Station

At home I use as stationary equipment the following items:

Transceiver: Yaesu FT-817ND

My FT-817ND

I think almost every radio amateur knows this little rig or at least has heard of it. For those of you who don't here are the main facts:

  • all amateur bands from 160 m to 70 cm (1.8 to 440 MHz)
  • receiver: 0.1-56 / 76-154 / 420-470 MHz
  • all modes (FM, SSB, CW, AM, digital, except D-Star)
  • output power: 5 W
  • really portable! (size of a book, build-in rechargeable batteries)

You can find more details in the [external link] RigPix database.

The most important advantage to me is that this is a all-in-one rig which can also be used for portable operations.
Furthermore it doesn't require too much space on my desk. I don't have a shack only for amateur radio. Everything is located in a small corner of my home office.

RF-Clipper Speech Processor

Operating in SSB mode as a QRP station (low power, only 5 Watts) is a little problematic. Due to the high bandwidth of a SSB signal compared to CW (Morse code) or digital modes like [internal link] PSK31 the signal to noise ratio is worse. Furthermore the human ear and brain can easier "decode" Morse code than human voices if there are many background noises (QRN, QRM).

Hence a very high efficiency is desirable when SSB shall be used.
There are several ways of how to increase the efficiency (RF output power compared to the spoken words). A more constant signal amplitude for loud and quiet parts of the signal is desirable.
Some use dynamic compressors, others audio frequency clippers for that. Both methods have disadvantages. Compressors have to be adapted to the speakers voice to get best results. Clippers cause distortions of the audio signal because the amplitude is cut at a certain level. The distortions can't be filtered fully in the audio frequency range.
The so called RF clipper does not have this disadvantage. How does it work? In principle it also clips the signal like a normal clipper. But the clipping is not performed in the audio frequency range but in the radio frequency (RF) range. Before the signal from the microphone is clipped it is mixed with an RF signal so that you get an amplitude modulated (AM) signal. Now the signal is amplified in that way that the lower amplitudes are e.g. 6 dB less than the full amplification. This results also in clipping of the high amplitudes and also causes distortions of the RF signal. But after the amplifier an RF filter is used to eliminate these distortions (harmonic oscillations etc.). The signal coming out of this filter is demodulated so that you have an audio signal again. But it has a more constant amplitude now. This signal is transferred to the radio's audio input instead of the standard audio signal directly from the microphone.
Experience shows that you achieve up 1-2 steps more on the S-meter compared to the standard microphone.

block diagram of an RF clipper
The block diagram of an RF clipper

Joachim, DF4ZS, has developped such an RF clipper which fits to the standard microphone of the FT-817ND (and FT-857, FT-897) if the standard microphone capsule is replaced by an electret capsule. You'll find more information on [external link] Joachim's homepage [in englischer Sprache]/[in German language] where you also can order assembled and calibrated modules.

Antenna: non-resonant, end-fed wire (random wire)

My requirements for a shortwave antenna:

  • usable on many bands as possible
  • inconspicuous appearance

My realization looks like that:

my random wire antenna  

The radiator is a 17.2m long wire of 0.35mm diameter, hence almost invisible. It is approx. 3m heigth and helb by a PVC tube in a distance of 12m from the house. At its end a 1.5m long fishing line fixed on a fence strains it.

A down spout connected and grounded with the lightning rod is the counterpoise. It is fed directly from 50 Ohm coax cable. For matching to the transceiver I use:

Antenna Tuner: LDG Z-11 pro II

my LDG Z-11 pro II (below) with my Yaesu FT-817ND
my LDG Z-11 pro II (below) with my Yaesu FT-817ND

Features:

  • completely stand-alone operationalbe (CAT interface is available but not mandatory for operation)
  • usable from 160m through 6m
  • matched impedances from 6 to 1000 Ohm
  • tunes already with very low power (100mW), but also up to 125W
  • 2000 memories for quick tuning
  • battery operation possible

With this tuner I can match my 17.2m long random wire from 3.5 through 50 MHz.

In future the tuner shall be operated in a weatherproof housing directly at the fed point. But also the current approach works very well.

SWR meter: AVAIR SX-601

SWR meter
My SWR meter AVAIR SX-601 (works from 1.8 to 525 MHz)

Doesn't it look very similar to the Diamond SX-600???? Also the technical data are almost identical. I think both come from the same (Chinese?) manufacturer and are only labeled differently.

Digital modes interface

Digital modes interface by M0AQC
Digital modes interface, open

For the digital modes (like [internal link] PSK31) an interface between the computer and the transceiver is needed. In order to avoid ground loops both items shall be connected with galvanic isolation. For the analogue signals the simpliest solution are isolating transformers.
For the (digital) transmission (PTT) signal opto-couplers can be used. Most digital modes programs use the RTS signal of the serial (COM) interfaces for controlling the PTT.

I use an interface made by [external link] M0AQC and am very satisfied with it ([external link] see other reviews at eHam.net)! It is one of the kind with isolating transformers and opto-couplers.

Power supplies

Switching power supply Difona SPS-1229

switching power supply Difona SPS-1229

This is a switching power supply with an output of 12 Volts and up to 30 Amperes. Although the FT-817 doesn't need so much power I purchased it because possibly in the future I use an external power amplifier and need the power then.
As long as I used an indoor antenna just half a meter away from the power supply I could hear significant noise from the power supply on all short wave bands. The frequency of this noise wasn't stable. But it can be controlled with a potentiometer in order to remove the noise from the current frequency. This helps but is a little annoying over the time.
Since I use an outdoor antenna in more than 10 meters distance from the power supply there is no recognizable noise anymore.

Switching power supply MAAS SPS-8041
(identical to Manson SPS-8041)

power supply MAAS SPS-8041

I use this as a light weight power supply for my holiday trips by airplane.
I was sceptical of a switching power supply like this. But I was pleasantly surprised! I ordered it directly at the German importer (Maas Elektronik). I tested it with my FT-817 in SSB mode by switching between power supply and internal battery pack (switching the PS on and off). During this test I used a dipole with approximately 5 meters distance from the PS. On an empty band (30 m) I could recognize only a very low increase of the noise with the PS switched on compared to battery operation. It is not 100% perfect but a very good compromise between weight and performance.
It delivers 3 to 12 V in steps of 1.5 V and up to 3 A.