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Project Cohiradia

COHIRADIA is an acronym for COnservation of HIstorical RAdiofrequency bands by DIgital Archiving.

COHIRADIA has two main goals:

  1. to give interested radio enthusiasts and collectors the opportunity to play back original radio signals recorded in the past on historical radio receivers. These signals should not contain only a single station, but a whole frequency band (e.g. medium wave) with all radio stations contained therein on the correct carrier frequencies existing at the time of recording. This allows all stations to be tuned-trough on the radio receiver.
  2. to record currently broadcast radiofrequency bands, especially in the AM range, at various locations around the world. The goal is to map the still existing landscape of active stations in the form of archive files in time before the technology finally will die out.

COHIRADIA is made possible by recording and playing back digitized radio frequency signals using software-defined radios (SDRs). Wideband recording directly from an antenna is now relatively easy with several SDRs on the market, while playback requires more advanced SDRs with transmit output. The initiator of COHIRADIA uses the STEMLAB125-14 from RedPitaya, which offers a high quality for recording and playback with 14 bit ADC resolution and 125MS/s sampling rate. Alternative TX-capable SDRS with similar or better performance specifications also exist.

The recordings can be played back by anyone who also possesses a STEMLAB125-14 or a suitable TX-capable SDR. The use of a uniform data format guarantees interchangeability between different platforms.

In order to build up a rich archive in as short a time as possible, interested amateurs are invited to make their own recordings and to make the data available to the Radio Museum and/or to report on the successful playback of files on historical radio equipment. Creative ideas for other applications (activities, museums, ...) are also very welcome.

The oldest existing recordings on MW and KW were made by the initiator in the years 2006 - 2009 in analog form on a video recorder and digitized in 2021 with a STEMLAB125-14. On these recordings there are still many European stations which have been switched off in the meantime. All further recordings from 2021 on were produced directly digitally, mainly on long, medium and short wave up to 30 MHz.

For the playback of the data files as well as for the creation of own recordings on the STEMLAB125-14 a first software version was created in Python and is available for Windows10 as exe program. The author has already created a GITHub repository for the sources, a release as an open source project is planned for the near future.

Hermann Scharfetter initiated and drives the project COHIRADIA. You can contact him via his profile to further develop the project.


Date/Time Contents Country Band
2023-01-01 23:01 Closure of RTL on LW, RX Luzern by Gianni Müller Luzern, CH LW
2023-01-01 21:55 Closure of RTL on LW, RX Graz Graz, AT LW
2023-01-01 21:49 Closure of RTL on LW, RX Neunkirchen Neunkirchen-Seelscheid, DE LW
2022-11-16 15:45 VLF/LW: Grimeton SAQ on UNESCO 50th anniversary day Graz, AT ULW/LW
2022-09-10 21:54 14min recording with the last 5 minutes Graz, AT MW
2022-09-10 20:57 last hour before all RAI MW transmitters Graz, AT MW
2022-09-10 20:35 recorded from a Ferry in the Adriatic Se Adriatic Sea MW
2022-09-10 19:32 recorded from a Ferry in the Adriatic Se Adriatic Sea MW
2022-08-18 18:11 MW in northern Greece, summer evening close to Parga, GR MW
2022-07-18 21:14 LW, strong Luxembourg effect on 162kHz/198kHz Lossburg, DE LW
2022-06-11 21:11 Luxemburg-Effekt auf Allouis 162 kHz, hi Graz, AT LW
2022-06-11 21:09 Luxemburg-Effekt auf Allouis 162 kHz, hi Graz, AT LW
2022-05-13 07:52 LW 13-05-2022 morning Neunkirchen-Seelscheid, DE LW
2022-05-02 21:57 wideband recording including LW and MW in one Neunkirchen-Seelscheid, DE LW&MW
2022-05-01 09:15 LW 01-05-2022 morning Neunkirchen-Seelscheid, DE LW
2022-04-27 04:00 MW California 27-04-2022, evening Los Gatos (CA), US MW
2022-04-19 17:59 MW California 19-04-2022, morning station IDs are broadcast at 01:20:00 (exact hour) Los Gatos (CA), US MW
2022-04-15 21:57 MW 15-04-2022 evening Neunkirchen-Seelscheid, DE MW
2022-02-27 00:00 MW 27-02-2022 Graz, AT MW
2021-12-31 23:30 Shutdown of the LW transmitter Topolna i Graz, AT LW
2021-12-31 23:30 Shutdown of MW transmitters in CZE 23:00 UTC: Liblice 2 and Ostrava Graz, AT MW
2009-01-01 09:57 KW, 49m band, analogue recording on VR Graz, AT KW 49m
2006-12-31 23:58 MW, 30/31-12-2006 short clip Graz, AT MW
2006-12-31 00:14 MW, 30-12-2006, part2 midnight Graz, AT MW
2006-12-30 23:08 MW, 30-12-2006, part1 midnight Graz, AT MW
2006-12-07 22:28 MW, 07-12-2006, part2, analogue VR Graz, AT MW
2006-12-07 21:58 MW, 07-12-2006, part1, analogue VR Graz, AT MW


Publication Date Title Author Statistics
2022-04-03 Hardware for COHIRADIA: Details and problems/solutions Hermann Scharfetter 8 423
2022-04-03 Software for COHIRADIA: Details and problem-solving Hermann Scharfetter 1 215
2022-04-03 Software für COHIRADIA: Details und Problemlösungen Hermann Scharfetter 1 341
2022-04-03 Hardware für COHIRADIA: Details und Problemlösungen Hermann Scharfetter 3 324
2021-12-19 Breitbandaufzeichnungen von historischen AM-Bändern Hermann Scharfetter 8 2465
2022-04-02 Wideband recording of historical AM radiofrequency bands Hermann Scharfetter 0 336