Is there a modification that exists for the Yaesu FT-70D to let it listen to more frequencies?

Discussion in 'Radio Circuits, Repair & Performance' started by KJ7GQH, Aug 14, 2019.

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  1. KJ7GQH

    KJ7GQH Ham Member QRZ Page

    So it seems that the FT-70D out of the box can only receive frequencies between 108.000 MHz - 579.995 MHz. I have seen some other HTs that are able to listen to HF frequencies. So is the FT-70D capable of doing this if it is modified, and do any modifications exist to add this functionality? Are there tutorials online or people who will do it for you if you pay them?
     
  2. AG6QR

    AG6QR Subscriber QRZ Page

    I don't think so. The published specifications for the FT-70D indicate that its receiver is a double conversion superhet, with first IF at 47.25MHz, and 2nd IF at 450 kHz. The issue is that, since all the standard reception frequencies are well above the 1st IF, the front end, mixer and image rejection filtering are set up for down conversion, and the circuitry would likely have to be changed significantly in order to convert HF frequencies up to 47.25MHz. It's not just a matter of reprogramming an oscillator -- there's a lot of other analog circuitry that would have to be altered, and the alterations would likely make the radio incapable of receiving its original range. If you had loads of space, maybe you could arrange different filters to be switched in and out, but there's not much available space in an HT.

    Several radios have modifications available to change the transmit range, because transmit range is often limited for regulatory reasons, while the circuitry may be technically capable of operating at least a bit outside its regulatory limits. But in the US, there's no regulatory reason to limit receive range, except for the old AMPS cell phone frequencies which are usually blocked. Limits on receive range often have a technical basis.
     

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