That is why a DC Block is such an important part of your test kit.
It is just a capacitor in series with the centre conductor in an
SMA-M to SMA-F adaptor.
Make sure it has a DC rating of at least 100V, preferably 200V. Many
of the units on Ebay, etc are only rated at ~20V DC isolation.
HTH Someone...Bob VK2ZRE
On 18/02/2025 10:51 pm, hwalker via
groups.io wrote:
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On Tue, Feb 18, 2025 at 12:14 AM, Reg Du Toit wrote:
I bought my SA ultra from Zeenko Aliexpress
It was fine and passed all tests and calibration then
I have only used it as a signal generator and did not
upgrade (v1.4 156)
While testing a transceiver I noticed the output level
from the SA ultra was low so this is what I've done
Did a self test and it fails on #3 and goes no further
?
Tests 3 checks the 30 MHz CAL OUTPUT signal level.? If it
is failing, try the following troubleshooting steps:
?
1.? Connect the CAL OUTPUT (top connector) to the RF INPUT
(bottom connector).
2.? Select MODE:Calibration Output:30MHz
3.? Select Spectrum Analyzer
4.? You should see comb lines with the main carrier at 30
MHz @ ~-35.6 dBm.
5.? If you don't see any comb lines or comb lines with a
carrier at 30 MHz well below -35.6 dBm then you either have a
defective attenuator (U38:PE4312C-Z) or RF input switch
(U22:AS179-92LF).
6.? Select LEVEL:LNA
7.? If you now see comb lines with the main carrier at 30
MHz @ ~-35.6 dBm then the RF input switch is working, and you
have a defective attenuator.? Selecting LNA switches out the
attenuator and switches in the low noise amplifier.
?
When the tinySA Ultra is used as a signal generator it is
subject to reverse voltage or turn on/turn off transients from
the device it is connected to.? The only reverse voltage
protection the tinySA Ultra has is its ESD protection diode.?
That diode is not meant for overload protection.??
?
I learned my lesson on a $5000 RF generator.? Thankfully
the tinySA doesn't cost nearly as much.
?
Herb
?
