Manufactured by Seiki Electronics Inc, Japan.

Indeed it does exist - I was lucky enough to buy a set offered on eBay, the variant of the Century-21 with built-in digital display. I had already found an advertisement with pictures of the identical set labelled as Lowe SRX-30D in the depths of the world wide web before.

Seiki Century-21D

Technical data

Power supply


  • 325 x 140 x 230 mm, weight 5.5 kg


Seiki Century-21D


The Double conversion Century-21, manufactured in the Far East, based on the Wadly Loop circuit principle, and the very similar Standard C-6500 are technically very similar to the Drake [SSR-1]]. With the designation Century-21D, the Japanese company Seiki Electronics Inc. also produced a set with a built-in frequency counter, which was an enormous technical improvement - why do you think Drake never equipped its SSR-1 with a frequency counter?

With dimensions of 325 x 140 x 230 mm, the set is the size of a standard tabletop receiver and has sa weight of 5.5 kg.

It can be powered by 110 / 117 and 220 V mains.

As with the Century 21, the front panel has a simple structure, but operation is not without problems if you have never worked with a set based on a Wadley loop circuit.

The upper half of the front panel is taken by the loudspeaker on the left and the tuning elements on the right. The MHZ - TUNE knob is used to select the desired MHz - band, in contrast to the analogue version, the MHz digit can be read from the green illuminated LED display, when the synthesiser is locked , the dim number lights up at full strength. With the large tuning knob, the kHz digit of the frequency can then be set with an accuracy of 1 KHz, exceeding the limits of the 1 MHz range is signalled by the receiver by illuminating the dots between the digits (9.9.8). For reception, the preselector must then be correctly set, one of the four preselector ranges is selected with the BAND switch and tuned to signal maximum with the PRE-SELECTOR knob.

In the lower half of the front panel, from the left, are the headphone jack, the RF gain and volume controls, the band switch for the preselector band ranges and the mode switch, the two sidebands in single-sideband mode can be selected separately. The „Clarify“ control is a fine-tuning control to be used for SSB and CW reception.

The rear panel is simply structured, next to the mains cable entry (no plug-in socket) you find from the left the jacks for the tape output, the mute switch (MUTE) and the banana connectors for antenna and earth as well as a coaxial PL/SO239 antenna connection.

The operation is in itself unproblematic, if you know the philosophy behind the Wadley Loop based receivers, but otherwise it can be quite a hassle so you might end up up with the suspicion, the receiver might be faulty.

The VOLUME control is used to switch on, turn it up until there is some noise from the loudspeaker, RF-GAIN is set to maximum, MODE to AM for broadcast station reception and CLARIFY to the middle position. If, for example, you want to receive the Austrian Radio Intl. on 6155 kHz, set the preselector BAND switch to the frequency range from 5 - 12 MHZ. With MHZ-TUNE the MHz digit of the operating frequency is set to „6“, the correct position is found when the correct digit is displayed and lights up brightly, a clear hissing noise should be audible. Now use the main tuning knob to set the kHz digits to 155 and the Vienna station should be audible. Use the PRE-SELECTOR to tune to maximum. If distortion and overload occur, which is not uncommon when a longer external antenna is connected, the RF-GAIN can be slightly reduced until the S-meter deflection is somewhat around 7 - 9. To receive SSB transmissions, the mode switch must be set to USB or LSB and the CLARIFY control is used for fine tuning until the speech no longer sounds like Mickey Mouse and the music sounds acceptable. In this case, the RF-GAIN must often be adjusted manually, but a narrow IF filter is used for SSB reception.

In practical use, the Century-21 impresses with its high sensitivity, it gets along with quite short auxiliary antennas or the built-in telescopic antenna, but it tends to overload on long-wire or active antennas, so that attenuation is necessary. The IF filters give the receiver a useful selectivity; they can possibly be replaced by narrower 455 kHz filters.

Seiki Century-21D Tuning takes some experience: with the need to operate MHz and kHz tuning, preselector and preselector range switch, rapid frequency changes are tedious. When a signal semms to be weak, it may really be the case that the antenna signal is poor according to the propagation conditions, or the reason could be that the preselector is slightly out off tune, the RF gain is still reduced, etc. - you quickly forget about some settings!

All in all, the Century-21D is a collector's radio, but thanks to the digital frequency display and the high sensitivity it is suitable for DXing. In my receiver collection, the concept of the Wadley Loop circuit with a frequency counter is rarely found, which makes the Century-21D resp. Lowe SRX-30D an interesting „exotic bird“ in the collection.

Technical principle

Double conversion superhet, frequency processing by means of a Wadley Loop circuit, digital frequency display.


The set is solid state.

Technical documentation


Further information

en/century-21d.txt · Zuletzt geändert: 2021/12/26 11:47 von mb