S E C T I O N S

The 75A-4 (Collins PN. 520 5052 00) Receiver is considered to be the ultimate receiver. This receiver is the result of near 10 years of continuous R&D by Collins Radio. The 75A-4 production cycles can be discerned by looking at the changes in the front panel (as well as other areas). For example if the Noise Limiter and Mode switch text are not on the same line (mode text slightly lower) you have an early production unit. The "S" Meter scale changed colors in the mid production cycle (Black verses Red). Much of this detail information is on other web sites. Look at the Links page to research more detail information on restoration.. When comparing the 75A-4 to its predecessors the immediate difference is the packaging. The 75A-4 is a smaller integrated package. The packaging externally and internally contributed to a more stable receiver suitable for single sideband reception. In AM operations with the wide bandwidth (6KHZ.), drift was not a big factor. SSB with the smaller bandwidth 2.1 to 3.1KHZ., drift is a factor. Additionally the receiver included positions for three filters. The standard filter supplied was 3.1 KHZ clearly stating that this was a sideband receiver. The most popular optional filters included CW (continuous wave) 500HZ. and AM (amplitude modulation) 6KHZ. (see the Filters page). A more through comparison can be made researching information available at other web sites The following page covers some of the modifications made to this receiver.