Sunday, October 04, 2015

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.

Saturday, October 03, 2015

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 sitevideos and all the articles in various magazines - we really appreciate your efforts and encouragement.

Tuesday, September 29, 2015

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.

Wednesday, September 23, 2015

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.

Saturday, September 05, 2015

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.

Tuesday, September 01, 2015

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.

Friday, August 21, 2015

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.