Solche und ähnliche Beschreibungen für MiG-19F, PF, S udn PM habe ich gefunden: 
"... Early MiG-19F (NATO Farmer-A) and MiG-19PF (NATO Farmer-B) shared the armament of the MiG-17, with two NR-23 and one NL-37 cannon. The MiG-19S (NATO Farmer-C) was armed with three 30millimetre NR-30 cannon and either bombs or rockets. This variant was largely manufactured in Czechoslovakia. The interceptor MiG-19PM (NATO Farmer-D) model deleted the cannon in favor of an RP-5 Izumrud (NATO Scan Odd) radar, and carried four beam-riding K-5 missile (AA-1 Alkali) (NATO AA-1 Alkali) air-to-air missiles. Mikoyan developed a two-seat trainer version, designated MiG-19U, but it was not produced (although the Peoples Republic of China produced a trainer version, the JJ-6). ..." 
http://read-and-go.hopto.org/ Soviet-fighter-aircraft-1950- 1959/Mikoyan-Gurevich-MiG- 19.html 
 
Auch wird gern die rote 21 aus Khodinka als Beispiel einer PF angeführt. 
 
An anderen Stellen wird der Unterschied primär an der Bewaffnung festgemacht: P = "Armament two 23mm cannon NR-23 in the wing-roots, or version Mig-19PF two 30mm cannon NR-30." 
 
Manchmal beschleicht mich aber das Gefühl, daß hier früher in Analogie zur MiG-17PF die Bezeichnung auf die MiG-19 übernommen wurde: erste Version mit Radar = PF 
siehe hier: 
" MiG-19 'Farmer-A' First prototype derived from the MiG-17 and using the MiG-17 fuselage, engines, and wing, the engines were replaced since the first examples failed to reach supersonic speeds 
MiG-19P 'Farmer-B' First production model with supersonic capability, but suffered control problems in transonic flight and was withdrawn due to high accident rate and poor engine performance 
MiG-19S 'Farmer-C' Much improved single-seat interceptor with new engines and redesigned tail surfaces to correct stability problems; most numerous model built 
MiG-19SF 'Farmer-C' Similar to the MiG-19S but with slightly improved engines 
J-6 'Farmer-C' First Chinese model license built by Shenyang, equivalent to the MiG-19S/SF 
MiG-19PF 'Farmer-D' First model equipped with radar 
J-6A 'Farmer-D' Chinese variant equivalent to the MiG-19PF 
MiG-19PM 'Farmer-D' First model armed with AA-1 Alkali air-to-air missiles 
J-6B 'Farmer-D' Chinese variant equivalent to the MiG-19PM equipped with a semi-active radar homing air-to-air missile derived from the AA-1 Alkali 
J-6C Original Chinese model similar to the J-6A and J-6B but optimized as a day fighter, included a braking parachute 
F-6C J-6C aircraft for Pakistan armed with AIM-9 Sidewinder air-to-air missiles and improved avionics 
J-6Xin Improved J-6A multi-role fighter model incorporating a Chinese-developed radar 
MiG-19R Reconnaissance variant stripped of armament to fit camera equipment 
JZ-6 Chinese variant equivalent to the MiG-19R, subvariants include high- and low-level reconnaissance aircraft and variants equipped with optical and infra-red sensors for day or night operation 
MiG-19UTI Two-seat combat-capable trainer, did not enter production 
JJ-6 Chinese variant equivalent to the MiG-19UTI but of indigenous design with a lengthened fuselage, braking parachute, and strakes on the rear under-fuselage to improve stability 
FT-6 Export version of the JJ-6 
S-105 Designation given to the MiG-19 in Czechoslovakia 
LiM-7 Designation given to the MiG-19 in Poland 
J-6 III New-build Chinese variant built as a high-speed day attack fighter, cancelled due to handling problems 
Q-5 Fantan Attack fighter based on the J-6 III 
J-6 IV Improved J-6C with a new all-weather radar and armed with PL-2 missiles " 
http://www.aerospaceweb.org/ aircraft/fighter/mig19/ index.shtml 
????? 
 
(OT) ich hoffe, ich überlaste oder gar Mißbrauche hier nicht die Kommentarfunktionalität ... sagt Bescheid, dann kann ich das alle sauch in Mails etc. hinterfragen ;-)