PA1B 0 - 36 dB Attenuator for QSO's

Last week, the info  on the interesting Attenuator page  of my web site was updated.
I added new info on the PA1B 0 - 36 dB Attenuator, specially designed for QSO's (Click)
I also placed new info on the PA1B 0 - 36 dB Attenuator, under the Tab's on the top of this Blog.

A simple way to reduce the power of your QRP transceiver, without modifying the set, is the use of attenuators.  This accurate PA1B  0 - 36 dB attenuator, is an excellent attenuator, to use in QSO's with very low power. This attenuator enables you, in contest QSO's, to go to the next setting instandly, when your call is not heard.
The combination   20 dB - 10 dB - 3 dB - 3 dB  is very quick to adjust in contest QSO's.
The choice of the values, makes it very easy to calculate the power at the output instantly.
This accurate Power Attenuator is designed for the use in QSO's.
With only 4 switches it is surprisingly fast and easy to operate.

Power Attenuator Calculator
I use the excellent Power Attenuator Calculator (Click), for the
design of the Power Attenuators.
With the Power Attenuator Calculator, you can design an attenuator for any input power.

Read more about attenuators on the attenuator Page.

On  my web site: Home - PA1B QRPp page 

PACC with QRPp

Although I had to take it easy, I had fun with QRP and QRPp in the PACC.
I found out that calling CQ was to much for my.
After just 3 QSO's, with 360 mW, in just less than 3 minutes, I had to take some rest.

So I decided to work in a relaxed way, with Search and Pounce.
I worked with Search and Pounce from 2.7 watts down to 1.8 milliwatts
When the S-meter goes up, my power goes down.

I frequently alternated S&P and calling CQ, with just 800 milliwatts.
While calling CQ with 800 mW, I made a total of  30 QSO's , in a number of short run's.
In the last 15 minutes of the contest I made a run of 13 QSO's with 2.7 W.
To my surprise, I noticed only a small difference between 800 mW and 2.7 W.

I worked YT6T with 8 mW and LZ6C with only 1.8 mW.
It's a long time since I could make QSO's with less than 5 milliwatts. hi
The signal of LZ6C wasvery strong:  S9 plus more than 20 dB.

REF CW contest 2013

This year I only participated for a total of 45 minutes on Sunday.

In a relaxed way, I used search and pounce with the use of the lowest possible power in each QSO.

The conditions were good for the use of low power on 14 MHz.
On 14 MHz all QSO are good for 1000 Miles per Watt.

Despite the short distance to France, 5 out of 6 QSO's are made with QRPpp*.

On 7 MHz I had to use the maximum power of 2.7 watts in most QSO's.

The changes in propagation can be very large.

In the afternoon, I met a station from Corsica, that I had worked earlier with 360 mW.

I tried to make an second QSO with 36 mW. His signal was S9 + 10 dB. He recognized my call and gave QSO B4. I gave a new report. But then we ended up, transmitting at the same time. So.....this QSO will probably not make it into the log. hi

I enjoyed the opportunity to work with very low power in the REF CW contest.

QRPpp* is the (not official) term that I use for a power of less than 100 mW. Bert PA1B QRPpp

QRPp in the ARRL int DX contest

In my first ARRL international DX contest, I used 5 watts. My exchange 599 005 gave no problem for the receiving station.  In CW of course given as:  5NN TT5.
It was obvious, that I was using QRP.

I very much like the ARRL international DX contest. In this contest, the DX stations, like myself, will give their power in the exchange. So the receiving station knows immediately, that I am working with QRP.

 When the S-meter goes up my power goes down. 

In most contest QSO's, I often use the Lowest Possible Power, in each QSO, using S&P.
When I hear a station calling CQ, I look on the S-meter to determine the power with which I will answer.

In later years, I reduced to 500 mW, when the propagation was very good. The use of 500 mW in a contest QSO is no problem, because most of the time, the response will be immediate and correct.

pwr? . . .100? . . . 1kW?  .  .  .  .  .  .  . 1W FB

The lowest value for the power in the Cabrillo file is 001.
Over the years, I found out, that when I was using 1 W, it was best. to use the exchange 599 001.

How to indicate, that I am using only 500 mW? Well, that's simple. The DX station give their estimated power. So for a power of less than 1 W, I also give the exchange : 599 001.

But don't think that all problems are gone with 599 001. Some stations keep asking pwr?, because they think that 001 is a number or they respond with 100? or even 1kW?.
In that case I will respond with:   599 1W 1W 

* I met operators, that fall out of their chair, when they realized, that my exchange 599 001 indicated, that I was using only 1 watt.
Two seconds of silence and an additional "1W FB", from a station that is transmitting not a letter to many, I consider a huge compliment. hi

Please notice that when you use low power, that any QSO between Canada or the USA with Europe with 3 Watts or less, is good for 1000 Miles per Watt.

Power of the FT-817 at PA1B's, after serious mis-match.

Power with WSPR

WSPR vs CW 13 dB

How much power should be used with WSPR?
WSPR is a beacon system. The WSPR data can be used to probe radio frequency propagation conditions.  
WSPR uses a low transmission speed.
The lower the transmission speed, the lower the power, that is needed. 

As you will see:  Please WSPR  with QRP.

Roger G3XBM asked Joe Tailor K1JT about the difference between "CW by ear" and WSPR.
Roger placed Joe's response in an entry
on his Blog:
WSPR versus CW - what's the improvement
Click to go to the article.

In a description on the WSJT web site, Joe gives a comparison between WSPR and CW by ear. 

For "CW by ear" Joe gives a SNR of -18 dB for a very skilled human CW opererator.

Joe gives a value of -29 dB for the SNR for a WSPR signal.

So the difference is 11 dB, but Joe estimates that for most operators, the SNR has to be even 15 dB. 

I estimate that the difference between WSPR and "CW by ear"  is about 13 dB for contest CW operators and 15 dB for most operators.

For an advantage of 13 dB, a power of 5 Watts in WSPR, can be compared with 100 W in CW.

So the power in WSPR can be 1/20th of the power in CW.

The value of 13 dB is guideline to estimate the power that you should use in WSPR to approach the situation that you use with CW. 

For an advantage of 15 dB a power of 5 Watts in WSPR, can be compared with 150 W in CW.

So the power in WSPR can be 1/30th of the power in CW.

Calculating with power, 15 dB corresponds to a factor 30,
13 dB is 20x, and 11 dB is 12.5x
Calculating with voltage, 15 dB corresponds to a factor 5.5,
13 dB is 4.5x and 11 dB is only 3.3x

I made a table below to compare WSPR with "CW by ear".

The table shows the values for 15 dB, 13 dB and 11 dB. So you can choose the value yourself.

Please note that a difference of 2 dB or 4 dB is very small compared to the large daily fluctuations (in dB) caused by the propagation.

I very much like the table of 13 dB. (20x)   I estimate that the value of 13 dB, is the value for the skilled CW contest operators. The values are easy to remember, since 100 W in CW can be compared with 5 W in WSPR. So when you use WSPR, please reduce your power to 1/20th of the power that you sue in CW.

If you want to analyse what is possible with QRP in CW, you can use 200 mW (23 dB) with WSPR.
This can be compared with 4 W in CW.

As a low power enthusiast I often use the lowest possible power in CW contest QSO's.
I often use less than 1 W. To analyse the possibilities with 1 W in CW, you should use a
power of 50 mW (17 dB) or less. hi

Please note that WSPR with 100 W can be compared with 3000 W, 2000 W or 1250 W in CW.

So gentleman, please:
                 Think in  dB,  and  WSPR  with   QRP.  hi.