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VU3NSH VFO

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Re: VU3NSH VFO

Postby IK6AIZ » Wed May 23, 2012 2:49 pm

Thanks again a lot Sarma!
I saw that the turns are 50. Like you told me the filter is to eliminate the 3rd harmonic (of 2 mhz),so if I use it like it is maybe I'll eliminate also the 9.3 Mhz frequency. Please do you think that I could reduce not only the number of the turns for 9 mhz vfo, but also reduce accordilgly the values of the capacitors(actually 470 and 3.9 Kpf), not modifyng the output impedance, that I suppose is 50 ohm?
Again, Thanks very much and my best regards.
73 IK6AIZ Ciro.
IK6AIZ
 
Posts: 23
Joined: Fri Nov 18, 2011 7:27 pm

Re: VU3NSH VFO

Postby IK6AIZ » Thu May 24, 2012 3:23 am

Thanks again gentle Sarma.
You 've understood that I'm not so able with calculations of filters. But I'll surely study to learn more about this matter! For now i'll try to adapt this filter in RM96 for 9.3 mhz. I downloaded the zip file, it's ok, there are the data for this filter. So, since I need to adapt it for 9.3 mhz, I'll try to decrease the number of turns,of course. But, I think I have to decrease also the value of condensers(actually 470 and 3.9Kpf). Should I try with, for example, 38 turns and 390 pf with 3.3Kpf? If I leave the filter with original values I think it would block the frequency of 9.3 Mhz.
Again, thanks a lot, I'll tell you about my observations.
73 IK6AIZ.
IK6AIZ
 
Posts: 23
Joined: Fri Nov 18, 2011 7:27 pm

Re: VU3NSH VFO

Postby mvs sarma » Thu May 24, 2012 10:31 am

dear sir,

It would not block. your fear is unfounded
any filter cant start cutting off just at the indicated frequency. he has indicated 9MHz as one of the frequencies. Instead of fearing, i suggest, make the coil and try

All the best.
If you did not get the output , then we check the situation. i hope the filter with 50T coil on IFT former , would work.
Regards
Sarma
mvs sarma
 
Posts: 636
Joined: Wed Oct 11, 2006 4:57 pm
Location: Hyderabad, India

Re: VU3NSH VFO

Postby IK6AIZ » Thu May 24, 2012 11:41 am

Hi Sarma,
thanks for this last reply. Well, I'll try making the filter that way. I was remembering that you told me that the filter has to eliminate the third harmonic (of 2 mhz),a d so I was fearing what I said. I don't have any spectrum analyzer to do tests comfortably, so I was supposing and asking before trying.
Well said, dear Sarma, I'll make the filter and let you know about results. I hope to realize a 21 mhz rtx by using 12.288 mhz quartzs on the bfo.
Very good things and see you soon.
With gratitude 73 IK6AIZ Ciro.
IK6AIZ
 
Posts: 23
Joined: Fri Nov 18, 2011 7:27 pm

Re: VU3NSH VFO

Postby mvs sarma » Thu May 24, 2012 2:57 pm

you can give a standard termination. then use rf probe and measure the value in Volts.
Regards
Sarma
mvs sarma
 
Posts: 636
Joined: Wed Oct 11, 2006 4:57 pm
Location: Hyderabad, India

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