MST400 QRP SSB Transceiver

A couple of years ago I built a DDS VFO from ozqrp  - see post here.

I was pleased with the design and decided to buy the PCB for the accompanying 40M SSB transceiver the MST400 v1 .

MST400 v1

This is a 40m SSB transceiver that has a power output of at least 5 watts of SSB.
from the manual , the specs are -

1. Complete SSB transceiver on a single PCB (just add a VFO).
2. Superhet receiver using a 4 pole 10MHz crystal filter.
3. 5W PEP minimum power output using a rugged power MOSFET output stage.
4. Unwanted sideband suppression is typically 40dB.
5. All spurious transmit outputs below -45dBc.
6. AF and microphone gain controls.
7. Easy to adjust and set up.
8. Front panel LED transmit power and modulation indicator.
9. Plenty of audio output to drive a loudspeaker.
10. High quality double sided PCB with groundplane, solder mask and silk screen.
11. Simple and easy to build using all through hole components.
12. No complicated coil winding required. Uses inexpensive commercial coil assemblies for tuned circuits.

I just bought the PCB and was able to provide most of the components from the junk box , the rest were purchased from bitsbox in the UK - my normal source of components.

Construction was completed over the course of a couple of evenings and was very straightforward thanks to the well written manual .

I boxed it up in a plastic case with aluminium end panels. I would have preferred to use an all metal case but this seems to work ok .  I may line it with self adhesive copper foil for screening purposes at a future date.

My heatsinking on the IRF510 output transistor is probably not ideal , but it didn't get too hot in use while producing about 8w power.

MST400 in case

While it is not fully finished it works well and I have had many contacts throughout Europe on it. .

The MST400 v1 has since been superseded by the v2 version and is now available for 80M, 40M and 20M as a complete kit .  Well worth a look for anyone interested in building their own QRP SSB transceiver. 

Spilsbury and Tindall SBX-11 Portable HF SSB Transceiver

A few months ago I managed to buy a Spilsbury and Tindall SBX-11 Portable HF SSB Transceiver on eBay.  This radio is a piece of Canadian history having been used for arctic and polar communications for over 40 years.

The SBX-11 is designed to provide 10w SSB on 4 crystal controlled channels in the range of 1.6 to 8 MHz.
It is self contained in a robust water resistant enclosure and is powered by 9 D cells - Alkaline or NiCAD.

SBX-11

The top lid of the SBX 11 covers the front panel and the hard wired microphone .

it also contains a set of brief operating instructions  -

the top lid clips on to the main body of the set to act as a stand

the bottom lid is the battery compartment which contains 3 tubes each with 3 D cells.

My set has already been converted to the amateur bands and has been crystalled for 1918 KHz, 3745 KHz and 7060 KHz on LSB.   Each channel requires 2 crystals and 2 coil packs , however there is a modification available for single crystal per channel.

Internal view showing crystal banks and RX/TX coil packs on right hand side -

As the set is crystal bound I hadn't much luck in making any contacts on it , however today was the IRTS 80m counties contest so I decided to try it out on 3.745MHz and I was able to make 4 contacts - EI2KA ( Cork) , EI9DZ ( Leitrim) EI8JN ( Galway) and EI8HL ( Waterford).

I was thinking about adding a DDS VFO to this set, however I think I will keep it in its original condition . Might try and add a 60m channel to the 4th position if I can get a suitable coil pack.

For more information on the SBX-11 see here .
VA7BC has posted an interesting video of the SBX-11 in use here.

see also SBX-11 group here  - https://groups.io/g/SpilsburySBX11/