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DAVE MCKAY G1JWG

    RACAL TRA6929 MINICAL

 

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The Racal TRA6929 set is a 6 channel HF radio that  operates from 2-7Mhz or 2.6-9Mhz with 1 watt RF out. It is 12v DC battery powered set, but later version were modified with the addition of a Zener diode so they could be powered with 18v through the front socket to make it compatible with the likes of the MA949, MA 935, MA927 power and audio units.

The crystals are Fo +10.7 one crystal per channel.

The set can operate on either LSB or USB by changing the sideband crystal from 10.6985Mhz which is for LSB to 10.7015Mhz which gives USB.

The front of the set has a 6 pin socket for audio equipment this is designated A-Audio in.   B-+12v.  C-TX key.  D-Ground.  E-N/C.  F-Audio out

FRONT OF SET (mine is a bit battered)

Note the dessicator located top right this can be unscrewed and placed in an oven to dry out and then will prevent dampness inside the set, provided it is sealed of course. This can be replaced with a suitable socket and the set used with an external VFO without affecting the look of the set too much.

SET OUT OF CASE TOP AND BOTTOM


VIEW FROM REAR BETWEEN PCB'S



RF BOARD UNHINGED

The positions for the 6 crystals can be seen in the red sockets, the two crystals on the right have Blue Tac on them because I was experimenting with using some cheap standard crystals which were 14.318Mhz which happens to give 3.618Mhz when used with this set and are not far removed from The Vintage and Military Amateur radio Society frequency of 3.615Mhz. The Blu Tac was needed to hold the crystals in place because the set takes pinned leads and the crystals were wired leads.

FULL INTERNAL VIEW OF SET

 

SIDE VIEW SHOWING POSITION OF CARRIER CRYSTALS

Although two carrier crystals can be seen only one is active, the other is so that LSB or USB can be selected but they must be physically swapped for this.

 

VIEW OF BATTERY CONNECTIONS ON REAR OF SET

 

VIEW OF BATTERY CONNECTIONS INTERNAL

Note the aluminium lining which is plastic coated. You need to be careful when recasing the set that this does not fold over and risk causing a short.

The designation TRA6929 indicated a US made set for UK made sets it would be TRA929

LINK TO PDF OF FUNCTIONAL BLOCK DIAGRAM AND CIRCUIT DIAGRAM OF TRA6929     MINICAL.PDF

 


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D. J. MCKAY G1JWG 2016