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I'm trying to listen in to the telemetry frequency for Wallops Island which is 411.325 MHz.

When I punch this into my radio (Baofeng UV-5R), the closest I can get is 411.320 MHz.

Will I still be able to pick this up?

I read I may have to adjust the squelch.

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    $\begingroup$ Depends on the bandwidth of the signal. But, being 5 KHz away it would need to be a wide signal like WFM. I have no idea if that signal is WFM or not but I guess it could be (but, likely not). $\endgroup$ – K7PEH Jan 2 '20 at 2:57
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    $\begingroup$ Thank you for your response. I just discovered that the analog frequency list is from 2017. As of late 2019 Wallops Island switched to the P25 digital system. I guess I can still tune in to the ISS. $\endgroup$ – Jeff Jan 2 '20 at 3:51
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    $\begingroup$ mhz is not a unit; the small m is for milli, that is 1/1000. You mean MHz, with a capital m for "Mega", which is 1,000,000; please don't mix these up. Also, hertz is abbreviated Hz. $\endgroup$ – Marcus Müller Jan 2 '20 at 11:30
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You might want to look in the manual of your radio. A lot of radios can be set up to tune in 6.25kHz steps, allowing you to tune to frequencies which are in between the frequencies you can tune to with the default 5kHz steps.

I don't have the same model radio so I can't verify this would allow you to tune to the frequency you want exactly, but it might be useful to know (and not limited to this radio but a lot of handhelds).

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Jefferey, this is a very easy question to answer, and the answer is no.

The Wallops Island telemetry transmitter is probably going to be a narrow band FM signal, and 5 kHz off is too far to be able to hear it on your Bofeng receiver which is also a narrow band receiver. You would normally need to be within 1 - 3 kHz of the frequency to hear it properly.

Also the squelch control has nothing to do with the frequency, but you would turn the squelch off when testing if you can receive a signal and then only turn it on to get rid of the FM hiss between stations once you have steady reception.

Even if the transmitter is AM or some other mode, 5 kHZ would generally still be too far off frequency to hear properly.

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That's a frequency error of about 10 parts per million. That is very much in the order of frequency uncertainty of your handheld's oscillator, anyway!


As different oscillators not being exactly the same is a problem for every radio communication, every communication standard is built in a way that allows for a receiver to deal with small frequency errors.

"Small", here, depends very much on the specific mode. A wideband FM speech signal can be dozens of kilohertz off, considering that what is most important is the derivative of the carrier's frequency over time.

If you're having an satellite phone: These satellites tend to fly around this blue marble at a rather high speed. High speed means high Doppler shift, and your phone would need to deal with that, anyway.

Think about the about 2€ worth of wifi chipset in a cheap wifi lightswitch: That thing has, with good luck, a 20 ppm-accurate oscillator. That means that the nominal 2.45 GHz frequency it wants to use is off by +- 49 kHz to begin with.

Think of any old AM radio, especially in the pre-PLL era: Do you think you'd be instantly able to set the frequency of the device exactly within, say, 20 kHz bounds, using a greasy knob pulling a rubber string connected to a dusty air+grime-core capacitor? You can do that, but because you are a great feedback loop, and can simultaneuously listen for the sound you're expecting and watch for the position of the needle on the frequency scale! (you're a closed-loop system compensating the inaccuracy of the knob frequency-setting mechanism)

No, all these devices rely on at least some tolerance in tuning, and on the ability to correct a detected frequency error.

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  • $\begingroup$ "Do you think you'd be able to set the frequency of the device exactly within, say, 20 kHz bounds" Yes. 20 kHz is an error of 20000 ppm. An old AM receiver doesn't have any kind of frequency estimation or correction. $\endgroup$ – Phil Frost - W8II Jan 2 '20 at 18:11
  • $\begingroup$ @PhilFrost-W8II you can, but that's because you are a "human-in-the-loop" control mechanism. (note, not talking about a good receiver, I was referring to an old AM "kitchen radio") You'd turn the knob until you hear the music come on. $\endgroup$ – Marcus Müller Jan 2 '20 at 19:54
  • $\begingroup$ Well yes, but your question certainly does read like that's what you're asking. $\endgroup$ – Phil Frost - W8II Jan 2 '20 at 21:15
  • $\begingroup$ @PhilFrost-W8II very fair point. Better with my edit? $\endgroup$ – Marcus Müller Jan 2 '20 at 21:27
  • $\begingroup$ yes, much better 👍 $\endgroup$ – Phil Frost - W8II Jan 3 '20 at 0:04

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