On 25 January 1923 a 0.5 kW transmitter in Oslo starts broadcasting on 682 kHz ( this frequency changes several times in the following years). The power is raised to 1.5 kW in February 1925. In that same year two more stations start broadcasting: Rjukan (0.05 kW) in October and Bergen (0.5 kW) in December. These powers are raised to 0.1 and 1 kW respectively in 1926. Also in 1926, two other stations are activated: Fredrikstad (0.7 kW) and Notodden (0.05 kW). The latter will raise power to 0.1 kW in March 1930.
In 1927 both Hamar (0.7 kW) and Alesund (0.35 kW) are activated while Porsgrunn gets a new 0.7 kW transmitter.
On 13 December 1929 a 60 kW-transmitter starts broadcasting on 608 kHz from Oslo-Lambertseter.

In September 1930 the Oslo station switches to longwave (uses frequencies from 253 to 283 kHz in the following years). Three stations are also activated that year: Trondelag (1.5 kW) in May, and Kristiansand (1274 kHz - 0.5 kW) and Stavanger (1247 kHz - 0.5 kW) in December.
In February 1931 Bodo (0.5 kW) starts broadcasting on 662 kHz.
On 14 January 1934 the Luzern frequency plan becomes effective. As a result Oslo uses 260 kHz instead of the planned 253 kHz. In May Finnmark gets a new 10 kW transmitter in Vadsø on 347 kHz and in July Trondelag (629 kHz) raises power to 20 kW.
Narvik (0.35 kW) starts broadcasting on 1222 kHz in February 1935. In December of that year Ẳlesund gets a new 10 kW transmitter in Vigra on 253 kHz.
In 1936 a number of stations get a new transmitter or raise their power: Tromsø (292 kHz) goes to 1 kW (ex 0.1 kW), Bodo and Stavanger go to 10 kW, and Kristiansand gets a new 20 kW transmitter in Flekkeroy on 629 kHz.
In February 1937 Notodden (1357 kHz) gets a new 0.25 kW transmitter while in November Bergen's two new transmitters in Askoy start broadcasting: Bergen I (20 kW) on 260 kHz, Bergen II (1 kW) on 1186 kHz (moves to 355 kHz shortly after).
On 1 November 1938 Bodø switches to 347 kHz.
In January 1939 Oslo-Lambertseter starts broadcasting on shortwave with 5 kW (before the marine station Jeloy was used sporadically). In February two stations get 100 kW transmitters: Stavanger (850 kHz) and Vigra (260 kHz). On 17 March Bodø switches to 253 kHz. In November Rjukan (1348 kHz) raises power to 0.25 kW.

In April 1940 NRK no longer transmits 24h but stops evenings at 2300utc. Hamar's new 1 kW transmitter (built in December 1939) is removed, the old one (0.7 kW) becomes active again on 519 kHz. On 13 April Porsgunn's antenna is blown up. The station returns on the air on 13 December on 1222 kHz. On 15 April the 100 kW transmitter Vigra is destroyed in an air raid; the Notodden transmitter is blown up (returns on the air on 30 April with 0.5 kW on 1294 kHz). On 28 May Narvik transmitter ceases broadcasting. On 2 June the Vadsø transmitter is destroyed in an air raid, a 0.2 kW transmitter takes over. On 7 September Vigra returns to air on 629 kHz with only 1 kW. And on 28 September a 1 kW-transmitter from Hamar starts broadcasting in Vadsø (in 1941 the power is raised to 10 kW again).
In May 1941 Namsos (1 kW) starts broadcasting on 961 kHz. On 1 November  the transmitter in Finnmark (347 kHz / 865 mtr, 10 kW) is starts relaying the German programmes for German soldiers.
The transmitter in Namsos is removed in 1942. In October of that same year Fredrikstad (1276 kHz) raises power to 10 kW.
In January 1943 the Bodø transmitter (10 kW, 253 kHz) is moved from Hernessmyra to Lop.
In October 1944 the Vadsø transmitter is once again destroyed in an air raid. In December 1945 the transmitter returns on the air with 1 kW. In October a mobile 20 kW transmitter starts broadcasting in Vigra on 282 kHz.
In November 1946 Namsos (1 kW, 961 kHz) returns on the air.
In January 1947 Notodden raises power to 1 kW. In June Lista (0.3 kW) starts on 1357 kHz (moves to 1294 kHz circa 1949), and in October Mosjoen (0.025 kW) starts broadcasting on 1357 kHz.
In 1948 Geilo (0.25 kW) starts broadcasting on 1348 kHz. On 15 March Narvik (0.25 kW) starts broadcasting on 1222 kHz. On 12 April Vigra (since 1947 on 629 kHz) gets a new 100 kW transmitter. In August Hamar (519 kHz) gets a new 1 kW transmitter. In December Svalbard gets a 0.025 kW transmitter in Longyearbyen, Oslo's power is raised to 100 kW, and Odda (0.25 kW) starts broadcasting on 1348 kHz.
In May 1949 Faberg (0.25 kW) starts broadcasting on 1348 kHz. In September Vadsø's power is raised to 20 kW.

On 15 March 1950 the Kopenhagen frequency plan becomes effective. New frequencies are: 155 (Tromsø), 218 (Oslo), 520 (Hamar), 629 (Vigra), 675 kHz (Bodo), 701 (Vadsø), 890 (Bergen I, Kristiansand, Trondelag), 1115 (Bergen II, Namsos, Notodden), 1313 (Stavanger), 1466 (Geilo, Narvik, Odda, Porsgrunn, Svalbard), 1484 (Faberg, Mosjoen, Rjukan), 1578 (Fredrikstad), 1594 (only briefly used), 1602 kHz (planned). In Decemver Mo-I-Rana (0.025 kW) starts broadcasting on 1115 kHz (raised to 0.04 kW in Feb. 1954).
In 1951 Roros (0.25 kW) starts broadcasting on 1115 kHz, Faberg moves to 1115 kHz. And in May Narvik raises power to 1 kW.
In January 1952 two stations start on 1115 kHz: Arendal (0.25 kW) and Sulitjelma (0.025 kW).
In 1953 two powerline transmitters of 0.25 kW start on 520 kHz in Sulitjelma and Langerak. In 1954 Svalbard raises power to 1 kW. The 0.25 kW transmitters in Alta (1115 kHz), Bronnoysund (1484 kHz) and Sandnessjoen (1466 kHz) start broadcasting, while a new 2x100 kW-transmitter Klofta (25 km northeast of Oslo) replaces Lambertseter (wich remains stand-by until 1974) on 218 kHz. In August the transmitter in Faberg is closed down.
In January 1955 Langerak raises power to 0.6 kW and moves to 300 kHz, while a 0.6 kW powerline transmitter in Sogndal starts broadcasting, but is closed down in December.
In March 1956 Glomfjord (0.25 kW) starts broadcasting on 1484 kHz. In June Nordkapp (2 kW) starts broadcasting on 1578 kHz (reduced to 1.3 kw in Nov. 1959). Three powerline 0.25 kW transmitters start broadcasting: on 300 kHz in Andalsnes and Aseral, and in Oppdal on 290 kHz. In November the transmitter in Hamar is closed down, while Roros moves to 520 kHz.
On 1 March 1958 a 2 kW powerline transmitter Tonstad starts on 300 kHz.
In 1959 Aseral raises power to 2 kW.

In September 1960 a 1 kW powerline transmitters Roldal (285 kHz), Sand (300 kHz) start broadcasting. In 1961 three new stations start broadcasting: Karasjok (1 kW) on 1484 kHz, Bo i Vesteralen (1 kW) on 1115 kHz, and Bygland (0.25 kW) on 290 kHz. In May Oppdal raises power to 1 kW, and in July Tonstad switches to 290 kHz.
In 1962 Mosjoen raises power to 0.25 kW while a 0.25 kW powerline transmitter on 285 kHz replaces Mo-I-Rana's mediumwave transmitter, and Kautokeino (1 kW) starts broadcasting on 1466 kHz.
In April 1963 Mo-I-Rana (0.04 kW) returns to air on 1118~1121 kHz; this replaces the powerline transmitter.
In 1965 Bergen I (890 kHz) gets a new 20 kW transmitter (the old one becomes stand-by). The powerline transmitter Aseral is closed.
In 1966 Trondelag (890 kHz) gets a new 10 kW transmitter while the powerline transmitter in Sand is closed down. In June a 1 kW powerline transmitter in Brokke replaces Bygland on 290 kHz. In the same year Porsgrunn reduces power to 0.25 kW and Bergen II is closed down.
In 1967 Kristiansand-Flekkeroy (890 kHz) gets a new 10 kW transmitter (the old transmitter remains stand-by). In Verma a 0.3 kW powerline transmitter starts on 290 kHz.

In 1972 the transmitter in Sulitjelma is closed down. A year later the transmitters Oppdal and Tonstad are closed down. And in 1974 the transmitter in Brokke is closed down. In July 1975 the transmitters Rjukan and Porsgrunn are closed.
In 1976 Vadsø gets a new transmitter (2x 10 kW), but the transmitters in Bronnoysund, Lista, Narvik, Notodden and Sandnessjoen are closed down. On 1 July 1977 the transmitters in Alta, Geilo, Glomfjord, Langerak, Mo-I-Rana, Mosjoen, and Roros are closed down. On 1 November 1978 the transmitters in Bergen, Fredrikstad, Kristiansand, Trondelag, Arendal, Bo i Vesteralen, Karasjok, Kautokeino, Namsos, Nordkapp, Odda and Verma are closed down.
When the Geneva frequency plan becomes effective, only Tromsø (155), Oslo (218), Vigra (630), Bodø (675), Vadsø (702), Stavanger (1314) and Svalbard (1485 kHz) are still active, 4 new 1.2 MW transmitters are planned for Tromsø-Vanna (153), Oslo-Bastoy (216), Smola (630) and Kvitsøy (1314 kHz).

On 15 June 1982 the transmitter in Kvitsøy (near Stavanger) starts broadcasting on 1314 kHz with 2x 600 kW (usually joined as 1.2 MW) and on shortwave with 2x 500 kW. On 2 March 1985 Vigra (630 kHz) gets a new 100 kW transmitter (the old transmitter was closed on 4 Nov. 1984, a 10 kW stand-by transmitter was used instead). In 1987 Roldal, the last powerline transmitter, is closed down.

On 2 December 1991 the NRK longwave transmitter in Tromsø (153 kHz) is switched off.
On 2 January 1995 Oslo ceases broadcasting on 216 kHz. In May 1999 the 20 kW transmitter in Rost replaces Bodø on 675 kHz.

In October 2000 the 100 kW-transmitter in Ingøy starts broadcasting on 153 kHz, Vadsø is closed down.

Other sound clips and images

    QSL for a broadcast of Radio Netherlands via 1314 kHz  (courtesy of Peter Vaegler)   97 kB (jpg)
    QSL of NRK Nordland on 675 kHz from 2002 (courtesy of Peter Vaegler)   51 kB (jpg)