Erik, I'd really recommend that you use a real, "solid" ground reference
on the instrumentation side, with +/- large (12-20 V) supplies, as
others have suggested.
Your most recent setup diagram indicates that you're relying on the
"differential" input of the audio PC card etc analyzer to allow
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 opamp's input. Your LPF only reduces, and
does not elimin
Hi Magnus,
I know what you mean about not needing a quadrature splitter - if you
have a very wide phase or delay tuning range - but I'm picturing getting
most of the way to quadrature with a fixed structure for a given
frequency, and only fine-tuning the phase over a narrow range, in order
to
I've been following the thread about Erik's DIY PN analyzer, and
wondering if it might be easy enough to use a frequency discrimination
method. I'm opening this in a different thread to avoid muddying the
water on the original (and long) one.
What I'm picturing is putting the DUT's output into
Thanks Gerhard, for putting up the schematic. After a quick look, I'd
recommend trying the following changes. Of course, I don't know the fine
details, so this is just from a general circuit perspective - could be
all wrong versus the actual situation.
1. Delete the Q7 circuitry including R10
All good comments about the isolation issues, but remember we're talking
about a desired 200 MHz amplifier system here, not a 10 MHz one, so RF
transistors are appropriate. This is a little different from the
original DIY PN test discussion, which is why I replied in a different
thread title.
Gerhard wrote:
"I have made a new isolation amplifier but I'm absolutely not happy with
the available transistors. Anything in sot-89 is either to slow (
Zetex/Diodes Inc, the 2N3904-alikes)
or is much too hot.
I want at least 200 MHz to have no phase shift at 100. BFQ19s gave me 1
GHz of BW. The
This may give some idea of how fast things can happen when the OCXO is
subject to drafts. I have this dual GPSDO box that usually is open for
experimenting, and have a setup comparing one of the 10 MHz outs to my
portable Rb reference. The 10 GHz multiplied output from the Rb is
indicated on a
After more experimenting and measuring, I think the RF is done enough. I
found that the main 20 MHz and the 300 MHz LPFs were letting a lot of HF
above 1200 MHz straight through. I believe the choke I used in the 300
MHz LPF has a self-resonance in that range - it's a wire coil molded in
plasti
Yes, that transformer sure looks burned out. It's hard to tell how big
it is from the pictures, but my impression is that it looks kind of
skimpy to run a FRK Rb plus whatever else is going on like a GPS RX and
uP system, and maybe battery charging too. You can easily estimate the
VA rating by
Continuing with experiments and spur measurements, I found that closing
the lid on the little filter box does seem to reduce the LPF's
effectiveness at the higher frequencies, but leaving it open reduces
effectiveness at the lower. I can sculpt it to a taller structure if
necessary, which would
I've been working on final design cleanup, mainly in the RF. I found
quite a bit of spurious LO harmonic content up to almost 2 GHz, with
some quite strong (-75 dBm). It was time to clean up the experimental
wiring layout, so I simplified the cabling and consolidated the RF stuff
onto the LPF b
Now that I have the "official" filter in place, I can wrap up the LF/DC
issues. This is the other extreme, so no SA here, just time domain view
with a Tek 7A22 vertical, which gets down to 10 uV/div, and has settable
BW steps from 100 Hz to 1 MHz. For very low f and DC, I use a HP3456A.
There a
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 coverage (100 Hz - 20 kHz). The 4271A is 1
MHz only, an
I managed to build a filter, using the values for a 9th order
Butterworth, 50 ohms, 25 MHz fc. The caps were fairly straightforward to
get nearly right on in values, with one or two (paralleled) selected
micas for each spot. The chokes were tricky. I decided to use IF-can
style adjustable ones,
Thanks all, for filter info. For reasons that will become evident when I
describe the LF/DC situation, I plan to use an all-passive LC LPF. I
assume I'll be needing a fairly high-order (like 9 or so) Butterworth
type response for good flatness, and enough stop-band rejection for the
higher freq
16 matches
Mail list logo
