Spectrum Analyser - screen dumps

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vk7jj
Posts: 102
Joined: Thu Mar 02, 2017 9:56 am

Spectrum Analyser - screen dumps

Postby vk7jj » Wed Jun 13, 2018 8:13 am

Thanks to Steve's terrific contribution in extending the useful application of the RSPs we're no doubt going to see some great applications.

This is a very humble start as I've been away and busy but busting to try it. One of the nice things about loops is their operation on even harmonics as per the 160m, 80m and 40m return loss plot for the simple 160m wire delta below.

Thanks again Steve, your software is going to make the hobby ever more fulfilling,

Regards, Phil VK7JJ

160-80-loop.png
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CaptainNemo
Posts: 142
Joined: Mon Jan 05, 2015 1:22 pm
Location: Genoa - Italy

Re: Spectrum Analyser - screen dumps

Postby CaptainNemo » Fri Jun 15, 2018 7:23 am

DIY filter -- poor engineering

Very useful tool!!!
Of course, in the past I did those measure with general pourpose sdr sw
now with this specific -- let me say professional -- tool it's another life!

20180615_090503.jpg
20180615_090503.jpg (101.43 KiB) Viewed 216 times


green line about -125 (dbFS ?) ---> rsp1 noise floor
red line about -75 ---> BG7TBL Noise source (enough flat for the price)
white line = DIY filter aimed to block RAI 1 Portofino 1575 kHz

cursor B shows the notch is at 1541kHz (not so bad) with 13 dB attenuation
the really bad is the dramatic attenuation of wanted signal (above 2000kHz)

poor design, poor implementation, poor of me! I will try again!!!

gio

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vk7jj
Posts: 102
Joined: Thu Mar 02, 2017 9:56 am

Re: Spectrum Analyser - screen dumps

Postby vk7jj » Sat Jun 16, 2018 2:43 am

I wanted to see the effect of the RSP1A medium wave broadcast band filter as I was not sure how far it intruded into the 160m ham band which starts at 1.8MHz.

First picture is with RSP1A with MW filter turned OFF and the second picture is with the filter turn ON.

Clearly, the filter works very well, so well that I now I know not to turn turn it on when using anything below 2Mhz, though when trying to listen to frequencies below 500KHz it may well prevent being wiped out by strong MW stations.

The white noise generator is too messy at those frequencies to be able to see clearly what is happening, I'll have to have another look at that later.

Phil VK7JJ

1A-MW-0.png
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1A-MW-1.png
1A-MW-1.png (42.61 KiB) Viewed 163 times

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vk7jj
Posts: 102
Joined: Thu Mar 02, 2017 9:56 am

Re: Spectrum Analyser - screen dumps

Postby vk7jj » Sat Jun 16, 2018 2:45 am

Here is another showing the FM filter OFF and ON:

1A-FM-0.png
1A-FM-0.png (45.6 KiB) Viewed 163 times

1A-FM-1.png
1A-FM-1.png (43.97 KiB) Viewed 163 times

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vk7jj
Posts: 102
Joined: Thu Mar 02, 2017 9:56 am

Re: Spectrum Analyser - screen dumps

Postby vk7jj » Sat Jun 16, 2018 2:54 am

Here is the return loss at around 52.5MHz of my discone antenna.

Many discone antennas use a vertical base loaded whip on the top of them to extend their low frequency response down to 50Mhz.

For those who are not familiar with "return loss" the best way to visualise the picture is to consider the antenna gain is "upside down", in other words the dip at 52.5MHz actually represents "better performance".

Here is a link to an excellent article on what it's all about:

https://www.rtl-sdr.com/rtl-sdr-tutoria ... se-source/

The setup used for all the pics I've posted is the same as the last item in the article Measuring the VSWR of an Antenna Tutorial

Just substitute your RSP for the RTL device.

Regards and thank you Steve :-)

Phil VK7JJ

discone-6m-whip.png
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SteveAndrew
Posts: 57
Joined: Thu Nov 16, 2017 11:06 pm
Location: Gold Coast, QLD, Australia

Re: Spectrum Analyser - screen dumps

Postby SteveAndrew » Sat Jun 16, 2018 3:06 am

Hi Phil and Captain Nemo

Thanks for taking the time to publish your screenshots. It's great to see the analyser being used in a practical application.

73's

Steve

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K9AQ
Posts: 5
Joined: Sat Jan 14, 2017 1:20 am

Re: Spectrum Analyser - screen dumps

Postby K9AQ » Sun Jun 17, 2018 4:35 pm

Here a display of the IMD products from my Elecraft KX3. I am using the internal two tone generator on the KX3. The output of the KX3 goes through a WaveNode bi-directional coupler, with an RF sampling port. I then run it through a step attenuator in front of the RSP 1. If you disregard the effects of the center frequency, this is a very useful measurement. The cursors clearly measure the dbm difference between the two tones and the IMD products.

Don
K9AQ
kx3 imd 50 khz span.PNG
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Last edited by K9AQ on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Spectrum Analyser - screen dumps

Postby Scannerz » Sun Jun 17, 2018 10:37 pm

Using a quick build cheap noise source circuit I found on the net, I ran a quick test of a 2mhz homemade High pass filter.

The transistors I used were SS9018 vhf/uhf npn.
The Noise circuit did not require any attenuation and I think it only draws 0.35mA at 9v.
And goes up to about 500mhz.

Noise circuit link: https://kb8ojh.net/projects/noisegen/

cheers Tony.
Attachments
noise_02.jpg
noise_02.jpg (138.03 KiB) Viewed 19 times

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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Spectrum Analyser - screen dumps

Postby Scannerz » Sun Jun 17, 2018 10:39 pm

The 2mhz High Pass test....forgot again.
Attachments
2mhhz HPass_001.jpg
2mhhz HPass_001.jpg (82.73 KiB) Viewed 19 times

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