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Spectrum analyzer fun

Gordon Gibby
 

Oh what fun!

Yesterday I built a simple capacitively coupled "probe" to be used with my (1st ever!) spectrum analyzer.   A series cap of 0.01/1kV, 4700 ohm resistor, and 100 ohm to ground, (should have used 50 but didn't have it) -- then coax cable to the spectrum analyzer.


Gives roughly 15 dB attenuation based on touching the tracking generator signal.


Allows me to actually SEE the oscillators and signals as I roam around the uBix.   Wow, the signals are TINY all around the receiver, and most of the gain must be in the audio section....


I built this for 2 reasons: primarilly so I can do this demo for our upcoming Extra Class course, and let people SEE mixers in action and oscillators and filters.   Sending in a 100kHz calibrator (harmonics every 100 kHz) shows ALL the signals heading into the 45 MHz filter --- and then poof, only 1 left afterwards!


2nd, I have a heathkit SB-102 with local oscillator problems and this will help.

​Fascinating.


Gordon Gibby KX4Z




 

Congrats Gordon! have fun.

Right now I am about to be admitted to the Mentuino hospital. Resullt of having fun with an Antuino.
I redid the IF amp and ended up with 0db at its output showing as -20dbm. Sounds simple but
almost gone nuts trying to fix it!

Raj


At 25-07-19, you wrote:

Oh what fun!

Yesterday I built a simple capacitively coupled "probe" to be used with my (1st ever!) spectrum analyzer.   A series cap of 0.01/1kV, 4700 ohm resistor, and 100 ohm to ground, (should have used 50 but didn't have it) -- then coax cable to the spectrum analyzer.


Gives roughly 15 dB attenuation based on touching the tracking generator signal.


Allows me to actually SEE the oscillators and signals as I roam around the uBix.   Wow, the signals are TINY all around the receiver, and most of the gain must be in the audio section....


I built this for 2 reasons: primarilly so I can do this demo for our upcoming Extra Class course, and let people SEE mixers in action and oscillators and filters.   Sending in a 100kHz calibrator (harmonics every 100 kHz) shows ALL the signals heading into the 45 MHz filter --- and then poof, only 1 left afterwards!


2nd, I have a heathkit SB-102 with local oscillator problems and this will help.

Fascinating.


Gordon Gibby KX4Z



 

is it too soon to share the fix?
--
David

 N8DAH
Kit-Projects.com

Shop is open!

Laurence Oberman
 

Awesome,
While I am an extra I would love a recording of that class as it will
have years of experience included :)
I did spend a bunch of money recently to take the Besser Associates RF
technology class to give myself a full refresh of all things RF.

Make me wish I had stayed in RF years ago instead of software.

Nice job Sir

Regards
Laurence

On Thu, Jul 25, 2019 at 4:41 AM Gordon Gibby <ggibby@...> wrote:

Oh what fun!

Yesterday I built a simple capacitively coupled "probe" to be used with my (1st ever!) spectrum analyzer. A series cap of 0.01/1kV, 4700 ohm resistor, and 100 ohm to ground, (should have used 50 but didn't have it) -- then coax cable to the spectrum analyzer.


Gives roughly 15 dB attenuation based on touching the tracking generator signal.


Allows me to actually SEE the oscillators and signals as I roam around the uBix. Wow, the signals are TINY all around the receiver, and most of the gain must be in the audio section....


I built this for 2 reasons: primarilly so I can do this demo for our upcoming Extra Class course, and let people SEE mixers in action and oscillators and filters. Sending in a 100kHz calibrator (harmonics every 100 kHz) shows ALL the signals heading into the 45 MHz filter --- and then poof, only 1 left afterwards!


2nd, I have a heathkit SB-102 with local oscillator problems and this will help.

Fascinating.


Gordon Gibby KX4Z