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.

---

[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)