Tuesday, April 19, 2011

Skanti Marinetta TRP 1

I got lucky! Ever since I made my GMDSS-GOC, I wanted one of those:

Skanti Marinetta TRP 1 portable survival radio
In the Scheepvaart en Transport College Rotterdam, where I studied for the GMDSS-GOC, those units are on display. You can only guess how happy I am to finally got one into my collection of marine radios. The best thing on this purchase, the set is complete with all standard accessories.
I would like to thank Willy PA0WMR for keeping this rig in near original state. Willy also stated that the transmitter delivers about 5W on 600m.

What is all the fuss about a yellow box anyways you may ask. And the question is well justified. First of all, the box, with the lid closed, swims ;-) It is yellow! (That would be a reference to Douglas Adam's Hitchhiker's Guide to the Galaxy).

OK, lets be serious, why am I so happy to finally posses one?
Having a look at the manual/schematics we see that the rig
  • has a modern (digital) design
  • operates on 500kHz, 2182kHz and 8364kHz
  • is crystal controlled
  • allows for CW and AM
  • has a built in dummy load
  • employs an antenna current meter
  • contains an ATU
  • can create its own energy (by means of cranks)
  • can be energized by an external source

500kHz, 2182kHz and 8364kHz are (former) distress frequencies and must not be use by ham- radio operators! 

Where is the hamradio use of these units? Well, we all hope for the 600m band. The 500kHz signal is created by a  2.000MHz gate-XO and digital dividers. Depending on what band we will finally get, this crystal can simply be replaced by a fitting one. However, since it is a digital XO, on simply could remove the crystal and feed a DDS generated signal into the digital gates.

According to the schematics, the transmitter's 8364kHz crystal can easily be replaced by a 40m crystal. However, the receiver employs some resonant LC-stuff with varactor tuning, which should not pose a major problem to modify to 40m, e.g. 7030kHz.

The receiver uses a 2682kHz crystal oscillator to the 2182kHz emergency frequency. The transmitter employs a 2182kHz digital gate oscillator. We got two options for ham-bands here, 160m or 80m. Both have pros and cons. 2182kHz originally is an A3 frequency. The wiring inside the TRP 1 is providing AM modulation accordingly.
On the 80m band, AM is used in places, hence, that would be a nice possibility to join the action. However, filters will have to be modified.
On the 160m band one may want to aim for A1 operation. A 1.843MHz crystal would do the trick here... However, the wiring will have to be changed to engage the BFO in the "2182kHz" labeled switch position.

What is the prospect for the future use of the rig?
I believe it would provide endless fun during field day operations. In particular when operated from cranks, independently from any power supplies.
The (yellow) box contains everything needed for QRP-ops, including a telescopic vertical antenna and a "long(er) wire" aerial.

I figure it could be reasonable to replace the TBA570 receiver with a NE612 superhet design for side-band use.
The XOs could be replaced by either a DDS or some synthesizers for enhanced flexibility.
Some PIC controls seem obvious, the automatic SOS-TXing is inadequate, obviously.

It all comes down to how much modification is actually wanted. Maybe the greatest fun can be obtained when staying as close as possible to the original functionality, i.e. AM on 80m, CW on 40m and 600m.

Other than that, it is an extremely nice addition to my marine radio collection.

2 comments:

  1. Nice radio. Wouldn't it be better that it stays original. Although I know you like to experiment...73, Bas

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  2. Hi Bas,
    yes, it would be better and... it will stay (more or less) original.

    My understanding is that it has been modified for 600m A1A, prior to my purchase. I have not opened the radio yet, hence I cannot confirm the state.

    My modification would be "soft", e.g. replacing a crystal (2182kHz -> 3705kHz/3615kHz), re-routing wiring, re-tuning filters etc. The case will definitely not be modified.
    If replacing for example the front end, I intend to bypass the original PCB.

    One idea: the switch for the automatic distress-keyer/sounder could be used as an input control to a PIC which could for example toggle between several frequencies in one band.

    73!

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