[hpsdr] Analog Devices note on protecting AD

[Terry Fox]

The other thing is that the Flex 6700 & 6500 have twice the sampling rate as 
HPSDR hardware (IIRC).  The additional gain from the added decimation 
(assuming apples-to-apples ending rates) might account for a little better 
performance.
73, Terry, N4TLF (formally WB4JFI)


-----Original Message----- 
From: Helmut
Sent: Thursday, May 21, 2015 2:09 PM
To: lstoskopf at cox.net ; hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Analog Devices note on protecting AD

***** High Performance Software Defined Radio Discussion List *****

Don't worry. The 16 Bit LTC is even slightly better than the 16 Bit AD and 
shows a bit higher SFDR. You have to compare the ENOB (effective number of 
bits).
I believe ADC protection of the HPSDR board is quite sufficient. BTW there 
was a nice article in MWRF titled 'Limiters Protect ADCs without Adding 
Harmonics'.

73, DC6NY

-----Ursprüngliche Nachricht-----
Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von 
lstoskopf at cox.net
Gesendet: Donnerstag, 21. Mai 2015 18:55
An: hpsdr at lists.openhpsdr.org
Betreff: [hpsdr] Analog Devices note on protecting AD

***** High Performance Software Defined Radio Discussion List *****

analog dialog Volume 49 – April 2015

Had a great time at Hamvention and enjoyed visiting at the booth and the 
banquet.  Just wish that Scotty had handed me my new board for the HF2 and 
RF1!

Had an interesting discussion with a proud Flex owner on how much superior 
their 16 bit AD chip with front end amplifier feedback is compared to the 
one we are using.  Having popped the AD in my QS1R from a few miles away 
lightning strike I see at least that value in having a cheaper device with 
some protection in front.  So I added one of the Clifton Labs exterior amps 
thinking that that would add protection.  Popped another AD.  Guessing that 
the spec sheet indicates a small diode drop PLUS VCC safety margin.  Had the 
preamp on and not the QS1R so the preamp possibly hit the AD with full VCC 
output.  Now I turn on the RX before the preamp.

Anyway, the above article is of interest.  As for the superiority of the 
Flex Analog device to ours????? Are 16 bits 16 bits?

Last year at the RSGB convention I had a short chat with Peter Chadwick 
about his old article on the topic of "are our receivers good enough?"  I 
have a complete HB transceiver built with the Plessey 1600 series devices 
and great crystal filters using devices for which he was an application 
engineer.  It hasn't been on the air for 30 years.  I need to drag it out 
and see how it still stacks up.

N0UU
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