Very Good Propagation with WSPR

With this table you can immediately judge the propagation from your WSPR spots.
For example, when your 1 Watt WSPR signal is spotted with a SNR of  -9 dB,
or higher, the propagation is very good.
If you notice that the propagation is very good, consider to reduce your power.

Judge the Propagation with your WSPR signal

A WSPR beacon with a power of 10 milliwatt, will ONLY be spotted, when the propagation is very good. WSPR with 10 milliwatt can be compared with a CW beacon with a power of  200 milliwatt.

Raspberry Whispers

On the interesting Blog of M0XPD is a very interesting article about WSPR experiments with the RPi.
Read the article: Raspberry Whispers by M0XPD.

I just visited the WSPR data base to collect a list of WSPR spots. And made an Analysis of the WSPR spots that M0XPD made on 30 meter with a power of 200 mW.

The stations that are mentioned in the article Raspberry Whispers have Excellent Ears. (Sensitive receivers)  The lower the Calculated Field strenght  in the better the propagating or the more sensitive the receiving station.

WSPR Analysis
The distance is given in steps of 100 kilometers.
A distance of 250 to 349 km will show up as 300 km.
PI4THT at a distance of 635 km, is placed in the category 600 km.

To compare spots, that are made with a different power (dBm), I calculate the lowest possible power of each spot, using the SNR and the power (dBm) of the transmitting station.

To compare the spots of stations at a different distance, I calculate the Field strength of each spot. This calculation includes the distance in km. In the table, I chose for microVolt/meter, to get nice values.

For one receiving station, the changes in Field strength follow the changes in the propagation to that station.

• The lower the Field strength, the better the propagation.

While comparing two receiving stations:

• The lower the Field strength, the more sensitive the station. 

The RPi is working well.

CQMM DX 2012

I just sent in my Cabrillo file for the CQMM DX contest. I had some trouble to make the entry. I logged on paper and made a Cabrillo file in Excel. But the robot refused my entry based on version 2. So I used an online webform to make the Cabrillo file in version 3.

We were invited out for a birthday, so I only had time on Saturday and only made one QSO before we left on Sunday. I used the Lowest Possible Power in each QSO.
I started, late around 19:45 local time, so the propagation to Europe was good. At first I made some more than 1000 Miles per Watt QSO's in Europe. About one hour later the signals from North and South America came through.
The signal of N2MM was stronger than S9. Carol was S8 through the 10 dB attenuator, so the QSO could be made with 80 mW. The exchange was 599 NAY . The Y means YL.  Later AA3B was also worked with 80 mW.
It is years ago that I met AA3B with just less than 100 mW, so you don't hear me complaining about the propagation. hi.

This CQMM DX contest brought 3 new DXCC's: FM, OX and CE.  
Martinique with 360 mW, gives a very nice QRPp more than 1000 Miles per Watt QSO.

This survey, showing the bands is also interesting. To North America was slightly less power needed at 15 m than on 20 m. Notice that the difference between 80 mW and 360 mW is just ONE S-point. 4x is 6 dB is one S-point.
By comparing the info in both tables, you can find out, on what band each DXCC was worked.
21 out of 28 QSO's were more than 1000 Miles per Watt QSO's. This is a staggering 75%.

QRPp How is it possible

When I started as a HAM, 20 years ago, I used my homebrew transceiver HM7, from Solid State Design, page 214...218, with an Inverted Vee, to work many different DXCC countries in Europe in CW. Because my power was only 500 mW, I had to look for stations, that I received with 599 or more, so the other station could hear my QRPp signal of 500 mW.
During daylight hours my RST would be 559, or even lower.
Please notice that a power of 500 mW is only four S-points weaker than 100 Watts.
See the PA1B QRPp page.

D and E layer
The radio wave is not attenuated when it is reflected by the E-layer. (Total reflection) But during daytime the signal is attenuated by the D-layer, when it passes through the D-layer.

During daylight hours, the signals are attenuated by the D-layer, which is absorbing

I discovered, that when darkness fell, the signals from the south of Europe would be very loud. So this made it easy, to make QSO's over a distance of 1000 km or more. When the D-layer disappears during the night, the signal can reach the the E-layer without attenuation in the D-layer.

The E-layer reflects the signal without attenuation

When the D-layer disappears, there is no attenuation in the radio path. The signal is reflected by the E-layer without attenuation. The attenuation of this sky wave is (only) 6 dB for a doubling of the distance. So the signal will be very strong.
At first, I did not realize, that my own QRPp signal, could also be an earsplitting 599, until I got genuine report from Italy, that my signal was S9, while using just 500 mW.

How low can you go

I was wondering, what the lowest possible power would be, if I would reduce my power in that situation with this excellent propagation.

If I reduced my power, so my RST would be 559, the difference is 4 S-point. This is a reduction in power of 4 x 6 dB = 24 dB which is 4 x 4 x 4 x 4 = 256.
So I could reduce the the power from 500 mW to about 2 milliwatts.

I was surprised by the low value, that I calculated, but this value is very realistic.
From 2001 on, I made many CW contest QSO's over more than 1000 Miles with 2.5 mW and 5 mW,
using PA1B homebrew attenuators.

I discovered that the frequency must be absolutely clear, when you use very low power.

Propagation, activity and antenna

The order of importance is: Propagation -  Activity - Antenna

 When I started as a HAM in 1990 I used a homebrew QRPp transceiver for 7 MHz, which I call the HM7 and an inverted Vee antenna.
In the 10 years that I used this CW transceiver extensively, I worked many European countries with a power of only 500 milliwatts in many normal QSO's and many contest QSO's. The excellent design comes from the book solid state design for the radio amateur.

I used this transceiver as a homestation and on holiday. Homebrew, QRP and CW (morse code) is a fabulous combination.CW is the most intriging mode of all. I noticed that you probably can not come closer to the signal, than in CW.

During the years that I used this TRX, I had great fun and I noticed that the activity on the band is more important than the antenna. With 500 mW the signals of the other stations must be S9 or more. Especially contest stations are eager to work everyone, so many QSO's can be made in a contest.
Further I discovered that propagation is more much important than the antenna. The Inverted Vee is not the best antenna, but the daily changes in the propagation can not be beaten by any antenna.

So to me, the order of importance is: Propagation -  Activity - Antenna