SDS100/200 Frequency Rounding

[Facsimile]

I'm curious as to why I cannot manually enter a frequency without the scanner automatically rounding? If I enter a site frequency on Sentinel, I can set it to whatever I want. For example, if I have a control frequency of 451.89375, which I do, I cannot enter that manually without rounding even if I set the step to the lowest setting. It has to be entered through Sentinel.

 

[doctordialtone]

I'm curious as to why I cannot manually enter a frequency without the scanner automatically rounding?

This is asked often.

Basically, the answer is it won't matter.

 

[Whiskey3JMC]

Read here. Set the band default for 450.0 to 6.25khz

 

[Facsimile]

This is asked often.

Basically, the answer is it won't matter.

Read here. Set the band default for 450.0 to 6.25khz

Thank you for the links. In conventional scanning, is "automatic" step the only option? In the event I wanted to compensate for drift.

 

[mmckenna]

Thank you for the links. In conventional scanning, is "automatic" step the only option? In the event I wanted to compensate for drift.

There should not be any noticeable frequency drift on modern radio systems. Scanners either.

 

[Facsimile]

There should not be any noticeable frequency drift on modern radio systems. Scanners either.

That's good to know, thank you. Always learning

 

[Ubbe]

Uniden doesn't reveal their scanners frequency accuracy but I took a look at a professional Motorola radio at it said +/-2ppm. That's parts per million and MHz are millions of Hertz. At 1MHz it could be +/-2Hz. At 800MHz that's +/-1,5KHz. A valid frequency error in that mobile radio would be 800,00150 or 799,99850

Any scanner are probably worse than that as it's filters are more wide to allow for more drift of its oscillators, as a scanner are usually not sent in for calibration as professional radios often are after a couple of years of use.
My Uniden BCD536 and Whistler TRX-2 are 1KHz off in their frequencies at 500MHz, at different directions. That's a 2ppm error.

But as mentioned the bandplans step size selected and programmed must match the frequency you would want to enter.

/Ubbe

 

[mmckenna]

Uniden doesn't reveal their scanners frequency accuracy but I took a look at a professional Motorola radio at it said +/-2ppm. That's parts per million and MHz are millions of Hertz. At 1MHz it could be +/-2Hz. At 800MHz that's +/-1,5KHz. A valid frequency error in that mobile radio would be 800,00150 or 799,99850

Any scanner are probably worse than that as it's filters are more wide to allow for more drift of its oscillators, as a scanner are usually not sent in for calibration as professional radios often are after a couple of years of use.
My Uniden BCD536 and Whistler TRX-2 are 1KHz off in their frequencies at 500MHz, at different directions. That's a 2ppm error.

But as mentioned the bandplans step size selected and programmed must match the frequency you would want to enter.

/Ubbe

Right, and when the radios are tuned, it's usually a goal to be less than 300Hz off channel. It's not hard at all to do a less than 10Hz off frequency on a modern quality radio and a little bit extra time. I've got 12 year old Kenwoods that will come down to a couple of Hz.

And when you figure in simulcast systems, they are using GPS disciplined oscillators for frequency reference. Digital systems usually require fairly close tolerances, also.

 

[KevinC]

Uniden doesn't reveal their scanners frequency accuracy but I took a look at a professional Motorola radio at it said +/-2ppm. That's parts per million and MHz are millions of Hertz. At 1MHz it could be +/-2Hz. At 800MHz that's +/-1,5KHz. A valid frequency error in that mobile radio would be 800,00150 or 799,99850

Any scanner are probably worse than that as it's filters are more wide to allow for more drift of its oscillators, as a scanner are usually not sent in for calibration as professional radios often are after a couple of years of use.
My Uniden BCD536 and Whistler TRX-2 are 1KHz off in their frequencies at 500MHz, at different directions. That's a 2ppm error.

But as mentioned the bandplans step size selected and programmed must match the frequency you would want to enter.

/Ubbe

All the APX-series are +/- 1.0 ppm or less (some are .9 or .8).

 

[JoeBearcat]

I'm curious as to why I cannot manually enter a frequency without the scanner automatically rounding? If I enter a site frequency on Sentinel, I can set it to whatever I want. For example, if I have a control frequency of 451.89375, which I do, I cannot enter that manually without rounding even if I set the step to the lowest setting. It has to be entered through Sentinel.

It's not rounding. The last digit is simply masked (not shown).