Gerard's Arena

54
Item nr.

Arena Table top

Largely modiefied but working.

**Data for Arena**
Production	France, 1936.
Bands	MW (540-1600kHz), LW; IF is 125kHz.
Tubes	2A7 (osc/mix), 58 IF), A257 (pre-amp, date coded: 5-VI), 47 (output), V580 (rectifier).
Semi- conductors	Diode detector.
Cabinet	Wood. Size 40x52x29 cm.
Power	AC (54W).

The Design

A radio of the thirties differs in some respects from a more modern radio of, say, 1950.

First, the tubes used are of a 2.5V filament type and the output tube is directly heated. Understandibly, these early tubes do not match the quality characteristics of later tubes.
The antenna circuit is a band filter; we need extra selectivity because of the low IF.
The radio does not have Automatic Gain Control (AGC).
The Intermediate Frequency is 125 kHz, which is very low compared to the values of 452 to 472 kHz that were used later.
The detector is a pentode, while in later designs separate diodes were used for detection.
The volume control is not in the signal path, but is a variable resistor in the cathode circuit of the IF amplifier (tube 58). Turning the knob varies the bias between 5 and 30 Volts, and with high bias there is almost no sound. Needless to say that the volume control does not affect the volume of the Phono input.
The speaker was originally a field coil type, with the field coil being used as a choke in the power supply. These speakers were connected to the radio chassis through three wires (with a plug in this case) and often had the output transformer mounted on the loudspeaker. In this radio the loudspeaker was replaced by an electromagnetic type, with separate output transformer and choke coil mounted under the chassis.

The year of this radio is partly a guess, but I would be surprised if I were more than one or two years off. The dial shows a lot of the stations agreed on at the Geneva conference of 1934. The A257 has a date code 5-VI, meaning May 1936.

Obtained	1/1997 from via Piet Hoen.
Condition	6; many modifications, plays well on MW.
Disposed	Sold 4/2016.
Sound sample	PLAY SOUND In 1936 not only this radio, but also the Oosterkerk in Zeist was built. After 60 years, the radio was just a worn out piece of furniture, but the church was still a weekly meeting place for hundreds of enthousiastic Christions. Church musician Willem Harold Boog plays Marche Triomphale on the church' Flentrop Organ. The organ piece was recorded from the pick-up entry; radio reception is a bit treble-depleted due to the rather narrow MF circuits.

This Object

A previous owner had refinished the cabinet at some time, and it was not done extremely well. Also some modernizations in the design were carried through, including the replacement of the old-style field coil speaker by a permanent-magnet type. So I didn't have to worry about originality with this radio.

In April 1999 I sanded and refinished the radio, and applied fresh speaker grille cloth. I did some repairs but the sound remained quite poor until I replaced the speaker (by a fifty years old Philips speaker) in March 2000. Also I modified the detector circuit and replaced the volume control by one that operates in the LF part of the radio, and installed a primitive AGC working on the IF tube 58. Now the sound is quite good, and the radio looks fresh, though not precisely original. That means, the value of the radio is probably not very high... but I don't care! It has been with me for about twenty years, and I like it, which is the most important criterion to a hobbyist.

A new repair was necessary in November 2006, when the radio stopped playing. The cathode resistor of the 58 was interrupted and I replaced it. Measurements showed that the B+ voltage in the radio was quite high, nearly 350 volts. I found out that this was not normal for these tubes; the choke coil, used to replace the speaker field coil, had a very low DC resistance, so I added a 1k resistor there. I introduced an AUX entry, connected directly to the volume control.

I did further maintenance in August 2015. Over the years, the radio had developed crackling noises, that could be silenced by the band switch. Because the set receives nothing on LW (GO), I decided to fix-solder the switch contacts to MW position. I also shortened some leads I had made in 2006, replaced dangerous wiring, and replaced the dial chord. In light of the decreasing number of AM stations, I checked the AUX entry to work well, so the radio can play well from an MP3 player or external DAB+ radio. And I made a back panel (photo right) to prevent dust in the radio, to find out that the cabinet is far from rectangular! The cabinet is not symmetric; the little "roof" is steeper on the left side! I do not know if the latter was intended.

Radios in Japan

In 2010, Walid Rhord borrowed my radio to shoot a movie, Little Boy, about Japanese people in the Second World War. You could see the movie here (but it's gone now).

Part of Gerard's Radio Corner.
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