G8LCO's blog

For the last year I have been running a Wellbrook ALA100LN preamplifier driven from a 8m x 2m wire loop for LF to 6m. Because I am close to a MW broadcaster 9 pole HPF and 9 pole LPF are used to remove the 0.55-1.6 MHz signals ( 1/2 V rms antenna output !! ).

Like many other WSPR'ers I have gone SDR. Recent 3 band spots have been from a KiwiSDR , a nice tool.
But from now on (5th November 2018) the RX is a Red Pitaya board running Pavel Demin's exceptional software on eight bands LF and up, I will continue using my 50cm. E field antenna which works very well and is almost invisible. Pavel has been very kind in assisting me over a silly set up error that came from You Tube!

There are now several WSPR users who run multiple stations with perhaps different receive antennae. The WSPR map shows all of the signals for all of the stations but the callsigns are all piled onto the same location so it is not possible to see all of the worked stations, only the top named one.

Whilst WSJT-X 1.60 works very well with CAT control, version 1.7 can have grave problems. The development of the WSPR Challenge (http://pe1itr.com/wspr_challenge/) has drawn attention to the severe database corruption that 1.7 can produce when the CAT looses sync with WSJT-x. You only have to look at the results of the band rankings to see that there are very odd scores that are due to cross band contamination.

VK2KRR has some spots from EI, G, PA and R.......... That's very big ears.

For many years people in the UK have joined up Christmas with the New Year to make a very nice long break, many Factories and Offices close down so there are a few more Hams around than normal. Some of them have taken the opportunity to join in the MF WSPR activity over the holiday period. So there are quite a few new people to welcome to MF WSPR.

I have been running two crossed active loops for well over a month now as well as the e-field active that has been up for about 10 years. Living with several antennae is always interesting, the ability to instantly compare always useful. For WSPRing all have virtues, the very broad e-field is always there as a reference of known sensitivity while the directive loops are quieter on the low bands. For size, very low cost and stealth the loops are very hard to beat, they also seem to receive at least as well as a top loaded Marconi on low bands.

Have now been using the loop for a few weeks now, have dropped the noise floor around 6dB by choking the loop feeder at the shack end.
Perhaps I'm around the floor now, doubling the loop area has not gained any s/n improvement, results now seem about the same as other UK stations. The loop is bandpass filtered, I have a simple method of sweeping the loop in place. The loop output goes into a HP 141 Spec anal with the Tracking gene driving a 6' square wire loop in the house so I can sweep the loop directly.

First use of the 4'square thin wire loop went well, pulled in Italy and Spain from near London. Not too bad. The basic idea is to use the thin wire loop as an untuned low Z sensor, this then couples to a High Z bandpass pair to exclude MW broadcast signals. A Jfet fronted amplifier provides 6dB gain with low noise and very good linearity to drive 30m of 50ohm coax back to the Shack.

Tonight is the first time that my new MF active bandpass loop has been used. I will still use the 1m E-field active antenna on other bands as it is very convenient to have a flat 1KHz-30MHz antenna for general listening.

The new loop has a 4' square thin wire loop feeding a two pole bandpass then a very linear 6 transistor amplifier with a gain of two. The sensitivity is equivalent to the E-field antenna at 1V/M. At MF both antennae are band noise limited, the H field is as far from houses as possible, the E-field needs a move but tree and shrub screening is an issue.