How accurate does tuning have to be on FM?

[KF5YDR]

I'm thinking about getting an MT500 or an HT220 and crystaling it for one of the wide-area repeaters in Houston as a battery-miser backup/emergency rig. Only draws 11 mA squelched!
Channel elements were available in 10PPM and 5PPM accuracy. 10PPM equates to ±1.4 kHz on 2m.

Is that close enough to work with 5 kHz deviation, or do I need to hunt down a 5PPM channel element? I don't have any concept of how accurate a modern synthesized HT is; I may be worrying about nothing.

 

[mikewazowski]

You should be able to put the radio on the correct frequency when you tune it after installing the crystal.

 

[KF5YDR]

For sure. I'm more concerned with drift (which is what the PPM spec deals with) once the radio is aligned and tuned.

 

[ko6jw_2]

I was just looking at the manual for my FT-817ND and its accuracy is plus or minus 4ppm or plus or minus 0.5ppm with a temperature controlled oscillator. The TCXO is really necessary for HF digital modes not for FM. The frequency accuracy is less critical for FM. After you install the crystal you can adjust the oscillator using a frequency counter to put the radio in the center of the channel. That should be sufficient.

 

[KF5YDR]

If the 817 is only 1PPM more accurate than the best Moto could do in the 70s, I'm not gonna worry about it.

Thanks y'all!

 

[zz0468]

10 ppm is perfectly fine.