5-10 watt Ultra LOW Noise Needed - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th November 2012, 06:32 PM   #11
dmills is online now dmills  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: High Wycombe
10db SNR is actually quite typical for trying to pull a weak DX station from half way around the planet out of the noise (And sometimes you have less margin then that), and that noise is not from the audio stages, so better ones will not improve things.

There will in fact be a line out available, probably intended for interfacing a computer for data modes, but it will be there.

73, Dan M0HCN.
  Reply With Quote
Old 24th November 2012, 06:38 PM   #12
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
Quote:
Originally Posted by dmills View Post
10db SNR is actually quite typical for trying to pull a weak DX station from half way around the planet out of the noise (And sometimes you have less margin then that), and that noise is not from the audio stages, so better ones will not improve things.

There will in fact be a line out available, probably intended for interfacing a computer for data modes, but it will be there.

73, Dan M0HCN.
I wasnt making comment on the quality of that reception, just that that is the expected outcome and no amplifier will fix that. the amp in a modern kitchen radio probably has several hundred times that SNR... (doubling every 3db)

as for the lineout, maybe, I dont know enough about this sort of thing, but it makes no mention of it in the datasheet and its pretty unlikely hes using it, but with everything else mentioned, wont provide any benefit.

basically dont expect good audio quality and nothing you can do to the unit to help with that.
  Reply With Quote
Old 24th November 2012, 07:08 PM   #13
dmills is online now dmills  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: High Wycombe
A better aerial system will help with that, but yea, hifi reproduction is not the objective in communications audio.

The audio stage will have a native SNR that is entirely in keeping with the sort of numbers typical of a cheap audio amp chip (And will in fact not be a million miles from the sand used in a kitchen radio), its just that the output of the demodulator is full of noise inherent to the communications channel in use, and NO audio amp can fix that.

73, Dan.
  Reply With Quote
Old 24th November 2012, 07:14 PM   #14
diyAudio Member
 
Join Date: Mar 2007
Location: Canandaigua, NY USA
IMO, U R mostly a bunch of pessimists! It might not help to have a better amp, but why not better filters, both in the radio and in some audio processing applied to the signal? We have all manner of analog filters, digital filters and software filters available to DIY. Noise can never be eliminated, but it can certainly be beaten down into the swamp for a while.
__________________
I may be barking up the wrong tree, but at least I'm barking!
  Reply With Quote
Old 24th November 2012, 07:22 PM   #15
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
to improve the 10dB SNR?

the noise will be of a constantly varying type, with plenty of it effecting the audio band, thus some difficulty in filtering, or I expect they might have tried that...

not a pessimist, a realist

Last edited by qusp; 24th November 2012 at 07:25 PM.
  Reply With Quote
Old 24th November 2012, 08:27 PM   #16
dmills is online now dmills  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: High Wycombe
A modern rig like that will have built in DSP doing all the usual stuff anyway (And there is actually plenty that can be done).

Note that that 10dB figure is really telling you what the SNR is at rated sensitivity, if the signal from the aerial is well above the rated sensitivity level then the SNR will improve in direct proprtion, the SNR with 50 or 100uV from the aerial at the frequency of interest might well be 40dB or so up on the figure with 1uV up it.

What does often help is a better loudspeaker (the built in ones are generally poor).

73 Dan.
  Reply With Quote
Old 24th November 2012, 08:49 PM   #17
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
ooooh 50dB? i'll go get my Stax =)

I figured the ratings may be something like that, thanks for the clarification, it may come in handy one day...

arent they doing this kind of gear digitally now? surely they could do better with sending code and error correction than sending noise and filtering with DSP?
  Reply With Quote
Old 24th November 2012, 09:28 PM   #18
dmills is online now dmills  United Kingdom
diyAudio Member
 
Join Date: Aug 2008
Location: High Wycombe
There are digital modes, but you usually find that for data rates compatable with speech codecs you need more SNR at the recever to get an acceptable BER then you do for just carrying 2.7Khz SSB analog audio.

Point is that SNR is set mostly by the ratio of the wanted signal to the noise at the aerial, essentially all modern rigs are more then quiet enougth that on HF they are not the limiting factor (This changes at VHF,UHF and microwave, but on HF the solar and galactic noise (Not to say the man made contribution) dominates what can be done.

Even DSP filtering is not always that useful, some simple filters, an osillator and a mixer driving a simple amp and pair of headphones will let you hear australian stations when the band conditions are right, and replying to them does not take much more....

Regards, Dan.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
ultra-low noise transistors. PCP Solid State 71 8th June 2014 06:03 AM
ultra low noise low distortion preamplifier needed neazoi Solid State 13 11th October 2011 01:03 PM
12au7 who has the best ultra low noise ??? prorms Tubes / Valves 3 23rd August 2008 12:40 AM
Ultra low noise VGA attenuator jackinnj Solid State 4 4th December 2003 06:24 AM
Ultra low noise filters tiroth Solid State 14 21st May 2002 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 08:31 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2