-----Original Message-----
>From: WB6BNQ <wb6...@cox.net>
>Sent: May 23, 2011 2:17 PM
>To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
>Subject: Re: [time-nuts] smallest rubidium
>
>David,
>
>You should have said so in the first place. Unless you are sure that the
>reference
>oscillator is the base for all the generated frequencies, it would not make
>sense to
>install a Rb source in the radio. You are correct concerning most of the
>"so-called" higher stability options in that they are barely worth the price
>asked
>for them and only meet specs in a tightly controlled environment.
>
For a lot of HF radios, the TCXO performance required is such that the actual
frequency be within 20 Hz of the displayed frequency (that's the NTIA
standard). 20Hz comes from empirical tests of how close the frequency needs to
be to not require a "clarifier" for intelligible speech on SSB. (probably
moderated, too, by what's easy and practical to do in a portable transceiver)
(http://www.ntia.doc.gov/osmhome/redbook/ed200801rev201009/M_9_10.pdf)
bear in mind that that there's two radios in this whole stackup, because the
transmitter has comparable frequency accuracy as the receiver. So the overall
frequency uncertainty is on the order of 30 Hz (sqrt(2)*20 Hz).
Hitting a 0.5 ppm accuracy (15Hz out of 30 MHz) is a fairly challenging spec to
meet over a wide temperature range.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
