Philips BX-925A
Philips Gloeilampenfabrieken, NL-Eindhoven

Swiss Army Communication Sets
Synoptic Table
Army Receiving Sets
Exxx Designations
E-600 / Autophon E39
E-601 / Zellweger E41
E-602 / Autophon E44
E-603 / Autophon E45
E-604 / Autophon E46
E-606 / Velectra
E-627 / Autophon
E-628 / Autophon
E-629 / Collins 51J-4
E-635 / Philips BX-925A
E-638 / Telefunken E108
E-639 / Telefunken E104
E-640 / Telefunken E127
E-643 / Collins 51S-1
E-645 / Siemens E311
E-646 / Zellweger
E-649 / Watkins-J.
E-655 / Racal
E-657 / Telefunken
Equipment List
Army Manuals
varia / copyright
about / contact

überarbeitet am 21.4.2012

There is some evidence that the Philips BX-925A has not only been evaluated by the Swiss PTT (post telegraph telephone service) but also saw use with the Swiss Army in small numbers.

Single conversion, I.F. 735 kHz

linear Analog dial,

AM, CW/SSB (with BFO)

210-540 kHz, 1,45-3,6 / 3,5-9,1 / 9,1-13,7 / 13,7-20,7 / 20,7-32 MHz

< 5 uV

Selectivity -6 dB
13 / 6 / 2,6 / 0,9 kHz

RF-Gain, two speed AGC, crystal filter, motor driven tuning, single crystal controlled fixed frequency

The communications receiver BX-925A is a bulky communications receiver made by Philips, in fact it is one of few commercial receivers made by Philips and it seems to me, it was no absolute success, as not many of these receivers have been ordered and appear on the second hand market.

The 16 valve receiver can powered from 110 - 245 V mains, the set in a heavy steelt cabinet with carrying handles has a weight of 32 kg, it's dimensions are 49 x 25,5 x 41,5 cm.

On the front panel, you find the sector type main frequency dial in the the left upper half, in the middle the fine tuning dial and at the right the signal strength meter.
The main tuning knob is located in the middle of the front panel, the band segment switch at the left and the I.F. bandwidth selector at the right.
leftmost, you find the switch for the internal crystal calibrator and the rotary controls for tone and antenna tuning, at the right hand the AGC switch, the controls for the noise limiter and the headphones jack.
In the bottom row of controls, you find the RG gain control, the BFO switch and BFO pitch control, the crystal filter control, a receive - transmit switch and the volume control AF gain.

To operate the receiver, select the correct mains voltage at the rear face of the radio and connect to mains, connect a long wire antenna to socket A1 or a dipole antenne to A1/A2.
The receive/transmit switch is only in use on connection with a transmitter, it should be in the REC position, use the volume control AF gain to turn the receiver on.
To listen to Radio Deutsche Welle on 6075 kHz, select band range 3, the respective frequency dial is now visible in the frequency dial window. Use the main tuning control and tune from the 6 MHz mark slightly up until You hear the typical german newsreader from Cologn shortly after the hour, - nowadays, shortwave broadcasting stations do not broadcast longer interval signals to identify the station any more. You might write down the numbers of the small logging scale on the main tuning dial and the number on the mechanically coupled 0 - 100 fine tuning dial, once you have found the station for easier tuning it in on later occasions. These procedure using logging dials and a logbook were replaced by electronic memories some years later. With the crystal calibrator active, you find a frequency mark every 500 kHz to make determining a frequency of an unknown station or tuning in a stastion on a known channel easier.
The RF gain should be turned up fully clockwise, the AGC should be set on 2 (fast) or 3 (slow), the bandwith to BROAD (to listen to a strong signal without adjacent channel interference), for AM reception, the BFO has to be turned OFF.
With the beat frequency oscillator (BFO) switched on, you can receive morse code (CW) signals and single sideband transmission e.g. in the amateur bands around 80 or 40 meters, use the BFO control to regulate the pitch of the morse code signals.

Normally, you tune the receiver with the main tuning knob slightly pulled out. In the position "press in", the BX-925A features motor driven tuning, the receiver is tuned up or down when you turn the tuning knob to the right or to the left.
The receiver can be used in crystal controlled fixed channel operation. Insert a matching frequency crystal (reception frequency + 735 kHz in ranges 1-3 or reception frequency - 735 kHz in ranges 3-6 respectively), after you have switchex to fixed frequency operation with a screwdriver, an "X" instead of a "N" for normal operation will be visible in the tiny window.

further literature:
d/e: Philips BX-925A at www.radiomuseum.org

© Martin Boesch 24.4.2012