Sev­er­al com­mu­ni­ca­tion modes allow ama­teurs to exchange still or mov­ing images over the air. Advances in tech­nol­o­gy have brought the price of image trans­mis­sion equip­ment with­in reach of the aver­age ham’s bud­get. This has caused a surge of inter­est in image com­mu­ni­ca­tion.

Ama­teur TV (ATV) is full-motion video over the air, some­times called “fast-scan TV.” Ama­teur Radio com­mu­ni­ca­tion takes on an excit­ing, new dimen­sion when you can actu­al­ly see the per­son you’re com­mu­ni­cat­ing with. In addi­tion, ATV has proved to be very use­ful in emer­gency and dis­as­ter com­mu­ni­ca­tion sit­u­a­tions.

Ama­teur groups in some areas have set up ATV repeaters, allow­ing low­er­pow­er sta­tions to com­mu­ni­cate over a fair­ly wide area. Since this is a wide-band­width mode, oper­a­tion is lim­it­ed to the UHF bands (70 cm and high­er). Dig­i­tal ATV folds nice­ly into a recent Ama­teur Radio tech­no­log­i­cal ini­tia­tive called high-speed mul­ti­me­dia (HSMM) radio.

The ham bands above 50 MHz can sup­port com­put­er-to-com­put­er com­mu­ni­ca­tion at speeds high enough to sup­port mul­ti­me­dia appli­ca­tions — voice, data and image. One approach adapts IEEE 802 tech­nolo­gies, par­tic­u­lar­ly 802.11b, oper­at­ing on spe­cif­ic Ama­teur Radio fre­quen­cies in the 2400- 2450 MHz band.

SSTV or “slow-scan TV” is a nar­row-band­width image mode that has remained pop­u­lar for many years in Ama­teur Radio. Instead of full-motion video, SSTV is for the exchange of pho­tographs and oth­er images. Indi­vid­ual SSTV pic­tures take any­where from 8 sec­onds to about 2 min­utes to send depend­ing on the trans­mis­sion method. These days most SSTV oper­a­tion is done in col­or using com­put­ers and sound­cards. Images are con­vert­ed into a series of audio tones rep­re­sent­ing bright­ness lev­el and col­ors. Since SSTV is a nar­row­band mode, it is pop­u­lar on HF on the same fre­quen­cies used for voice oper­a­tion.


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