Simple copper pipe loop for 40m

After several false starts, including complex schemes involving stepper motors and long rods, I've settled on a very simple design for a loop that nicely covers 40m.

The loop is about 1m in diameter, a cat is shown for scale.

Contrary to some other designs, I've put the coupling at the top. Two turns on a FT-114-43 toroid. (Since this picture I've anchored things with some cable ties and removed one turn to get a lower SWR).

The tuning is at the bottom. I needed an extra 180pF to get this on to 40m. A larger knob is better, a reduction drive would be even better. (Tuning is very sharp).

Here's a rough drawing of the circuit:

Sitting at the table in the back yard yields decent reception - not as good as the full size dipole - but not bad.

The 3m length of copper pipe was a standard cut length at the local hardware store.

To find where the loop was resonant and make sure it was working, I used a miniVNA pro  and the vna/j software. I'm running Ubuntu Linux and ran in to some problems getting vna/j running. The trick is to remove the open source Java implementation and install the version from Sun. Also there's the JNI libraries that are required the Arduino IDE that needed to be removed to get it running.

Here's the plot showing the SWR dip at 7.1Mhz to 1.4:1. The KX3 tuner nulls out the mis-match without problem.

I've transmitted up to 50W SSB without any bad things happening.

Another visit to the Kurrajong Radio Museum

I visited the fabulous Kurrajong Radio Museum once in the past with my partner in tow and while she found it "mildly amusing" I thought it was time for a repeat visit.

I contacted Ian via the email on the site to organise the visit in advance and he was most gracious with his time and knowledge.

With Mal, VK2BMS and Robert VK2ZNZ in tow we met up with Jules, VK2EXT for a grand tour. Some photos from the day:

SDRPlay receiver with SDR Console

Since eliminating the annoying interference I was suffering, I've returned to the pleasure of tuning around on HF. A while back I bought the US$150 SDRPlay receiver. Getting it going with some of the common software is a bit of a trial due to the proprietary driver that's needed.

SDR Console is a very nice SDR receiver program that works out of the box with SDR Play. (Be careful on their site, they accept ads that portray themselves as bogus "download" buttons).

SDRPlay is more expensive than the RTL-SDR TV dongles but it's really worth it. They have a 12 bit A/D and capture a much larger part of the spectrum so it's easier to see the whole band and find stations.

Here's what AM shortwave stations look like.

And here's 40m LSB on an active Saturday afternoon.

A tiny snippet of video shows how it looks when running.

I'm running this on a Lenovo ThinkPad X201 with Windows 10. It's a Core i5 processor at 2.4GHz with 4GB of RAM. The software reports only about 4% CPU so there's plenty of headroom. You would struggle to run this on a cheap netbook.

One tip - there are keyboard commands for moving the IF and tuning up and down but they're disabled by default. There's a setting and then you can use PageUp and PageDown to move IF and arrow up and down to tune. Fine tuning is by holding the Control key.

Locating the source of local HF interference

In recent weeks my reception of HF radio, particularly on 40m (7MHz band), has been marred by nasty broad band interference. I had thought it was from a neighbour's TV.

Using a portable shortwave radio with a strength meter, I walked around the house trying to find the cause but it just seemed to be strong everywhere that mains wiring went.

After shutting down all computers I turned off the house main switch and the interference was gone.

By plugging things back in, one by one, I found the culprit.

Many of us suffer HF interference and the more computers and appliances we have the more likely it is, but this experience shows that it can be located and removed.

Sydney meetup with Peter VK3YE and Stephen VK2BLQ

A rare pleasure today to meet up with home brew hero Peter, VK3YE, who was visiting Sydney.

Stephen, VK2BLQ and I caught up for a chat and Stephen brought along a phasing receiver for Peter to inspect.

We had an entertaining discussion on many topics and I hope one day to get Peter along to an ARNSW Home Brew Group meeting for some sort of chat.

Thanks Peter for all your great work to help ham radio and home brew on the web site, videos and all the articles in various magazines - we really appreciate your efforts and encouragement.

Update

Peter mentioned that he was close to publishing a book about QRP operation and that book is now available on Amazon. Minimum QRP is well worth a read.

Peter shares his considerable practical experience of ham radio in an easy to read and informative book. It covers equipment (including commercial and home brew), antennas, bands, propagation, modes and operating procedures that give the reader valuable tips on how to enjoy success in the challenging art of low power operation. The focus on QRP is, of course, valuable for operators working at all power levels.

Peter has always been generous with his contribution to the hobby of amateur radio and this book adds to the information available to newcomers. I look forward to more from VK3YE in the future.

Great cover by the way.

Everything looks better from a drone

Last weekend I was invited to film a friend's property from my drone. I'm a pretty poor flyer but the result is nice. It was a fabulous day for flying.

A weekend away at the faded Hydro Majestic

Pip and I took advantage of a "Spring Escape" in a "Heritage room" at the Hydro Majestic in Sydney's Blue Mountains.

Not being from Sydney, I don't recall the glory days of old but do remember years of passing the place while it was being refurbished.

At $167 per night, the "Heritage" rooms turn out to be a nod to our convict heritage. As one reviewer on TripAdvisor writes, "there's hardly enough room to change your mind". We rang reception and paid considerably more to upgrade to a more spacious room with a nice view of the car park.

The staff were nice and presumably we're not the first to react this way to a room even they refer to as "compact".

There's not much to do at the place but compete for a chair that gives a glimpse of the pleasant view.

Some cushions would be a nice addition. The free Wifi is very slow but functional.

Drop in for a glass of wine on the way to an AirBNB but I don't recommend staying here. Staff were nice though and General Manager Ralf B is amusingly responsive on review sites.

ozQRP MDT Double Sideband transceiver kit review

I learned of the Minimalist Double Sideband Transceiver (MDT) kit from the video review by VK3YE and thought it might be a fun project.

The price is $75 but it includes everything you need except a microphone. The parts are well packed and clearly marked. The circuit board is excellent quality and all parts fitted well.

The manual is very clear and I found construction quite smooth.

The only confusion I experienced was figuring out which way around the BD139 transistors go in the board (the label side is closest to the edge of the board).

I spent a lazy Saturday on and off doing the build in short bursts. Late in the afternoon I was tuning around and the direct conversion receiver sounds excellent. The carrier nulling was easy and from what I can hear off air transmit audio sounds good. So far no one has responded to my CQ calls for a report but I'll get back to you when that milestone is passed.

It's a great kit for a constructor with at least a little experience. A very compact rig that could be good to take on a hike.

Update: First contact with Mal, VK2BMS who said the audio sounds good although a little basey - which is probably more due to the microphone than anything. Mid dial was 7.10604 so that's good to know.

With the second varicap link open mine covers 7.090 - 7.127MHz. Tuning is quite sensitive so I wouldn't want more range without a multi-turn pot so I think this is a good range.

Just had another contact with Ian, VK3AXH in Ballarat who gave me a 5 and 3. He's running 200W and I'm running about 2W DSB. He commented that the rig is "doing a remarkable job". I do find that after switch on it drifts a bit but it's a pleasure to use.

Radio data link for $1

John, VK2ASU, showed a little data link he'd built at a recent home brew group meeting at Dural and I've started experimenting.

Here's the transmitter.

They only say it’s on 433MHz but mine seems to be on about 433.9112. I can pick it up on a little hand held scanner and given that there’s no antenna connected the range seems excellent. There is a plated hole to add an antenna. I make it 17cm for a quarter wave.

I’m using RadioHead’s ASK mode here.

With an arduino sketch example.

These are the modules I bought for $1 (including postage) on ebay.

Applications of such a link are things like sending back temperature or battery voltage readings from remote sensors.

My plan is to slow down the transmission rate, test on uhf and then get it to work on 40m with the Frog sounds transceiver.

Helping a soon to be new ham in Bowral

Recently I had a very pleasant train trip to Bowral to assist and old friend, and soon to be amateur radio operator, William.

I was able to make the full return journey using my Opal card at no cost, which was an unexpected bonus.

William lives on a nice sized block near the centre of Bowral. Here he is in a very nice shed.

By the time I turned up, William had the rig up and running with a run of coax to a simple dipole in the back yard. I was very impressed with how far he's got. Electrical noise seems to be a significant problem though.

I brought along an antenna analyser and it turned out that the dipole was rather short for 40m and was nicely resonant at 9MHz. We replaced the simple centre connection direct to co-ax with a proper balun and made a longer dipole.

Unfortunately the two trees are a little close together but we managed to get everything going (after the picture above was taken) by having down hanging ends. (Also I did put the co-ax through the strain relief on the balun.

Here's William's operating position:

I responded to a call and had a good contact with a chap in Victoria who gave us 57.

The electrical noise could be from high voltage power lines running just a house away or it could be from an appliance in the house - more investigation is required.

Thanks William for the hospitality and I look forward to our first on air contact.

ARNSW Home Brew Group meeting

Another interesting meeting today with lots of "show and tell" and a talk on filters. Here's some photos.

Bob had a high quality component analyser with probes that work with surface mount components.

The room was enthralled as always.

A prototype weather station with links from the remote sensor working over Bluetooth.

Convenor Peter VK2EMU at the helm.

John VK2ASU demonstrated a wireless link running over 432MHz using a $1 transmitter (but he recommends a more expensive receiver).

Stephen, VK2BLQ has constructed an amazing SSB phasing transmitter for 80m.

Eric showed the new Powerpole distribution box from the Waverley Amateur Radio Society.

The full kit is $35 - much cheaper than commercial equivalents.

Cameron, VK2CKP, showed his arduino controlled rotator.

Eric talked about filters and why you shouldn't open email enclosures while running Windows.

Low price 40m CW transceiver "frog sounds"

There's a very low cost CW transceiver for 40m available out of China on ebay dubbed "frog sounds".

For just $19 including free postage you get a decent kit with circuit diagram. I put mine together in about two hours and it worked first go.

The circuit is available via this link. Basically it's a conventional NE612 LM368 direct conversion receiver. The transmitter ads a side tone generator using some NAND gates.

As I've observed before you can't purchase the individual components for the price of the whole kit and the board and documentation is decent.

Update not all smooth construction for some.

John, VK2ASU, sent this:

"Built the Frog Sounds transceiver today. Many problems and many hours spent trying to fix. Have it going to a degree. Getting 1 watt out on 12 volts compared to 3 watts on the previous one.

One major problem I found is that the holes are not all plated through perfect and this stopped the receiver until I found it. The rx works now but "deaf". More time and effort to go.

Decided to do a search on the net if others had problems. Yep!

Here is a link to look at and this.

When you solder a component in make sure you let enough solder to flow into the hole to work right through. There is a hole about in the middle of the board (when it's all built you will find). It is at the end of a track which then goes through the board to the underneath. I had to scrape insulation off both sides and add a wire through it.

For all that the circuit looks really good it's a shame that the board is so bad.

On the plus side the keying is crisp and the sidetone quite good."

Liking Google Photos

Google has done such a great job with Google photos that it puts Apple's equivalent to shame. Apple has had face identification for some time but the genius here is that it doesn't wait for you to name people, it just groups by face.

Now, for some reason this feature is disabled for Australian users by default. To enable it I followed the instructions here and used an Android device as they suggest. I used TunnelBear for the VPN and all went as described.

I'm currently in the process of copying 22,000 photos from my iPhoto and Aperture libraries up using Google Photos Uploader app for MacOS. Unfortunately, although I have 100Mbps download speed my upload speed is just 2Mbps and so the upload will take several days.

It would have taken much longer as the Mac goes to sleep when idle. To stop it sleeping during the mega-upload I'm running Caffeine which is free from the app store.

I hope Apple responds to this competition, they need to do the following:

• Offer an unlimited (image size capped is fine) photo archive
• Cut the price of their cloud storage (for 1TB: Google is $10/month, Apple is $25/month)

WWDC is next week but I doubt this is on the agenda. Interesting times.

Download this show wins IT journalism "best audio program" award

Marc Fennell does everything on this show, producer, presenter, interviewer, editor, music mixer and talent wrangler. All credit to the new generation of tech-savvy media stars. It's a privilege to be a very small small part of the show.

Congratulations mate!

Very low cost i2c LCD interface board

Listening to the marvellous Soldersmoke podcast I learned of these serial interface boards for driving an LCD display using just two pins of an Arduino. These boards are just $1 out of China on eBay. Amazing.

With some help from Brainwagon I was soon up and running.

The little board solders nicely on to the back of standard Hitachi LCD boards.

I'm stunned that China can manufacture stuff like this for such great prices. Everything I make will have a display.

SM1000 FreeDV in a box arrived

Very excited this week when the SmartMic 1000 arrived. This is a FreeDV digital voice codec in a very nice box. It's designed so you can hold it in your hand rather like a big microphone and just talk in to it to transmit and receive digital voice.

The case has 3.5mm sockets for everything and also an RJ45 socket for a single cable connection. It's like the Signalink boxes and has a similar internal jumper system for wiring it. I followed the instructions and quickly had it working with my FT817.

The button marked "select" on the front switches between analog passthrough (so you can hear what the radio hears) and digital mode.

To test transmission, I listen off air and decode with the FreeDV app. My scatter plot looks reasonable I think:

I can hear my voice decoded so the next step is some contacts on 14.236 where I'm listening and calling.

Notes: 

• Mic Gain control operates in reverse.
• Select button switches between analog and digital. On power on it defaults to analog.
• Back button isn't used.

Stephen, VK2BLQ, also has one of these and I was able to receive him on 40m, here's a snippet.