Audio for radio communication

Today at the ARNSW Home Brew meeting at dural, Mathew Magee, VK2YAP gave a talk about audio for radio communication. He spoke for about an hour and I've roughly edited it down to 17 minutes.

The noise in the background is heavy rain on the metal roof. Thanks so much to Mathew for giving permission for me to record the talk.

Lazy days at Port Stephens with dolphins

This week we took a couple of days out, during off season, north of Sydney at Port Stephens. The water must be very clean here as dolphins swim right up to the jetty:

We went on a "wave watching" boat trip and the dolphins like riding the "pressure wave" at the bow of the boat apparently for the fun of it:

While wandering around, I had a play with the new Instagram for iPhone.

It emulates bad analog film to good effect.

I spend a lot to get a lens that doesn't vignette and yet it is kind of nice.

This narrow focus effect doesn't work so well for me. It seems artificially abrupt.

During our time away, I did have to work but was able to do it via a 3G modem without any trouble.

The place we stayed was virtually empty. I took the UV-3R and listened in to the marine VHF channel 16 on 156.800 which was kind of fun.

UV-3R Torch with bonus VHF/UHF/FM SDR Radio

A new toy just arrived...

While not quite a "gift", for AU$40 (+$15 postage), it's pretty cheap for a tiny transceiver with a state of the art software defined radio inside. The feature that gets most prominence on the box is the "high illumination flashlight" feature.

I bought via eBay out of Hong Kong and it turned up 9 days after I ordered, which seems excellent. Despite the box getting a bit of a bash, all was well inside.

This one came with a USB programming cable, Windows software, separate antennas for VHF and UHF, a soft case, charger and charging dock. It seems to work fine.

These units set an amazing low price point and while the quality of the plastic is not as good as a "name brand" rig, given the advanced technology inside, the UV-3R is leading to a lot of discussion and even modifications.

Check out:

• Yahoo Group
• Reviews
• Data for the RDA1846 chip.
• Improved LPF mod.
• Volume reduction mod or here.

From the data sheet: "The RDA1846 is a highly integrated single-chip transceiver for Walkie Talkie applications. It totally realizes the translation from RF carrier to voice in the RX path and from voice to RF carrier in the TX path, requiring only one micro controller.

The RDA1846 has a powerful digital signal processor, which makes it have optimum voice quality, flexible function options, and robust performance under varying reception conditions.".

I wish we would see this technology in low cost HF equipment.

Solar powered ham shack gets a new controller

The new ham shack is up and running. The 65W solar panel is placed simply on the north facing side of the roof. There is some shade during the day but it seems to be producing enough for my operating time.

The little charge controller supplied by Jaycar was really meant for a night light so I purchased something more elaborate from Hong Kong via Ebay made by ProVista Technology. It's a very nice unit.

It's an ISC3020 which is rated at 30A input and load current. It has a very informative multi-page LCD display. Here it is both charging and supplying power and the battery is at 13.8V.

Both current drain and charge current are available. Here's charge current of 4.8A.

I paid AU$75 + $20 postage from Ebay seller greensolarwind and it came in 10 days.

Ham shed build

Ever since we filled in the swimming pool a few years back, I've noticed that there's enough space in the back yard for a shed. Here's a likely spot:

This morning the truck arrived with all the bits.

Although offered as a kit, I'm glad I paid to get the guys to do the construction for me. The sheer weight of some parts, such as the solid floor would have been difficult for me, let alone getting the walls up and square. This shed is 2.3m x 2.9m.

It's on piers but has a very solid floor over that. I'm confident it will not be flooded even in the biggest rains we've seen. After the floor was done, the walls went up quickly.

The walls are pretty solid wood and I'm hoping they'll provide enough insulation for winter and summer nights. If not I'll add insulation and lining later.

Definitely a two person job.

Almost to lock up stage after a couple of hours:

We had some extra carpet stashed away which makes it rather luxurious. It's going to take a while to get all my radio and electronics bits arranged satisfactorily.

The solar panel was simply laid on the roof and I'm keen to see how practical it is to power the whole operation this way. For now I'll run an extension cable out with mains for soldering iron and CRO but later I'll probably get mains power on.

Re-routing antenna coax is going to take a bit of time but I expect to be back on air within a day or so.

I can recommend the supplier Outdoor Living & Lifestyle and their installers are just wonderful blokes. They even had an industrial strength radio, that runs on the same rechargeable batteries as their tools, to keep them entertained:

I looked at metal sheds, they are much cheaper (particularly if you don't count the concrete floor you need to put down), but in the end spent $3,600 total for what you see above, including delivery and installation.

Towards a solar powered ham station

Great news, I'm getting a shed. Every man needs a shed and the plan is to move my ham radio gear into it.

It's still a few weeks off but I'm going to try to power it mostly from a solar system which ideally should be able to keep a small WSPR station going indefinitely.

Solar panels seem to vary a great deal in price, specialist solar shops seem very expensive, Jaycar is in the middle, and eBay vendors are suspiciously cheap.

There are rumours around that the cheapest solar panels in from China lie about the power output and that's why they are so cheap.

I purchased a 65W panel with a small charge controller from Jaycar for $400 and also bought a 26Ah battery. I don't recommend this particular charge controller, Powertech MP3128, as it's designed to run a night light (the sales person didn't mention this). The load voltage only comes on when the solar panel is in darkness, so I'm connecting direct to the battery which risks fully discharging it. Better controllers monitor this and protect the battery.

To see if I can keep a station going, I've rigged up the solar panel, just next to the house, only vaguely north, the charge controller and a transceiver that draws 1.3A on receive, and rigged up a very simple voltage logger using an Arduino and a netbook. (I won't use this transceiver for WSPR but thought it was a good test load for experimentation).

The Analog input on the Arduino measures up to 5V so I'm using a roughly 4:1 resistor voltage divider to feed it. The software in the Arduino sends a measurement every 5 seconds over the USB serial link. On the netbook, I use pyserial to read lines with the measurement, prepend the date time stamp and append to a file.

Here's the Arduino code:

const int analogInPin = A0;  // Analog input pin

int sensorValue = 0;        // value read 

void setup() {

  // initialize serial communications at 9600 bps:

  Serial.begin(9600); 

}

void loop() {

  // read the analog in value:

  sensorValue = analogRead(analogInPin);            

  // print the results to the serial monitor:

  Serial.print(sensorValue);

  Serial.print("\n");      

  // wait before the next loop

  // for the analog-to-digital converter to settle

  // after the last reading:

  delay(5000);                     

}

Here's the simple python code on the netbook:

import serial

import time

DEVICE = '/dev/tty.usbserial-A4001KYJ'

ser = serial.Serial(DEVICE, 9600, timeout=60) # 60 seconds

line = ser.readline().strip()

while len(line):

    print "%s\t%s" % (time.asctime(), line)

    line = ser.readline().strip()

Today is mostly cloudy with very occasional full sun so I'm losing charge at this point. I'll gather data for a while and prepare a longer term graph but here's the first hour or so.

An Arduino and a netbook running Linux is a very useful combination.

Only a little sun this morning and now mostly cloud through the day.  I used matplotlib to draw the voltage chart to a PNG image like this:


import matplotlib
matplotlib.use('Agg')


import matplotlib.pyplot as plt
import csv


INFILENAME = 'log.txt'
VOLTSCALE = 42.4186


datareader = csv.reader(open(INFILENAME,'r'), delimiter='\t')
points = []
for row in datareader:
    if len(row) > 1:
        volts = float(row[1]) / VOLTSCALE
        points.append(volts)


plt.plot(points)
plt.ylabel('Volts')
plt.show()
plt.savefig('voltgraph')

Here's how it looks:

With overcast skies the solar panel couldn't keep up with the 1.3A load and in the end I turned it off. I'm quite impressed with the Arduino for data logging and matplotlib for drawing graphs - much nicer than gnuplot which I've used in the past.

I'm informed that a good place to get solar panels (in Australia anyhow) is Rockby. They are certainly cheaper than retail stores and more reputable that some suspiciously cheap Ebay sellers.