QDFA Still Preliminary

We are beginning to become hysterically enthusiastic about the QDFA.

QDFA Preliminary Tests

We are underway. Yesterday and this morning we were quite frustrated. First, I managed to switch polarity from the battery and thought the phaser preamp was dead. So we replaced it with another preamp. Tests today revealed that it was by no means dead, so it was refitted.

We were taken aback by the low signal level compared to the reference antenna, a beverage directed towards North America. Testing on groundwave signals yesterday afternoon was not promising at all. So we thought something was wrong, and tried every possible way to find out what it was. No luck. So this morning we made some more measurements and called the QDFA Helpdesk, aka Dallas Lankford.

Following his advice we connected two preamps with a total of 24 dB to the antenna. The noise floor barely moved. Dallas also informed us that the QDFA doesn't work too well on groundwave signals. Groundwaves is all we got at the moment of writing, but it now appears that the QDFA works as it should. A beacon on 348 to the SE is attenuated some 10 dB more relative to a beacon on 399 to the NW. Groundwave signals to the SE on 657, 1134 and 1449 kHz are much more attenuated than 399 (which is in the desired direction).

So: It works. We will not know how well until we have skywave signals, especially waiting for Longyearbyen 1485 which is in the desired direction.

QDFA Setup Completed - Minor Flaw Prevents Testing

OJ and I worked fast and efficiently to get the QDFA finished before the rain started in the evening. It is now up, but not yet running. Looks like we'll have to wait until Saturday until we get it going.

The red wine is very good, though.

QDFA Setup Underway!

OJ Sagdahl arrived today at 1300 local. The QDFA setup is now underway, at present we are soldering all the leads and preparing for the outdoor work later today. Weather is surprisingly pleasant for September; 16 Celsius and sunny. Rain expected towards the evening so we're keeping the pace up (but allowing ourselves the odd beer can in between).

More as it happens. Updates will be frequent!

QDFA Antenna Countdown, 7 Days Remaining

Only a week now until OJ Sagdahl and I will test run the QDFA antenna. All primary and secondary main supports are up. Four 200-ft lengths and one 300-ft length of twin-lead wire have been cut and ends tinned. Two 17Ah batteries for the QDFA preamp are fully charged. The four 60-ft horisontal lengths of the deltas are cut and will be mounted today.

And I got my second Perseus SDR a week ago.

KGIM 1420, KSDN 930 Aberdeen SD Verification

Back when I was hunting veries, I sent a report to KGIM-1420 and KSDN-930, both in Aberdeen SD. They didn't respond at the time, a pity since I had heard KGIM only once and KSDN wasn't particularly easy to hear either. A follow-up yesterday was quickly taken care of though, and a friendly confirmation was emailed back. Both reports are from October 2007, although I heard KSDN on a number of occations in 2008 and 2009.

All those who believe that Aberdeen is a junction in South Dakota should know that the city is the county seat of Brown County, has a population of around 25,000, is susceptible to flooding and that a hospital is the largest employer. If we dare to trust Wiki. Of course, Aberdeen is also a junction in South Dakota.

Running The QS1R SDR On a Netbook

In previous postings, I have tested the SDR-IQ and the Perseus on the MSI Wind netbook, to see if relatively low powered netbooks can run processor-intensive software like software defined receivers. I was able to run two parallel instances of the SDR-IQ, and I also managed to run the Perseus in 1600 kHz recording mode when I overclocked the processor. All well so far.

So what about the QS1R? It appears to demand a little more from the processor than the Perseus, but the graphical user interface is responsible for most of the load. Once the GUI is minimised, the QS1R runs very light indeed. Otherwise, CPU load is around 20-40 %. I tried to lower the Panadapter Update Rate to around 5 fps and that may have caused a slight reduction in CPU load.

The GUI is scaleable, which is an advantage over Perseus with its fixed window size. Perseus is a little too large for the Wind's 1000 x 600 display, while QS1R can be adjusted to fit.

Since a recording function is not yet implemented, I don't know how well the Wind will handle a QS1R in recording mode.

The picture shows the QS1R in demod mode. The conclusion is: There is no problem running a QS1R with a netbook like the MSI Wind or similar. The processor is an Intel N270 Atom running on 1.6 GHz. This, and newer Atoms with higher speeds, are found in many netbooks nowadays.

QDFA Project Underway

The Quad Delta Flag Array (QDFA) which was tested with great success in Grayland, WA is going to be tested in Kongsfjord too this autumn. Supports are being bought and built, and 10 (!) 5-metre fishing rods were bought at a Finnish travel fair a few weeks ago. And the "Central Processing Unit", the phaser, arrived from the US today, thanks Dallas. Two 17Ah batteries are on their way, to power the 30mA Norton push-pull preamp (see photo). And lots of other stuff needs to be purchased, not least proper weather insulation. The Arctic winter only meters on shore is a hostile environment. Needless to say we are very excited as to how well this new antenna design will perform here.

The air photo shows the layout of the QDFA as a red line. My cabin is on the right.

July 11 Update! A high-res picture of the phasing box is here.

Kongsfjord - An NDB Hunter's Heaven?

I did some NDB DX some years ago, but I've done very little of it lately. I know that great NDB DX is possible though, since I've heard several 50-watt Papua New Guinea stations in the 1600-1700 kHz range.

One of my January Perseus files contained a recording down to 200 kHz, and well-known NDB DX-er Roelof Bakker (NED) offered to compile a log of what was heard on Jan 10 at 1430 UTC. The list left me stunned. I need to take up this part of the hobby...

Roelof made a very detailed report which you will find here. All from a few seconds, one late afternoon when conditions weren't really out of this world. One can but wonder what can be heard with a little more effort. Thanks very much for your detailed report, Roelof!

Sensitivity Measurements - Bjarne's Receivers

I’ve owned a few receivers over the years. I’ve measured the MW sensitivity on most of them, and on one I borrowed.

Receiver	500 kHz	1000 kHz	1500 kHz
Telefunken E-1501[1]	-108 dBm	-112 dBm	-112 dBm
Racal RA6790/GM	-108 dBm	-109 dBm*	-109 dBm
EAC R-390A	-116 dBm	-116 dBm	-112 dBm**
JRC NRD-525	-112 dBm	-114 dBm	-115 dBm
Icom IC-R75[2]	-111 dBm	-111 dBm	-110 dBm
Icom IC-746Pro[3]	-112 dBm	-112 dBm	-111 dBm
Icom IC-703[4]	-110 dBm	-113 dBm	-113 dBm
Icom IC-7000	-102 dBm	-109 dBm	-111 dBm
Icom IC-R1500	-96 dBm	-96 dBm	-96 dBm
Etón E1	-112 dBm	-114 dBm	-115 dBm
SDR-IQ	-101 dBm	-101 dBm	-101 dBm
Perseus[5]	-105 dBm	-103 dBm	-104 dBm
QS1R/QS1R ext.preamp[6]	-93 dBm/-105 dBm	-94 dBm/-105 dBm	-95 dBm/-106 dBm

*Measured on 1100 kHz. On 1000 kHz there was a tone (spurious signal?) that prevented measurements.

** Surprisingly low. Measurements on 1400 and 1600 kHz showed -114 dBm sensitivity.

All measurements made with 400 Hz tone, 30% modulation on AM with AGC off and "wide" bandwidth (nominal 6 kHz except RA6790/GM; nominal around 4.5 kHz, and Etón E1, nominal around 7 kHz).

And the winner is… not very surprisingly, the EAC R-390A, but with the NRD-525 a very close second. At most locations, sensitivity is not always an issue. But at my location, sensitivity certainly is. The 525 is no more in my possession, but the R-390A will stay.

The SDRs lack a few dB to be up front, but they have other virtues. There will never be a perfect radio.

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[1] Attenuation pad removed below 1.6 MHz

[2] Fully Kiwa-modified

[3] Attenuation pad below 1.8 MHz removed, and preamp enabled

[4] Attenuation pad below 1.8 MHz removed

[5] Preamp on/off, dither off, preselector off. Other settings give less sensitivity. 500 kHz reading actually 800 kHz.

[6] A Wellbrook, 11 dB (nominal) preamp was put in the signal path to compensate for the QS1R not having an internal preamp (unlike the other receivers)