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  #1 (permalink)  
Old 05-15-2018, 11:40 PM
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Default Reception for aviation bands

recently purchased RTL-SDR Blog brand V3 Dongle with dipole antenna kit

trying to receive aviation transmissions
found information on what length to set dipole antenna to receive those freqs

my question:
how is it my handheld scanner with rubber duck antenna produces good reception

yet the SDR with the (outside) antenna set at the required length and set perpendicular to the ground sounds horrible

is it the sensitivity/quality of the handheld vs the SDR
am really interested to know the reason(s).
thanks
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Old 05-16-2018, 7:34 PM
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I'd start with the dipole.

Mine had the 2 conductors touching inside the section where the telescopic elements screw together. The plastic cap just pops out. See image.

You can just check the plug end, if you have a multi-meter, check the that the center pin and outside (nut/thread) has no continuity (high ohms - reading should be approx 100K)

Then I'd check settings in whatever SDR program your using. Since you didn't mention it or any settings, we can't help there yet.

Quote:
is it the sensitivity/quality of the handheld vs the SDR
am really interested to know the reason(s).
Probably. Let's stick with what we can work with. The SDR program settings, feed line and antenna.
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Old 06-12-2018, 8:07 PM
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checked...no short between contacts

here is a screenshot of the settings used
red line at 123.900 MHz (peak shown)

not getting any reception.

any suggestions?
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Old 06-12-2018, 9:23 PM
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Couple of thing i would change,first in the Controller, click on RTL-AGC and set the slider to about 40.2. Second thing I would change is the Radio section I would raise the Bandwith to about 12500 and the Order to about 200. In the AGC I would click on the AGC and set it to about 80. You might want to click on the Correct IQ also. You should be able to hear as much on your V3 dongle as you do with your scanner.

The above is how I have my V3 setup to listen to the air band and I was quite impressed with the reception. Give those setting a try, adjust them to see how they work, you will be surprised at the difference.





MB
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Old 06-12-2018, 10:28 PM
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RF gain is far too low.
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Old 06-13-2018, 1:50 AM
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As 'slicerwizard' says, the single most important thing on the screenshot is that your RF Gain is far too low.

Bandwidth of 6000 is fine for airband (you seem to have confused the setting with the channel width/stepsize). 12500 is too wide

Do you actually need to use 'snap to grid'? I find it easy enough to tune civil airband without bothering. If you are concerned about the 8.33kHz channelization there is a plugin that will autochange to the 8.33kHz channel frequencies if you enter the channel names ("Avia band 8.33 calculator" on the Russian plugins site) in the same way that aircraft radios now do this.
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Old 06-13-2018, 8:44 AM
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Quote:
Originally Posted by morfis View Post
As 'slicerwizard' says, the single most important thing on the screenshot is that your RF Gain is far too low.

Bandwidth of 6000 is fine for airband (you seem to have confused the setting with the channel width/stepsize). 12500 is too wide

Do you actually need to use 'snap to grid'? I find it easy enough to tune civil airband without bothering. If you are concerned about the 8.33kHz channelization there is a plugin that will autochange to the 8.33kHz channel frequencies if you enter the channel names ("Avia band 8.33 calculator" on the Russian plugins site) in the same way that aircraft radios now do this.
In the air band, my SDRSharp defaults to 12500, can't be changed? Snap to Grid "forces frequency to snap to frequency steps selected when drag tuning" as per the user guide I have.

MB
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Old 06-13-2018, 10:47 AM
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Overwrite this to the SDRSharp.EXE config file. It will give the extra step sizes (Aviation, NXDN). It's easy to add extra step sizes
Also, you can edit the Band Plan to Step Size 8330 for the desired frequencies..

<add key="stepSizes" value="1 Hz,10 Hz,100 Hz,500 Hz,1 kHz,2.5 kHz,3.125 kHz,5 kHz,6.25 kHz,7.5 kHz,8.33 kHz,9 kHz,10 kHz,12.5 kHz,15 kHz,20 kHz,25 kHz,30 kHz,50 kHz,100 kHz,150 kHz,200 kHz,250 kHz,300 kHz,350 kHz,400 kHz,450 kHz,500 kHz,1 MHz" />

Last edited by 78turbo; 06-13-2018 at 10:52 AM..
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Old 06-13-2018, 11:27 AM
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Thanks for that 78turbo, I added 3.125 in SDRShaop.exe, but I am not sure what system uses it.
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Old 06-13-2018, 11:31 AM
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I have found that there many NXDN systems that are using the 3.125 splits, along with some IDAS sites.

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Originally Posted by moonbounce View Post
Thanks for that 78turbo, I added 3.125 in SDRShaop.exe, but I am not sure what system uses it.
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Old 06-13-2018, 1:48 PM
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Just so I have this right, you are talking about the airband when you are saying you have found NXDN with some IDAS.?

Thanks
MB
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Old 06-13-2018, 1:53 PM
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I was referring to you asking what systems used that 3.125mHz split. Those would be NXDN and IDAS. I have not listened to the airband that much. Sorry for any confusion.
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Old 06-13-2018, 2:06 PM
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No problems, I am full of confusion lol.
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Old 06-14-2018, 2:20 AM
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Quote:
Originally Posted by moonbounce View Post
In the air band, my SDRSharp defaults to 12500, can't be changed? Snap to Grid "forces frequency to snap to frequency steps selected when drag tuning" as per the user guide I have.

MB
.
I've never had SDRSharp default to 12500 steps for airband - it would make absolutely no sense for it to do so? With the older 25kHz channel allocation you would need to take two steps to get to each valid frequency and with the new 8.33kHz channel allocation there are times you'd potentially hear two channels at the same time.

I understand what 'snap to grid' does - I just haven't found it necessary when tuning airband - if I was going to use it on civil airband I'd want it to work at 8.33kHz steps (SDRSharp can do that BUT it would not match the ACTUAL frequency allocations and hence why the Russian plugin should be used)

Perhaps the following rough table using your settings will help show the relationship between your step size and bandwidth settings (based on 8.33kHz channelisation as that seems to be what you wanted). You will see that every second 12.5kHz step includes TWO 8.33kHz channels
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Old 06-14-2018, 7:49 AM
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Quote:
Originally Posted by morfis View Post
I've never had SDRSharp default to 12500 steps for airband - it would make absolutely no sense for it to do so? With the older 25kHz channel allocation you would need to take two steps to get to each valid frequency and with the new 8.33kHz channel allocation there are times you'd potentially hear two channels at the same time.

I understand what 'snap to grid' does - I just haven't found it necessary when tuning airband - if I was going to use it on civil airband I'd want it to work at 8.33kHz steps (SDRSharp can do that BUT it would not match the ACTUAL frequency allocations and hence why the Russian plugin should be used)

Perhaps the following rough table using your settings will help show the relationship between your step size and bandwidth settings (based on 8.33kHz channelisation as that seems to be what you wanted). You will see that every second 12.5kHz step includes TWO 8.33kHz channels
Morfis, in my original post I was advising the OP that his bandwidth was too low that it should be raised to 12500, then you posted and said that I must be "confused with the step size". In my original post, I did not make reference to the stepping size. In my second post I said that the version of SDRSharp that I am using defaults to 12500 and it cannot be changed, that was in was again in reference to my original post regarding the bandwidth, nothing to do with the stepping size.
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Old 06-14-2018, 12:26 PM
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I run my bandwidth at 8. For stepsize I can run either 8.33 or 25000 and even 12500. Works fine for me. Plenty of activity..
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