Thanks Ed.
I don't have a problem understanding how the TCXO's work. Maybe I was
not clear enough. ;-) Taking your example from below, having only the
TCXO-1 it is surely *not* drifting 140 Hz at 28 MHz within the 4 or 5
seconds of the EXREF update cycle (same as the TCXO-3 will not drift by
28 Hz in that time), otherwise the K3 would be a *very* crappy radio.
;-) Think you are missing the time domain here. ;-)
So my question still stands: What's the real value of the TCXO-3 over
the TCXO-1 when using the K3EXREF? Unfortunately I do neither have the
measuring equipment to measure below 1 Hz drift (and I'm not seeing that
amount with my TCXO-1 only K3) nor a TCXO-3. So will the radio drift by
0.0014 Hz with the TCXO-1 + K3EXREF within those 4 seconds and the
TCXO-3 will bring it down to 0.00028 Hz? Then I'm probably fine with the
TCXO-1 and even the most sophisticated digital modes available. ;-)
73, Olli - DH8BQA
Contest, DX & radio projects: http://www.dh8bqa.de
Am 13.03.2016 um 04:23 schrieb Edward R Cole:
Olli,
Referring to page 8 in the K3 Owner's Manual (may be a different page
for the K3s):
"Frequency Stability +/- 5 ppm for the TCXO standard; +/- 1ppm for
the optional TCXO."
TCXO-1 and TCXO-3 respectively mentioned above.
ppm means one part per million (1Hz per million Hz which is 1Hz per MHz).
So frequency drift is proportional to the operating frequency.
1ppm at 10-MHz is 10-Hz;1ppm at 28-MHz is 28-Hz
TCXO-1 provides 5ppm (+/- 50 Hz at 10-MHz and +/- 140 Hz at 28-MHz)
TCXO-3 provides 1ppm (+/- 10 Hz at 10-MHz and +/- 28 Hz at 28-MHz)
the basic frequency stability is determined by which TCXO is installed
in your K3.
EXREF "essentially" checks frequency drift of whichever TCXO you have
installed at a fixed time interval of about 4-seconds. It uses a high
stability 10-MHz external signal to compare with the 49.380-MHz TCXO
and corrects the drift that occurs over the 4-second interval.
My measurements of the TCXO-3 show about half the published spec of
1ppm (14 Hz at 28-MHz) and the EXREF limits the drift of the TCXO-3 to
about 2 Hz. If I had the TCXO-1 installed, I would expect five times
as much drift.
So which TCXO you install directly impacts frequency stability. The
EXREF reduces that by about an order of five. The EXREF is not the
source of stable LO but merely improves what you have installed. Does
that clear it up?
73, Ed - KL7UW
The question to ask is what amount of frequency stability and accuracy
is important for your type of operations.
Date: Sat, 12 Mar 2016 08:17:32 +0100
From: Oliver Dr?se <dro...@necg.de>
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] 10 MHz external reference - GPSDO
Message-ID: <56e3c28c.90...@necg.de>
Content-Type: text/plain; charset=windows-1252; format=flowed
Why would I need the TCXO-3 instead of the TCXO-1 when using the K3EXREF
if the accuracy and stability is provided by the EXREF? Am I overlooking
something here?
Tnx & 73, Olli - DH8BQA
Contest, DX & radio projects: http://www.dh8bqa.de
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com
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