Carl, your and Val's comments below have nailed the story of the GU74B precisely; that is what I'd meant in my earlier comment about good tubes being in the hands of good amplifier designers who prop
Hi Jim, Instead of a 3-holer GU74B amp why not use a single large GU84B tube with its 2500 Watt rated plate dissipation? I reckon if you need to use more than one tube to meet a given Po target in a
Jim, if you operate your GU74B tube at no more than 800W CW or PEP output in AB1 SSB service then the tube will have a very long service life. DO NOT push it up to 1000 or 1200 Watts Po like some ham
Carl, The GU84B and the so called 4CX1600B are completely different tubes. Similarly the 4CX1600U / GS23B is quite different from the now extinct GU91B. However, the readily available GS23B makes an
George, comparing Tx triodes with tetrodes is akin to comparing apples with oranges, so things must be put into proper context. The 3CX1500A7/8877 and 3CX800 are indeed fine / best of breed SSB linea
Yes Val, a freshly factory minted Svetlana GU74B/4CX800A is indeed pricey compared to the older date code NOS variety....but still much cheaper than say the current list price of an Eimac/CPI 3CX800A
Ian, Peter V, Peter C, You are 100% correct in your spot-on the mark comments below! Much nonsense has been promulgated on this forum to the contrary :-( A savvy RF amplifier designer can indeed extr
Carl, The GU84B and the so called 4CX1600B are completely different tubes. Similarly the 4CX1600U / GS23B is quite different from the now extinct GU91B. However, the readily available GS23B makes an
Charles, I'm presently designing, building and testing a homebrew solid state HF amplifier with similar specs to the DX2400L. The amp comprises a twin pair of 1200 Watt pallet modules based on 4 x SD
Not Freescale parts Jerry, but the capable ST Micro SD2943 RF MOSFETs that typically yield circa 400 Watts per device. I'm using four devices in parallel push-pull per nominal 1200 Watt module; two 1
Hi Jeff, I presume you are referring here to the Russian GU84B tube...the 4CX2500 notation is a misnomer as such a tube was never actually produced within the US Eimac tetrode family. Leigh VK5KLT He
Bill, I agree with your sentiments below...these fine GU74B tubes remain plentiful and amplifier owners don't need to panic yet; though prudence would dictate holding a few spares whilst they remain
Gentlemen, I would not worry too much about the lack of specs; they would be quite predictable and probable mediocre in respect of IMD performance. All that really counts is that users of the Expert
Jim, I think some of these small footprint SS amps are just so compelling and attractive to hams, particularly the DX Expeditioners who lug them to remote locations, prospective purchasers rely more
Good point of clarification here Jim! Leigh VK5KLT NO! Only the "imperfections" in a transformer are inductive (and capacitive, and resistive). The relatively inductance that we see in the circuit is
I'm always intrigued and puzzled why so many hams place so much reliance on inherent brute force device survival per se when placing their amplifiers through this kind of severe load and phase angle
Hi Jim, Yes, fully agree with your point ## 1 below. But, I'll happily trade a bit of efficiency in exchange for clean IMD anytime. Your point ## 2 was implied in my original comment; so we're again
Yes I do concur here George; that's an impressive device survivability capability all right! Nevertheless, as an amplifier designer using this device I'd still build-in the aforementioned ancillary s
Hi Carey, It is disconcerting to hear this unprincipled cowboy story. If you want an honest and reliable and fairly priced source of Russian military surplus tubes then you can't go past Dr Alex Garv
Yes, I concur with Mike's advice about the higher plate voltage on the 4CX1000A; I'd suggest circa 3000 V under load or about 3200 V under zero-signal conditions. That operating loadline will work ni