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From: =?iso-8859-1?Q?Jos=E9_Manuel?= <jpradoes@telefonica.net>
To: rsgb_lf_group@blacksheep.org
References: <404DB140.4040408@usa.net>
Date: Wed, 10 Mar 2004 11:10:42 +0100
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Subject: LF: Re: Ionospheric doppler ?
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Hi Alberto ad all:

When you install the GPS I think that you´ll probably find short-term
variations in the same order, + - 100 nsec.

73 de José, EA1PX


----- Original Message -----
From: "Alberto di Bene" <dibene@usa.net>
To: "LF Mailing List" <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, March 09, 2004 12:57 PM
Subject: LF: Ionospheric doppler ?


> Hello Group,
>
>   I made yesterday an interesting experiment and would like to know your
> opinions about it.
> Waiting for the weather to become such to allow me to go on my roof
> to install there a GPS antenna, in the meantime I started to play with an
> inexpensive radio-controlled clock, made by Conrad, bought a few years
> ago at the Friedrichshafen Messe in Germany, which receives the DCF-77
> signal.
> This clock has an output meant to drive an external electro-mechanical
> hand clock, and on this output there is, of course, an 1pps pulse.
>
> I have an HP-5328B Counter, with a 10811 OCXO which is always (24/7) on.
> My shack is in the basement, with a constant temperature of 21 Celsius,
> no drafts,
> so any variations in the measured frequency or time is real, and not an
> artifact
> of the counter.
> The 5328 has a sort of reciprocal counting feature, where you can use an
> external signal as a gate for an internal 100 MHz oscillator, phase
> locked to
> the OCXO. In addition you can prescale the external signal.
>
> So what I did was to prescale by ten the 1pps signal from the clock,
> then used
> this 10 second interval to count the internal 100 MHz oscillator, giving
> a resolution
> of 1 ns.  If everything were perfect, I should have obtained a count of
> exactly 10^9.
>
> What I measured was a value that differed from the ideal by an amount
slowly
> changing with time, ranging from -80 ns to + 120 ns. The count was very
> consistent from period to period, showing no short term random jitter.
> In one case I measured a variation of about 100 ns in a time lapse of
> roughly
> one hour.
>
> I am by no means an expert in propagations and ionospheric effects, so
> my question
> is : are the values I measured compatible with what is known about
> ionospheric doppler ?
> If not, what else could be an explanation of that slow change ? I would
> tend to exclude,
> for the reasons reported above, an artifact of the HP counter.
>
> Thanks for any explanations
>
> 73  Alberto  I2PHD
>
>
>
>
>