[OZAPRS] Brisbane APRS

[Glen English VK1XX]

hmm

how much sag is that  in kHz, or even better Hz/sec ?


On 29/10/2017 6:35 PM, vk4tec at tech-software.net wrote:
> http://59.167.159.165/aprs.jpg
>
> -----Original Message-----
> From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of Glen English VK1XX
> Sent: Sunday, 29 October 2017 5:00 PM
> To: ozaprs at aprs.net.au
> Subject: Re: [OZAPRS] Brisbane APRS
>
> Andrew, there are a few checkpoints to this
>
> 1) I gather you know precisely what frequency error your spectrum analyser has.
>
> 2) I gather your spectrum analyser , if FFT / digital  type, has sufficient resolution bandwidth to tell a non aliased story.
>
> 3) It is not usual for station's TX  PLL /synthesisers to not be fully settled during the keyup phase, and take 30- 100mS to establish fine frequency lock .
>
> 4) I would expect +/- 5ppm for most radios, that being about +/- (5 x
> 145.175 Hz)
>
> 5) It's probably not going to hurt much until +/- 1kHz, and not really hurt until +/- 2kHz, depending on the TX deviation. (IE how far outside the Receiver IF filter the modulation protrudes, as the received signal will be asymmetrical in the receiver's IF passband, the higher the deviation, the greater the extremes)
>
> How far out are they ?
>
> -glen
>
>
> On 29/10/2017 5:51 PM, vk4tec at tech-software.net wrote:
>> Hello
>>
>>  
>>
>> I just had a quick look on 145.175 MHz on a spectrum analyser.
>>
>>  
>>
>> I can see stations off frequency
>>
>>  
>>
>> I can see transmitters shifting frequency on keyup
>>
>>  
>>
>> Andrew
>>
>>
>>
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