On 7/13/22 5:24 AM, Dan Kemppainen via time-nuts wrote:
Erik,
Just a thought. The 7805 in your schematic appears to be a big part of
the signal chain. I've run into issues with 78xx series regulators
being noisy. Spent a few weeks chasing down noise issues in some
equipment and the 78xx
On 7/12/22 3:51 PM, ed breya via time-nuts wrote:
I forgot to mention that you should also consider possible effects
from the RF present, on the LNA. This can be more significant than
SMPS frequencies getting where they don't belong, especially since the
RF is intentionally right at the
On 7/12/22 8:53 AM, Erik Kaashoek via time-nuts wrote:
I'm struggling with the noise floor.
First tests where done with a 5nV/sqrt(Hz) opamp. Noise floor with
shorted mixer output at 10kHz was -140dBc/Hz. Then I tried with
1nV/sqrt(Hz) opamp, but that made no difference, noise floor at 10kHz
On 7/10/22 4:19 PM, skipp Isaham via time-nuts wrote:
Hello to the Group,
I'd like to get some opinions and war stories regarding GPS reliability at
high RF level and elevation locations.
Background: Three different hill-top GPS receivers, all different types, using
different antennas mounted
On 7/10/22 9:07 AM, Bob kb8tq via time-nuts wrote:
Hi
Yes it is a pain to implement dual supplies. I ponder that issue every time
I build one of these setups. I’ve built a lot of them …. If you are going to
do a single supply, setting up a “virtual ground” is probably the best way
to go. Do it
On 7/7/22 8:55 AM, Bob kb8tq via time-nuts wrote:
Hi
Yes, you do need to know the system gain. Since we are talking about
gain at audio, measuring the gain directly is not a crazy thing to do. One
of the things that makes audio spectrum analyzers a nice tool for this that
they eliminate the
On 6/20/22 2:39 AM, Magnus Danielson via time-nuts wrote:
So, a counter is really like an ADC for phase, with wide bandwidth
input and a sub-sampling mechanism (trigger/time-base). Through
processing frequency estimates can be provided. Aliasing occurrs in
the sub-sampling. Modern counters
On 6/12/22 6:30 PM, Bob kb8tq via time-nuts wrote:
Hi
Tear into some of your SC cut based OCXO’s. Take a look at the crystal package.
For
bonus points, open up the crystal package. If you have the gear to test it,
take a look
at what the gas *is* inside the package. ( Good luck with that :)
On 6/10/22 1:57 PM, Dr. David Kirkby wrote:
On Fri, 10 Jun 2022 at 17:39, Lux, Jim via time-nuts
wrote:
On the subject of rapid warm up. I suppose if you had a need, one
could
dump as much power as you need into the heater. Turn on oscillator,
lights in room dim for a few
On 6/10/22 12:13 PM, Richard (Rick) Karlquist wrote:
I think there is a severe misunderstanding of this issue.
First of all, "rapid warmup" is a red herring. The real
issue is "rapid frequency stabilization".
Indeed. But to a certain extent, that's why oscillators don't have 5
second warm up
On 6/9/22 8:53 PM, Bob kb8tq via time-nuts wrote:
Hi
There happen to be *some* AT cut based OCXO’s that beat the typical
SC cut on warmup … just saying …. :)
Bob
On the subject of rapid warm up. I suppose if you had a need, one could
dump as much power as you need into the heater. Turn on
On 5/31/22 3:23 AM, Carsten Andrich via time-nuts wrote:
On 31.05.22 01:10, glen english LIST via time-nuts wrote:
Be aware not to confuse the antenna ground plane (the patch will
always have its own plane because the top metalization must be fed
against a plane or counterpoise - and a
On 5/26/22 8:18 AM, Bob kb8tq via time-nuts wrote:
Hi
The real answer to the problem is to dig into the bowels of 1940’s electronic
craft.
There are various methods for setting up an L/C filter. You short this / open
that sweep
to find a dip or a peak. You move it to the “right” place. Just
On 5/26/22 8:24 AM, Richard (Rick) Karlquist wrote:
The tweezers are really good *only* for single components - even if they
come with test leads, that's for measuring something like a motor start
capacitor.
I tried using tweezers (cheap ones to be sure) to measure a moderately
complex
On 5/25/22 3:16 PM, ed breya via time-nuts wrote:
Thanks Mike, for info on LCR alternatives. It's good to know of others
out there, if needed. I have an HP4276A and HP4271A. The 4276A is the
main workhorse for all part checking, since it has a wide range of
LCZ, although limited frequency
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