None, they represent the same unit. Original King Radio part numbers were 9 digits. For example, 066-3056-01. During the Bendix and King merger (i.e. Bendix/King), a new part numbering system was created that converted these 9 digit part numbers to 12 digits. Therefore, 066-3056-01 became 066-03056-0001. Despite this numbering change, units that were originally from the King Radio design still have the 9 digit part number format on the unit dataplate. The 12 digit format for King units appears to be used for catalog and internal Honeywell purposes only. Therefore, any unit that has a zero in its third to last number (i.e. XXX-XXXX-X0XX) has a 9 digit part number (i.e. XXX-XXXX-XXX) on its dataplate / ID Plate.

This does not pertain to the comm selector channel spacing.

With the evolution and growth of airborne travel and the necessity for more usable frequencies in the VHF communications spectrum, the "channel" spacing became smaller. To avoid interference between channels the bandwidth of the RF stages was decreased from 50khz to 25khz. In doing so, another problem was introduced. If the ground transmitter or the air to air transmitter was not capable of tighter frequency tolerances, it was possible the 25khz RF selectivity would not allow the receive signal to pass and the aircraft crew could miss critical voice communications.

Due to the presence of older, outdated equipment in some countries, some manufacturers (namely Bendix/King and Collins) produced VHF comm radios with the 50khz receiver selectivity. With the recent mandates and technological advancements in Europe and South America, the requirements for the 50khz versions has diminished. If an operator were to use a 50khz version radio in the position of a 25khz, they would potentially have channel crossover and or an increase in background noise.

The A models superseded the original models. The A models include all of the upgrades that were available via Service Bulletins for the KY-196/197. These improvements include the following:

• Expansion to 760 from 720 (i.e. 135 to 136 MHz)
• 9 channel memory
• Remote frequency transfer capability

The products improvements in the A models include some technical and production improvements which enhance the overall reliability of the radio. The A models utilize a different mounting rack than the original KY-196/197 radios.

In January 1989 Bendix/King changed from a nine digit to a twelve digit part numbering system. The new, larger 12 digit numbers allowed for the inclusion of software version into the last two digits of the part number for certain units in which software changed frequently such as EFIS and TCAS processors. Therefore, the two digits immediately preceding the software version indicate the hardware version of the unit.

Different software versions imply different operational features and/or interface capabilities and software modifications imply software repairs (bug fixes) to insure proper operation of these features and interfaces. Software version upgrades frequently require hardware modifications to the unit. Such hardware modifications accompanying software version upgrades do not necessarily change the hardware version of the unit.

Navigation (Nav) and Communication (Comm) radio receivers and transceivers are available as separate, individual radios or as a combined Nav/Comm unit. A Nav/Comm unit is sometimes more economical in price than the 2 separate Nav and Comm radios and usually requires less panel space. Obviously, one disadvantage to the combined Nav/Comm unit is in the case of unit failure you lose both nav and comm functions since the entire unit is removed.

KN-53 Nav: KY-196A Comm: KX-155 Nav/Comm:

 

The part number for the terminal contact pin that is used on most Silver Crown units is 030-01107-0000. Previously, Honeywell (Bendix/King) offered them in preset amounts based on the unit that were being used with (ex. 030-01107-0064 for the KX-155). Currently, you simply purchase the amount of -0000 pins required.

As of 2010, the List Price for each contact pin is $5.98. Therefore, in most cases, it is less expensive to buy the entire unit installation kit.

The original gas discharge display (GDD) for the KY-197A has been phased out by Honeywell. A new display with LED technology is available for the KY-197A by way of Service Bulletin 9. The new LED provides a brighter, sharper display with longer life. SB 9 consists of replacing the display and one resistor, removing two resistors, and adding two wires.

Please note that the Service Bulletin mainly applies to KY-197A -30/-60 with S/N 15080 and below; and KY-197A -10/-11/-12/-31/-32 all serial numbers. Units will serial numbers above those stated have Mod 9 incorporated during original manufacturing.

Southeast Aerospace can update your KY-197A to the new, more reliable LED display for approximately $770 with a lead-time less than 5 days. For complete details, please contact Southeast Aerospace Tech Support at shop@seaerospace.com.