On 5/21/2011 11:37 AM, AA8K73 GMail wrote:
As your FMT sickness progresses, you will be concerned about the
accuracy of the 10 MHz reference that you feed into the Flex. At this
time I am satisfied with a Trimble Thunderbolt GPSDO.
There are also some good Rubidium sources available cheaply. At least
1e-9 accuracy without tweaking. There are GPS-disciplined Rubidium
oscillators around, probably the best you can do at the ham level
without having access to a Caesium source. The Thunderbolt is very good,
however.
You will also discover that as you tune PowerSDR, the frequency may be
slightly off the Hertz shown, due to DDS rounding.
Yes, but the DDS algorithm is known (with SR off), so for a given PSDR
indicated frequency in Hz, it is possible to back-calculate what the
true frequency is. I seem to remember someone (Brian?) doing
measurements on this, and it is completely repeatable. I don't recall
the calculation, but it is available.
I want to experiment with a marker signal that I can derive from my
GPSDO, although I try to do the FMT with just the transceiver and the
GSPDO.
You can pickup a PTS160 synthesizer pretty cheaply, and that will give
you markers to 0.1Hz when locked to a good reference (standard option).
For finer spacing, use a simple divide by 10 and get markers up to 16MHz
at 10mHz accuracy.
I've got all the gear to do it; I really must participate in a FMT at
some point. I have however used similar techniques to measure the
frequency of a 1296 beacon to a few tens of milliHerz.
GL & 73, Alf NU8I
Scottsdale AZ DM43an
160m > 24Gigs
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