17 May, 2015

The ultimate WSPR spot

A spot reported by K1JT must be the ultimate goal for the WSPR mode. K1JT, Joseph Taylor, is the Nobel laureate who first developed this mode and other related two-way modes like JT65 and JT9.

My 0.1 W 21 MHz WSPR transmitter regularly makes it over the Atlantic, but never before to K1JT. The SWR was something like 7:1, but apparently that works fine, both for the transmitter and for radiation.

The antenna is a 13 m doublet oriented with the broadside facing East-West (the EU spots in the figure are from my Ultimate 3 on 21 MHz with another antenna and at another location). I feed the doublet with 450 ohm ladder line to a 4:1 Elecraft balun which is connected to the Ultimate 2 transmitter.


07 May, 2015

Ultimate software is up to date

As I have mentioned several times on this blog, I have thoroughly enjoyed WSPR modes ever since Hans, G0UPL came out with the first Ultimate QRSS/WSPR kit.

That means that I have three different versions of the kit. Since Hans has kept on updating the software and even published the compiled versions, it is also possible to upgrade even the old ones.

I have done that and the displays here show the Ultimate 3, the Ultimate 2, and the Ultimate 1 with the latest software.

It is possible to upgrade the chips in-circuit, but I found that it is simpler to remove the chip temporarily from the socket and move it to a simple veroboard with crystal oscillator components. It is connected to my Ebay version of the USBtinyISP.




29 April, 2015

First 475 kHz WSPR decoding

Tonight I made the first successful decoding of WSPR on the 630 m band. What inspired me was all the talk on the Elecraft reflector on the new synthesizer which in addition to having less phase noise, also allows the K3 to go below 500 kHz. I don't have that synthesizer, but the discussion reminded me of the low frequency converter I built many years ago. It converts 0-1 MHz to 14-15 MHz. Using the KXV3 transverter interface of the K3 it was easy to interface and get up and running.

The first signals I decoded are shown in the water fall above, and their origin in Germany and the Netherlands is shown in the next figure.

According to WSPRnet, PA0A's 2 Watt transmitter is 784 km away from me, and DK7FC's 1 Watt is 1164 km away.

The converter is quite simple and is based on a 74HC4053 switch used as a mixer with a 74HC04 for a 14 MHz oscillator. It is the design of SM6LKM, but with a different oscillator frequency and a simplified output filter compared to his. It is one of many small projects that I have built in Altoids tins.

The antenna used was my trusty old 80 meter horizontal loop which has been the main work horse for making my 8-band DXCC (more than 100 countries on all bands 3.5 - 28 MHz) possible. It is fed with ladderline into a 4:1 Elecraft balun in the shack.

Perhaps the next step is to finish the 475 kHz filter of my Ultimate 3 WSPR transmitter and see if others can receive me? That is going to be more of a challenge antenna-wise.


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: