The TCXO used in the 5000A is spec'd at +/-0.5ppm (0.5Hz at 1 MHz)
frequency stability over temperature (0-50C). This is +/- 72Hz at
144MHz. Also, the TCXO can drift +/- 1ppm per year as it ages. The
amount that a crystal drifts as it ages typically slows down as it gets
older, but the manufacturer of this TCXO doesn't provide a spec for
that. So, assuming it is on frequency when new, 2M frequencies could
drift as much as 144Hz/year. Now add in the fact that most rigs used by
2M ops have less frequency stability than the 5000A, only having to tune
+/-100 Hz on 2M isn't bad. I use a rubidium oscillator for an external
10MHz reference. When it is giving a lock indication, the frequency
accuracy is better than 5 ppb (5Hz at 1 GHz). So at 144 Mhz, my
frequency error is less than 0.72 Hz. I still find myself tuning +/-
100-200Hz for most of the local 2M hams.
73,
Clay W7CE
On 1/26/2011 6:52 AM, Kevin Hobbs wrote:
Hi
When listening on 144 MHz . I notice that I need to tune a little low to
make voices readable . ie: I have to listen on 144.199900 or so instead of
144.2.
Anyone else notice this?
73 Kevin
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