Homebrew 10 watt dummy load

For years I use a very simple homebrew 50 ohm - 10 watt dummy load.
At a moment, I realized that 20 resistor of 1000 ohm in parallel, form a resistor of 50 ohms.

So I bought twenty 1000 ohm - 1/2 watt resistors and soldered them on a PL 259 connector.
Through the green tube runs a wire, to connect the wires of the resistors to the left, with the
center conductor of the connector.
The twenty resistors can dissipate a power of 10 watts.

The dummy was measured in a workshop of Rohde & Schwarz.
At the moment I can not find the report of the measurement.
I first wrote that the dummy load was 49.9 ohms, but I now remember
that it was 49.8 ohms.
I was surprised the resistors had an accuracy of better then 1%. hi

10 watts - 50 ohm HF dummy load

  

Spring

Looks like it will be spring.
We have very nice temperatures.
Yesterday my wife and I went for a walk in Rhijnauwen, along the Kromme Rijn.

Langs de Kromme Rijn

Sneeuwklokjes

Guust is 57

Guust

Guust is 57.
Wat een verassing.
Zo'n 40 Jaar geleden was Guust mijn favoriete stripfiguur.
De boeken zitten in een doos op zolder,
maar mogen (nog) niet weg.

Toen ik de Google doedel zag, moest ik ook aan de meeuw, juffrouw Jannie en de flaterfoon denken. Hi.

Flaterfoon

HA-DX contest 2014

I had great fun with low power in the HA-DX contest.

I had to rediscover, what my Inverted vee would do.
In earlier contest I experienced, that I would need the full power
on 7 MHz and 3.5 MHz.

From the Cabrillo log:
SOAPBOX:       I fixed my Inverted Vee temporarily after a storm last year
SOAPBOX:       One wire is flat on the roof, but I still make QSO's
SOAPBOX:       Had great fun with QRPp and QRP from 100 mW to 5 watts
SOAPBOX:       Thanks for the activity in the contest

On 14 MHz my antenna is still working well.

In many QSO's on 40 m and 15 m, I had to use the full power of the FT-817.
But when the S-meters goes up, I can reduce the power.
I could also make QSO's with QRPp.
I had a remarkable QSO with HG8C.
When I gave my call with 500 mW, there were other stations also calling, but he came back for me.
This doesn't happen often. hi. Most of the time I must wait, till the frequency is clear.
I even had a QSO with 50 mW with RM22HD outside the contest.

REF CW 2014

In the end of January I participated in the REF CW contest.
In recent years I made many QSO's in this contest with 50 mW.

The top of my inverted vee was broken last year in a storm and I made a temporaly repair. One of the wire lays on the roof.
So I had to experience how the antenna would work.

On Saturday I made 2 QSO's on 20 m with 50 mW and 100 mW.
On Sunday I made 14 QSO's on 40 m.
In these QSO's I had to use the full 5 watts of the FT-817 due to the antenna.

Further I made a number of QSO's on 20 m with a power of 50 mW to 500 mW.
The inverted vee with one wire on the roof works for 20 m.
But on 40 m it takes more power to make QSO's.

When the propagation is good, it's not that difficult the make QSO's with very low power.
On Sunday the signal of F6KNB was S9 + 10 dB. So I decided to try a power of 50 mW.
I gave my call just once and got an immediate respons. FB.

ARRL International DX CW

I started late, because the grand children stay with us this weekend.
This afternoon we went to the park in stead of participating in the ARRL int. DX contest.

My inverted Vee is still temporaly fixed after a storm last year.
One wire lays on the roof.
But I can still make QSO's even with low power in many different contests.

I need more power than the usual 1 or 2 watts, that I use most the time.
So I use the maximum power, that is about 4 or 5 watts.
Even the stations that I receive with S8 are more difficult to QSO than last year.

After a few hours in the contests there are 15 QSO's in the log.
But it's still fun to participate in this fine contest.
There was only one station, that was puzzled by my exchange 599 003, when I use about 2.5 Watts. hi
Let see what tomorrow brings.

DL1SDZ's WSPR spots with 0,5 milliwatt

On his blog Hajo DL1SDZ reports spots made with 200 mW down to 0,5 mW on 30 meters.
He reduced the power from day to day.

Hajo wrote me that the 4 last spots with 1 milliwatt were actually made with 0.5 milliwatt.
In the WSPR data Hajo uploaded the spots of 0,5 mW as 1 milliwatt, since this is the lowest value that can be used. (1 mW is 0 dBm)
Because my excell sheet can not calculate with a power lower than 1 milliwatt, I left the values for 1 milliwatt in the analysis of yesterday .

But today I calculated the lowest possible power for the value of 0.5 mW by hand
and made the next table exclusively for the spots with 0.5 mW.

The calculated lowest possible power is, in some spots, only one step lower.

This table show 4 spots in stead of 3.

The table below that I made yesterday, does include spots of 400 km or more,
so it does not include the spot by HB9JAQ

Click to enlarge

This analysis shows the calculated lowest possible power.
The lowest possible power is calculated from the power sent and the SNR.
The lower the lowest possible power, the better the propagation.

WSPR with 200 mW down to 1 mW by Hajo DL1SDZ

More and more operators discover the use of very low power with WSPR.
On his blog Hajo DL1SDZ reports of spots, made with 200 mW down to 1 mW.
Hajo reduced the power from day to day, as shown in the second analysis.

The first analysis shows the calculated lowest possible power.
The lowest possible power is calculated from the power sent and the SNR.
The lower the lowest possible power, the better the propagation.

Click to enlarge

The analysis below shows electrical field strength.
In this calculation the distance is also included.
The lower the field strength, the better the propagation.

Click to enlarge

In the analysis all spot over 400 km and more are in cluded.
Thanks Hajo, for the interesting experiment.

Analysis of G3XBM's 40m WSPR spots with 5 mW

G3XBM left WSPR running with 5 mW on 40m for 24 hours.
Roger concluded that his signal was in the noise most  of the time.
He also concluded that he would need 2 W.
http://g3xbm-qrp.blogspot.nl/2014/01/40m-5mw-summary.html
The analysis below shows that the conditions changed dramaticly after the 7 spots with 5 mW.

The header of the table shows the Calculated  Lowest Possible Power in mW (Click for info), 
which is calculated from the used power (Pwr Sent  in mW) and the SNR.

The better the propagation, higher the SNR and

the lower the Calculated Lowest Possible Power will be.

The analysis
9 UTC gives the spots that were made in the hour from 9:00 till 9:59 utc.

This first line shows, that the power that was needed for the spots was 1 W down to 2 mW

In this hour, half of the spots that were made with 2 W could be made with 100 mW.

The white circles indicate the power with which half of the spots could be made.

The lower the power needed, the better the propagation.

From 9 utc till 14 utc on the 18th there are 11 spots with a calculated lowest possible power of 5 mW or less. So it was possible to make spots with 5 mW.

WSPR with 5 mW
From 14 utc Roger reduces further to 5 mW and over 24 hours only 7 spots were made, shown in the yellow coloured part of the table. In the red part of the table there are no spots since the power that was used is 5 mW. In the red part I show the receiving stations and their SNR.

Back to 2 W
You would expect more spots, since the 24 hours before showed many more spots that could have been made with 5 mW. But the conditions changed dramaticly.
The last part of the table shows spots that were made with 2 W.
At 20 utc on the 20th at least 500 mW is needed.
And at 5 utc and 7 utc spots could have been made made 5mW

G4ILO Whispering with 20mW and 1 mW

Julian G4ILO did an interesting experiment with WSPR. 
He used a power of 20 mW and 1 mW and was heard over large distances.
I made a table of the spots with both 1 mW and 20 mW.
I left out the few spots that were made with 50 mW.

The table below shows an interesting phenomena.
When 20 mW is used, the  calculated lowest possible power is 20 mW or less.
When 1 mW is used the calculated possible power is 1 mW or less.

The Lowest Possible Power is calculated from the used power and the SNR.

The SNR for a solid copy with WSPR is -29 dB.
When a signal is received with a SNR of -19 dB, this signal is 10 dB stronger, 
so the power could be 10 dB reduced and still be solid copy, but then with a SNR of -29 dB.
The Lowest Possible Power is 20/10 = 2 mW 
22 Spots were made with a Lowest Possible Power of 2 mW.

The tables below show the distance, the receiving station and the power that was used.

WSPR Propagation Analysis

Changes in propagation give huge changes in signal strength. 

WSPR has a SNR that can act as an S-meter. 

But if you want to compare WSPR spots, you also have to take 

into account the output power of the transmitter. 

WSPR Propagation Analysis

I use the calculated lowest possible power

in milliwatt of each WSPR spot, when

• the spots are all made over the same distance
• the spots are made with different power.

The lower the calculated lowest possible power, 
the better the propagation.

Solid copy

The SNR of a WSPR signal can be as low as -33 dB.

But a WSPR signal that is received with a SNR of -29 dB will be a solid copy.

Calculated Lowest Possible Power
A signal with an SNR of -19 dB is 10 dB stronger,  can be reduced with 10 dB
(1/10th of the power) and still be solid copy, but then also with a SNR of -29 dB.

The better the propagation, the stronger the signal and the higher the SNR will be.

The more the power can be reduced and the lower the Lowest Possible Power will be.

But the frequency must be clear, to actually receive a signal with the Lowest Possible Power.

G4ILO Whispering with 20mW

Yesterday Julian G4ILO wrote on his interesting Blog about his advantures with WSPR with low power:

Many people who operate the weak signal mode WSPR use too much power. 
If you don't use very low power (QRPp) you'll never find out what this mode is capable of. 
So to remind myself I thought I'd do some whispering on 10m using 20mW of power. 
It's easy to use low power with the Elecraft K3 as the power level is adjustable in 0.01 watt increments. 

The power of 20 mW that julian used to WSPR can be compared with 400 mW in CW. (13 dB --> 20x)

Today I visited the WSPR database to make the following analysis.
In each spot I calculated the lowest power what could be used, to be received with a SNR of -29 dB.
The stronger the signal, the lower the lowest possible power.
The stations that received the strongest signals are ON7KO (600 km), LA9JO 1900 km) and ND6M (6600 km)

Beeldenlaan

Het lange pad.

Moet je eens kijken, 

het is nu vijf voor vier. 

T'is het maar tien minuten lopen

van daar naar hier.

Gisteren ben ik met de eFiets naar Rhijnauwen geweest om te wandelen.
Het was heerlijk zonnig weer.
Aan het eind van de Beeldenlaan van Oud Amelisweerd naar de Vossengatsedijk, realiseerde ik mij dat ik over dat pad slechts tien minuten gedaan had.

Aanvulling:
De foto heb ik genomen na mijn bezoek aan de tentoonstelling van Armando
in Oud Amelisweerd vorig jaar in oktober. Presentatie in Prezi.
Halverwege de Beeldenlaan had ik het zo warm, dat ik mijn jas heb uitgedaan.

Merry Christmas

Click to enlarge

My personal Christmas card shows winter pictures of my favorite canoe spot.
The water is called: "Oude Zederik" and runs from Meerkerk to the river Lek.
It's a beautiful area with water and reedbeds.
The windmill is rebuild in recent years and is visible from the A27.

Young artist

Glijbaan - The slide  -  Click to enlarge

The young artist at work

The original drawing

 
This weekend our granddaughters stay with us.
On Saturday the younger of the two (4) made a drawing.
My granddaughter had asked me, how I made the colors on a drawing, that I have made.
So I sugested to color her drawing, while she was painting another drawing.
The young artist said: WOW, when I showed her the drawing with the colors. hi

Our elder granddaugther painted birds

 

On Sunday it started to rain, when we had planned to go to the park.
So it was time for panting.

When the rain stopped, we went to the park.