On 07/24/2010 02:33 PM, Don Collie jnr wrote:
I need a frequency reference for my frequency counters, it needs to be accurate
to at least +or- 1 part in 10,000,000.
!0MHz would be OK, but also 5, or 1. Due to technical "improvements", the
4.43361875 MHz colour subcarrier which is available on the analogue TV system here in New
Zealand, is no longer referenced to a Rubidium standard, and can be about +,- 1Hz in
error. I have a communications receiver, and have been thinking of using this with
Lyssajous
figures on an oscilloscope, with the receiver tuned to WWVH in Hawaii, but a
GPS might be a possability, if there is satellite coverage here in
Invercargill, southern NZ. Bearing in mind I don`t need extreme accuracy, what
is my best option, please?.................................................Don.
For that level of quality, consider getting a cheap rubidium like the
LPRO of Ebay. The prices is fairly humane. Build it into a box with a
power-supply and a heatsink. Adding a fan helps to keep cooling
sufficient at high temperature. If you want to be fancy, you can even
put a servo-loop on the fan. Rubidiums have temperature stabilisations
which wants a fairly high temperature (70 degrees and 130 degrees) but
needs cooling, the higher cooling-plate temperature you allow yourself,
the better the cooling must be, but the less heat is actually cooled off
and thus consumed on the powerlines.
Ah well.
Optionally adding a PPS output with a SYNC input would ease comparision
with a simple GPS. Adding a multi-turn high quality potentiometer for
manual EFC tuning to keep it inline with GPS would suffice for your
needs. You might want some form of voltage reference to give the
reference voltage to the potentiometer. Maybe a REF10 would suffice.
The +/- 1 Hz on the PAL subcarrier is within the standard, so they are
allowed to relax it to that... but it is a pitty they don't lock it up
to propper reference. The only guys doing PAL transmissions here in
Sweden is the radio-amateurs. I would not bet that their carrier and rig
is locked to a atomic reference at all times.
Cheers,
Magnus
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