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Spectrum Analyser - screen dumps

Posted: Wed Jun 13, 2018 8:13 am
by vk7jj
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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Re: Spectrum Analyser - screen dumps

Posted: Fri Jun 15, 2018 7:23 am
by CaptainNemo
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
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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

Re: Spectrum Analyser - screen dumps

Posted: Sat Jun 16, 2018 2:43 am
by vk7jj
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
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Re: Spectrum Analyser - screen dumps

Posted: Sat Jun 16, 2018 2:45 am
by vk7jj
Here is another showing the FM filter OFF and ON:
1A-FM-0.png
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1A-FM-1.png
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Re: Spectrum Analyser - screen dumps

Posted: Sat Jun 16, 2018 2:54 am
by vk7jj
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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Re: Spectrum Analyser - screen dumps

Posted: Sat Jun 16, 2018 3:06 am
by SteveAndrew
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

Re: Spectrum Analyser - screen dumps

Posted: Sun Jun 17, 2018 4:35 pm
by K9AQ
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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Re: Spectrum Analyser - screen dumps

Posted: Sun Jun 17, 2018 10:37 pm
by Scannerz
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.

Re: Spectrum Analyser - screen dumps

Posted: Sun Jun 17, 2018 10:39 pm
by Scannerz
The 2mhz High Pass test....forgot again.

Re: Spectrum Analyser - screen dumps

Posted: Tue Jun 19, 2018 2:35 pm
by JohnAE5X
Elecraft KX2 on 80m - Steve's program (and RSPDuo) compared to HP:

https://ae5x.blogspot.com/2018/06/compa ... lyzer.html

John AE5X