Silly question, when are you on the air?

Started by SWLVK5ANDY, Dec 13, 2024, 06:55 PM

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SWLVK5ANDY

Quote from: VK5TOM on Dec 21, 2024, 11:36 AMAndy have you played with receiving adsb signals locally with your rtl sdr?

I have done, and the data was very interesting (you could say I've been connected to aviation in one form or another as long as I've been working).  Being not far off the flight path into Adelaide airport and reasonably close to Parafield and Edinburgh there is always something new out there.

Saying that, I've just changed from a windows operating system to a Ubuntu based one, so I'm still searching out new applications that work. 

For anyone interested in computers, there is a form of Ubuntu called "Dragon OS" which is specifically designed for ham radio / sdr use.  It has tons of built in apps that cover a multitude of topics, and as it was designed for that purpose they save a lot of head scratching when you try to install them. 

SWLVK5ANDY

OK, the latest installment....

I had a chance over the past week to tear down the long wire I had installed as "not doing anything useful" and constructed a 2 metre / 70 cm antenna out of a couple of wire coat hangers.  Not the more professional job, but it will do as a starting point.

At this point I would have added a picture but I haven't worked out how to yet....

Anywho, Sunday morning 09:00 I tuned into the WIA broadcast on the 2 metre frequency, and after a bit of fiddling I got something that sounded like a human voice.  Using SDR++ it sounded better on USB/LSB rather than just AM, and a bit of tweaking meant I could work out with various versions of AGC I could more or less pick up what was being said.

(For those familiar with SDR++ for some reason it worked best with sampling disabled, I and Q selected gave me variations on just noise).  I have some great pictures, but... well see excuse above!

Now the problem.  Every 15 seconds or so the signal would get drowned out by noise, obviously man/machine made as it has a consistent tone to it and was across swathes of the 2 metre band and beyond.  It would last for two seconds or so, then go, then after about 15 seconds it would repeat.  Pictorially it looked like a peak at the highest and lowest frequency, and the bit in the middle was just noise but at a higher level than the baseline noise.  For those of you who have heard of it, it could almost be described as a "bathtub curve".  Depending on how I zoomed in to the spectrum display changed how many were displayed and how far apart they are.

Obviously I'm getting interference from something, so I will now go off and see if I can do some more investigation and see what I can work out. 

I'll keep you posted

VK5MCH

#17
Hi Andy,

Did you try to listen to the broadcast on 147.000 NFM?

I just tested my RTL-SDR on 2 metres on my GP-93 with all the SDR software at my disposal including ++/play/HD-SDR and everything works fine.
Mick VK5MCH

SWLVK5ANDY

Mick, No I didn't.  And I never thought to try it, next chance I get I will.

Andy

VK5DLZ

I purchased a RTL SDR unit a while back, and had no luck with anything other than local FM. I was quite disappointed in it.

Then a friend who had just got his Standard license brought Paul's (VK5PH) Ironstone Kiwi SDR to my attention. The world of amateur radio suddenly opened up to me and I spent many hours listening in, to the point where I decided to sit the radio licence and get my own transceiver and join in.

I binned my RTl SDR, sat for my Foundation then Standard, purchased a Yaesu FT-710, and now quite enjoy the hobby from the other end.

SWLVK5ANDY

Great post, thanks for sharing it.

I've had my RTL SDR for a couple of years now, and while I could agree that I have been dissapointed at times, I've been around RF systems most of my life so I took it as a challenge to find out what was disappointing and seeing if I could remedy it.

I'm still planning to get my license when I get the time, but for the moment I need to spend more time on the likes of KiwiSDR to see what is out there and then see if I can pick it up myself.  My only issue is that the closest KiwiSDR does not appear to cover the 2 metre / 70 cm bands 

VK5AAD

Quote from: SWLVK5ANDY on Dec 31, 2024, 09:41 AMMy only issue is that the closest KiwiSDR does not appear to cover the 2 metre / 70 cm bands 

You won't find any that do, simply because the KiwiSDR device only tunes 10kHz to 30MHz. It does that in one 30MHz "chunk" though so in a multi user environment for example, one user can be tuning NDBs at 248kHz and another listening at the same time on the 10m Ham band without interfering with each other.

There are other networked SDRs around but only cover a maximum 10MHz at a time, so tend to be single user or only one has control of band being tuned.

The RTL-SDR Blog devices are not bad if you have a genuine one and understand their limitations, especially on HF and below. I have 2 V3 and a V4 RTL-SDR Blog device and they have their uses,  For more serious HF listening especially I prefer either my RSPdx or the Airspy HF+ Discovery.  I could spend more money on devices like the RSPduo and do diversity tuning but I discovered Amateur Radio and have spent too much on transceivers  :)
Richard.
Former IT Security serf
Recycler of human body parts

SWLVK5ANDY

Thanks for that.  I picked up an ATS-25 SDR which is supposed to be good for the HF bands, so when I manage to get a decent 10 metre antenna set up I can cross check it against the closest KiwiSDR.

SWLVK5ANDY

OK, I've got another question for the good people of this forum.  I have the opportunity to put up a vertical antenna of a decent length so which band is most popular around here?  10 metre and 6 metre are both viable options, so which one gets the most traffic? 

VK5MCH

There's plenty on both 6 and 10 metres. 10 offers a lot of voice especially of a weekend as there is always a contest somewhere in the world.
Mick VK5MCH