Re: Open HPSDR Hermes (14 bit ADC, EP3C25) Transceiver Card


Mark, I flashed on one of the favorite 6-meter hacks I communicated with. The other ham worked at a military radio repair facility. They had huge bins of 6AC7 receiving pentodes in metal encased bulbs. He took a large number of them, 100 or so, and ran them in parallel inverted in an oil bath. He burned them out like popcorn running at 1 kW.

I envisioned that as a way to achieve a nice linear class A amplifier with each transistor running very nicely in its receiver front end power range. It might just work. I'd not bet against it.

{^_-}   Ah memories of hacks gone by. He had thousands of those octal base tubes. It has me giggling again.

On 20220225 09:48:24, oldjackbob@... wrote:
On Fri, Feb 25, 2022 at 08:16 AM, Conrad, PA5Y wrote:
Look here at figure 3a, this is a Class A RF amplifier with no pre-distortion running at 2W per tone. The IM3 is -51.48dBc, this is at 950 MHz.

Good grief! This entire topic of your claims of wildly spectacular IMD3 numbers for your K3S and 890S has nothing to do with tiny amounts of power at 950 MHZ! The radios we're discussing (and the 7300 and the ANANs) operate at HF, not gigahertz!

And we've always been talking clearly in terms of final PA stage IMD3 levels, not some measurements taken at a transverter jack.

Show me the measured IMD3 from your K3S or 890S at the output of the PA finals at any power level over 5 watts, at any frequency the finals are designed to operate at, and show me it's anywhere near -50dB. Go ahead, I'll wait...


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