[AMRadio] speakers


Bernie Doran qedconsultants at embarqmail.com
Fri Mar 19 11:06:45 EDT 2010


Nope. I have seen them on the spectrum, and you only need 15 kc of rx, place 
carrier on one side. I have a R390A being rebuilt and expect it in about 
three weeks, it has a 16 kc filter and a low Z IF output that I will run to 
a separate sync detector/ amp.     I had hopes for the SDR thing I bought, 
but have given up as a usefull receiver. noise floor is way to high, 
probably 20 DB above my 75A4 and the audio from AM still sounds " different" 
. Also a moderatly weak AM station is unreadable compared to my 75A2 and 
75A4.    I did feed a sine wave into the SDR and observed that the lower 
half is shifted, sort of leans and is tighter, the shocker was the 
appearance of ocassional steps in the sine wave, like the first computers 
years ago.  Makes me wonder what it does to a complex waveform ( voice).  by 
no means am I  implying that I can hear 15 KC anymore.   The SDR does make a 
great bandscope and I do not know what I would do without it now, was on a 
few days ago, about 10 AM,   3.700 + or - and was watching four other AM 
QSOs in that area, More AM than ssb!!!! " and I go on and on"   Bernie
----- Original Message ----- 
From: "Jim Tonne" <tonne at comcast.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Friday, March 19, 2010 10:38 AM
Subject: Re: [AMRadio] speakers


>
> Bernie:
>
>> there do appear to be some SW BC that
>> transmit up to about 15 KC.
>
> I seriously doubt that!   International shortwave
> regulations require a flat response to 4500
> Hz and a sharp rolloff above that.  I don't know
> the required degree of attenuation at 5 kc
> but I think 35 dB down is an accepted standard.
>
> 15 kc response would require a 30 kc receiver
> bandwidth - most unlikely.
>
> - JimT   W4ENE
>
>
>
>
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