Icom 761 / 765 Differences

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David H. Johnson:
I realize the 761/765 transceivers are the last non DSP transceivers from Icom.  But I can't find what the real, actual differences are between the two models.  Any information will be appreciated.  Thanks,  Dave

Stu:
One difference is the 761 has TXCO CR-64 high stability crystal oscillator already installed,(factory installed) where the ic-765 this is an option.And the ic-765 has more option with filters.
There may be more but these two differences come to mind.Good luck

Gerry Pement:
The IC-761 was introduced in 1987 which was a lot like the IC-751A that had all the options Auto Tuner like AT-150, Keyboard, Power Supply, UX-14 computer interface and FL-52A second if 455 Khz. Filters that were options or external peripherals on the 751A were included on the 761 which was Icom's first large base sized large radio. Competing with Kenwoods TS-930 & 940 and Yaesu's FT-980, FT-ONE and FT-767GX that were on the Marketplace at that time. In 1988 Icom introduced their Flagship Radio for many years the IC-781 which had everything including the Kitchen sink! It had many new state of the art features including the new generation DDS synthesizer, band stacking registers the keyboard had single touch band buttons and direct entry of Frequency was a second function of the keyboard. Band Stacking registers remembered the Frequency you were last on that band when you changed bands. The next year Icom introduced the IC-765 to replace the IC-761. A lot of the features that first came out in the IC-781 were included in the 765 the DDS synthesizer, the Band Stacking Registers, the Auto tuner was updated from the older Preset design to Microprocessor with memories. During that 1989 Icom had a Patent Dispute in Japan concerning Icoms great Passband feature of the 751A and 761 resulting in the 765 having only IF Shift from the Factory.  The IC-751A for a short time in 1989 had IF Shift instead of Passband Tuning when that dispute was settled 751A's once again had Passband Tuning I guess Icom could not have Passband Tuning in the 765. Passband Tuning reinstatement was a easy mod for both radios. The IC-765 also lost the great FL-80/FL-44A Filter combo used in the IC-751A and 761. There was a Passband Tune mod for the 765 that made the IF Shift  or Passband Tune selectable but the FL30/FL96 wider & cheaper filter combo Passband tuning was less effective in the 765. The 765 still had the dual 500 hz filters for CW and RTTY. Both the 761 & 765 had slots for optional 250 hz Narrow Filters for the 9Mhz and 455 Khz if stages. I hope that helps.
73
Gerry VE7BGP    

Mark Hall:
IC-761 to IC-765 Receiver Front End Comparison thru 455 Khz IF Stage.

I have both the ‘761 and ‘765 service manuals and did a comparison of the receiver front ends of each at the block diagram level.  They appear identical with the following exceptions:

1) First IF Frequencies are Different:  ‘761 is 70.4515 Mhz      ‘’765 is 69.0115 Mhz  Filtering after the first IF appears to be identical implementing a monolithic crystal filter (MCF) followed by a dual gate mosfet IF amplifier. It would appear that the INRAD roofing filter replaces this MCF.  INRAD also makes an "Experimental" roofing filter (but not in kit form with the amplifier PCB) for the IC-761.  It should be possible to purchase the '765 INRAD kit, replacing the '765 filter with the '761 filter.  The INRAD kit is only $125.

2) ‘765 includes an additional 9 Mhz  monolithic filter right after the 9 Mhz second mixer, but before the Noise Blanker.  FL-23 is called a Monolithic filter in the parts list, and has a 9.0115 Mhz  Center Freq. with a bandwidth of 15 Khz.  This FL-23 filter is used elsewhere in both the ‘765 and ‘761, so shouldn't be hard to find. Should not be difficult to install this in the '761.

The receiver front end schematics are very similar (possibly functionally identical), but were redrawn, making direct comparison a bit complicated.  I will attempt to make detailed schematic comparisons over the next couple weeks. 

’73  mark   KI4Z

David Heinsohn:
I can't disagree with anything that has been posted. I will say that I had all 3 radios. I chased DX and maybe did a contest or two or three.  At one time I had a number 1 DXCC. The 751A was the first nice radio built by Icom. Note here A model. The 761 seemed like just a blown up version of the 751A. It did receive a bit better.

Next came the 781. My Dx contest buddy had one. I couldn't tell it was any better receive wise than the 765. I liked the 765 over the 751A or 761. I had a bunch of filters in it. Did the passband mod, and can't recall what else. Likely more. I built my own computer interface, and logging, computer control etc.  I still have a 765. It is a fine base station radio. You do have to deal with the trimmer capacitor issue. Oh I had an Autek QF1-A active audio filter hooked up too. They are nice on CW. Help to get rid of interfering heterodynes on SSB.

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