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**I7SWX** · 19-05-09, 09:07

Re: Super PERSEUS operante sui 144MHz come IF per i 10GHz

Carissimi amici,
Ho contattato Jeffrey Pawlan, WA6KBL, per trovare la possibilita� di scaricare il file relativo alla sperimentazione che ha effettuato con il Perseus quale IF a 144MHz per le operazioni SHF a 10GHz.
Il file e� presente presso la pagina web del suo club locale, www.50mhzandup.org
Mi ha anche aggiunto anche le seguenti interessanti informazioni sulle misure e sull�applicazione � facendo presente la possibilita�, con il suo set-up, di �vedere� il rumore della luna a 10GHz � io posso solo sentire quello delle HF � hi
Certamente e� un set-up per chi opera sulle SHF ma la lettura (mi dispiace e� in inglese) fa bene a molti ed e� un aspetto di �imparamento� di cose nuove.
73
Gian
I7SWX

Dear Gian,

I thank you for your emails and your efforts.

Here is the simple way to allow people access to the PDF:
I placed the article on my local group's website www.50mhzandup.org
so people can download it from there. It is in PDF but requires Reader v7 or later. My wife and I made that website ourselves.

You may also distribute the following additional clarification:

A few people not familiar with all digital receiver measurements questioned the dynamic range of 80dB which I reported in the article.
So here is a clarification:

IP3 is not really applicable to A/D converters as the 3rd order intermodulation products do not increase at all from nearly no signal to complete full scale input. So there is no 1dB compression and there is not a real predicted imaginary intersection of the real signal with the 3rd order spur unless you do that right at the full scale of the A/D converter.

The dynamic range in the article was the difference between the measurement of the noise floor and the level of the first spur that appeared. This is SFDR. If you ignore the spur then the receiver has a usable dynamic range more than 20dB greater than this. As written, that first spur was a 4th order product.

Have you measured the SFDR of your EME LNA? I think you will find that the LNA is your limiting factor for that measurement. Remember that the SFDR is not the 1dB compression range. Most low noise HEMTs are run at such low voltage and current that they produce many spurs at moderate signal levels.

The MDS level of -140dBm at 10GHz is impressive. I think this would be quite sufficient to see the moon noise at 10GHz with a reasonable antenna. That number could be even lower if you were using this IF receiver with your 1296 downconverter and a good LNA at the feed. The MDS is a
function of the system noise figure and is determined by the those components in the system at the antenna and immediately following it. It is not really affected by the IF. Just use the cascaded system formula for NF + gain. The IF is many stages behind the antenna. For an EME system, don't forget to take into account the cable, connector, and relay loss ahead of the LNA. Then take into account the cable loss between the LNA and the downconverter.

73,

Jeffrey Pawlan WA6KBL

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Super PERSEUS operante sui 144MHz come IF per i 10GHz

Super PERSEUS operante sui 144MHz come IF per i 10GHz

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