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


Um, 51dB (the fractions are imaginary) is not all that good even at 1 kW. It's better than what you can buy today, for the most part. But. it's not very good when 60 dB to 70 dB is available and achievable.


On 20220225 10:15:01, Conrad, PA5Y wrote:

Well I did say at 0dBm! Clearly. It is not my fault that you have PS fan boy eyes.






From: <> On Behalf Of oldjackbob via
Sent: 25 February 2022 18:48
Subject: Re: [SDR-Radio] Open HPSDR Hermes (14 bit ADC, EP3C25) Transceiver Card


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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