Checking correct nyquist filter values for 70cm...?
Checking correct nyquist filter values for 70cm...?
Hi All
I know I need to make changes for 70cm to the Nyquist filter values
and change L1,2,3,4 and C13/14/15/16/17/18. I have all ready
changed to a AD8345 for but need to check I am puting the components
in the right order before I solder them....!
I this order correct...! L1 and L3=33uh C13 and C16=1.2nF
L2 and L4=27uH C15 and C18=3.9uF and should I leave
or do I need to change C14 and C17 currently both 1.2nF..?
Any help or advice greatly received.Finally a Digital Tx I can
just about afford and a great project keep up the good work.
73 Paul
M0PDA Suffolk
I know I need to make changes for 70cm to the Nyquist filter values
and change L1,2,3,4 and C13/14/15/16/17/18. I have all ready
changed to a AD8345 for but need to check I am puting the components
in the right order before I solder them....!
I this order correct...! L1 and L3=33uh C13 and C16=1.2nF
L2 and L4=27uH C15 and C18=3.9uF and should I leave
or do I need to change C14 and C17 currently both 1.2nF..?
Any help or advice greatly received.Finally a Digital Tx I can
just about afford and a great project keep up the good work.
73 Paul
M0PDA Suffolk
Re: Checking correct nyquist filter values for 70cm...?
Hi Paul,
the values we were using with the" poor mans DATV" were designed for 1Ms but worked ok at 2Ms. However, Rob, M0DTS, has come up with some better values for use with the DigiLite on 70cm. The values go from left to right on the serialiser o/p towards the modulator ( hope that makes sense,lol? Here's a copy of his posting, hope it helps.
73
Malc
Re: Nyquist filter coils L1,L3,L2,L4
Postby M0DTS » Sat Nov 26, 2011 9:36 pm
We may have an issue with values being used for 2Ms on 70cm configuration...
If i remember correctly:
2Ms we should be using 560pf/12uH/2n2/15uH/560pf
1Ms it should be 1n2/27uH/3n9/33uH/1n2
Rob
M0DTS
the values we were using with the" poor mans DATV" were designed for 1Ms but worked ok at 2Ms. However, Rob, M0DTS, has come up with some better values for use with the DigiLite on 70cm. The values go from left to right on the serialiser o/p towards the modulator ( hope that makes sense,lol? Here's a copy of his posting, hope it helps.
73
Malc
Re: Nyquist filter coils L1,L3,L2,L4
Postby M0DTS » Sat Nov 26, 2011 9:36 pm
We may have an issue with values being used for 2Ms on 70cm configuration...
If i remember correctly:
2Ms we should be using 560pf/12uH/2n2/15uH/560pf
1Ms it should be 1n2/27uH/3n9/33uH/1n2
Rob
M0DTS
Still Checking my Nyquist filter values for 70cm...?
Hi Malc
Thanks for your reply.I think I understand your
comment about looking at it from left to right from
the "serialiser o/p towards the modulator" whilst
looking at the Digilite circuit diagram...?
If I have understood you correctly for 1Ms I need
C13=1n2 L1=27uH C14=3n9 L2=33uH C15=1n2
and then repeat this for the remaining for L3 & L4
C16=1n2 L3=27uH C17=3n9 L4=33uH C18=1n2
I don't have the values for 2Ms without ordering
yet more components so will have to give the
above values a try and see how it goes. Still waiting
for back order inductors from Farnell so may be the
new year before it's finshed.
73 Paul
Thanks for your reply.I think I understand your
comment about looking at it from left to right from
the "serialiser o/p towards the modulator" whilst
looking at the Digilite circuit diagram...?
If I have understood you correctly for 1Ms I need
C13=1n2 L1=27uH C14=3n9 L2=33uH C15=1n2
and then repeat this for the remaining for L3 & L4
C16=1n2 L3=27uH C17=3n9 L4=33uH C18=1n2
I don't have the values for 2Ms without ordering
yet more components so will have to give the
above values a try and see how it goes. Still waiting
for back order inductors from Farnell so may be the
new year before it's finshed.
73 Paul
Re: Checking correct nyquist filter values for 70cm...?
Hi Paul,
yes that's the way it works. If you are using the v5.7 PCB Dave has some pads for SMD inductors which are available from Farnell. You will have to remove the solder mask but I have used SMD inductors in some of my modulators and although the 'Q' is not as good they do work.
Good luck with the build.
73
Malc
yes that's the way it works. If you are using the v5.7 PCB Dave has some pads for SMD inductors which are available from Farnell. You will have to remove the solder mask but I have used SMD inductors in some of my modulators and although the 'Q' is not as good they do work.
Good luck with the build.
73
Malc
Re: Checking correct nyquist filter values for 70cm...?
If you have the components for the 4MS filter then you can just double up each inductor and capacitor to give the same impedance at 2MS. Inductors in series and capacitors in parallel.
Brian
Brian
Re: Checking correct nyquist filter values for 70cm...?
Hi
Can anyone supply me with wire ended inductors values 12uh and 15uh two of each
for my 70cms nyquist filter.
I could put two 5.6 and two 6.8 in series but if I could get the correct ones the board would
look better
I have a quantity of 5.6uh and 6.8uh which I could exchange and will cover all postage costs.
73's Mike G1LWX
Can anyone supply me with wire ended inductors values 12uh and 15uh two of each
for my 70cms nyquist filter.
I could put two 5.6 and two 6.8 in series but if I could get the correct ones the board would
look better
I have a quantity of 5.6uh and 6.8uh which I could exchange and will cover all postage costs.
73's Mike G1LWX
Re: Checking correct nyquist filter values for 70cm...?
I have a couple left over here Mike, send me your delivery address & I'll drop them in the post, I dont need any of yours as I have too many of the other ones as it is. Tony
Re: Checking correct nyquist filter values for 70cm...?
I'm also looking for the components that are different between the 23cm version and the 70cm one.
I ordered a second print to start building a 70cm version.
But i don't have the items for the filter.
Can someone supply them to me?
i can play with paypal.
please PM me:
on4bhm (at) telenet.be
thanks
I ordered a second print to start building a 70cm version.
But i don't have the items for the filter.
Can someone supply them to me?
i can play with paypal.
please PM me:
on4bhm (at) telenet.be
thanks
Re: Checking correct nyquist filter values for 70cm...?
I have managed to construct a version of the Digilite for use on the 70cm band. I'm using the same serialiser and the same basic modulator circuit. Although some people have managed to get the modulator to work on 70cm using the AD8346 chip, it is not really intended to run at that frequency. I have therefore replaced the AD8346 with an AD8345 which is identical physically but is intended to run at lower frequencies. The Nyquist filter also needs to be modified to allow the transmitter to operate at 2Ms/s and keep the required bandwidth down. For 1Ms/s use Nyquist filter values 1.2nF/33uH/3.9nF/27uH/1.2nF.
For 2Ms/s use 560pf/12uH/2n2/15uH/560pf.
The above extract is from the Digilite Web Page on http://www.g8ajn.tv/ page 2/5
Hope this Helps
all other parts are the same.
Keith
For 2Ms/s use 560pf/12uH/2n2/15uH/560pf.
The above extract is from the Digilite Web Page on http://www.g8ajn.tv/ page 2/5
Hope this Helps
all other parts are the same.
Keith