On November 15, 1945, amateurs in U.S. are allowed back on the air -- but only on 10 and 2 meters. By 1946, Amateurs get most of the bands back except for 160 Meters, this was used by LORAN and other services and was not available to Amateurs. Over the next several decades 160M would be reopened, a little at a time.

1945 - Amateurs are allotted the 6 meter band 50-54 Mc. The 2 1/2 meter band is moved to 144-148 Mc. With the exception of some FM, all phone operation is with AM.

1945 6 Meters. Pioneers utilized CW, AM, and experimented with NBFM. Antennas included rhombics, corner reflectors, folded dipoles, and of course Yagi's. The first 2-way QSO involving "skip" was reported to have taken place on April 23, 1946 when W1LSN of Exeter, NH worked W9DWU of Minneapolis, MN. This and many other contacts were made on that night via a combination of aurora and sporadic-E. The distance of this contact was 1100 miles.

1946 - Amateurs make the first Meteor Scatter contacts. On the night of October 9, 1946, the night of the Giacobind-Zinner Comet, and its associated meteors, Amateurs made their first two-way contacts via meteor scatter on the 6M band, the propagation lasted 3 hours with reports from the east and midwest part of the USA. However it was not until Oct 22, 1953 that a 2M two way contact was made between W4HHK and W2UK. Transoceanic 6M contacts are made in late 1946.

http://www.ac6v.com/history.htm 
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In November 1945, U.S. amateurs were allowed back on the air on the 10 meter, 5 meter, and the new 2 meter band. The 5 meter band from 56-60 mc was temporary--by March 1946 we were moved in the great post war frequency shuffle to our new 6 meter home from 50-54 mc. As for the new 2 meter band, it replaced our old 2 1/2 meter allocation which ran from 112-116 mc.

http://www.twiar.org/aaarchives/WB026.txt
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The World War II ended on August 17, 1945. No more than 4 days later, the US hams were back on the air on VHF ! Europe restarted more slowly. The format of English licence changed, allowing more flexibility, and the first stations were heard on the air in 1946. By Summer 1946, the US hams saw all their amateur bands restored from 3.5 to 30 Mc.

New modes were introduced, and more frequency spectrum was allocated for amateur operation world wide, reflecting the importance that is attached to it by the international community. The old 5 and 2.5m bands were replaced with the new 6 and 2m bands, always active nowadays.

http://www.astrosurf.com/luxorion/qsl-ham-history9.htm
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1947 After the Second World War, the ITU held a conference in Atlantic City New Jersey U.S.A. with the aim of developing and modernizing the organization. Under an agreement with the newly created United Nations (UN), it became a UN specialized agency on 15 October 1947, and the headquarters of the organization were transferred in 1948 from Bern to Geneva.

Amateur Radio was defined and still is, as “A service of self training, intercommunication and technical investigation carried on by duly authorised persons interested in radio technique solely with a personal aim and without pecuniary interest.”

http://www.ham-radio-europe.co.uk/why%20is%20amateur%20radio%20unique.htm
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Radio Conference took place in Atlantic City, New Jersey, on May 15, 1947

10GHz is probably, in the UK at least, the most popular of the amateur microwave bands. It has seen some sixty years of development since the first experimental contacts made by W2RJM and W2JN in the USA during 1946. These two "pioneers" could not have known what was to follow their 2 mile (3km+) contact! A year later, in 1947 the world 3cm record was extended to 7.65 miles after a contact between W6IFE/3 and W4HPJ/3. W6IFE is now the callsign of the San Bernardino Microwave Society, the oldest amateur microwave group in the world and one with a fascinating history of its own.

http://www.g3pho.free-online.co.uk/microwaves/history.htm
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But some interesting ‘straight' receivers were also being built, a good example being one by Hodinin, OK2MV, who incidentally was the first OK to work England on 58 MHz in June 1947, with G5BY at the other end (who else?).

http://www.uksmg.org/50yrsof50megspt5.htm
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While the first 3 cm contact was made in May of 1946 (James W2JRM and Charles W2JN, 2 miles (3.22 km)), Tommy W6IFE (shortly before returning to California) and W. Kenedy W4HPJ, quickly stretched this record out to 7.65 miles (12.31 km). These early contacts would serve as an indicator as to how successful this band would eventually be. To this date, 3 cm. is by far the most populated of the microwave bands above 13 cm.

Tommy W6IFE is credited with opening the 9 cm band [The ARRL UHF/Microwave Experimenter's Handbook, page 1-8]. Early on, Tommy had to construct both ends of the microwave equipment used on his microwave shots. On June 5, 1947, Tommy is credited with working 186 miles (299.46 km) on 9 cm.

April 25, 1948, Tommy W6IFE is credited with working a 150 mile (241.5 km) record path with W6ET on the 13 cm band.

http://www.ham-radio.com/sbms/historyOW.html
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anniversary of the World Record contact between Clarrie VK5KL and Eugene W7ACS/KH6 took place at 1240 CST (0310 UTC) on 26 August 1947 on the six metre band, 50 to 56 MCs. (At the time, frequencies were referred to as Megacycles or MCs, or megs for a short title.) Clarrie made the contact while he was living in Darwin. VK5 callsigns then were used for South Australia and the Northern Territory. The distance was considered to be 5350 miles or 8610 km. I presume Clarrie will open a bottle of champagne to celebrate the memory of that contact 50 years ago!

http://www.uksmg.org/vkww.htm
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In 1947, the World Telecommunications Conference in Atlantic City allocated amateur bands worldwide and added 2 metres, 70 centimetres, 23 centimetres and harmonically related microwave bands. One must remember that amateurs used keyed continuous wave (c.w., morse) or, in the case of telephony transmissions, amplitude modulation (a.m.)

http://www.qsl.net/gi8flq/4m&up_gi_history.html

Worldwide Frequency allocation of hamradio bands before Atlantic City Conference kc/s 1 715 - 2 000 (shared) 3 500 - 3 950 ,, 7 000 - 7 200 (exclusive) 7 200 - 7 300 (shared) 14 000 - 14 400 (exclusive) 28 000 - 30 000 (shared) Mc/s 58,5 - 60 (exclusive) ______________________________ Worldwide Frequency allocation of hamradio bands agreed on Atlantic City Conference kc/s 3 500 - 3 800 (shared) 7 000 - 7 100 (exclusive) 7 100 - 7 150 (shared) 14 000 - 14 350 (exclusive) 21 000 - 21 450 (exclusive) 28 000 - 29 700 (exclusive) Mc/s 144 - 146 (exclusive) 420 - 460 (shared) 1 215 - 1 300 (exclusive) 2 300 - 2 450 ,, 5 650 - 5 850 ,, 10 000 - 10 500 ,,

Representatives of many national Telecommunication authorities on common photo on the end of Worldwide Radiocommunication Conference in Atlantic City, N.J. USA 1947   Picture and info abt. this conference from Czech hamradio magazine "Radioamater 1947"

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Amateur radio VHF development after WW II. in OK

Since 1946 were used Rules from 1938 year which allocated:  56.0-60.0, 112-118, 224-230, 408-420, 2.300-2.450, 5.250-5.650, 10.000-10.500 & 21.000-22.000 Mc/s bands. CW and Phone (AM) operation were allowed with input up to 50 W.

Based on the Atlantic City Conference were in May 1949 published new "License Rules for Radioelectric experimental transmitting stations" which replaced Rules from 1938 withall ammendments from 1946.
Operation bands - 50-54 Mc/s (temporarily), 144-150 Mc/s (part 146-150 temporarily), 220-225 Mc/s (temporarily), 420-460 Mc/s together with aeronautical navigation, which can't be interfered, and 1215-1300, 2300-2450, 3300-3500 (temp), 5650-5850, 10000-10500 and 21000-22000 Mc/s.

source http://www.ok1uu.com/1952.htm 

In 1954 new Rules reallocated VHF bands for all ham radio operators to: 85.5-87 MHz, 144-150 MHz *), 220-225 MHz *), 420-460, 1215-1300, 2300-2450, 3300-3500, 5650-5850 MHz, 10.0-10.5 a 21.0-22.0 GHz.
Note *) changes since 15.3.1959:  2 m band limited to 144-146 MHz, 86 and 220 MHz bands terminated.

In 1961 the 70cm band was limited to 430-440 MHz,  3 GHz band terminated and 5 GHz limited to 5650-5800 MHz.

Since 1979 was ham radio band 20GHz reallocated to 24000-24050 MHz, in 1982 were added 24,050-24,250 GHz, and 47,000-47,200, 75,500-76,000, 142-144 a 248-250 GHz.

source http://www.crk.cz/CZ/VYVKONC.HTM
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Prepared from internet sources by OK1VPZ in Oct. 2007.