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Re: [Amps] QRO 2500DX MARK lll 4CX800

To: "Leigh Turner" <>
Subject: Re: [Amps] QRO 2500DX MARK lll 4CX800
From: "Jim Thomson" <>
Date: Wed, 3 Apr 2019 08:13:21 -0700
List-post: <>
Subject: RE: [Amps] QRO 2500DX MARK lll 4CX800

<Of course any of these amps when married up with a modern SDR exciter
<running Pure Signal IMD cancellation feedback produce truly state-of-the-art

<In the Tx tetrode tube space today there are very few choices to be had.....


## The only modern SDR xcvr for sale on the market right now, with...Pure signal... is the ANAN 7000 + 8000 xcvrs, which,imo, are not ready for prime time. Esp judging by the 37 K postings of various issues..on their yahoo group, that I belong to. Pure signal will really take ahold when Icom, Yaesu, Kenwood start using it in their future products.

## Heres my take on tubes Leigh. Why mess with a tetrode in the 1st place ? Tetrodes offer ZERO advantages over a high mu GG triode. Heck, you dont require a socket on some triodes, nor regulated screen supplies, regulated bias supplies, screen and anode current protection, + compensation on the input for stray tube C, + neutralization etc, etc.

## A dead simple, single chinese 8877 GG triode amp makes more sense. 2 x 3-500Z is also dead simple..and instant on, no grid current
protection required..perhaps a simple  fast  3agc  grid fuse  at most.

## From a HB perspective, why bother with a complicated mess, like the typ tetrode ? A simple 3CX-3000F7 requires no socket, instant on, rebuildable, 5-8 kw pep out..or CCS cxr, and -59db IMD-3. Most hams will die before the tube does. Moot point, cuz your kids can have it rebuilt,
use it..then  pass it on to their kids.

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