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Re: Those of us members in the HALF Century (or more) Wireless Association

 

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Decades ago hams often operated on USB on 7.297 kHz so their opposite sideband wasn¡¯t out of band.? Opposite sideband attenuation often wasn¡¯t as good as it is today.? On the other hand, transmit IMD (splatter) with tube PAs was often much lower than today with solid-state PAs. ?

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As to IMD splatter in general, Apache has PureSignal pre-distortion and Icom with the 7610 has DPD (digital pre-distortion). The reduction in splatter is dramatic, including distortion products on the opposite sideband.? Transmitter specs today often quote opposite sideband rejection more than 50 dB.? That would be with a single test tone and not indicative of the actual splatter power in the opposite sideband.?? The IC-7600 was particularly poor in this respect.? It appeared the opposite sideband rejection was only 20 dB, which in reality was just IMD splatter.

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Rob, NC0B ??

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From: [email protected] [mailto:[email protected]] On Behalf Of Rick W4XA
Sent: Sunday, March 31, 2024 1:05 AM
To: [email protected]
Subject: Re: [DRAKE-RADIO] Those of us members in the HALF Century (or more) Wireless Association

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Hi Gary,

You are indeed in the minority knowing this gem of information!? The old ARC-5? 5.000-5.500 MHz VFO was perfect for this use!

I spent a fair amount of time trying to explain why I was using USB on 40 and 75 operating from Military (and civil) transport type aircraft from 1981 to 2018.?? I have since retired and even now, still use USB on 40 and 75.

You see, only "amateurs" and CB'ers use lower sideband on any MF/HF band.?? The rest of the MF/HF world standardized with USB long ago.

One would think that if those "amateurs" were really serious about inter-operating with the rest of that MF/HF world, and actually be "ready" for emergency communications with MF/HF Marine and Land Mobile services (many of which have radios that don't operate on LSB) those "amateurs" would also agree to "standardize".??

But it will never happen.?


--

73/Rick

W4XA
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