Thanks, Tom. This newsgroup is truly educational. I'm slowly learning
that out there, somewhere, just about every possible convention or
nomenclature is used by someone for some purpose. I'll bet I'm the only
kid on my block now who knows what dBu and dBv mean. And I guess Len is
the only kid on his block that knows they sometimes mean dB relative to
1 uV, as well -- ah, what's a factor of 775,000 one way or the other,
anyhow.

dBu = dumb ******* unit.

Roy Lewallen, W7EL

K7ITM wrote:
This page: http://decibel.biography.ms/ mentions both dBv and dBu.
Says in "electrical voltage" (probably with reference to audio
industry), dBu and dBv both mean dB relative to 0.775V -- generally
0.775Vrms, but dB taken as 20 log(V/0.775), without reference to a
particular impedance.

But the same page says dBu or dB(lower-case Greek mu: "micro") as radio
power is dB relative to one microvolt per square meter.

Go figure. It all points out the need to be careful to define your
terms if there's any chance of ambiguity. If you're not careful, your
reader may think dBu refers to Dallas Baptist University, or Deutsche
Billiard Union, or Duluth Business University... though the
capitalization would be wrong for those.

Cheers,
Tom

Hi

Thanks to all of you... like Roy said, this newsgroup is very
educational... now I have enough information to make some
experimentation with this mixer and oscillator... actually, the mixer
is an Analog Devices AD607 and the oscillator is a Linear LTC6903...
I'm planning to build my own rig...

Thank you so much.

Hern=E1n S=E1nchez
HJ4SZY

Hi Hern=E1n,

Hope a couple comments will be helpful:

I'd suggest you reconsider using the LTC6903. The data sheet says it
has a lot of jitter, which will translate to huge phase noise... If
you connect up just the LTC6903 and listen to its output on a good
receiver, if it doesn't sound like a clean tone (SSB/CW mode receiver)
or a noisless carrier, that's what it's going to add to whatever signal
you want to listen to when using it as an LO for a receiver. There are
probably some very decent low-power LO designs in the QRP community
that you could adapt. May be difficult to get wideband digital
control, which it looks like you might be trying to get with the LTC
part.

I suppose the AD607 is pretty tolerant of levels at the LO input, and
it's a relatively high input impedance. You don't have to waste power
by adding an external 50 ohm resistor. Get the LO input voltage level
close to the suggested value or a bit more and you should be fine.

Cheers,
Tom

nanchez wrote:
Hi

Thanks to all of you... like Roy said, this newsgroup is very
educational... now I have enough information to make some
experimentation with this mixer and oscillator... actually, the mixer
is an Analog Devices AD607 and the oscillator is a Linear LTC6903...
I'm planning to build my own rig...
=20
Thank you so much.
=20
Hern=E1n S=E1nchez
HJ4SZY

On Mon, 06 Jun 2005 11:12:03 +0000, W3JDR wrote:

I think that would be dBuv not dBv which is Ref 1V


I've never seen "dBv" refer to 1uv either. Always 1V.

Joe
W3JDR


"Roy Lewallen" wrote in message
...
wrote:
. . .
"dbv" (sometimes "dbu" but rarely) refers "0" as 1.0 microVolt,
almost any characteristic. Not seen much in specifications,
though.
. . .


Interesting. I've many times seen dB relative to one volt as dBV, and dB
relative to one microvolt as dBuV, but never dBv meaning dB relative to
one microvolt, or dBu at all. Do you have any references that show these
unusual usages?

Roy Lewallen, W7EL

--
Korbin Dallas
The name was changed to protect the guilty.

On Tue, 07 Jun 2005 01:54:14 -0700, Roy Lewallen wrote:

dBv = 1v
dBu = 1 uV
dBm = 1 mw
dBw = 1 w
dBk = 1 KW

Thanks, Tom. This newsgroup is truly educational. I'm slowly learning
that out there, somewhere, just about every possible convention or
nomenclature is used by someone for some purpose. I'll bet I'm the only
kid on my block now who knows what dBu and dBv mean. And I guess Len is
the only kid on his block that knows they sometimes mean dB relative to
1 uV, as well -- ah, what's a factor of 775,000 one way or the other,
anyhow.

dBu = dumb ******* unit.

Roy Lewallen, W7EL

K7ITM wrote:
This page: http://decibel.biography.ms/ mentions both dBv and dBu.
Says in "electrical voltage" (probably with reference to audio
industry), dBu and dBv both mean dB relative to 0.775V -- generally
0.775Vrms, but dB taken as 20 log(V/0.775), without reference to a
particular impedance.

But the same page says dBu or dB(lower-case Greek mu: "micro") as radio
power is dB relative to one microvolt per square meter.

Go figure. It all points out the need to be careful to define your
terms if there's any chance of ambiguity. If you're not careful, your
reader may think dBu refers to Dallas Baptist University, or Deutsche
Billiard Union, or Duluth Business University... though the
capitalization would be wrong for those.

Cheers,
Tom


--
Korbin Dallas
The name was changed to protect the guilty.

Korbin Dallas wrote:
On Tue, 07 Jun 2005 01:54:14 -0700, Roy Lewallen wrote:

Just for the record, no, I didn't write this:


dBv = 1v
dBu = 1 uV
dBm = 1 mw
dBw = 1 w
dBk = 1 KW


Roy Lewallen, W7EL

Hi.

Thanks for your suggestions....

Yes, I'm trying to do some digital control to the frequency of LO using
the LTC part. I will think in another way to do that...

I'm looking for an oscillator of about 33MHz to replace the LTC part...
any ideas ?

About the AD607 comment, I have a voltage divider to couple the
previous LO output to the level of LO input of AD607... is it what you
mean ?

Thanks

Hern=E1n S=E1nchez

Hi again.

One last question (for this thread) about jitter... how low it needs to
be ? The LTC6903 datasheet says it's 1% (max value).

Thanks

Hern=E1n S=E1nchez

nanchez wrote:
Hi again.

One last question (for this thread) about jitter... how low it needs to
be ? The LTC6903 datasheet says it's 1% (max value).

Thanks

Hern=E1n S=E1nchez

Because I work with high-speed ADCs, I'm most familiar with articles
about jitter in sampled systems. A sampler and a mixer are pretty
similar, and you should be able to learn a lot from things like Analog
Devices ap notes AN-501 and AN-756, and even the data sheets for
converters like the AD6644 and AD6645. For example, the SNR for an
AD6644 sampling a 30MHz sinewave at 65Msamples/sec is degraded
perceptably by clock jitter of 0.15psec, which is about 0.001% jitter,
expressed as a percentage of the clock period.

I'd post links to the pdf files for those ap notes, but the form I have
them in, they are too long to reliably include in a posting. Just go
to http://www.analog.com/en/index.html and enter AN-501 or AN-756 into
the search box. Also, if you enter "jitter phase noise" (without the
quotes) into a Google search, you'll get LOTS of references.

http://www.maxim-ic.com/appnotes.cfm...te_number/3359 is an ap note
on conversion between clock jitter and phase noise.

Disclaimer: I have not reviewed any of these apnotes critically for
accuracy.

Cheers,
Tom

Yes, a voltage divider should do fine. It may be convenient to have
the voltage divider output look approximately like a 50-ohm source, but
from what I can see in the AD607 data sheet, there is no requirement
that the LO come from a 50 ohm source. You just want to deliver a
voltage to the LO input pin which is equivalent to -16dBm across a 50
ohm resistor: in other words, about 35mV RMS or 0.1V peak-to-peak. I
expect that if your level is anywhere between 0.1Vp-p and 0.2Vp-p, or
even more, or perhaps even a bit less than 0.1, it should work fine. I
didn't notice anything very explicit in the data sheet. about it.

Two choices for digitally-controlled LO are DDS (direct digital
synthesis) and PLL (phase locked loop). Each has its strong points and
drawbacks. Do you want to keep the power very low? What sort of
frequency resolution do you want? How simple do you need to keep the
circuit? How critical is it that the LO not have any noticable
spurious outputs? -- I still suspect that the QRP community has already
done some nice work on LOs that might suit your need.

Cheers,
Tom