Re: Composite TX noise


Paul NN4F
 

I’m sure Franco will comment on this once he returns from Dayton

--
Paul Jones - NN4F
EladUSA Sales/Support

On May 18, 2019, at 17:20, Clint Chron <kiheiman@q.com> wrote:

Hi Conrad,

Sorry, I am still confused. What level of phase noise are you expecting to see for the Duo? What kind of performance impact are you seeing on the operation of the Duo, if the TX phase noise is higher than what you expect?

The QST product review for the Duo showed a TX composite phase noise of -135 dBC/Hz with a 10 Khz offset on 20M. I measured -131 dBc/Hz on the Duo's RF Out jack - which would be TX phase noise. On page 96 of the Duo user manual, Elad shows a Master Clock phase noise spec of -130 dBc/Hz at a 10 Khz offset.

From Rob's Web site, for the receiver local oscillator noise test (with 10 Khz offset), I see:

K3S -144 dBc/Hz
K3 -138 dBc/Hz (-140 dBC/Hz in QST Product Review)
Flex 6400 -145 dBc/Hz (-150 dBc/Hz in QST Product Review for 6300)
IC-7300 -137 dBc/Hz (-130 dBc/Hz in QST Product Review)

I would put the Duo in the same class of radio as the IC-7300.

I am not aware of anyone else being able to use the referenced R&S test instrument to measure phase noise (not sure what the ARRL test lab uses), but using notch filters and high performance spectrum analyzers is a pretty standard setup for these kinds of tests. Can you run the notch filter/spectrum analyzer test and see if you get the same results as what the R&S instrument is showing?

73
Clint
W7KEC





-----Original Message-----
From: EladSDR@groups.io [mailto:EladSDR@groups.io] On Behalf Of Conrad, PA5Y
Sent: Saturday, May 18, 2019 7:53 AM
To: EladSDR@groups.io
Subject: Re: [EladSDR] Composite TX noise

The ARRL measurements are wrong or I do indeed have a duff radio. From talking to a few others (who do not want to put their head above the parapet) we all seem to have similarly duff radios. At 28 MHz I see -116.8 dBc/Hz, 14 MHz could be 6dB better, not 18.2dB better.

20 log10 (N) dB = 20 log10 (28/14) dB = -6.02dB so -122dBc/Hz would be expected.

So going from 28 to 50 should be 5dB worse or so. At 50 MHz I measure -112 dBc/Hz @ 10kHz which is pretty close to 5dB worse than -116.8 dBc.

I think that we have to consider the TX and RX path quite differently. For a start there is more clock multiplication in the TX path. The fact is that these measurements are correct for my radio. Also -135dBc/Hz at =10kHz just about adequate but not very low. Trust me I did not want to believe what I measured with a calibrated $160k instrument but the measurements are real. I would be MOST happy for someone with a Perseus and an FDM-DUO to publish their measurements. I measured a lot of other radios as well. You can take these measurements as fact for my DUO.

So if you have a Perseus and an FDM DUO you can measure your TX composite noise, this will be close to PN only results because there is hardly any AM contribution and the composite and PN are effectively the same.

This is why I was reluctant to publish these results, the ELAD sycophants will treat me like a pariah. The measurements are correct, don't shoot the messenger, instead lets try and improve this performance.

Is there a schematic anywhere?

73

Conrad PA5Y

-----Original Message-----
From: EladSDR@groups.io <EladSDR@groups.io> On Behalf Of Clint Chron via Groups.Io
Sent: 18 May 2019 16:00
To: EladSDR@groups.io
Subject: Re: [EladSDR] Composite TX noise

The Elad Duo QST Product Review from May 2016 shows a very low TX composite phase noise - about -135 dBc/hz on 20M with a 10 Khz offset. Some of the QST performance measurement processes are controversial, but the process for measuring TX phase noise is pretty straightforward.

If the Duo has too much oscillator phase noise, then that would degrade other receiver overload measurements. I do not see that happening. The NPR results for the Duo is in the 70 db area - that matches other high performance receivers such as the K3S, Flex 6000 series, etc.

73
Clint
W7KEC

-----Original Message-----
From: EladSDR@groups.io [mailto:EladSDR@groups.io] On Behalf Of Conrad, PA5Y
Sent: Saturday, May 18, 2019 6:44 AM
To: EladSDR@groups.io
Subject: Re: [EladSDR] Composite TX noise

Hello Chris, I can do that. I have an extremely low PN 5.461333 MHz oscillator that uses a very high spec SC cut crystal and a Wenzel 10 MHz OCXO either of which could be used. Rob Sherwood did measure the RM with a Wenzel oscillator and I think that it was quite good. He's at Dayton so I will wait until he gets back to ask him.

The receive sounds subjectively quite clean to me.

I will try to measure the RM this weekend.

Regards

Conrad

-----Original Message-----
From: EladSDR@groups.io <EladSDR@groups.io> On Behalf Of Chris Bartram via Groups.Io
Sent: 18 May 2019 15:26
To: EladSDR@groups.io
Subject: Re: [EladSDR] Composite TX noise

Hello Conrad,

Those graphs certainly do display a cause for concern. I certainly don't doubt their veracity. It could be quite informative to make some measurements of the receiver reciprocal mixing performance using a low-noise crystal oscillator.

73

Chris

G4DGU


















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