donderdag 14 augustus 2014

Schematic and building info of the 6 watt Power Attenuator

Power Attenuator for 6 watts
20 - 10 - 7  - 3 dB     by PA1B
This Power attenuator is  fast in CW QSO's, because
7 dB and 3 dB can be switched instandly..
The attenuator is also very accurate.

Power Attenuator
All attenuator sections are designed for an continuous input power of 6 watts. To reduce the number of resistors, I chose for asymmetrical sections in the attenuator.
The power resistors, with a lower ohmic value, dissipate 
most of the power and an other resistor is added in parallel, to arrive accurately on the wanted ohmic value. 
The power attenuator sections of 20 dB and 10 dB are build with 7 resistors, since they must dissipate much more power than the other sections.

The large resistors are resistors of 2 watts. The resistors with 2 stars (**) are resistor of 1/2 watt and the resistors with 1 star (*) are resistors of 1/4 watt.
I built my attenuator with metal film resistors of 2 watts, 600 mW (*) and 400 mW (*)

6 Watt Power attenuator built with resistors of 2 watts, 1/2 watt and 1/4 watt by PA1B
Click to enlarge

The switches on the front.      20 - 10 - 7 - 3 dB        
Reversed order
The schematic goes from left to right.
Please notice that the layout on the switches, inside the box goes from right to left.
So you will find the the resistors of 150 ohm and 330 omh to the right.
Notice the reverse order with respect to the schematic
R2 and R5 are also placed

Naar Blijdorp met Eneco

Als trouwe klant van Eneco, kregen een aanbieding om met Eneco gratis naar Blijdorp (Rotterdam Zoo) te kunnen gaan.
Dus besloten we al snel om met onze kleindochters te gaan.

We hebben genoten.

Apen met roze konten leidde tot grote hilariteit.

Neushoorn, Giraffen en een opa's lieveling, de otter

  Eneco, bedankt voor het fijne bezoek.

dinsdag 12 augustus 2014

PA1B 20 - 10 - 7 - 3 dB power attenuator measured

We measured the new built 6 watt PA1B  Power Attenuator, in the shack of Mischa PA1OKZ.
The attenuator is built with metal film resistors of 2 watts, 600 mW and 400 mW, from the E12-series.
I was curious how well the metal film would do HF.       Click for schematic

* The 20 - 10 - 7 - 3 dB  sections are very accurate until 10 MHz
* The 20 and 10 dB  sections show an accuracy of 0.1 dB to 0.2 dB at 30 MHz
* When all sections are switched OFF, the attenautor has a attenuation of
    0.13 dB at 1 MHz  to 0.61 dB at 30 MHz.
    This "extra" attenuation is frequency dependent.

Relative attenuation
The purpose of an attenuator is to attenuate the signal with the value 
of the sections, that are switched "ON".
In this table the attenuation with all section switched OFF is 0 dB.
The table shows the "extra" attenuation of this section, when a section is switched "ON ".
Relative attenuation of the PA1B  20 - 10 - 7 - 3 dB power attenuator    
At 10 MHz all sections are very accurate.
The 10 dB and 20 dB sections are more frequency dependent.
The section of 3 dB is the most accurate section. The section of 7 dB has an accuracy of 0.1 dB.
The section of 10 dB and 20 dB show an accuracy of 0.15 dB at 30 MHz.

I am very content with these values, considered that the resistors are resistors of 5% from
the E12-series. The measured values of all resistors in this attenuator, show that the accuracy of the resistors is about 2 %.

Absolute attenuation
This "extra" attenuation is caused by the fact, that the circuit formed by switches is not 50 ohm.
The value of 0.13 to 0.61 dB is typical for the switches that are used and the distance between the switches.
We measured about the same values in another attenuator with two section of 20 dB and one of 10 dB, that is built in the same way.
Absolute attenuation of the PA1B  20 - 10 - 7 - 3 dB power attenuator     
Inside of the box of the attenuator with simplified schematic

woensdag 30 juli 2014

Building a 6 watt power attenuator

I am building an attenuator with metal film resistor of 2 watts, 600 mW and 400 mW.
Sorting out the resistors
Click to enlarge
The store had no resistors of 1 watt, so I bought the power resistors
of 2 W and made a redesign of the attenuator.
All the resistors are metal film resistors.

The attenuator is designed to for a continuous power of  6 watts.

To the right you see the blue  box with the resistors that are needed.
The 3 dB and 7 dB sections both consist of 6 resistors each.
The 10 dB and 20 dB sections dissipate more power.
They consist of 7 resistors each.

     Outside of the box with the 20 dB section to the left.                         Inside of the box. 20 dB section to the right.                     Switches set to 17 dB                                                                             Switched mounted               
Next step soldering the resistors. 

zondag 13 juli 2014

Accurate and fast 5 watt attenuator for QSO's

Fast in QSO's
A simple way to reduce the power of your QRP set to milliwatt level, without modifying the set, is the use of attenuators. The combination of 20 dB, 10 dB, 7 dB and 3 dB is fast to switch, when you want to increase your power in QSO's. In one move, one attenuator section is switched OFF and an other is switched ON, to increase the power with a step of 3 db or 4 dB.

5 watt Accurate and Fast Attenuator for QSO   20 - 10 - 7 - 3 dB
All attenuator sections are designed for an continuous input power of 5 watts. This is 10 watts in CW.
The attenuator sections consist each of 3 compound resistors, which each are formed by a number of resistors in parallel. These resistors are a power resistor of 1 watts and a some resistor of a modest power (1/4 watt). The resistors with a star * can be 1/4 watt. Or you can chose  1 watt resistors for all resistors.
The power resistors, with a lower ohmic value, dissipate most of the power and an other resistor is added in parallel, to arrive accurately on the wanted ohmic value. The power attenuator sections of 20 dB and 10 dB are build with 9 resistors, since they must dissipate much more power than the other sections.

With two or more resistors from the E12-series in parallel, you can accurately make any value you want.
The resistor value of the combination is most of the time within 1% of the theoretical value.
This is why an accurate attenuator section, must always consist of 6 resistors or more.
Checking the value with an ohm meter and picking the resistor, with the higher value by hand, will improve the accuracy of attenuator section to 0.1 dB.
Notice that when you use the attenuator as an accurate attenuator, the accuracy of the attenuator is largely determined by the 20 dB and the 10 dB  sections.

Simple layout
The choice of placing resistors in parallel, leads to a very simple layout of the attenuator sections.
There's NO need for a PCB. hi.

Table for the fast and accurate  20 - 10 - 7 - 3 dB    5 Watt  Power Attenuator

donderdag 10 juli 2014

First place in the YO DX HF contest 2013 for CS8/PA1B

Today I received a beautiful Award of the YO DX HF contest.
Last year I partcipated while on holiday on the beautiful island of Saõ Miguel on the Azores.

During the contest I used an end fed wire on the roof of the hotel.
In the contest I used my FT-817 with 2.5 watts or less and a homemade light weight keyer.

The envelop from Romenia arrived in the rain.
When my wife entered the room with the wet envelop, she said:
"I hope all is OK".
I immediately recognized the envelop of the YO DX contest.
Despite the rain the Award is in good condition, because it is plasticized.

My thanks goes to Ovidiu YO2DFA, the contest manager of the
YO DX HF contest.
CS8/PA1B   First place in YO DX HF - Azores - Single OP - 14 MHz - Mix 

zondag 22 juni 2014

Two eQSLs over more than 2000 Miles

RF9T  2080 miles and 800 mW gives 2600 MPW
In the batch of eQSL cards,
I received a card from from RF9T.

With a distance of more than 2000 Miles to UA9, its easy to make a more than 1000 Miles/Watt QSO, when I reduce the power below 1 Watt.

The eQSL card of RK9UE was received earlier and was made with even less power. hi

RK9UE  3126 miles and 360 mW gives 8684 MPW
1000 Miles per Watt is not as difficult as it seems.
When you hear a station over a distance of  500 miles (800 km), just reduce to 500 milliwatts.

dinsdag 3 juni 2014

PACC 2014

The PACC is the annual contest from the Netherlands.

In other contests I always work with search and pounce with very low power, but in the PACC
I operate by giving CQ myself. Most QSO's were made with the highest power of my FT-817.
Last year the top of my inverted vee broken during a storm. I repaired the antenna temporarily.
One wire lays on the roof. Still I managed to make more than 130 QSO's.

I notice a difference with this antenna but the differences  due to changes in propagation, are larger.
I made more than 130 QSO's with 29 different DXCC's, with less than 5 watts.

Because we had visitors I could not start at 12:00 utc.
I did not wake up early on Sunday.

 De top van de Inverted V hangt slechts een paar meter boven het dak, nadat ik hem weer
provisorisch opgehangen heb, na een storm verleden jaar. Een draad ligt gedeeltelijk op het dak.
Tot mijn verbazing maak ik nog vele QSO's met QRP en zelfs met QRPp.
Dit wijst er op, dat de propagatie belangrijker is dan de antenne.
Ik maakte 138 QSO's met 29 DXCC landen met 500 mW tot 5 W in de contest.
Bedankt voor de activiteit in de PACC.

As a milliwatt and QRPp enthusiast very much like the "DX contests" in which every one works every one.

OP1A  in the PACC  2011

zaterdag 24 mei 2014


Here are some eQSLs' from the last batch.
The QSO's are all made QRPpp using the Lowest Possible Power.
QRPpp is the (not official) term, that I use for a power of less than 100 milliwatts.
Also known as two digit milliwatting.

Making QSO's with very  low power is not that difficult.
It´s all a matter of propagation.
The changes in propagation can be hugh.
So when the S-meter goes 20 dB up, the power can be reduced with 20 dB.

Look for a CQ of a station with an earsplitting S++ signal.
Answer with low power, with the excellent timing that you always use.
Don´t suspect anything, but be prepared after you give your call.
Most of the time, other stations are answered.
But than suddenly, the frequency is clear and you will be heard.
It´s possible that you are surprised, that you hear your call, being send immediately correct.
And before you know it, you also get an exchange. What was that? What number did he gave? hi.

9H1XT    1205 Miles   3.6 mW   334841 Miles per Watt

IV3ZXQ   550 Miles   22 mW   25002 MPW

SM5QU   740 Miles   36 mW   20549 Miles per Watt

SV1ENG   1318 Miles   98 mW   13453 Miles per Watt

S56M   588 Miles   80 mW   7349 Miles per Watt

OE2008S   445 Miles   98 mW   4698 Miles per Watt
See me smile from ear to ear after such a QSO.  

woensdag 21 mei 2014

Notes from the SP DX contest

I never use a fixed power, but adjust my power from QSO to QSO.
Before I answer the CQ, I adjust my power to:  500 mW,  1 W, 2.5 watts or 5 watts.
If the signal is very strong, I use the S-meter to determine the power that I wil use.
For example: a signal of:  S+ + 10 dB, I can answer with 50 mW,
using an attenuator of 10 dB.

To enter or write down  the call and to set the power, at the same time, is impossible,
So I am always too late for the first opportunity to answer.
And sometimes, I even switch to the wrong setting, which can be to low or to high. hi

Using the lowest possible power is great fun, but can also be a nerve wracking enterprise.

Interesting Experiences      Wow's and Woo's from my handwritten notes, made during the SP DX 2014
* In the QSO with SP8HW I realized that listening is very important.
    When I started to answer a CQ, I heard an other station answering, in the background.
    When he stopped, I gave my call twice, in the clear and made the QSO with 500 mW.
* I worked 3Z50AYP in a hurry. I was so excited, that I used 500 mW instead of a lower power.
    After the QSO it was quiet on the frequency. But a dupe will be impossible. ;-(
* SP6EIY can not hear me with 500 mW and 1 W. Maybe later.
* I seized the opportunity to switch back to 500 mW, while waiting  for a very loud station.
    It's important to immediately adjust to 500 mW, after a QSO with 1 W or 5 W.
* I had to push to make a QSO with SP2GJV with just 50 mW, which is quite remarkable.
    There was a lot of QRM in the background.
* Station after station, visited SP3FYX.
    I had to have a lot of patience, not to increase the power to 5 watts.
    And finaly, to use just 500 mW.
* I love chirpping stations. I work SP7.... with 5W.
* Worked SP9YFF with 500 mW, before I got the call complete.
    I realized that . . . FF was a new one.
* After the QSO with SN8N, I realize that I should have used 50 mW instead of 500 mW.
    The signal was earsplitting loud. S++
* One station after the other goes in to the log. It 's a mix of 500 mW and 5 W.
* It's very busy. I have to look for stations that are calling CQ with no takers.
* SP6ZDA At the last moment, I decide to switch in the 10 dB attenuator.
    Resulting in a QSO in the clear, with just 50 mW.
* Now I recognize new stations by the last letters of the call.
* 3Z8Z fades. I need 5 W.
* The numbers of my computer program and the Morse Machine differ.
    I correct the Morse Machine.
* SP9MZS Earsplitting signal. But the setting is wrong, so 500 mW instead of 50 mW.
    Next time better.

    I could make all these fine QSO's, thanks to all the fine operators in the from Poland.

maandag 12 mei 2014

eQSL avalanche

Last week the number of eQSLs in my eQSL inbox had risen to more than 100.
Between these QSLs were many 1000 Miles per Watt QSL's.
For these QSL's, I determine the distance and calculate the Miles/Watt.
I mention these numbers in the comment field of the individual eQSL.

Last week I replied many eQSL's.
  F6KDF  435 Miles and 8.5 mW gives 51128 Miles/Watt
It took me a few days, to reply manually,
on the eQSL site.
So I was glad, that I had reduced that number
to about 10 remaining eQSLs.

But when opened my eQSL inbox a few days later, it knocked my socks off.
There were 208 eQSL's in my inbox.
This number is very large to reply manually.

A doubling in a couple of days.
And what if that number doubles again?

donderdag 8 mei 2014

G4ILO Whispering with 20 mW and 1 mW

This is an other analysis of the data collected from the
WSPR database for spots of Julian G4ILO.
Julian transmitted with a power of 1 mW and 20 mW.

The table shows, that the spots that were made with 1 mW, 
were about 10 dB weaker than the spots made with 20 mW

The table shows a selection stations that received spots made with both 20 mW and 1 mW
To compare spots over different distances, I use the 
Calculated electrical field strength, E, in microVolt per meter.
For details see the WSPR Propagation Analysis page of this Blog.

The lower the electrical field strength the better the propagation.

A power ratio of 10 means 10 dB
Please notice the the value for E is given in Volt/m, so a Voltage ratio of 10 means 20 dB
Which is indicated at the top of the table.
A Voltage ratio of 10 is a ratio of 100 in power.

The table shows stations that received the signals, that were transmitted with 1 mW and 20 mW.
Notice the difference in field strength in spots made with 1 mW or 20 mW.
The difference in field strength between the spots of 1 mW and 20 mW is about two steps in this table.
This is about 10 dB.
This is no surprise because, the difference in power between 1 mW and 20 mW 
is  10 log (20 / 1) = 13 dB.

The differences in propagation are huge
The field strength of the spots made with 20 mW, received by ON7KO over 600 km, 
show a value of 0,3 microV/m to 0,03 microVolt/m. 
The ratio in voltage is 10 and the ratio in power is 100, which is 20 dB. Wow

maandag 5 mei 2014

SP DX contest

Poland - Voivodeships
My objectives
As a milliwatt enthusiast I tried:
* to make as many QSO's with the
   lowest possible power
* to make as many 1000 Miles per Watt QSO's as
* to work as many different prefixes as possible for the
   BQC- Marathon.

1000 MPW
The distance to many of Voivodeships is more than
500 miles  from my QTH in JO22na.
Only the distance to the Voivodeships Z, B, D and
a part of W, is less than 500 miles.
With a power of 500 mW, and a distance of more than 500 miles,
these QSO's will be, more than 1000 Miles per Watt QSO's.

Crippled antenna
This year I did not expect much of my Inverted Vee.
Last year the top broke and I fixed the antenna temporarily.
The top is now just 2 meters above the roof.
And recently I found out, that the 300 ohm ribbon is damaged, so only one wire is still connected
But the antenna worked better than I expected.
Click here to read about the state of the antenna.

1000 Miles per Watt
The number in red, show the QSO's with more than 1000 Miles per Watt.

zaterdag 3 mei 2014


General Vladimir Zaimov
I just started in the ARI DX contest.
This is an interesting contest for a low power enthusiast like me,
because this is a DX contest, so I can work any station, so many stations can be worked with low power.
For the first QSO, I selected the very strong signal of OM5WW and worked him with just 50 mW.

The second station was LZ69VZ.
I like stations with special calls, so I gave him a call.
After exchanging the numbers, something very remarkable happened.
I got a question. At first I though that I had to repeat my call.
And repeated my call. But the question was . . . .
So the question was: what power do you use?
I immediately thought, this must an operator, that had met me many time before and knows from my QSL cards that I often use low power. And indeed, the operator is Gosho LZ1ZF, who I meet in many contests.
I gave: 500 mW. hi

Thank you Gosho. My 1000 Miles per Watt QSL for LZ69VZ will be on his way in a few weeks.
If you hear Gosho, give him a call.

dinsdag 29 april 2014

Congratulations! Your log was accepted!

I just sent in the Cabrillo log for the SP DX contest and the CQMM DX contest.
Just in time, because I had almost forgot.
Often I leave the shack after the contest, when the contest ends in the afternoon.
Sometime I spent some time on the log in the same evening.
But often I forget the contest at all, until the next weekend.

After the contests I had little time to send in the Cabrillo files.
But today I luckily remembered.

The most important part of the Cabrillo file is the Category.
Wrong category, no award.

I always spent much time on the Soapbox comments.
It's great fun to mention in the Soapbox, a single QSO made with very low power,
for example 10 milliwatts, using an attenuator.
Or the number of QSO's made with more than 1000 Miles per Watt.
Or a QSO that I made with South America, during the CQMM DX with just 2.5 W
But this can take quite some time to calculate and write about it.

75 Characters
The Cabrillo file of the SP DX was immediately accepted.
The Cabrillo file for the CQMM DX was rejected at first.
The Soapbox line which are restricted to 75 characters in a line, so they were tooo long. hi.

Notes on paper
In the SP DX contests I made notes on paper during the contest.
I had great fun with QRP and QRPp in both contests.
So I wanted to catch these special moments, that I experienced,
while using the lowest possible power in these contest QSO's.      (Click to See the Notes)