15 April, 2015

A beauty of a crystal radio

This past weekend during Hammeeting - the largest Ham rally in Norway - I met Per LA9DTA.

He showed me his beautiful crystal radio. It can be seen in the center of the table, with some close-ups below. The design has a printed coil and the whole design is made on a PCB which was shaped as shown in the image. It has a bandswitch and a Soviet low forward voltage Ge diode.

I fell for his design, but with the lack of longwave and medium wave transmitters here I am not sure if I would have much use for it. That is unless I set up one of my transmitter projects to support a radio like this.

I was demonstrating WSPR with my Ultimate 3 transmitter. It can be seen on the right hand side of the table. I wanted some fresh spots as I was giving a presentation later that day entitled "WSPR, JT65, JT9: Digital modes by Nobel laureates K1JT for HF DX with simple equipment". As I was spotted both on 40 m and 80 m I was happy with the performance. Per had also brought his Ultimate 3. Not the modified 11-band version, but just a plain one this time.

08 April, 2015

Car upgrade to LEDs

It was time to upgrade the interior lights in my 2004 Volvo. I got some lamps from Ebay specified as 42 mm LED Festoon, 80-85lm, 12V. As many others have experienced also, they kept on glowing faintly after the door was closed. But when the ignition was turned off the lamps were completely off also, so there was no danger of draining the battery. Still this is not the way one expects lamps to behave.

One can get more expensive LED lamps which avoid this faint glow, "Canbus error free" seems to be the way to specify this. But mine were of the plain type, and the problem seems to be the leakage current in the FET switches that turn the lights on and off. It is tiny, but enough to give a voltage large enough to turn the LEDs on. An additional resistor load will lower the voltage below that threshold.

02 April, 2015

All continents in one night on WSPR

For me South America, Australia, and Africa are quite rare on WSPR. But they all heard my tiny 0.2 W signal the night between 31 March and 1 April in addition to North America, Asia and Europe. That's a new one for me and worthy a brag post on the blog, I think! Hopefully, it may also inspire others to try low power WSPR.

In Australia and South America I was heard on the 10 MHz band, in Africa on 21 MHz, in Pakistan on 14 MHz, while 7 and 10 MHz worked into Siberia. North American stations also heard me on the 7 and 10 MHz bands.

This was on my untuned 80 m horizontal loop fed with open-wire feeder and a 4:1 balun. This shows both that the bare-foot Ultimate 3 kit is very tolerant of loads with SWR much different from 1, and that WSPR gives amazing results.

31 March, 2015

Low power longwave transmitter experiment

Many places in the world, low power transmitters in the medium wave band are allowed. I am talking about regulations like in the US where FCC part 15 allows up to 100 mW input.

In Norway we have a particular permission for members of the Norwegian Radio Historic Society to transmit up to 500 mW on 216 kHz in the longwave band. I'm not sure if this is output or input power [it's output power]. The permission is meant to cover a personal collection of historic radios. The frequency is the one used by the main transmitter north of Oslo from 1954-1995 running 200 kW. The frequency is still allocated to Norway, so I guess that is why we may use it this way.

09 February, 2015

Finally got my Ultrafire WF-501B as I wanted it

As I wrote in my blog post a few days ago, I got the intensity down for night vision for my red flashlight. But I wasn't quite happy with the level and wanted to reduce it even more. To do that I had to unsolder 6 of the 8 AMC7135 350 mA constant current ICs on the PCB of the AMC7135*8 2800mA 4-Group 5-Mode Circuit Board.

These constant current chips are all run in parallel with the VDD input for control. The 8-pin Atmel ATtiny13A chip controls all VDD inputs in parallel from its pin 6. When the VDD pin is low there will be no light. I haven't measured this, but I am assuming that this pin is pulsed in order to reduce current down from the maximum.

My measurements for the High, Medium, and Low settings are:

04 February, 2015

Dimming my Ultrafire WF-501B

I got this red LED flashlight as a Christmas present. But unfortunately the intensity was way too high for what I intended to use it for. A soft red light preserves your night vision, and is ideal for use with a telescope in the dark as was my intention. But if the intensity was as high as before the modification, night vision would suffer anyway.

I then found this YouTube video describing how the controller circuit board could be replaced by one with more functions. As recommended I therefore ordered an AMC7135*8 2800mA 4-Group 5-Mode Circuit Board with 8 AMC7135 current regulators in parallel. The image shows the original circuit board as connected before the modification in the front in the image and the new one behind it.

The new board gave me the choice of one of 4-groups:
  1. 3-mode: Lo (5%) - Hi (100%) - Strobe
  2. 3-mode: Lo (5%) - Mid (30%) - Hi (100%)
  3. 2-mode: Lo (10%) - Hi (100%)
  4. 5-mode: Lo (5%) - Mid (30%) - Hi (100%) - Strobe - SOS

30 January, 2015

- Hardly any young people are becoming hams anymore

This is what Ed Muns, W0YK, said in an interview the other day, and goes on with "because they see this as kind of old school stuff."

A year ago the ARRL web site said: "Amateur Radio showing steady growth in the US". AH0A's website with statistics over the US ham population backs this up with the curve shown here. Even in my local club we are now seeing young people signing up for licence classes. 



How different perspectives! How has an old radio amateur like W0YK come to believe in the myth of declining numbers of hams?

27 January, 2015

0.2 Watts to South Africa

This is a new one for me: Norway-South Africa on 30 m WSPR in the middle of the night. Again I am amazed at what this mode can accomplish, and also what my little Ultimate 3 kit is able to do. 

The antenna used on my side was my trusty old 80 m long horizontal loop fed with a 4:1 balun and no tuning beyond that (SWR 7:1). Output power was from a single stage BS170 driven at 5 Volts, or about 200 mW in a 50 ohms load. In this particular antenna, the output is most likely much lower. 

ZS6KN is the only non-European station who has heard me this night on 30 m, with a marginal SNR of -27 dB.