May 30, 2008

Getting the most out of your rig; the TS570SG modification

One is never satisfied....

Making that QSO on 50Mhz largely depends on being there at the right moment.
However, some rigs offer that tiny bit of extra performance which is sometimes needed to hear the other guy at all.

I always enjoyed the ergonomics and user interface of the TS-570SG. This medium sized rig is a joy to use and easy to carry during holidays. I use it already for two years now as my main 50Mhz rig.
In order to enhance its performance I opted for two modifications:
  • Exchange the std 2400Hz SSB filter for an Inrad 2100Hz
  • Add a temperature controlled crystal heater from Kühne Electronics (DB6NT)

Installing the SSB filter
The original Kenwood 2400 Hz (YK88S) is taken out and exchanged for the Inrad 2100Hz (#94).
The '2100' offers better sound quality thanks to a near optimal filter shape. Its bandwitdh is a perfect balance between the std. wide 2K4 and the thin sounding 1K8.

The TS-570 does have one optional filter slot, but that is already taken by a 400Hz Inrad CW filter.

The filter is installed upside down, using insulating material and hot glue.Two customized pieces of RG316 are been used to connect it to the pcb.

Installing the crystal heater

you will find all info on this 13 euro (only) product.
Just slide it on the crystal of your main LO and apply hot air to let the heath shrink tube do its job.

How does it perform?
I was able to make a qso with this S7 YU-station on 6m while another SV-station S9+20 was at only 1.5Khz above. Subjectively this is surely different from the past. But since I cannot do an A/B comparison this means ZILT. It only proves that the SV station had a clean signal.

I have been very active on 6m these last two weeks since Es propagation has just started.
I managed to work: I, 4X, SV, ON PA,UR,LZ, LX, DL,EA,CT,YO,LZ,YU, HA, OM, SP,4L, ES,OH,YL,EA8,ER,CU,IS,9H,EI,EA6
Inter-continental: KP4

Am I happy?

No, not entirely.
The TS570 still does not sound optimal. I know it suffers from some phase noise and this is shown by the fact that I have a hard time hearing the other station. It is buried in noise and garbage. The other stations are worked on first or second call with 100W. A soon as I can hear them I can work them easily. But on many occasions I cannot read their reply or report. Very frustrating. Changing settings on the rig does not help. Using the calibrated SSB Electronics masthead preamp doesn't help either.

Picked up an IC-746 with Inrad filters from a friend who does not use it. I have had such a rig in the past too; they are very very nice to operate at 50Mhz and 144. Within minutes during a hectic Es bandopening I'm on a roll; this is just wat is needed.
The Icom is in a different league. Both on reception quality and ergonomics it does for me what it takes on 6m; quick and versatile operating options. RX is better, now I can hear into the noise layers and hear dx at sub-consious level.

Wkd: V4, 8P9, TA, EA9, T9 (again 2 new countries :)

May 16, 2008

RX Audio Interface to your PC

Whenever doing AF analysis with help of any audio spectrum analysing software at your pc, you're probably facing several interfacing issues:
  • 50Hz hum
  • RF interference from various sources
  • Bad ground/ ground loops
  • gain/impedance mismatching
The first 3 are referred to as 'pin 1' issues in the world of professional audio. In one word, proper grounding architecture & shielding, or the lack of.
Mind you, the audio input on your sound card is usually already a disaster having bad or failing ground contacts. Next the pc has analogue and digital circuitry, there's a cable to your TRX and there it is susceptible to RF. Not to mention the many ground loops etc..

I have been successfully using Spectran, a freeware audio analyser programm by I2PHD and IK2CZL.
When the audio is directly linked to my sound card input you get the below result (volume settings at zero):

My sound card is an old 16bit Soundblaster compatible type. Any current 192KHz/24bit High-End sound card will lower the noise floor by some additional 10 -15db. For the required measurements this old 16bit card has proven to bemore than adequate.

How to get a 'clean picture'
  • Use properly shielded cable
  • Install an audio isolation transformer
To conquer the 'pin-1' issues I opted for an audio isolation transformer. These usually are 600 Ohm, which might introduce small mismatches. I terminated its output, added some RF filtering on the output and finally put it in a box with both 3.5mm Jack as well as std RCA in-/outputs:

With the RX Audio Interface inserted (as near at the sound card input as possible), you get the following result:

May 6, 2008

SteppIR @PI4TUE- part 1

Last weekend we started building the SteppIR 3el yagi for our clubstation PI4TUE at the University of Eindhoven. On the above pic: on the right front Aurelio, PC5A, on the right back Rens, PA3FGA and me in the left corner.

First all parts are checked.

Glass fibre tubes are treated with rough sandpaper in order to create a better grip.

Boom and motor sections are ready & tested.

Next action:

  • Remove current Fritzel FB33 yagi from the roof (220ft AGL)
  • Install new SteppIR 3el yagi
  • Install new coax cable