Attenuator for the FT-817 by G4EFE

On my Blog post about the Power attenuator for the FT-817, that I published in SPRAT, I got a very nice comment from Martin G4EFE.

Martin writes:
Hi Bert - I just built this into a tiny 25x25x50mm metal enclosure. Of course, it works great.
Looking forward to some QRPp WSPR from the IC703.

Attenuator built by Martin - G4EFE

As you can see, the attenuator is built in a beautiful, small enclosure.

Power

The maximum power of the attenuator is about 1.5 W. With a derating of 33% the nominal power of the attenuator is 500 mW. I advice to use the lowest power setting of the transceiver. For my FT-817 this is  500 mW.

Martin will use a IC703. This transceiver can make 100 mW at it lowest setting.

Thank you Martin for sharing the info and good luck in QRPp.

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.

Attenuators and tuning

50 Ohm attenuators
The attenuators shown on the PA1B Attenuator page are all very accurate 50 ohm attenuators. The accuracy is obtained by placing two, or more,  resistors in parallel, to form the required ohmic values very accurately, with resistors from the E12-series.
But the accuracy of the attenuators is also dependent on the termination of the attenuators. 
When the attenuator is terminated with 50 ohms, the attenuator will show also an input impedance of 50 ohms and most important, will give the right attenuation.

Setup

The attenuator will be placed behind the set. The SWR-meter is not shown in the drawing, but is placed between the attenuator and the tuner (transmatch). I work with this setup, as long as I work with the attenuators and by doing so, I made many fine QRPpp QSO's, using an inverted Vee as antenna.

The right setup.        Tune, as accurate as possible, for a SWR of 1:1,

Tuning

Tuning is done with the attenuator on bypass (0 dB). Tune carefully to get a SWR of exactly 1 : 1. When the SWR is 1:1, the input of the tuner will show an impedance of 50 ohms, so later with the attenuator switched on, the attenuator is terminated with 50 ohms and the attenuator will give the right attenuation. It's very important to tune for 1:1 as accurate as you can, to get a termination with 50 ohms for the attenuator.

SWR

I got an e-mail from a follow Blogger, Mike VE3WDM. He was using the autotuner of the Elecraft K3. The K3 is connected to  the SWR-meter, which is connected to the attenuator, which is connected to coax to the antenna. Mike wrote that he had a SWR of 1.6 : 1, with the attenuator on by-pass. Since the autotuner is in the set and the SWR-meter is behind the set, this means that the coax to Mike's attic antenna shows an impedance of 31.25 ohms or 80 ohms. (50/1.6 or 50x1.6)

The e-mail of Mike made me realize, it is not possible to use the autotuner in the set, together with the attenuators. The tuner has to be behind the attenuator. However, it is always possible to use another (homebrew) tuner behind the attenuators. Mike later said that he will place a tuner behind the attenuators and will turn off the tuner in the set . 

So place the tuner behind the attenuator and tune as accurate as you can to get a SWR of 1 : 1, to get the right attenuation. 

Russian DX 2012

Last week I participated in the Russian DX contest. One of the support wires of the inverted vee was broken, so the wire ran from the top of the mast to the raingutter and then vertically along the house to one meter above the ground. Still I made QSO's with very low power.

The conditions on 14 MHz were good, so I used to lowest possible power.
On 7 MHz I had to use the maximum power of 2.7 watts in all QSO's.
The most remarkable QSO was made with PW7T with a power of 2.7 watts.
The numbers in red are indicating more than 1000 Miles/Watt QSO's.

IARU HF Worked DXCC Coutries

In the IARU HF World Championship, I used
the Lowest Possible Power in nearly every
QSO using a FT-817 that can be adjusted to:
360 mW, 800 mW, 1.8 W or 2.7 W and an
Inverted Vee.
For a power lower than 360 mW, I use
homebrew attenuators.

Worked DXCC Counties
In the IARU HF 2011 I worked 36 DXCC counties.

Propagation
If I compare this overview of the IARU HF contest with similar overviews from 9 years ago, when the the number of sun spots was higher, the difference is that the UA stations that are worked with 8 to 80 mW now, in 2003 could be worked with 5 mW to 50 mW.
This influence of declining sun spots over the years is far less than the daily fluctuation.
In every contest it's still possible to work with QRPp and make more than 1000 Miles per watt QSO's

Activity
It is great to participate in a contest with "World Wide" activity.
This activity is almost as important as the propagation.
I met stations with Excellent Ears and many stations with very good operators.
As you can see, I had great fun with low power.
Thanks to all these fine operators.

The Lowest Possible Power

In many CW contest QSO's and other QSO's, I use the lowest possible power.
When a received signal is S9, I answer with 500 mW.
And when the signal is S9 + 10 dB, I use 50 mW.
I get 50 mW with the FT-817 on 500 mW and an attenuator of 10 dB.
When I change band, while the propagation is very good, I first look for very strong stations.

Using the Lowest Possible Power

Using low power is not difficult, if you keep your eyes on the S-meter. (1)
Before I answer a CQ, I first adjust the FT-817 to the power, that I want to use. (2)
Then I send my call just once or twice and then I listen. (*)
With many other stations answering, I have to be patient.(3)
If the station still calls CQ, without answering other stations, after I have sent my call (*), then I know that my signal is not heard.
When I am sure that my signal is not heard (4), I double the power (5) and try again. (*)
Don't loose your cool in (6), because the frequency has to be absolutely clear, for this weak, but readable, signal to be heard.
If my 50 mW signal is also not heard, I will have to increase to 100 mW. But...
Suddenly my 50 mW signal is heard (7) and I hear my call and receive a report. Then I only have to send my report and log the QSO. (8)

Increasing the power
Doubling the power is the optimal step to increase the power.
This is a step of 3 dB. A step of 1 dB is too small and 10 dB is too large.
Using the lowest possible power is actually QRO-ing with low power.
.

The FT817 loses 3 dB

In the rush to join the net of PI4NWG, I did not notice that the tuner that I always use for 145 MHz, was on the wrong band.
At first my signal was heard, later everyone agreed that Bert was not heard.

When Rob PA1X mentioned that there was something wrong, I started to check, but it was already too late.
Due to the serious mismatch, the FT-817 delivers less power.
At first I thought that the PA of the FT-817 was deceased.
But later, on the dummy load, on HF the Rig showed a sign of live.
The maximum power is now 2.5 W and the lowest power is abt 300 mW.

I can still use the FT-817 with reduced power. In many contest QSO I use the lowest possible power. I can still make 50 mW using 0.5 W and an attenuator of 10 dB.
I will miss the position for a power of 980 mW, as being the highest power for QRPp

Over the last months I encouraged other Bloggers, to use less power than 5 watts, to make a 1000 Miles per Watt QSO, when the distance is less than 5000 miles.
The maximum power of 2.5 W from the FT-817 will still give 1000 MPW to Canada and the USA.
But I will miss the extra punch of 5 watts, that I only use if necesarry.