Tag Archives: amateur radio

My second homebrew Arduino/si5351 Digital VFO-Controller

Back in February 2017 I scratch-built my first Arduino and si5351 VFO. Here’s my second one.  It is a generic Nano/si5351 module wired up to Farhan’s Raduino circuit. The si5351 is on an Adafruit breakout which includes a 3.3v regulator and crystal.  Everything else is as per Raduino other than the presence of a second 7805 regulator for the LCD (and a 1000uF electrolytic storage capacitor) which will allow testing of Pavel CO7WT’s scheme for saving the VFO frequency to the Arduino’s EEPROM when the power drops.

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Three Summits in the Yarra Ranges: Federation Range, Mt Strickland and Mt Donna Buang

Activators have been bemoaning the poor state of HF propagation recently. But when planning an August SOTA activation in Melbourne, the propagation forecast runs a distant second to the weather forecast. If the HF propagation is bad you might not get the 4 contacts, but if the weather is bad you might get seriously bogged or snowed in.  If nothing else you’ll come home wet and miserable.  So I studied the weather report carefully for Friday the 4th of August. A series of three low pressure systems of varying strength were on the weather map bringing low temperatures, strong winds, rain and snow down to 900 meters. Friday morning looked to afford a break. I considered Mt Matlock (VK3/VC-001) but when the morning came after an evening of steady rain I opted for Federation Range (VK3/VN-029) near Lake Mountain, figuring that walking 5km each way through slushy snow would be better than driving 50km each way along the pot-holed water-logged C511. As it happened, it was the right choice.

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Homebrew 40m SSB rig gets CW, keyer, break-in, AGC and metering

A couple of ‘solder sessions’ finished all the wiring, debugging and testing required to deploy my Arduino Nano keyer and SWR/power meter, and the LED LDR AGC and S-meter modules into my homebrew 40 meter SSB rig (MST Mk1 from OzQrp).  Before reassembly I sprayed the front and rear panels, and added my preferred DecaDry white lettering and a protective coat of  clear satin sealer. It’s now resplendent with all the expected features of a SSB/CW monoband portable rig.

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Arduino CW keyer for a BiTx or other homebrew rig

It’s been 3 years since I got my MST400 Mk 1 40 meter SSB transceiver going and started using it for SOTA activations. For those not familiar with it, it’s like a kit version of the BiTx40 from 2013. It has a similarly spec’d monoband superhet receiver, 10MHz IF, and IRF510 5 watt power stage. The circuit on a page is here. It’s been with me for nearly all of my 65 activations (over 400 SOTA activation points) around VK3. Now, with HF propagation approaching cycle lows, it is time to do what I should have done ages ago… add CW.

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Hotham SOTA weekend 2017

Q: How many SOTA activators does it take to change a light globe?

A: Nine. One to alert the impending globe change (subject to weather), one to take the bulb and socket to the top of a summit, one to spot when in sight of the bulb, four to replace the bulb while logging UTC and local conditions, one to take photos as the replacement is done, and one to upload the globe replacement details into an online database and write about it all on a blog.

Nine. That’s how many VK3s spent the weekend at Peninsula ski lodge on Mt Hotham for the 2017 SOTA Hotham weekend. It was my first attendance. I met Brian VK3MCD, Peter 3PF, Alan 3FDIM, Ken 3KIM, Ron 3AFW, Glen 3YY, Allen 3ARH, Tony 3CAT and Ron and Glen’s partners for two days of SOTA activations, map reading and socialising.

 Morning of Sunday 26th Feb 2017, looking out the Peninsula lodge window south.  

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Saving an Arduino-controlled Digital VFO frequency over a power cycle

Following the success of My First DDS VFO, complete with Arduino script programming, I found myself interested in mimicking more of the features of the digital dials in ‘real’ rigs. Like dynamic incremental speed-tuning, where the tuning rate increases or decreases dynamically depending on how fast you spin the dial. More on this later. A more achievable feature is to have the band, mode and VFO come up on the frequency where you left it at the last power-down. This involves writing these parameters into the Arduino’s EEPROM, using the EEPROM library.

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QRP by the Bay 4th Feb 2017

QRP by the Bay for February 2017 was held on a blistering 36 degree day at Victory Park, Chelsea Beach. As I approached it looked like about 2,000 people had come to QRP by the Bay, and many of them dragging beach umbrellas and esky’s. Looked like a ripper of a summer QRP party. Parking the car took me 15 minutes. I wondered what Peter Parker had done to pull such an impressive crowd. Alas, when I got to the hallowed tables, there were about a dozen of us, the other 1,988 people having walked blissfully past the squid pole and BITX rigs for the golden sands and cooling waters of Chelsea Beach. Their loss.

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More power to the activator (choosing a new LiFePO4 pack)

When the time came recently for a new battery, I jumped onto HobbyKing and was bewildered by the range of options, even after limiting the search to a particular current capacity, in my case 4-5AH, and 4S (4 cells). Wishing to leverage the ‘wisdom of the SOTA crowd’, and at risk of reopening the “whats the best battery for SOTA” chestnut, I posted to the yahoo SOTA_Australia group:

I’m buying another LiPo from HobbyKing. This battery will be for general purpose 5 watt txcvr use, but will also be used to power an afterburner of the W6JL type, using a pair of IRF2Z24N hexFETs, for up to 50 watts. My question is, what do I make of the discharge figure on the LiPo packs, which varies from 10c to 35c? I presume this is the rate at which the battery can supply current under load, the higher the better. A higher discharge figure might be important when powering an afterburner, which might draw current peaks of many amps on voice peaks. Prices seem to correspond with higher discharge figures, from as low as $25 (10c) up to $55 (35c) for packs around the 4AH rating.

My only current Li-XXX asset.  

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2016/17 rollover party on Mt Disappointment VK3/Vc-014, and the christening of ‘Summit Prowler Two’

I left my plans for 2016/17 rollover late, and when I checked sotawatch alerts 24 hours out, there must have been 15 summits manned. From lunchtime on I was due at my brother’s QTH in Doreen, north of Melbourne. So I chose Mt Disappointment, which is an hour’s drive from my place and 45 minutes drive from the lunch destination. This gave me time for a leisurely activation on the picnic table near the summit. This was also to be my first attempt to activate a summit on 30 meters CW with the newly finished Wilderness SST rig.  It all went to plan. With 4 CW QSOs on 30 meters bagged, I switched to 40 after rollover for a bunch of hunt-and-pounce QSOs. Here’s a video that offers a taste of the CW and SSB signals heard and worked.

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QRP by the Bay, Saturday 5th November 2016

QRP by the Bay is a regular homebrew, experimenter’s and portable ops show-and-tell hosted by Peter VK3YE at Chelsea Beach. This was my second event, which followed in the now established tradition.  This year it attracted about two dozen people and a variety of projects appeared on the tables. The weather was not ideal, it was very windy and cool, but the squid poles went up nonetheless.  Peter’s video of the event is here, and another one of the 160 meter bayside portable QSO here.

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