Weak Signal and QRSS Web page

VK2DDI Grid Square QF55hf

Feb, 19, 2011:      (A complete rebuild of this site is well overdue!  However I am not sure when I will have the time to do that.)

NB - My former call sign (VK6DI) is no longer assigned to me.  Current operations are limited to 'receive only' as VK2DDI.  My sole antenna is a PA0RDT Mini-whip.  I receive very well on all bands up to approx 10 MHz.

QTH is near Berry Mountain New South Wales (Elevation 512M ASL).  QRSS and WSPR uploads are ongoing dependant of course upon local lightning or lack thereof.

Live Images of my receive activities can be accessed from here.

Final update as VK6DI (Near Perth) - April 13, 2009:

NB - All activity from this location has now ended.  With a little luck a new site will replace this one later in the year.

Thanks go to all who have contributed to my success in receiving milliwatt level (and less) signals, both QRSS & WSPR.

The current QRPp DX record to this location is held by WB3ANQ.  Larry's 0.5 mW QRSS, & 1 mW WSPR signals have been received here many times.

Several other stations are not too far behind Larry's record.  Their sub-20 mW DX
signals have been decoded here using the WSPR mode on 30M.

Thanks are due to Alan VK2ZAY who has generously provided both disk space & bandwidth to archive my old VK6DI web pages for future visitors.

LF-NDB / SDR-IQ file archive available

Beginners Guide to 30M QRSS reception, view or download from here.

My (West Australian) NDB Log:

Download (date sorted) as PDF
Download (freq sorted) as PDF

QRSS NEWS Archive:

6 April 2006, 1200 hours local time:    80 Nanowatt test as per previous details with VK6JY (see below).

(Update: 4 May 2006, signals were detected at 50 nW)

4 April 2006, 1450 hours local time:    200 Nanowatt tests as per previous details with VK6JY (see below).

14 March, 2006, 1736 hours local time:    NVIS 40M QRPp tests with John, VK6JY produced good results at powers down to 50 uW.  See image below.  John is located in Albany at grid square OF84wx and is some 383 Kms south of me.  Powers below 50 uW were not attempted  due to time limitations.  Clearly success at reduced power levels would have been possible.

VK6JY 50 uW

Simple low dipole antennas were used at both ends of the path.

March 17, 2006, 1000 hours local time:   Further tests on 80M with VK6JY at 63 uW and 16 uW revealed results similar to previous 40M tests a few days earlier.

VK6JY 16 uW

John's TX antenna was an 80M dipole at 8M above ground level (AGL).  My RX antenna was an 80M full wave loop at 5M AGL.

Feb 1, 2006:    30M QRSS experiments were conducted with WB3ANQ using a measured power output of 961 microwatts into Larry's outgoing 50 ohm coax line.  (Lets call it 1 mW!)  Full details of Larry's end of the operation are available from WB3ANQ.

Real time Skype VoIP communications during peak propagation times enabled Larry and myself to accurately determine that band conditions were favourable for an attempt to break the 1 mW barrier into VK6 at a time near to my local sunrise.  Larry's power output was gradually reduced as conditions were seen to improve, and eventually I was fortunate enough to capture Larry's weak 1 mW Argo trace entering Western Australia.  Later in the day, and near to sunset my time, Larry's 1 mW signal was also detected on the long path.

Not surprisingly previous 1 mW tests with WB3ANQ had proved unsuccessful using my low 40M dipole as a RX antenna.  The balance of the equation was tipped in our favour on this occasion, due I believe, to the recent erection of 50 foot high 30M inverted V dipole at my end of the path.  Interestingly Larry's similar TX dipole had at the time of this test been damaged by high winds.  Larry eventually decided to switch to an alternate dipole some 20 feet lower.  Once that was done, Larry's signal appeared from out of the noise amid much rejoicing at each end.

Larry's 1 mW and 1 Watt signals can be seen as triangular waveforms slowly sweeping between 10140065 and 10140070 Hz in the 2 screen captures hereunder -

  WB3ANQ at 961 uW

  WB3ANQ at 1 Watt

Note that the lower 1 Watt comparative image was received on my 40M dipole some weeks prior to the 1 mW test.

Due to the minimal signal strengths involved, Larry's periodic CWID was not visible in any of the 1 mW images.  Clearly such minimal signals are also well below any receiver's audible noise floor, and so cannot be detected by ear.  It was only due to Argo's effective 0.34 Hz QRSS3 bandwidth that this signal was detectable.

1 mW short path #1
1 mW short path #2
1 mW short path #3
1 mW short path #4
1 mW long path #5

Subsequent tests run with Larry, WB3ANQ have since yielded a weak trace at 500 microwatts.

An older example of the results obtainable using minimal TX power, can be seen in the 30M QRSS long path screen capture shown below as also received from Larry, WB3ANQ's HP signal generator (
QRSS3 modulated).  My receiving antenna at that time was a low 40M dipole.  (Yes I do mean a 40M dipole!)


Internal Links:

Pedersen Ray Experiments on 40M (VK6DI)

Live screen Grabber 

External Links:

I2PHD / IK2CZL (Weak signal and other Software)
What is QRSS?

Other external QRSS Links:

Knights QRSS (Reflector)

Email link to VK6DI is HERE
Please report any problems or inaccuracies within these pages.

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