1900–1910: Fol­low­ing in the foot­steps of Mar­coni and oth­er pio­neers, thou­sands of young exper­i­menters built sim­ple “spark” trans­mit­ters and receivers to send Morse code mes­sages around their neigh­bor­hoods — some­times caus­ing inter­fer­ence to com­mer­cial and mil­i­tary communications.

1910–1920: To address the inter­fer­ence prob­lem, licens­ing was intro­duced in 1912. Ama­teurs began to orga­nize them­selves into clubs, form­ing the basis for today’s nation­al asso­ci­a­tions in Aus­tralia (1910), Great Britain (1913), and the Unit­ed States (1914). The World War caused ama­teur sta­tions to be shut down but led to advances in radio tech­nol­o­gy that were quick­ly adopt­ed by ama­teurs, once allowed back on the air, in their quest to span greater distances.

The Twen­ties: Vac­u­um tube (valve) tech­nol­o­gy replaced spark, reduc­ing inter­fer­ence and increas­ing range. The remark­able prop­er­ties of the ionos­phere were har­nessed by ama­teurs to achieve glob­al com­mu­ni­ca­tion using rel­a­tive­ly low trans­mit­ter pow­er and anten­nas that could fit in a typ­i­cal back­yard. To retain access to “short wave” spec­trum ama­teurs had to over­come pres­sure from com­mer­cial and gov­ern­ment inter­ests; the IARU was cre­at­ed for that exact pur­pose. Morse code remained the dom­i­nant mode used by ama­teurs despite the growth of AM broad­cast listening.

The Thir­ties: Ama­teur radio grew dur­ing the Depres­sion as an inex­pen­sive and pro­duc­tive pas­time. It became pos­si­ble to con­tact ama­teurs in 100 dif­fer­ent coun­tries, even though there were few­er coun­tries then. Tele­vi­sion and the explo­ration of VHF spec­trum occu­pied the atten­tion of the cut­ting-edge tech­nol­o­gists while oth­ers built their own AM trans­mit­ters and voice com­mu­ni­ca­tion became pop­u­lar. Pro­pa­gan­da broad­cast­ing impact­ed the short waves, cre­at­ing a new chal­lenge to ama­teur spec­trum access.

The For­ties: World War Two caused ama­teur radio to be shut down in most coun­tries. Once again, tech­nol­o­gy was advanced by wartime need. After the war, sur­plus radio equip­ment was plen­ti­ful and inex­pen­sive. This allowed ama­teurs to upgrade their sta­tions and for the first time to explore UHF and microwaves. A new mode, radiotele­type (RTTY), began to be heard on the ama­teur bands as a result of the sur­plus bonanza.

The Fifties: Tele­vi­sion broad­cast­ing posed a chal­lenge for ama­teurs, requir­ing new diplo­mat­ic and tech­ni­cal skills to address “TVI” (tele­vi­sion inter­fer­ence) to their neigh­bors’ and fam­i­lies’ sets. In spite of this it was a decade of rapid growth. Sin­gle side­band (SSB) dra­mat­i­cal­ly increased the effi­cien­cy and reduced the nec­es­sary band­width of voice com­mu­ni­ca­tion. Mobile oper­a­tion became pop­u­lar. Toward the end of the decade a peak in the sunspot cycle gave ama­teurs the best ionos­pher­ic prop­a­ga­tion ever expe­ri­enced, before or since. Ama­teurs tuned into the first sig­nals from space after the first Sput­nik was launched. Heathk­its, com­plete sets of com­po­nents with step-by-step instruc­tions for assem­bly, cap­tured a large share of the equip­ment market.

The Six­ties: Ama­teur radio offi­cial­ly joined the Space Age with the first ama­teur-built satel­lites. Ama­teur two-way com­mu­ni­ca­tion by reflect­ing sig­nals off the moon (Earth-moon-Earth, or EME) was achieved, first on 1296 MHz and lat­er on 144 MHz. Back on Earth, SSB became the dom­i­nant HF voice mode. Sep­a­rate HF trans­mit­ters and receivers began to dis­ap­pear from ama­teur sta­tions, replaced by trans­ceivers with many cir­cuits shared between the two func­tions. Good equip­ment from Japan began appear­ing in ham shacks through­out the world. Some coun­tries began to issue licens­es for VHF and high­er fre­quen­cies with­out requir­ing Morse code ability. 

The Sev­en­ties: Long-dura­tion satel­lites made satel­lite com­mu­ni­ca­tion a per­ma­nent fea­ture for space-mind­ed ama­teurs. Bol­stered by a large domes­tic mar­ket, Japan­ese man­u­fac­tur­ers became dom­i­nant glob­al­ly. VHF and UHF repeaters surged in pop­u­lar­i­ty, extend­ing the range of mobile FM equip­ment. In the mid-70s the “CB boom” became the biggest source of new­ly licensed radio ama­teurs as more-seri­ous hob­by­ists fled the chaos of the Cit­i­zens Band. The decade end­ed with the impor­tant World Admin­is­tra­tive Radio Con­fer­ence (WARC-79) where the many years of work by the IARU led to suc­cess­ful defense of exist­ing ama­teur bands and new allo­ca­tions at 10, 18, and 24 MHz.

The Eight­ies: Micro­proces­sors became the vehi­cle for rapid devel­op­ment of the dig­i­tal dimen­sion of ama­teur radio. Pro­pelled by the adop­tion of a stan­dard for dig­i­tal data com­mu­ni­ca­tion known as AX.25, “pack­et radio” became a pow­er­ful new tool for mes­sage for­ward­ing. Anoth­er adap­ta­tion of a com­mer­cial stan­dard, known in its ama­teur ver­sion as AMTOR, brought error-free data com­mu­ni­ca­tion to the HF bands. The manned space pro­gram entered ham shacks around the world as ama­teurs were able to com­mu­ni­cate direct­ly with an astro­naut aboard the Space Shut­tle in Earth orbit, the first of many to fol­low on the Inter­na­tion­al Space Station.

The Nineties: Dra­mat­ic polit­i­cal events in east­ern Europe led to sig­nif­i­cant changes for radio ama­teurs there. Glob­al­ly the Inter­net rep­re­sent­ed both a chal­lenge and an oppor­tu­ni­ty: com­pe­ti­tion for the time and atten­tion of tech­no­log­i­cal­ly mind­ed youth on the one hand, an unprece­dent­ed medi­um for infor­ma­tion exchange on the oth­er. The dig­i­tal rev­o­lu­tion con­tin­ued to fuel ama­teur radio devel­op­ment; few ham shacks were with­out at least one per­son­al com­put­er inte­grat­ed into the sta­tion. PSK31, a dig­i­tal mode designed specif­i­cal­ly for ama­teur radio use and not based on a com­mer­cial stan­dard, offered weak-sig­nal per­for­mance and nar­row band­width com­pa­ra­ble to CW.

The 2000s: The intro­duc­tion of WSJT, a suite of open-source pro­grams designed for weak-sig­nal dig­i­tal com­mu­ni­ca­tion by ama­teur radio, spurred a wave of prop­a­ga­tion obser­va­tion and inves­ti­ga­tion using tech­niques adapt­ed from radio astron­o­my. Dig­i­tal voice became pop­u­lar. Soft­ware defined radios (SDRs) offered capa­bil­i­ties that were unimag­in­able just a few years ear­li­er, at prices ama­teurs could afford. The 2007 World Radio­com­mu­ni­ca­tion Con­fer­ence (WRC-07) made the first-ever low fre­quen­cy (LF) ama­teur allo­ca­tion at 136 kHz.

The next two WRCs, in 2012 and 2015, allo­cat­ed new ama­teur bands at 472 kHz and near 5 MHz respec­tive­ly. WRC-19 adopt­ed a dra­mat­ic improve­ment of the ama­teur 50 MHz band in Region 1, pro­vid­ing a degree of glob­al har­mo­niza­tion in this intrigu­ing part of the spectrum.

The ama­teur exper­i­menters of a cen­tu­ry ago would be amazed at what ama­teurs can do today — and there’s more to come!