Photo extracted from video clip
in the original photo some raindrops were visible but they have vanished in the conversion from video

After the radio contacts dried up, and while the rain was still light, I packed away and set off back to the car.

Rain visible to the west on the return trip

After reaching the car and stowing the gear in the back, I sent a message to my WhatsApp group reporting that I was back in the car and en route home.


Travel distance to parking position. About 10 km from Tuggeranong town centre, south Canberra, via Point Hut Crossing over the Murrumbidgee river.

Walk distance from parking spot: about 5km each way.

Terrain and slope: along vehicle trails and fire trails. Some steep sections. Some rocky ground with slippery sections, care advisable. Six gates to climb over or go around (in one case only).

Summit elevation: 925m

Accessibility: good

Permission required: None. Location is the Bullen Range nature reserve, open to the public except in periods of total fire bans or when notified on the ACT Govt website.

Phone coverage: Optus and Telstra services are readily accessed here.

Booroomba Rocks VK1/AC-026 on 16/11/2019

I was invited to accompany Andrew Moseley VK1AD on this activation.  It had been some time since we activated together so it was an extra pleasure doing this one.

The previous time I activated this summit was actually also a joint activation with Andrew.

The main thing we both noticed both enroute to the parking area and on the walk up to the summit was how dry the bushland was, areas which were previously green and even slightly damp were bone dry this time.  The long drought had certainly made its mark even in southern VK1.  We both thought that the hot summer that has been forecast will probably discourage activations in the bushland to the west and south of Canberra, due to the risk of bushfires.  Walking an hour into dry bushland does not make much sense and in fact risks not only the walker’s health/safety/life, but also risks the life of rescuers.  Summer may be a quiet period in terms of local activations in the forests near Canberra.

The walk up to Booroomba Rocks features large rocks like these



The climb up to the highest of the three peaks comprising the Booroomba Rocks cluster requires descending into the bush between the two southern peaks, then climbing back up through bush and then onto the rocks, after which it is an easy walk up to the tree that my telescopic pole was lashed to, to support my wire antenna.  I operated on 40/20/17m and also called cq on 10m just in case something was happening there.  I made contacts with other mountain activators in New Zealand and in Japan, as well as several contacts with home stations within NSW, Victoria and South Australia. My total contact count was about 12.

Andrew VK1AD operated on 144, 1296 and 2403, using an FT817 driving transverters on the higher bands, each with a PCB antenna seen in these pictures.  He made at least 4 contacts on each of those bands.  A number of Canberra operators called him as well as several on other summits, including Ted VK1BL on Mt Ainslie and Bill VK1MCW on Mt Stromlo.  Wade VK1MIC called in from his home station as did Peter VK1JH and Matt VK1MT.  Dermy VK1DB also called on 144 to give his brand new callsign a workout.  He recently passed the advanced licence course.

I was pleased to find this climb was much easier than last time I came up here.  On that day we first activated Pheasant Hill and then came up to this one.  My feet were very sore after that day, possibly due to my walking boots being too tight.  On this occasion I wore the Merrell mid boots I had worn on my walk in Spain, which are still in good condition and still comfortable.  I did have a few aches the next morning, but that’s ok.

A good day spent playing radio and I got home in time to prepare for a social function in Canberra later that day.

Mt Gillamatong, 2nd Nov 2019

To get back into some sota activations I drove out to Braidwood and walked up Mt Gillamatong. I set up the gear and antenna near the trig point but was disappointed to find high noise levels and an almost unusable 20m band. And I had left my logging tablet at home as well as the 2m fm antenna – but that would have been unusable anyway as the FM HT did not work, see below.

I had a contact with ZL1BYZ on 20m band cw, no other callers there. Went to 40m and worked an S2S with Peter VK3PF/p (very low at that stage) and Steve VK7CW at better strength, called for a while on ssb on 7090, no replies. Noticed a JA had been spotted on Sotawatch calling cq on 18 mhz so went up there, scraped in a contact. Then worked another Japanese operator at a home location. Geoff ZL3GA then, still on CW on 18 mhz and by now it was after 0000 UTC so a second contact with ZL1BYZ was made.

All up, only 7 contacts, all on CW, despite some time spent calling CQ on SSB.

A message from Canberra chasers asked about 2m FM possibilities. I had the HT but its battery was flat and I had no spare. Sorry about that, guys.

After getting back to the car I visited the Braidwood Bakery and ordered a pepper steak pie and a coffee.

The KX3 in the sun, unfortunately

Not my dish

Base of the pole with guys

There’s an eagle up there to the right of the pole

On the way down the hill, looking east towards Braidwood

SOTA activations in Spain (3)

The next day after arriving in Pamplona and the activation with Guru EA2IF arrangements were made for another activation which would be NV-119 San Cristobal. This activation was made with Ignacio EA2BD. He had already activated this summit during this year.

The antenna, one I had borrowed from Andrew VK1AD, was a LNR EFHW and was setup as an end fed half wave for 20m.

With the antenna fed directly from the KX3 it was showing a SWR or 2.5 so I put the Elecraft T1 into the circuit, producing a 1.0 swr for the kx3.

This setup enabled me to make a number of contacts on both cw and SSB, on 20m. As it was the middle of the day we did not expect any dx and there was no signal from the USA or further afield.

Ignacio and I pose for the selfie

Yes I’m having fun…

I record here my sincere appreciation of the effort made by Ignacio to help me with this activation, also he drove twice to Roncesvalles, the second time was to retrieve the logging tablet which I accidentally left at the Bar there.

After the activation I was invited to join Ignacio and his wife and daughter for lunch at their apartment. This was a very pleasant occasion for me and I felt very honoured to be a guest in their home.

Thanks again, Ignacio EA2BD.

Qualifying a summit – making 4 interstate contacts – using the 500 milliwatt Pixie morse transceiver hi hi

I built up the Pixie kit, having bought it a year ago or more, just to see how it worked and intended to try it out on a SOTA activation.

Being invited to accompany Andrew VK1AD to Mt Marulan for a return visit, having done the same in December 2018, I decided to take the Pixie along to see if it could make even one contact with 40m conditions as dicey as they are at present.

I set up the station to use the Pixie, with the ZS6BKW doublet fed through an Elecraft T1 tuner and the choke balun recently built. (Did I write about that? Maybe not.)

I listened for a minute or two on the Pixie’s 7023 khz and could hear VK2ARZ calling CQ with a very high offset frequency, my guess was that he was on 7025 so would not hear me operating on 7023. The Pixie’s receiver is a direct conversion receiver without any inherent selectivity so if my ears had 10 khz frequency response I would have heard stations out to that offset in both directions, ie. higher and lower in actual frequency, eg. A signal on 7013 would produce a 10 khz frequency difference so the 10 khz would be coming through the receiver, as would a 7033 khz signal also produce a 10 khz audio frequency. My 69 year old ears don’t have that bandwidth any more, they have an inbuilt low pass filter.  🙂

So I spotted myself on Sotawatch using the vk port-a-log software on the android tablet, called CQ using the little blue hand key, listened, then called again. A big signal loomed in the earbuds and it sounded like a bug being used. Was it Steve VK7CW, yes, it certainly was, after the call letters marched across my ears and I logged the contact using the tablet. What strength was he? I didn’t know, sounded pretty good so I gave him 579. Received 559 in reply, not bad for half a watt. Steve said he was running an FT817 at 5 watts out. Monster power.

Three more contacts, regulars John VK4TJ in Toowoomba, Peter VK3PF in Churchill Victoria, and finally Paul VK3HN from Melbourne made it into the Pixie log and I’d qualified the summit in 11 minutes using a Pixie half watt, two transistor + one IC transceiver, that had cost me $9 for the kit.

In between the contacts I could hear some weak signals and I wondered how strong they were, perhaps they were others who I wasn’t hearing well enough to copy. So after completing the 4th contact and calling another CQ just to be sure I had worked all who were there, I transferred the antenna to the KX3 and had a better listen to the weak signals. They were weak on that radio too, and I think they were dx stations, probably US operators in a contest of some kind.

Pixie 500 mw transceiver as built above, and as used, below

L-R: Elecraft T1 tuner top left, Pixie PCB, 3S LIPO battery, hand key. The Pixie board is about 2″ x 2″ or 50mm sq. 

The rest of the activation was fairly straightforward using the KX3 and the same doublet antenna, some contacts on 80m, most on 40m, the Shires contest was running so I had to look up my shire, I quoted GM2 (Goulburn Mulwaree) so I hoped that was correct.

Edit: updated image links following migration of blog to WordPress.


WIA AGM weekend in Sydney 25-27 May

The Wireless Institute of Australia’s Annual General Meeting (AGM) was scheduled for the weekend of 25-27 May and I offered to give a short presentation about SOTA as one of the technical presentations on the Saturday afternoon.  ARNSW which operates from its site at Dural in north-west Sydney was also scheduling a morning of exhibitions in association with the WIA AGM events and coinciding with its monthly trash n treasure event.  So we were invited to exhibit there and explain SOTA to interested people.

The initial contact for the exhibition was Compton VK2HRX and we collaborated on the nature of the exhibit to be set up.

On my way to Sydney I called in at Mt Gibraltar, sota reference VK/IL-001 to make at least 4 contacts and qualify for the 4 points available from that summit.  I found that a short time earlier, Peter VK3PF had been at that site.  During my operation I heard Peter at good strength, activating another summit nearby, Mt Alexandra VK2/IL-005.  We made our S2S contact of course and while I would have liked to follow Peter to that summit, I wasn’t sure I had enough time (actually I would have).

I reached Parramatta in western Sydney at about 3pm and checked into my hotel, reorganised my back pack, changed my clothes and then took the train into Sydney, stopping at Town Hall station, very convenient as the evening event was located at the Town Hall in the Marconi room.   After some announcements and speeches by various officials of the Waverley Amateur Radio Club, which was celebrating its own 100th anniversary, a fascinating presentation was given about the achievements of Australia’s signals intelligence network during the 1940s.  The presenter was David Dufty, the author of The Secret Code-Breakers of Central Bureau: how Australia’s signals-intelligence network helped win the Pacific War.  His enthusiasm and knowledge of the subject and how he came to learn of the details was very interesting as it followed my visit to Bletchley Park in the UK three years ago.  So many details had been kept secret until relatively recently, it seems.

On the Saturday morning the formal AGM was run and as has been the norm recently, this went fairly quickly and was over within an hour.  In the open forum session following the formal phases, a lot of questions were asked about the outcome of the recent ACMA review of the examination and callsign allocation contract.  It seems there are still a lot of fine details yet to be clarified.

During the afternoon session of technical presentations I presented on the subject of SOTA, explaining how the award works, how summits are verified and approved and gave some statistics on the number of activators and chasers, contacts made, etc.

I ended my presentation with a short personal history of involvement in SOTA and how it relates to my health, which I am sure is much better than it would otherwise be.  I suggested that activities that involve you getting out of the shack and out into nature are not only fun from a radio perspective but are approved by our partners, so what more could you want?

At the dinner on Saturday evening the group heard a great presentation on the Apollo program and what we have gained from it, from Prof Fred Watson, Astronomer at Large for the Australian Government.  I found his presentation highly entertaining and informative, he is a very good speaker and if you ever get a chance to hear him speak I recommend it (he has a weekly spot on ABC local radio’s evening program).

On the Sunday morning we went to Dural and set up our exhibit promoting SOTA.  A number of clubs from the Sydney area also exhibited, also ALARA, the WICEN group and CREST had stands.

Here are a few photos from our stand and others:

We handed out about 30 copies of our SOTA brochure and had some good chats with various people who wanted to know more.

Overall we thought the exercise was well worth while.

After I left Dural I headed up to Mt Tomah VK2/CT-043 in the Blue Mountains.  I operated until just about sunset near 5pm local time, after which I closed down and packed up the gear in the rapidly cooling evening air.

The next morning I drove up to Mt Bindo a little earlier than planned as there was a forecast of low temperatures and a high probability of rain.

I did qualify the summit, with 5 CW contacts and 4 SSB contacts, during which my pole collapsed three times.  After the third collapse in a very strong gust of wind, I decided to pack and go, as the clouds to the west were looking dark and I wasn’t really sure of my way down the mountain.

Only a short time later, I was 20km away enjoying a hot coffee at Oberon. It started to snow and I was really glad I didn’t get caught in that on the hilltop with radio gear at risk.

On the way from Oberon southwards to Goulburn, there was quite a lot of snow on the roadside and in the countryside.  So glad I wasn’t still on a mountain in that.  A big change from the weather I had enjoyed three days earlier on the way up to Sydney.


SOTA activation at South Black Range VK2/ST-006 to complete the MG award

Leaving Canberra at 7am and heading out via Hoskinstown to the South Black Range summit, I was ready by 8:30 am to make contact with a group of SOTA enthusiasts back in Canberra.  The plan was to first use 146.5 fm to make local contacts with whoever was there.  Then go to 1296 MHz ssb to make a few contacts there, and then go to the HF bands.

Right on time, Andrew Vk1AD spotted himself on showing he was set up and ready for the morning’s contacts with a group of SOTA trainees at Mt Stromlo.

Also Matt VK1MA, Al VK1RX and Ian VK1DI were on other summits.  These four operators were on air on the first day of SOTA in VK1, 1st Feb 2013 and we were all on air when each of us have qualified for the 1000 point Mountain Goat award.

We made our contacts and after the 4th contact, several goat bleats were heard on my radio.

Rock, cairn and Trig at South Black Range
The unique shape of the VK2/ST-006 hilltop. The cairn and trig are on top of a huge rock.

I then moved to 1296 and made contacts with Andrew VK1AD and Bill VK1MCW.  The contact with Bill was made on CW as a first for 1296 SOTA in vk1.

After that it was 80m and 40m.  Conditions were favouring longer distances on 40m and it was necessary to use 80m to make contacts into Sydney or into the Melbourne area or any points closer in.

After spending several hours on the summit and getting colder all the time, it being only just above freezing point, I was suddenly surprised by hearing a voice.  There was Matt VK1MA walking towards me grinning and offering me a Mountain Goat ale.  We are lucky in Australia to have a boutique brewery that has produced this very aptly named ale.

After completing the activation and packing away, Matt helped me carry all the equipment back to the car down the hill a bit, then I headed off to Mt Cowangerong to make it a double activation for the day.

Looking happy having completed the Mountain Goat summit

the operating position at South Black Range. tripod for 1296 antenna at rear.


Guyed mast at Cowangerong

Setup at Mt Cowangerong. 2m halfwave on the left attached to a tree, the guyed pole on the right supporting the HF wire antenna.

The doublet wire used for HF contacts at Cowangerong can just be seen here, at the top of the telescopic mast