Brian – LF and CW Adventures

SDR or IC7000 … how do they compare?

I have had a NooElec SDR dongle and upconverter for a while now. Up until the last few days I have just “tested” it and checked out the software but never got too serious about receiving using the SDR for CLEs and NDB hunting.

As mentioned in the previous post, I have exhausted the reach of my current receive systems, gaining only a few new NDB stations (for example) when propagation conditions are exceptional. The SDR looks like a new tool to allow me to expand my listening times.

I like HDSDR and its features suit my current needs. Recording overnight reception for analysis later is what interests me right now. I played around with this last night and found that the reception is similar but possibly not quite as sensitive as my IC-7000 and Spectran using the same antennas. I’ll need more hard data and some experimentation to be convinced that is true.

The recording issue leaves me with a problem … I use a laptop for the shack computer as I can run on battery power to eliminate charger noise while I listen. Recording would only be available for as long as the battery lasted which is under 2 hours. The storage required for 1 hour of recording at the second lowest bandwidth is about 6.7 GB and that is problem #2 … I have only 28 GB free on the laptop drive (3 hours or so without crashing the computer).

Potential solutions include re-building one of my desktop computers and stocking it with some TB drives (a serious undertaking) or adding external drive capacity and power supply filtering to the laptop.

I’ll start by testing the external drive setup with my existing equipment to see if it is worth an investment. I worry about using a USB 1 connection for data transfer (older laptop), this may become an issue so I need to test this further.

PS: I also looked at KiwiSDR as well. I live in a remote place and it would be interesting to run a listening station!

UPDATE:

After a few days of recording and comparing levels on all antennas I have concluded that the differences in S/N and signal level is smaller than I can measure. Each antenna has a different “best frequency range” so I must keep that in mind for future reference!

The Beverage Project

Having basically exhausted my receive capabilities on the NDB and 630m band with the inverted L antenna (I still get a few new signals each month) , I went looking for an antenna that would push my listening limits. I have a lot of acreage handy so I thought about beverage antennas.

There are many good articles (and some questionable ones) on beverages. I purchased ON4UN’s Low-Band DXing and started there. KW2P’s Blog has some information on coax beverages and W8JI’s beverage page is packed with advice.

After much research and many hours with azimuth maps, auroral oval maps and design calculators I have settled on a plan for some 3 meter (10′) high 2-wire beverages in the bog near my house. You can walk in the bog with boots on and there is little standing water. I hope the ground resistance is not too low for a beverage to work effectively.

The image below (north is up) shows the complete layout. The build will come in phases so as not to work myself too hard!

The sparsely treed area is the bog. Power lines are 30 meters (100′) to the west of the house (N-S alignment) with nothing but bush and mountains for many hundreds of km (or miles) to the north and east.

Phase 1 will be the 90º – 270º (green) antenna. This will give me access to the east coast of North America (90º), something that eludes me at present. The opposite direction will hear the South Pacific and Australia.

At 400 meters (1300′) long, it is more than a full wavelength at 160m and about 0.6 wavelength at 630m. It should work quite well as long as my ground resistance is not too low … we’ll see how that goes.

Phase 2 will be the 120º – 300° (orange) antenna. This will face the American mid-west and South America (120º) with the 300º end facing Eastern Asia (Japan, Philippines, etc.).

Phase 3 (red) is the experimental antenna. It faces Europe at 30º and New Zealand at 210º. The reason it is experimental is that I live on the southern edge of the auroral oval. Europe is directly through that oval all of the time and I cannot hear stations on that side of the world with my present setup.

What will I hear on the beverage? I’m not sure but that’s why I want to build it …what will actually happen? The nice thing is, I can move the antenna bearing if I do not like the result.

I’ll leave this post with that thought and check in again with the 2-wire transformer boxes and feedpoint switch.

160 Meter Dipole

I put up a 160 meter dipole a short while ago.

Due to my currently limited “launch” equipment (throwing a weight over a tree branch) it is only about 10 m (30′) up at both ends and only 7 m (21′) at the center support. The center insulator is “attached” to the corner of my roof for now.

The feed line vertical drop is only about 5 m (15′) due to restrictions in house construction. This makes it less than ideal for a top loaded ‘T’ antenna on 630 m. It does work for 630 m (non-resonant) but not efficiently.

It works well on 160 m and tunes on all bands (some very badly!). I’m assembling the parts for an air cannon so that I can launch a line over the 30 m (100 ‘) trees near my house.

The load coil and tuner will be next … more to come!

Some “new” reading material …

I had to take time off from my vacation to go back to work last week and found the following reading material in my mailbox, thanks to the newly retired colleague that thought of me when cleaning up to move south.

There are three images (use the arrows!).

They are 1960’s era UK wireless magazines absolutely packed full of advertising with a few technical tidbits thrown in. The previous owner(s) had removed some of the best tech pages but what was left is really great to read.

The cover art is exceptional. Modern magazines are all about the photograph, these are excellent hand-drawn renderings.

DGPS signals

I had noticed some louder, wide bandwidth signals , compared to CW NDB signals, in the “NDB band” and was grumbling about them covering up some possible NDB signals.

It turns out that they are DGPS (Differential GPS) stations that transmit (continuously) information about the GPS satellites, their errors and their health. Other messages are sent listing other surrounding DGPS stations, etc. Check out the DGPS guide (PDF) for more information.

I tried to decode the stations using Spectrum Lab software but cannot seem to get the terminal (decoder) program to hear the signal to decode. Everything else seems fine, the terminal is “connected” to the right point in the virtual circuit … I’m stumped.

I suspect that I have missed a step or two in the setup sequence. Note that while Spectrum Lab is quite powerful, part of that power comes from it’s complexity and ability to be configured in many ways. This means that there are many ways to set up the software … and many ways to “break” it so that it does not do what you want. I’m in the latter category right now and need to learn more!

I found that DSCdecoder (trial version) works flawlessly for DGPS signals. It also covers DSC and Navtex signals so I need to try those out as well.

There seems to be a different problem now … I do not have enough time in the evenings any more!