Quick Trapped 15/20m Dipole

This dipole was a last minute idea.  I am taking a multi-band EFHW and 10/20/15/12/10m switched dipole away to Japan, although the switched dipole takes up a lot of space.  A smaller dedicated 15/20m dipole would be a good idea.

In the junk box I had some T50-6 cores.  The only high voltage capacitors I could find were 100pF ATC SMD parts.   To make a 15m trap, 11 turns are needed according to the formula on toroids.info.

The toroids were mounted on some single sided PCB.  Two holes at each end of the PCB strain relief the wire connection to the traps.  As time was short, the PCB foil was dremel’d away to suit the connections.

The traps were tested using a coupling loop to the homebrew antenna sweeper and with a little squeezing, they tuned to 21.1 MHz, a sort of compromise.

The toroids were then soldered properly on the PCB.  For a starting point, a 3.4 metre length was used for the inner wire and a 1.7 metre length used for the outer wire (away from the feed end).

The lengths were based on about 5% less than half wave.  The lengths needed a bit of trimming, first resonating the inner length for 15m and then trimming the outer length for 20m.

Before covering in heatshrink

The homebrew antenna sweeper was used for tuning the antenna.   The 15 metre bandwidth is quite narrow, below 2:1 between 21 and 21.25 MHz.  About 1.5:1 mid way.  This is a bit narrower than I wanted.  The 20 metre bandwidth is fine with a good match between 14 and 14.3 MHz.

 

 

 

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FT817 Battery Upgrade

With an overseas trip coming up, thought it was a good idea to upgrade the battery in the FT-817.  I have been using a very tidy solution for nearly 5 years now consisting of a Hobbyking 3 cell 2500 mAh pack.  This is still working well, although I like to use 18650 batteries if the gear is transported in an aircraft.   The end solution isn’t as tidy as the Lipo one, but works fine.

For this trip, I obtained some 3400 mAh protected Panasonic cells from Ebay.   These cells have an inbuilt circuit that limits the discharge current to 5 amp or so and also controls over discharge, a condition that can ruin the cells.  The cells worked out at about $10 each delivered.  The first thing I did was check the rated capacity.  On a 1 A discharge, the measured capacity was 3000 mAh, not bad, maybe a 0.5 A it would have come close to 3400 mAh.

Then the battery was fitted or should I say attempted to be fitted to the 3 cell carrier that I use in the FT-817.  The battery would not fit, it was too long by about 2mm (70mm long compared to 68mm).  This was sort of expected, as the protected cells have a small PCB at one end that is encapsulated with the battery.  Jaycar electronics have two 18650 cell holders, a single cell and a dual cell holder.  The single cell holder takes the longer battery, but not the dual cell unit.

The dual cell holder was dremel’d out (is there such a word?) around the positive end to remove some plastic that was jamming on the collar of the battery.  It fitted after this modification, so the single and dual holders were glued together with Polyurethane glue.  This resulted in a strong three cell carrier.

It all fits (sort of) in the FT-817.  The battery and holder are a couple of mm too high for the battery flap to go back on.  This is not a big deal as when the leather case is on, the batteries are covered.  I will have to come up with a better long term solution though. Yesterday the battery was used in an activation at Mt. Ritchie, and the volts held up well, with plenty of capacity remaining.

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Cells Installed

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Mt Hotham SOTA Weekend

Once again, Brian, VK3MCD hosted a SOTA weekend based at Mt. Hotham.   A ski lodge was our base and we were surrounded by many tempting summits.  Sarah and I left straight after work on Friday night and after a 5 hour drive via Omeo, arrived at the lodge rather tired.

Other SOTA enthusiasts already there were Alan, VK3ARH, Alan VK3FABT (Base Command!), Paul VK3HN, Tony VK3CAT, Ron VK3AFW, Peter VK3PF, Ken VK3KIM and of course Brian VK3MCD.

After a brief planning session, we hit the sack and arose relatively early on Saturday to go to our respective summits.  HF bands have not been good of late, so we all had 2 metre equipment as fallback.  If HF failed, we could work each other summit to summit.

Sarah and I headed for the Twins first (VK3/VE-017).  Despite the dry conditions, the badly rutted road proved too rough for my SUV so we then went to plan B which was Mt Blue Rag (VK3/VE-021).  This summit is just off the Dargo road and no problem with the road.  The fog slowly cleared while setting up the End Fed Half Wave (EFHW) for 40m and as expected there was little Near Vertical Incidence Skywave (NVIS).  Stations worked were VK2, 4 and 5 to qualify the summit using the Elecraft KX2.

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Ebenezer Range

Next stop was Ebenezer range just out of Harretville (VK3/VE-081), as we hadn’t done this one before.   From Harrietville, the Cemetery road was followed until it T intersected with Wet Gully Track and Albion Track.  Turning right into Wet Gully Track we eventually arrived at Ebenezer Range after some rather steep sections just before the summit.   Alan VK3ARH and Tony VK3CAT were on Feathertop, so we managed a summit to summit just as they were about to leave on 2 metres.  To qualify the summit, the EFHW was set up again and 40m used despite poor conditions.  We heard that Ron VK3AFW had cooked his Subaru attempting a summit near Omeo.  Luckily he was able to get back to Omeo where the car probably still is.

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Mt Loch looking towards Feathertop

We could have continued on to Albion Point, but we were running later than expected and a little low on fuel, so we went to Bright to tank up and then back to Hotham were I hiked over to Mt. Loch (VK3/VT-005).  Its a pretty easy walk, about 3.5km each way.  Loch was qualified on 2 metres easily thanks to VK3FABT Alan back at the lodge and Alan VK3ARH and Tony VK3CAT who were still hiking back from Mt. Feathertop.  At one point we could just see each other when they were on the Razorback and the sun was in the right position.  Just a couple of dots on the next range.

After Mt. Loch, we went back to the lodge and cleaned up for a Happy Hour atop Mt. Hotham for the sunset.  It was quite brisk on the summit where Tony set up a 160m station and managed to qualify on 160.  Alan VK3ARH set up a 20 metre station and we worked John, ZL1BYZ.  The night was finished off with a dinner at the General on Mt. Hotham.

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Alan and Ron on Hotham

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The crew on Hotham on Saturday evening

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Brian at Happy Hour on Hotham

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Sarah on Hotham

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Sun going down along with the temperature

On Sunday, we had a leisurely drive to Mt Buffalo where we activated The Horn (VK3/VE-014) and The Hump (VK3/VE-019).  Both summits are easy walks, The Horn was activated solely on 2 metres thanks to Alan VK3ARH on Albion Point and the crew over on Blue Rag Range (Peter VK3PF, Ken VK3KIM and Ron VK3AFW).  On The Hump, 40 metres was used to qualify the summit in slightly better HF conditions.  After these summits, we made our way home to Melbourne via the Hume Freeway.

Way back from the Hump

Way back from the Hump

Thanks Brian, for hosting another great Hotham weekend!

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BITX40 V3 and Raduino

The latest built up Bitx from HF Signals looked like a bargain too good to pass up.  At only USD 59, you get a built up Bitx 40m metre transceiver with an Si5351a frequency synthesiser for tuning.

I ordered it on the 3rd of January and it arrived on the 18th January to Australia, not too bad from India.  The kit arrived well packed inside a plastic food container which kept everything safe on the way.  India post sent a tracking number but it didn’t update during transit, so it was a surprise to see it arrive unexpectedly.

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At this price it hardly makes sense to do you own pcb, source components and debug!

The main radio transceiver PCB is a well soldered and neat SMD layout. Also included are standoffs, wiring assemblies connectors and pots.

It’s a bit larger than some of my existing 40m homebrew transceivers at 128 x 114 mm for the main board.

I would like to convert it to 20 metres as there are already several homebrew radios on 40m in the SOTA kitbox.

When time permits, a PCB lightweight case will be made for it. It will be interesting to see how it performs!

At the garden’s expense, it was wired up this afternoon and tested.  It powered up OK and receives.  The minimum discernable signal is about 0.1uV, similar to the KD1JV rig.  There is a low level clicking in the receiver at a rate of about 10 Hz, presumeably from the digital side.  The tuning method takes some getting used to.  A potentiometer is used for tuning, the mid range of the pot sort of fine tunes, and when you get to the edges, it fast tunes in 10kHz steps.  Sometimes it flips back and forward in 100Hz units.  I found that connecting the PA power ground reduced the background noise in the receiver a bit.

The receiver draws about 175mA.

The mic., PTT and PA power were wired up, but unfortunately, no RF.  It looks like there is RF in there somewhere, but it is not making it to the antenna connection.  A PTT increases the current to about 400mA and a whistle doubles that, but no RF out.  If the PA power is removed, so is the TX current.  Maybe its the relay.

Yep, it was the relay.  After removing it I found that it doesn’t switch either set of contacts despite making a slight click with 12V applied.   That would also explain the strange noise when switching from TX to RX as the receiver amp is not disconnected.  The coil measures 900 Ohms.  This one from Altronics will probably do as a replacement.

Relay fixed and it seems to be functional, although down on output power.  The case made from PCB for it below.  A top half will house the speaker.  Dimensions of the box (outside) are 173 x 122 x 47 mm.  The controls were kept as close as practically possible to keep the size of the box down.  It will be used for SOTA, so the smaller the better.

The transceiver seems very susceptible to power supply noise.  The Raduino produces quite a bit of noise that can be heard when tuning and generally when idle.  This can be removed with a series 10 Ohm resistor to the Raduino supply and a 470uF capacitor to ground on the Raduino side.

It is basically working although there are rather loud clicks between TX and RX as well as a burst of carrier on PTT.  To get around some of the susceptibility to noise on the power rails, a small filter board was added between the DC in and receiver, Raduino and PA DC power.  The board also has a 1N5408 shunt diode across the DC in case of reverse polarity. RF out is also down, something to look at when time permits.

The RF out issue turned out to be a measurement problem not a radio problem.  Its transmitting about 4.5 W @ 12V.

The PA heatsink was changed for this one from Jaycar that provided a bit more cooling plus it did not hang off the board as far as the one supplied.  It has mounting pins although the holes had to be isolated from the ground plane.

Finished case, just need to add some labels.  Also see method to make speaker holes using strip board as a template / drill guide.

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Briarty Hill VK3/VC-029

Briarty Hill, VK3/VC-029 is located in the Warramate Flora and Fauna Reserve located near Seville East in Victoria.  This was my first visit to Briarty Hill, it’s only worth a point and you do have to work for it!

After parking at the gate on Yarralock Way, its a rather indirect hike to the summit.  On the way up, I took the “scenic” route which was about 4km and a rise of about 335 metres.

The return trip was 6.4km and slightly more direct taking a few goat tracks back.

img_20161112_143653From the gate at the entrance to the reserve, it is about 575 metres to the narrow track on the left at S37.73818 E145.49209.

The track didn’t appear to be in regular use, there were a few trees down here and there and some bracken growing over the track.

See the map below for the GPS track of the hike.  The highlighted route is the way down from the hill, the lighter deviations show the way taken on the way up.  track-down

It was raining very lightly on the way up which was nice to keep the walk cool.  We have a mosquito plague at the moment due to the wet spring, and this made operating difficult at the top.

At the top there is a radio tower running from a noisy generator, so I set up just down the road a bit for a bit of quiet.

Despite the warm temperatures, I put on a beany and jacket with hood to protect myself from the mosquitos.  The loaded 40m / 20m / 10m End Fed Half Wave was erected on a 7 metre squid pole.  The rig used was an Elecraft KX2.  40m was not much good for close in NVIS, although signals from VK2 and VK7 were strong.  On 20m ZL2AJ was worked.

I used Peter, VK3ZPF’s Portalog app for logging and found it to be very mozzie proof!

After about an hour, the gear was packed up and I left for the car via a more direct route!

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Yet Another EFHW Matcher

While on the lookout for a more compact housing for the End Fed Half Wave matcher, I came across this perfectly sized enclosure at Altronics (Hammond 1551).  At 50mm x 35mm x 20mm, it is just right to hold the FT-82-43 core, a BNC socket at one end and a terminal at the other. The case is just a bit too small to fit a banana jack as it would protrude too far inside, so a 4mm bolt, washers, nut and wingnut make the antenna connection.  A 4mm nylock nut holds the wingnut from coming off.

The toroid is the same one as used here, with a 3 turns bifilar wound primary over a 24 turn secondary.  A 100 pF and 45 pF capacitor are in parallel across the primary to improve the match.

This is quite a bit smaller than the earlier versions and is a better fit with the KX2 and antenna in the case.  Total weight is 38 grams.

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Thoughts on Elecraft KX2 Transceiver for SOTA

After some time getting used to operating the new Elecraft KX2, it was time to take it out on a SOTA activation.   With a break in the weather, Federation Range, VK3/VN-029 looked like a good choice as it qualifies for the current winter bonus.  It is also a nice walk of around 9 km return from the Lake Mountain car park.

Trying to keep things light, the only antenna taken was the 40/20/10 metre trapped/loaded End Fed Half Wave which was supported by a 7 metre squid pole (of course, the usual medical pack, emergency shelter and water were packed as well).  Two sets of home made,  3 cell 18650 packs came along for power, one internal and the other as a backup.  The radio, spare battery pack and microphone fit pretty well in the Action Cam case from Target.

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Once on air, the KX2 is very easy to operate with a big display, it’s nice to see the ALC, SWR, RF power out and S meter all at the same time without switching functions.  The battery capacity display is a real help for pacing the activation if you are short on power.  One thing that has always annoyed me about activating is getting the UTC time each time you put an entry in the log, the clock on the radio makes this easier.  I guess one solution is VK3ZPF’s portalog, which have used a couple of times.  Other solutions for UTC in the past have been GPS Navigator display, mini LCD clock  and mobile phone.

Reported audio was good and a comment was made that it sounded much like previous activations with the FT-817.  The microphone is a bit disappointing as mentioned here. I had heard that the internal speaker of the KX2 distorts at lowish volumes, but found it fine during the activation.  The KX2 has a few little gaps an a few holes in the case, I might have to make a few bungs or covers for these.  I can see ants filling up the radio (Mt. Selma or Mt. Reynard) or moisture splashing in while operating.  The FT-817 is better in this regard, despite having Mt. Reynard ants exiting for days later after an activation.

On the weight side of it, the KX2 with internal battery weighs 535 grams.  The FT-817 with internal battery weighs 1170 grams.  The overall physical volume of the KX2 is a bit less as well.

After the activation and a following short activation at Mt. Gordon, the battery capacity used was 0.6 Amp Hour (of a 2.2 Amp Hour pack).

Despite the FT-817 and KX2 being very different radios, here are some noted pros and cons of each radio:

FT817 Pros:

  • Cheaper.
  • 160m, 6m, 2m and 70cm bands.
  • Pretty durable, only problem after 4 years of SOTA was the power button rubber.
  • Good TX audio.
  • Two antenna sockets. (useful for two bands)
  • Nice mechanical construction.
  • Versatile radio.
  • Proven radio.

FT817 Cons:

  • High receive current consumption.
  • Heavier.
  • Small display is hard to read.
  • Small knobs and buttons.
  • Getting quite old now but holds up well.

KX2 Pros:

  • Low receive current consumption.
  • 10 Watts output.
  • Easy to read display.
  • Larger controls widely spread out.
  • Rich software features such as filters, voice memories.
  • Battery amp hour + current display, clock.
  • Metering in general
  • Nice form factor.
  • Lightweight.
  • Can use hand held with internal mic and whip antenna.
  • Good support for software updates and utilities on the Elecraft website.

KX2 Cons:

  • Price. (at least in Australia)
  • Gaps in mechanics.
  • Microphone a bit sup par in mechanics for price. (gaps in plastics, wobbly pressel)

The KX2 is certainly going to get some use in future SOTA activations!

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Hut ruins at Federation Range

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