Trial Run Results for Three Types of Whip Antennas

AnirbanSen

Member
If someone is tampering with it, the spider is one of the easiest to restore.

And i wouldn't be surprised if they would just destroy something more solid with more force.
If someone wants to do damage to an antenna installation, they'll find a way.
Exactly my sentiments.
If you see the picture here, someone is actually taking the trouble of climbing the ladder to the very top.
(Point to note, the antenna is mounted not where intended on the picture, but the diagonally opposite corner (closest to the airport) + least restrictive view of the horizon.)
 

AnirbanSen

Member
I have RTL-SDR Tripple Filtered LNA. Eliminates Cell/Mobile signals.

Note:
The Bias-T and DC adapter in the photo are NOT supplied with the LNA. I have purchased these separately
Why did you purchase the Bias T when you yourself have made a good design? What extra feature/protection does the commercially sold Bias T have to offer?
 

ab cd

Senior Member
Why did you purchase the Bias T when you yourself have made a good design? What extra feature/protection does the commercially sold Bias T have to offer?
My DIY bias-t was made usig tv splitter with F-connectors. The LNA's connectors are sma. Also having a screw terminal for DC adapter wire is convinient. This bias-t is not costly only $4.
 

AnirbanSen

Member
Just reporting:

There was a small thunderstorm today. As soon as the rains started, I found the signal going off completely.

The 1/4 wave ground plane was again on its side which is most likely the handiwork of a vandal. I wonder who it is since it requires the ability to climb ladders and most people may not feel its worth it. On the other hand, I don't want to rule out wind gusts completely.

Usually, even with the antenna on its side by 90 degrees, close by aircrafts can be spotted. I reconnected some of the F-connector from the antenna to the lightning protector, but to no avail.

I finally concluded that the amplifier installed barely two weeks ago was busted. The damage was most likely storm/rain related since the last signal generated by Graphs 1090 was exactly when it started raining). Perhaps due to the rain or the vandal's handiwork, the load (antenna) had become disconnected leading to the antenna going poof!

So, best not to invest in that antenna. Let's see if the seller will refund/exchange.

While I await the rtlsdr blog's antenna (which is in transit), I am back using the satellite amplifier at 17V DC.
 

AnirbanSen

Member
I have some spare cam to monitor my cat remotely. But power and weather proofing is an issue. Rains have not fully subsided.
 

AnirbanSen

Member
1) I cannot discount the possibility that this vandal is some large bird trying to sit on the antenna or on the mount and fiddling with the antenna.

2) I took a long sewing needle (the long ones used to knit wool) and taped it with the last length of the RG6 almost till 1mm of the radials leaving the coax. Can this cause reduction in signal?

3) I also installed the RTLSDR Triple Filtered LNA which @wiedehopf recommended. But the ADS-B range is barely 50 miles!!!!

I also plan to change the antenna sometime by cutting in half a 8 ft AmazonBasic RG6 coaxial (triple shielded) and using each 4 ft as separate single piece antenna wire. I would coat the radials and the lead wire with transparent nail polish (top coat) to prevent oxidisation of the copper. Perhaps this might keep the copper a bit more gleaming.
 

AnirbanSen

Member
1) Removed the knitting needle
2) Removed the Bias-T/DC Block from the front end of the LNA

No change.

See the drop in range from the inline amplifier to the RTLSDR amplifier:
dump1090-localhost-range-6h.png
 

wiedehopf

Member
Maybe one of your SMA adapters for the rtl-sdr LNA is not working correctly. (RP-SMA?)

Switch off the voltage and see if the reception changes, if it doesn't, the LNA might be the wrong way around.
(there was one case where it was the wrong way around in the housing so that one user had to install it backwards)

You might also want to test the rtl-sdr LNA spectrum
https://forum.flightradar24.com/threads/11450-Do-I-need-a-Filter-Find-RF-Signals-In-Area

Some of them are defective, a spectrum, even only 5 minutes will show you what's going on.

How much amplification is the inline amplifier rated at?

At last, i'm sure you measured the voltage without the load, so the voltage at the top can still be the problem.
Try feeding 4 V and 5 V at the bottom and check how the reception changes.
If it changes a lot, you can also try feeding 5.5 V, checking the voltage without the load doesn't give you the voltage drop.
Voltage only drops when the load is connected.
 

AnirbanSen

Member
1) I double checked the SMAs and it appears fine. In fact, the same setup had been operating on the inline amplifier (20dB). I also double checked the connectivity between the lead/radials and the F connector entering the lightning protector.

2) Switching off the voltage DOES NOT change the reception. Turning the LNA in reverse removed ALL the signal.

3) There are green LEDs inside the LNA and when powered, I could see the green light bleeding out faintly in the dark. So I guess the LNA is being powered.

You think its a defective LNA?
Consider the graphs below:
dump1090-localhost-signal-24h (1).png


Earlier signal was the inline amplifier working at 17.5V DC.

The voltage measured (at the power supply) with the load connected is 4.27V. The supply voltage at the LNA location is now 4.50V without load. I only powered slightly lower because you had earlier said the thermal noise may be an issue at 5V.

In the current set up, I cannot immediately boost to 5.5V.
 

AnirbanSen

Member
The first section is the inline amplifier. The second section is the rtl-sdr LNA. Been using at AGC. Also noticed huge > 3dBfs signal. Reducing gain to 32/20 did not increase the number of airplanes or range.

Cannot measure LNA current presently.

See the heatmaps here. I've updated the post. As per heatmaps, the signal is very good.
 
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wiedehopf

Member
Your multimeter can't do current? :/
Isn't the power supply where your receiver is?
Putting the meter in series with the power supply is all that is needed to measure the current.

Anyway with such a strong signal i doubt that the power supply is the problem.
Are you sure you succeeded in changing the gain?
The graph looks like way too strong a signal.

Anyway you'll want to record a spectrum for the LNA: https://forum.flightradar24.com/threads/11450-Do-I-need-a-Filter-Find-RF-Signals-In-Area

It will show if the LNA is defective.
Pretty sure they will send you a new one if you send them the spectrum and it's not what it should be.
 

AnirbanSen

Member
Anyway you'll want to record a spectrum for the LNA: https://forum.flightradar24.com/threads/11450-Do-I-need-a-Filter-Find-RF-Signals-In-Area

It will show if the LNA is defective.
Pretty sure they will send you a new one if you send them the spectrum and it's not what it should be.
The spectrum is here: https://forum.planefinder.net/threads/do-you-need-a-filter-find-out-rf-signals-affecting-ads-b-reception-in-your-area-cell-mobile-etc.1027/post-8752

Your multimeter can't do current? :/
It can, but everything is soldered up. I'll check this in a day or two.

But as per the spectrum, it is working fine. Then, what could be reducing the range? Reducing the gain in steps has not resulted in increasing the range till now. Am I missing something? Strong signals have been eliminated with gain of 38.
I will double check the antenna when I can. Put a different antenna and check.
 
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