Look on the "Blueprints" page of the section from your link: link
"Tank T-26-1 mod. 1940, equipped with radio transmitter. It has a sloping hull below the turret and a conical turret with punched gun mask, commander's "PTK" periscope and whip antenna.[1]"
--M. Kolomiets, M. Svirin,"T-26 Legkiy Tank" Frontovaya Illystratsiya, No. 1, 2003
"Tanks intended for company commanders were equipped with a radio set and a hand-rail radio antenna on the turret. Later the hand-rail antenna was replaced with a buggy-whip antenna, because the Spanish Civil War and Battle of Lake Khasan demonstrated that the hand-rail antenna unmasked commander tanks for enemy fire."
"After 1937, all tanks started to equip with a 71-TK-3 radio."
(They're talking about receivers only. Scale of deployment is a matter of debate.)
link (Says they were for the BTs, but link for example, shows the installation location in the turret bustle. Finnish experiences confirm this (http://www.jaegerplatoon.net/TANKS3.htm):
"Later T-26 tank models were sometimes equipped with radio, but these tanks were a minority of the manufactured tanks. The first radio that the Soviets used for equipping T-26 model 1933 tanks was 71-TK-1 and later production vehicles were equipped with 71-TK-3. … As mentioned in earlier with armoured cars and T-26E tanks, the Finnish experiences concerning captured 71-TK-1 and 71-TK-3 radios were not too positive. Before Continuation War these captured radios had been installed to T-26 tanks reserved for tank company and tank platoon commanders, but these radios proved unreliable. The original receiver used in them had a tendency of constantly more or less changing its frequency on its own, which made reception of radio transmissions uncertain."
opens up the all-plastic M5 Stuart kit recently released.