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jasonomb
Joined: 19 Sep 2009
Posts: 12
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 19 Sep 2009 5:05 transmiter vhf uhf |
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RFMD,RF2514,I want to know how to change the frequency?
The DT said ,It can fine-tuned via internal varactor diodes, but when I change the voltage of Pin10, the frequency didn't change,,,,,who can help me??thanks
Last edited by jasonomb on 22 Sep 2009 9:14; edited 1 time in total |
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Mazz
Joined: 03 Nov 2001
Posts: 592
Helped: 80
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19 Sep 2009 11:05 VHF/UHF TRANSMITTER |
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Pin 10 is not the Varactor access, but the VCO tank.
Pin 12 gives you the access to VCO tuning.
I've noticed you added an inductor on VCO. If you want to run at lower freqs, just be aware that the available divition ratio is the proper one to give you lock condition in the synth.
I hope it can help.
Mazz
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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27 Sep 2009 2:54 Re: VHF/UHF transmitter- how to change the frequency? |
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| I use the pin12, but the frequency also did not change 。。IS my design has any problem??
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27 Sep 2009 2:54 Ads |
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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27 Sep 2009 2:55 VHF/UHF transmitter- how to change the frequency? |
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| Is someone use the Rf2514 before???Help!!!
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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28 Sep 2009 9:20 VHF/UHF transmitter- how to change the frequency? |
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| who can help me????
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biff44
Joined: 24 Dec 2004
Posts: 1835
Helped: 244
Location: New England, USA
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28 Sep 2009 13:50 Re: VHF/UHF transmitter- how to change the frequency? |
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There is no external tuning port on this chip! If you try to inject a DC tuning voltage into pin 12, you will be bucking the internal charge pump circuit, which is internally connected to the varactor diodes. They mislabeled the pin 12, it should not read "charge pump" output, it should read "connection point for loop filter capacitors".
This chip is obviously designed only for phase locked operation, not for manual tuning, so the only way you can change the frequency (slightly) is to pull the frequency of the reference crystal oscillator by using varactors in parallel with the crystal.
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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12 Oct 2009 7:46 VHF/UHF transmitter- how to change the frequency? |
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| NOW,I using the varactor C1 3-10PF , the frequency change too much, how can I change the frequency slightly??
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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14 Oct 2009 3:55 VHF/UHF transmitter- how to change the frequency? |
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| waiting for your answer·············
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BigBoss
Joined: 17 Nov 2001
Posts: 1039
Helped: 63
Location: Earth
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18 Oct 2009 0:03 Re: VHF/UHF transmitter- how to change the frequency? |
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| jasonomb wrote: |
| NOW,I using the varactor C1 3-10PF , the frequency change too much, how can I change the frequency slightly?? |
The only way to change the output frequency is to change the reference frequency.The output will be changed by factor of 32 or 64 depending on programming.
The reference frequency can be changed by slightly by connecting a trimmer capacitor in serial but don't forget, changing in reerence frequency will be resulted 32 or 64 times in the output frequency..so 1kHz changing will be 32 or 64 kHz at the output..
This is not a robust solution...
The best solution is to use another programmable PLL is to provide a variable but stable reference frequency for the main PLL..
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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19 Oct 2009 3:51 VHF/UHF transmitter- how to change the frequency? |
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I understand now, thanks
Added after 1 hours 9 minutes:
If I off the power 3.3V of pin10,pin11,
let the PLL charge pump is disabled,then use 3.2V supply,is that ok?The frequency will change ???
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jasonomb
Joined: 19 Sep 2009
Posts: 12
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20 Oct 2009 9:29 VHF/UHF transmitter- how to change the frequency? |
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Mazz
Joined: 03 Nov 2001
Posts: 592
Helped: 80
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20 Oct 2009 17:07 VHF/UHF transmitter- how to change the frequency? |
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I'm sorry but you request is not really detailed to give an answer, IMHO.
You're saying that you need to change the frequency, but:
what is the freq. you are running now?
what is your target freq?
do you need a lock condition or will you run in free oscillation?
Mazz
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