Generating a stable 26MHz and 19.2MHz from 10MHz
Hi Magnus: I goofed, it's actually 5.12 MHz, the driving crystal
standard for the ICOM 260A 2 meter transceiver synthesizer. I want to
use it with a transverter for moonbounce, hence would like to start out
with a solid reference frequency. Might even be overkill. See, I knew it
could be done with (almost) some 7400's :-)
Thanks for the hint! The thing to do then is to pick off some of the
existing xtal frequency, and as you say count to the common denominator.
A little varicap in the crystal circuit can then be driven by the phase
comparator...
Should not be too hard to do...
Don
Magnus Danielson
Don,
On 07/02/2011 09:48 PM, Don Latham wrote:
Hi Anders:
I need something to give 2.048 MHz from a 10 MHz source, and have not
too aggressively tried to find a way; have followed with interest many
suggestions from TN's. I found a company called Vectron that makes,
ostensibly, very nice frequency translators, with an fin and an fout,
with reasonable phase noise characteristics (?), the data sheets are
available and intriguing, but I spent an hour or more trying to find a
way to actually buy one.
Getting 10 MHz to 2,048 MHz isn't all that hard. You can do it in good
old 4000 CMOS series if you need to. What application to you need it
for? I recognice it as a standard telecom frequency and well have in
fact implemented 10 MHz to 2,048 MHz conversion (even if that was not
the primary target). The wideband noise needs isn't very daunting in
telecom applications, but long-term stability is another thing.
If you really do not need to have very good wideband phase-noise, a 4046
and a few dividers will help you.
10 MHz and 2,048 MHz has the highest common frequency in 16 kHz, so you
need to divide by 625 on the 10 MHz and 128 on the 2,048 MHz. If you
settle with the 4046 oscillator or chooses an off the shelf VCXO depends
on what you need, but it is not too hard and too expensive to come by.
Cheers,
Magnus
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Don,
On 07/03/2011 12:29 AM, Don Latham wrote:
Hi Magnus: I goofed, it's actually 5.12 MHz, the driving crystal
standard for the ICOM 260A 2 meter transceiver synthesizer. I want to
use it with a transverter for moonbounce, hence would like to start out
with a solid reference frequency. Might even be overkill. See, I knew it
could be done with (almost) some 7400's :-)
Thanks for the hint! The thing to do then is to pick off some of the
existing xtal frequency, and as you say count to the common denominator.
A little varicap in the crystal circuit can then be driven by the phase
comparator...
Should not be too hard to do...
Don
So true. 10 MHz and 5,12 MHz is a little different. You need to divide
by 125 to knock the 5's out of 10 MHz and get 80 kHz and then a divide
by 64 from the 5,12 MHz if you choose to go the PLL route.
It should not be too hard.
For relative low feedback division rations it is fairly easy to achieve
decent results.
Keeping the comparator frequency high ensures that the loop filter can
do a decent enough job to keep the comparator frequency and overtones
out of the sidebands without being forced into tight PLL bandwidths.
For a step-up PLL of low ratio the loop filter can be very simple and
always lock up without too much difficulty. Even a passive lag can do at
times. As always, shaping up things with an active PI loop filter is
better. It all depends on the requirements.
Just make sure that you do not get a high Q cause that is a real downer.
I'm not saying that PLL is the best way to do things at all times, but
for some applications the performance needed and applicability of a PLL
makes it a fairly low hanging fruit, so just go for it. I guess that for
your application it could very well work good enough.
Cheers,
Magnus
I finally took the plunge and ordered a thunderbolt on eBay and it
showed up on my doorstep today.
Of course, I haven't saved those old emails about where to get things
such as GPS antennas and power supplies. If someone could please point
me to sources, I'd appreciate it.
Also, is there anyone in the Houston, TX area (SE side) that has a TB
up and running that would allow me to plug my new TB into a working
setup to see if it is indeed functional? They have a 7 day return
policy and I won't have any means to do a checkout otherwise.
Keith
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Col Keith E. Brandt, MD, MPH
[1]wd9get@amsat.org
Goodbye cruel world that was my home-
there's cleaner space out here to roam
Put my feet up on the moons of Mars-
sit back, relax, and count the stars
*This message transmitted with 100% recycled electrons
References
- mailto:wd9get@amsat.org
Hi
You obviously will need +12, -12 and +5 supplies at the proper current levels. Any GPS antenna that will run on 5 volts will work for checkout. There are good pictures on the web showing what power goes to which pins. Current levels are < 10 ma on -12, ~ 300 ma on +5 and a bit under 1A at turn on on +12.
Once it's all wired and seems ok - sImple check out:
- Download Lady Heather and get it installed.
- Grab a serial cable and use an ohm meter to check that pins 2 and 3 are wired right.
- Fire it all up and the software will tell you what's going on.
There's about a 90% chance it will fire up and run fine. If not, get it replaced.
Bob
On Jul 6, 2011, at 7:14 PM, Keith E. Brandt, WD9GET wrote:
I finally took the plunge and ordered a thunderbolt on eBay and it
showed up on my doorstep today.
Of course, I haven't saved those old emails about where to get things
such as GPS antennas and power supplies. If someone could please point
me to sources, I'd appreciate it.
Also, is there anyone in the Houston, TX area (SE side) that has a TB
up and running that would allow me to plug my new TB into a working
setup to see if it is indeed functional? They have a 7 day return
policy and I won't have any means to do a checkout otherwise.
Keith
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Col Keith E. Brandt, MD, MPH
[1]wd9get@amsat.org
Goodbye cruel world that was my home-
there's cleaner space out here to roam
Put my feet up on the moons of Mars-
sit back, relax, and count the stars
*This message transmitted with 100% recycled electrons
References
- mailto:wd9get@amsat.org
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