The input frequency was 3900khz. verified by my freq counter and my
oscilloscope. The 815 just doesn't do a good job on frequencies at the
edges of a large range apparently. I didn't show it but when I had the
scan range from 3500khz to 4khz it the 815 showed the carrier to be at
3900khz.
The same thing probably applies for the 48.91333 signal. For a 3900khz
signal the vfo would be at 48900khz so the 815 is off by about 13khz at
the edge of the scan.
The 45Mhz signal should pass through the 45Mhz filter. Yet it is
knocked down further than the 48.9333mhz signal. That's why I wonder if
the 48.9Mhz signal isn't just being picked up out of the air by my
probe.
I will be working in the yard most of today. If I get a chance tonite
to put everything back together I'll try using the tracking generator
as you suggest. I don't know why I didn't think of that! I appreciate
the suggestion.
That should even work if I just set the TG to run from 3875khz to
3950khz and feed it in the antenna while leaving the vfo set to
3900khz.
I set the sig gen to 3900khz and the radio to 3900khz as well during my
tests.
Thanks for the help.
tim ab0wr
On Fri, 04 May 2018 15:52:33 -0700
"ajparent1/KB1GMX" <kb1gmx@...> wrote:
3.83333+45= 48.3333? Or if on the other side it would be
45-3.8333=41.1667 image C30 look at marker 1D as that likely the LO
leakage so that about right. Image C216 has a solid signal at 45MHZ
but the LO indicates 48.91333
I see neither frequency in the scans that close enough to pass
through the filter (its only 15khz wide!).
Have you simply dialed the sig gen or the VFO until the signal
appears at 45.0000mhz (or the speaker)? Based on what the SA is
telling you your not putting a signal in the passband of the filter.
Since I have a DSA815T (its a handy machine!) I'm inclined to believe
its telling you that.
If you have the 815T use the tracking generator. Simply put TG ar
45mhz with say 50khz span and inject that into the?filter matching
network (50 ohm point) and look at the output.? You should see the
filter pass band though the insertion loss with external circuits
loading it will be higher it should be under 10db on a guess.? Hint
use a lower sweep rate or auto locked to RBW.
The only way that filter would die is if you applied force to it
ripping the leads out or shattering the quartz. Even then have pulls
I've dropped on concrete that are fine.? Recently I helped someone
with another kit and the problem was a ball of solder under the
crystal causing a lead to ground short.? It Ohmed out. If I had to
guess the series inductor (ohm it) is open or maybe a short at the
cap should be checked for.
If you truly believe its dead and there are no shorts bridge it with
a wire.
Allison
