The following list contains the aeronautical radio beacons that were active in Finland in the mid of the 1950s. All information is outdated and may not be used for navigational purposes.
At this time there were exclusivly non-directional beacons (NDB). The identification of the en-route beacons consisted of three letters and began with either OI or OJ. Radio beacons for the approach to airfields had two letters, mostly according to the name of the airfield.
Radio beacons and airways

Northern part (Source: DoD)

Southern part (Source: DoD)
Explanations

Abbreviations
approx. | approximately | |
civ | civil | civil operator |
GP | Glide path | Glide path transmitter |
ILS | Instrument Landing System | (Approach and landing aid) |
IM | Inner Marker | Marker beacon just in front the runway |
kHz | Kilohertz | (Unit for frequency) |
L | Locator | Non-directional beacon for the approach |
LLZ | Localizer | Localizer transmitter |
LMM | Locator Middle Marker | Combination of Middle Marker and Locator |
LOM | Locator Outer Marker | Combination of Outer Marker and Locator |
m | Meter | (Unit for length) |
MHz | Megahertz | (Unit for frequency) |
mil | military | military operator |
MM | Middle Marker | Marker beacon |
NDB | Non-directional beacon | Non-directional beacon on long or medium waves |
NM | Nautical Miles | (Unit for length) |
OM | Outer Marker | Marker beacon |
PRMG | ПРМГ Посадочная радиомаячная группа | Soviet / russian military instrument landing system |
RSBN | РСБН Rадиотехническая система ближней навигации | Soviet / russian military radio navigation system |
SBA | Standard Beam Approach | Approach system, Lorenz system, predecessor of the ILS |
THR | Threshold | Runway threshold (most often with number of runway) |
transf. | transformed | Coordinates were converted from a different reference system, therefore there may be deviations. |
VAR | Visual-Aural Rnange | |
VOR | VHF Omnidirectional Radio Range | |
W | Watt | (Unit for power) |
WGS84 | World Geodetic System 1984 | (geospatial reference system, GPS coordinates) |
Directory
For historical information only, do not use for navigation or aviation purposes!
Halli: Air Base (Kuorevesi, Hallin lentoasema)
Halli: NDBN6151 E02451 (approx.)
Google MapsOIM, 389 kHz
Operated on request.
Helsinki: Malmi Airfield (Helsinki-Malmin lentoasema)
Runway 19:
Helsinki/Malmi: Järvenpää NDB182°/15.7 NM to THR 19
See Järvenpää NDB.
Helsinki/Malmi: Korso LOM182° to THR 19
See Korso LOM.
Helsinki/Malmi: LocatorN6015 E02503 (approx.), 182°/0.54 NM to THR 19
Google MapsM, 408 kHz
The locator was slightly displaced to the west of the extended runway centerline. Operated on request.

Helsinki Malmi Airfield, 1951 - At the beginning of the approach lights in the north is the NDB "M". (Source: DoD)
Helsinki: Vantaa Airport (Helsinki-Vantaan lentoasema)
Helsinki/Vantaa: LocatorN6019 E02459 (approx.), 043°/1.0 NM to field
Google MapsU, 375 kHz
Runway 22:
Helsinki/Vantaa: ILS 22HK, 110.3 MHz
To runway 22 (223°).
Helsinki/Vantaa: Korso LOM223°/3.94 NM to THR 22
See Korso LOM.
Helsinki/Vantaa: MM 22
223°/1.09 NM to THR 22
Dots Dashes, 75 MHz
Helsinki/Vantaa: LocatorN6020 E02459 (approx.), 223°/0.66 NM to field
Google MapsH, 414.5 kHz
Also listed with frequencies 314.5 and 375 kHz.
Helsinki/Vantaa: IM 22
223°/0.29 NM to THR 22
Dots, 75 MHz

NDB approach to Helsinki Vantaa Airport in 1953 - The radio beacon Korso "OJZ" (approx. in the center of the picture, here not designated) was located at the intersection of the approach courses for Vantaa and Malmi. (Source: DoD)

Helsinki Vantaa Airport, 1953 - At this time, the airport has only one runway, the second one is under construction. (Source: DoD)
Ivalo: Airfield (Ivalon lentoasema, Avvila girdingieddi)
Ivalo: NDBN6840 E02732 (approx.), 214°/3.56 NM to field
Google MapsIV, 370 kHz
Järvenpää: NDBN6031 E02506 (approx.), 182°/15.7 NM to Helsinki Malmi
Google MapsOJA, 396 kHz
Operated on request.
For historical information only, do not use for navigation or aviation purposes!
Joensuu: Airfield (Joensuun lentoasema)
Joensuu/Onttola: LocatorN6240 E02935 (approx.)
Google MapsJ, 305 kHz
Operated on request.
Joensuu/Onttola: LocatorN6240 E02938 (approx.), 283°/0.86 NM to field
Google MapsF, 340 kHz
Operated on request.
Joensuu/Onttola: NDBN6239 E02941 (approx.)
Google MapsJO, 320 kHz
Operated on request.
Jungsund: NDBN6311 E02140 (approx.), 161°/8.1 NM to Vaasa
Google MapsOJV, 357 kHz
(Korsholm). Operated on request.
Jyväskylä: Air Base (Jyvaskyla, Luonetjärvi, Tikkakoski, Jyväskylän lentoasema)
Jyväskylä/Luonetjarvi: LocatorN6224 E02540 (approx.), 307°/0.73 NM to field
Google MapsL, 407 kHz
Operated on request.
Jyväskylä/Luonetjarvi: NDBN6224 E02539 (approx.)
Google MapsOIV, 369 kHz
Operated on request.
Kauhava: Airfield (Kauhavan lentokenttä)
Kauhava: NDBN6307 E02303 (approx.)
Google MapsOIQ, 352 kHz
Operated on request.
Kemi: Airfield (Tornio, Kemi-Tornion lentoasema)
Runway 19:
Kemi: SBA 1933.3 MHz
To runway 19 (186°)
Kemi: OM 19
186°/1.84 NM to THR 19
Dashes, 38 MHz
Kemi: NDBN6548 E02436 (approx.), 186°/1.5 NM to field
Google MapsOJG, 399 kHz
Operated on request.
Kemi: IM 19
186°/0.17 NM to THR 19
Dots, 38 MHz
Korso: LOMN6022 E02504 (approx.), 223°/3.94 NM to THR 22
Google MapsLocator: OJZ, 387 kHz
Korso LOM was located at the intersection of the approach courses for Helsinki Vantaa 223° and Helsinki Malmi 183°.
Kuopio: Air Base (Rissala)
Kuopio/Rissala: LocatorN6301 E02748 (approx.), 332°/0.77 NM to field
Google MapsK, 310 kHz
Operated on request.
For historical information only, do not use for navigation or aviation purposes!
Kymi: Airfield (Kotka, Kymin lentokenttä)
Kymi: NDBN6033 E02655 (approx.)
Google MapsOJF, 354 kHz
Operated on request.
Mariehamn: Airfield (Maarianhaminan lentoasema)
Mariehamn: LocatorN6008 E01955 (approx.), 202°/0.76 NM to field
Google MapsS, 376 kHz
Operated on request.
Mariehamn: NDBN6007 E01957 (approx.), 286°/1.67 NM to field
Google MapsOJD, 392 kHz
Operated on aerodrome times from 0500 to 2000 weekdays.
Oulu: Air Base (Oulun lentoasema)
Runway 12:
Oulu: NDBN6458 E02513 (approx.), 116°/3.9 NM to field
Google MapsOJU, 385 kHz
Oulu: LocatorN6456 E02519 (approx.), 116°/0.75 NM to field
Google MapsO, 406 kHz
Parkano: NDBN6200 E02302 (approx.)
Google MapsOJQ, 373 kHz
Operated on request.
Parola: NDBN6101 E02421 (approx.)
Google MapsOIP, 377 kHz
(Hattula). Operated on request.
Pori: Airfield (Bjorneborg, Porin lentoasema)
Pori: LocatorN6128 E02148 (approx.), 124°/0.56 NM to field
Google MapsP, 318 kHz
Operated on request.
Rovaniemi: Airfield
Rovaniemi: LocatorN6634 E02550 (approx.), 221°/0.6 NM to field
Google MapsR, 414 kHz
Operated on request.
Rovaniemi: NDBN6632 E02548 (approx.), 018°/1.4 NM to field
Google MapsOJN, 394 kHz
Operated on request.
For historical information only, do not use for navigation or aviation purposes!
Sodankylä: NDBN6722 E02639 (approx.)
Google MapsSO, 364 kHz
Operated on aerodrome times from 1000 to 1430.
Tampere: Härmälä Airport (Tampere-Härmälän lentoasema)
Tampere: NDBN6129 E02345 (approx.), 210°/1.0 NM to field
Google MapsOIT, 328 kHz
Operated on request.
Turku: Artukainen Airport
Turku: Locator
260°/0.8 NM to field
A, 355 kHz
Turku: Locator
080°/1.04 NM to field
L, 380 kHz
Turku: Locator
260°/4.1 NM to field
TU, 410 kHz
Turku: NDB
OJY, 361 kHz
Runway 08:
Turku: ILS 08TU, 109.5 MHz
To runway 08 (080°)
Turku: OM 08
080°/4.1 NM to THR 08
Dashes, 75 MHz
Turku: MM 08
080°/1.29 NM to THR 08
Dots Dashes, 75 MHz
Turku: IM 08
080°/0.4 NM to THR 08
Dots, 75 MHz
Utti: Air Base (Utin lentokenttä)
Utti: NDBN6053 E02655 (approx.)
Google MapsOIU, 316 kHz
Operated on request.
Vaasa: Airfield
Vaasa: LocatorN6303 E02146 (approx.), 161°/0.56 NM to field
Google MapsW, 406 kHz
Operated on request.
Vihti: NDBN6024 E02420 (approx.)
Google MapsOJJ, 366 kHz
For historical information only, do not use for navigation or aviation purposes!