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

Simon Brown

Watching on-air on 80m and comparing to all other rigs people use.


Simon Brown, G4ELI


From: <> On Behalf Of Conrad, PA5Y
Sent: 25 February 2022 09:13
Subject: Re: [SDR-Radio] Open HPSDR Hermes (14 bit ADC, EP3C25) Transceiver Card


I KNOW for a fact that the IC7300 is not clean. Please provide me some evidence to the contrary. I have measurements with a R&S FSWP Signal analyser out to a 1MHz BW. You guys are looking in an SSB BW which is fine unless you happen to be 130kHz away, then you will hear plenty of splatter from the IC7300. I tested the IC-7300 as a result of hearing this on 50MHz. In other words the lab tests were driven by on air experience.


You are spreading misleading and incorrect information.




Conrad PA5Y


From: <> On Behalf Of oldjackbob via
Sent: 24 February 2022 23:12
Subject: Re: [SDR-Radio] Open HPSDR Hermes (14 bit ADC, EP3C25) Transceiver Card


On Wed, Feb 23, 2022 at 12:24 PM, Max wrote:

I just think if we follow good design and signal chain management that superb, clean signals can also be generated without the need for PS, that's all.


I disagree. My signal is my signature. Audio clarity is admittedly important but what matters most to me is a splatter-free signal, and in that regard nothing comes close to what PS can produce. As I stated earlier, even the best Class A amplifiers only have -40dB splatter. PS starts at -60db and often pushes -70dB. That means that PS reduces splatter to less than 1% (and at times only 1/10 of 1%) of what even the best traditional equipment can produce.

I also agree with Simon that the 7300 (and also the 7610 for that matter) produces an extremely sharp-edged signal with unarguably less splatter than is achievable with any other non-ANAN radio. It was explained to me by Ray N5LAX that the reason those radios are so clean splatter-wise is because ICOM embedded an algorithm into the firmware that functions very similarly to PS in the sense that it corrects for non-linearity in the PA, but it is a fixed-value (i.e., static) correction only, not a real-time self-adjusting correction value such as is employed by PS. NOTE: I have not been able to verify that info, but that is what was told to me over-the-air by Ray when I commented that I had no idea how the 7300 could produce such a clean, sharp-edged signal. So I'm repeating it here.

IMO it's unwise and short-sighted to summarily dismiss the game-changing value that PS brings to the hobby. Its benefits are so unarguable that I (and Rob Sherwood) often wonder why the big-name radios don't offer it as a standard feature. It's free, so utilize it for goodness sake!



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