Has anybody home brewed a transistor based VFO to drive the digilite?
I have tried with a BFR106 without success.
Any comments welcome Mike G3TOI
low noise vfo
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This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
Re: low noise vfo
Mike
There's no reason why a good vfo should not work. My article in CQ-TV 245 described the use of a COMTECH module, which is a transistor VFO with a bit too much phase noise (induced by the pll).
What frequency are you trying at?
Dave
G8GKQ
There's no reason why a good vfo should not work. My article in CQ-TV 245 described the use of a COMTECH module, which is a transistor VFO with a bit too much phase noise (induced by the pll).
What frequency are you trying at?
Dave
G8GKQ
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mikenicholas
- Posts: 10
- Joined: Thu Jun 19, 2014 3:26 pm
Re: low noise vfo
Hi
I am using 23 cms 1249 at the moment with an ultram with good results but the aim is to have all home brew
I can get a similar picture on an analyzer of the home brew vfo but with more close in noise and side bands.
This is both with and with out PLL control
The modulator I use is home brew but closely following the digilite, but with individual control on each of the four chanels to the mixer
I also matched each nyquist filter for phase shift
Regards G3TOI
I am using 23 cms 1249 at the moment with an ultram with good results but the aim is to have all home brew
I can get a similar picture on an analyzer of the home brew vfo but with more close in noise and side bands.
This is both with and with out PLL control
The modulator I use is home brew but closely following the digilite, but with individual control on each of the four chanels to the mixer
I also matched each nyquist filter for phase shift
Regards G3TOI
Re: low noise vfo
OK Mike
I found Tutioune very useful for measuring and visualising (on the quadrature constellation plot) the effect of phase noise. Also, an RTL-SDR with SDR-sharp well zoomed in was good enough to see the phase noise difference between the Ultram and COMTECH-based LOs. The screenshots in the article show the difference.
Frequency accuracy did not seem to be too important. Some receivers will accept at least +/- 400 KHz.
Are the levels the same?
73
Dave
I found Tutioune very useful for measuring and visualising (on the quadrature constellation plot) the effect of phase noise. Also, an RTL-SDR with SDR-sharp well zoomed in was good enough to see the phase noise difference between the Ultram and COMTECH-based LOs. The screenshots in the article show the difference.
Frequency accuracy did not seem to be too important. Some receivers will accept at least +/- 400 KHz.
Are the levels the same?
73
Dave
-
mikenicholas
- Posts: 10
- Joined: Thu Jun 19, 2014 3:26 pm
Re: low noise vfo
Hi Dave
I have a better wave form than the comtech as per your article in cqtv
The wave form I get from the Ultram is about the same as you show, so I am begining to think, what else.
I can not get a pic across the shack, however, I have not yet tried to raise the local repeater just in case my local oscillator is swamping the RX in the shack, a porty, that is the next move.
I have again checked the levels and using the ultram as a standard of 11 dbm mine is within the range of the AD 8346 mixer which I am using, in the range of just > 1 dbm
I have now got the analyzer in bits, chasing an intermittent fault
Thanks for info
Mike G3TOI
I have a better wave form than the comtech as per your article in cqtv
The wave form I get from the Ultram is about the same as you show, so I am begining to think, what else.
I can not get a pic across the shack, however, I have not yet tried to raise the local repeater just in case my local oscillator is swamping the RX in the shack, a porty, that is the next move.
I have again checked the levels and using the ultram as a standard of 11 dbm mine is within the range of the AD 8346 mixer which I am using, in the range of just > 1 dbm
I have now got the analyzer in bits, chasing an intermittent fault
Thanks for info
Mike G3TOI