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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 28th Jan 2021, 1:58 pm   #1
Steve G4WCS
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Default Ft-767. Is it deaf ?

Ive been doing some back to back testing between the little Sommerkamp and the Yaesu ft-767gx.

Been doing a bit of back to back testing. feeding signals into both radios from the SMDU, with the sommerkamp 4uV (disclaimer its not been calibrated in terms of output level) is just discernible . The Yaesu, with the RF preamp switched in is 10uV for the same signal/noise by ear.

Heres a comparison on a station on 20M. May be a difference due to the different antennas in use, but the station is coming on comparably on both radios, but the signal meter on the Yaesu seems quite “mean” .

https://youtu.be/d4lF9LYa_VM

The sensitivity “difference” across the bands on both radios is the same, and Ive had plenty contacts on the Yaesu, so Im undecided whether the Yaesu is deaf/faulty, or the sommerkamp is just a lively little set. On paper both radios have the same spec on receive. What does the forum think ?
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Old 28th Jan 2021, 6:26 pm   #2
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Default Re: Ft-767. Is it deaf ?

My rule is "If the noise goes up when an aerial is connected (tuned to a quite spot) the receiver is sensitive enough". S meters are a very variable thing.
 
Old 28th Jan 2021, 6:39 pm   #3
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Default Re: Ft-767. Is it deaf ?

I don't have the diagram for the 767 but I do recall that on the FT747 and FT757 there was a design 'quirk' which involved the use of a grain of a PCB mounted grain-of-wheat lamp bulb as a fuse in the receiver input circuit. I recall at least one case where an FT-747 which was thought to be 'a bit deaf' was looked at and the little bulb was found to be open-circuit. The real surprise was how well it had been working, all things considered, with the bulb open-circuit.

I have no idea whether the 767 continued in the tradition of using a lamp fuse on the input circuit, but if it does then it may be worth checking.
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Old 28th Jan 2021, 10:48 pm   #4
Steve G4WCS
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Default Re: Ft-767. Is it deaf ?

Evening, yeah thought about the fuse bulb and also pin diodes. There isnt a fuse bulb but its full of pin diodes. Theres also a switch for a separate receive antenna that can go noisy.
I may be werreting unneccesarily, had another play on 20, and apart from there being more twinkly leds on the sommerkamp there isnt much difference (with the rf amp switched in) I remember my ft-757 being a bit on the deaf side, Harry Leeming checked it out and it was within its spec
https://youtu.be/c08P6tHf9cg
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