Trial Run Results for Three Types of Whip Antennas

AnirbanSen

Member
This LNA is proven and has 3 filters on board: https://rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/

It's 27$ including shipping, with 3$ added for slightly better shipping.
I'll try this out after checking out the existing filter. The antenna would now be placed on the higher roof. The location would not be very easily accessible and possibly quite dangerous for vandals. It seems the vandal is an old lady.

No matter if you use a filter in front of the LNA, i would highly recommend using one behind the LNA.
(no matter the type)
If you are confident you can solder the SAW filter to 2 connectors while keeping the losses acceptable, go ahead.
But at GHz frequencies such undertakings require knowledge about the subject.
I can put this between the power inserter Bias Tee and DVB-T.

What really affects the efficacy of SAW and Bandpass Filters? Not finding clear literature online comparing the two.

FUTURE:
Anyway, whenever the components are gathered and I restart the new installations, I plan to use the following sequence:
First, I determine which antenna is the best. For this, I would be testing on the Pi powered by a power bank with a mobile hotspot - all on the roof with 1m of coax.

The PCB antenna would be easiest and everything can be housed in a PVC pipe. However, if the coax spider or the SO-239 spider works better, then mounting it on the roof may tough. Exposure to pollution, temperature, wind has already made the old coax spider look quite sad under a month.

When the first part is done, I'll be adding the filter(s) and re-testing. Finally, I'll rig up the LNA+ BiasT and the entire length of coax and bring the Pi back down to the apartment. Ultimately, I aim use a 230V AC to 12 V DC, 12-5V DC buck converter, and a 7Ah battery to build continuous power supply. I really wish I could borrow a VNA from somewhere.
 
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wiedehopf

Member
I've put somewhat flexible glue on my spider.
It has survived the winter 20 cm next to the chimney of our wood furnace.
It's black but performance is not affected.

It's mounted to a narrow PVC pipe (electrical cover tube, kinda flexible) with the glue, the cable comes out the bottom of the PVC pipe.
I wanted to pull it out and replace it with the PCB antenna, taping that to the same tube while the cable goes down the center.
But i didn't bring a knife or tool on the roof so the spider has stayed :)
 
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ab cd

Senior Member
20190614_175113.png20190614_175159.png

On phone cannot make better sketch than this one. The horizontal line between two inductors is core wire of Coax
 
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AnirbanSen

Member
Thanks. Have been travelling a bit. But this is exactly how I imagined.
I may be using a switching power supply of 230 to 12V DC and use that the power the Bias-T,a d a buck converter of 5V to power the Pi.

Testing will commence as soon as the weather obliges.
 

AnirbanSen

Member
While awaiting the LNAs and in-line amplifiers (no idea when they would arrive), I decided to test 4 antennas last night on the roof.
i) The DVB-T stock antenna (original length)
ii) The PCB 1090MHz antenna (with and without a Bandpass filter)
iii) A 4 legged SO-239 spider (with bandpass filter and with a HDTV amplifier)
iv) A 8 legged handy coax spider (with bandpass filter and with a HDTV amplifier)

2871


#The stock antenna was picking more signals than my regular handy spider that is mounted few floors below. I wanted to use this as a "control" antenna.
#The PCB antenna was quite disappointing. This would have been the best candidate for a roof mount inside a PVC pipe. Also, keeping the antennas straight proved to be a challenge but ultimately done with a notebook.
#The 4 legged SO-239 was good, but since I couldn't solder 4 more legs in the middle of the connector, its performance was poor. The solder was just not adhesive enough on the steel.
#The handy spider did apparently pick up signals from 250 nm+ away according to FlightAware when both the filter and the amplifier was on.
I checked using @wiedehopf's Graphs1090 and Planefinder Client's Stats Page where the receiver bandwidth hit 6kbps (peaking). (In comparison, the present handy spider on the lower floor peaks at 2kbps)

The testing was late night/early morning when the flights activity starts reducing. I will do some more testing at a better time if its breezy.

Any ideas on how best to mount a coax spider about 1 ft higher than a wall? I was thinking of using an old dish tv mount. Alternatively, a metal rod bent in the shape of an L so that its slightly away from the wall and higher. I also have to think of ways to keep a powered LNA and BIAS-T in a waterproof container below the antenna.

Any other designs that could work better than the spider? (Knowing I don't have a VNA for testing)
 

Stealth

New Member
[QUOTE

Any ideas on how best to mount a coax spider about 1 ft higher than a wall?
[/QUOTE]

Some decent glue for around 400mm (about a foot or so) should pin the co-ax and allow another foot to extend above the wall. However, at the end of the day, unless you have a superb situation, you will need to look at whether you want want to:
1. Get great results
or
2. Play around with bits and pieces

If it is #2 then keep fiddling, if its #1 then find a way to put up a decent antenna and stop wasting your time.
 

wiedehopf

Member
Check if the PCB antenna is missing solder joints on the connector.
Seems that is the case with quite a few of the ones sold without the tube.

If any of the pads are not soldered to the ground of the connector, solder those joints if you can.

That's why i linked a specific seller for that PCB antenna with tube, because the quality is known.
Anyway if you can add the solder joints the performance should improve.


Also be sure to provide only 3.3 or 3.5 V via the bias-t for the rtl-sdr LNA (that's the one under way?).
At higher voltages it gets unnecessarily hot and the performance is not improved as far as i can tell.
If you only have 5 V, just put a 7 to 10 Ohm resistor in line.

This should extend life of the LNA significantly and might even improve reception due to reduced thermal noise.
 
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AnirbanSen

Member
[QUOTE

Any ideas on how best to mount a coax spider about 1 ft higher than a wall?
Some decent glue for around 400mm (about a foot or so) should pin the co-ax and allow another foot to extend above the wall. However, at the end of the day, unless you have a superb situation, you will need to look at whether you want want to:
1. Get great results
or
2. Play around with bits and pieces

If it is #2 then keep fiddling, if its #1 then find a way to put up a decent antenna and stop wasting your time.
[/QUOTE]
I want to be free to play around, but I am thinking of getting a bent L made of iron or an old dish TV mount. The place will experience high heat and winds and torrential rain as well.

Probably finalise on the handy spider fixed sealed with epoxy. This will have the option of easy replacement as well as changing the antenna for a collinear later.
 

AnirbanSen

Member
Check if the PCB antenna is missing solder joints on the connector.
Seems that is the case with quite a few of the ones sold without the tube.

If any of the pads are not soldered to the ground of the connector, solder those joints if you can.

That's why i linked a specific seller for that PCB antenna with tube, because the quality is known.
Anyway if you can add the solder joints the performance should improve.


Also be sure to provide only 3.3 or 3.5 V via the bias-t for the rtl-sdr LNA (that's the one under way?).
At higher voltages it gets unnecessarily hot and the performance is not improved as far as i can tell.
If you only have 5 V, just put a 7 to 10 Ohm resistor in line.

This should extend life of the LNA significantly and might even improve reception due to reduced thermal noise.
Will check for the solder joints.

As for the LNA, the LNA you linked is from a European site. They play by the rules and any packet stating contents over USD20 gets stopped at customs. Sorting that is a headache.
From Aliexpress, that LNA was not available.

So I have ordered 2 basic Saw filters and 2 10-2000Khz LNA (supposed to required 12V). Also, 2 in-line amplifiers were ordered which is also on some ship somewhere.

Waiting for those to arrive for now.
 
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wiedehopf

Member
Not what i meant.
The outer conductor of the connector needs to be soldered to the board in 4 places. (or 2 places, not sure, just check if there are unsoldered pads at the connector)
Otherwise one of the ground planes isn't directly connected and the signal doesn't like that.

How did you hold the antenna anwyway?
If there was anything near the PCB that will reduce performance.

Too bad you couldn't get the rtl-sdr LNA :(
It really provides superior signal quality.

But it seems you are already getting good reception so i'm sure it'll be ok.
 

AnirbanSen

Member
2872


2873


Antenna was held up by the connecting wire and a paper notebook to the side. Definitely not the best way, but not so bad for such an abysmal performance.

The rtl-sdr LNA - will get it after I evaluate the existing stuff.

I returned home today to see that my feeder, despite being "online", was not receiving any signal. I added the HDTV amplifier yesterday and it could be that the amplifier overloaded the DVB. Seems to be working after keeping it off for 10 mins. (Rebooting Pi did not help).
 
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derbysatellite

New Member
Hi,
So my first attempt was the coax spider with an f connector. Unfortunately, the results were very bad.
No aircrafts were picked up in the 8 hours that this Pi was connected.

Initially, the connection was made with a 7 metre RG6 (75 ohm) added to by a 5 metre RG 176 (which is thin enough to connect with an MCX connector).

I figured the signal loss would be significant and eliminated all but 10cm of RG176 but kept the 7 metre RG6. Still, there was nothing being picked up. What could have gone wrong? There were no line shorts - I had a multimeter to test with.

I will next attempt the cantenna and the coke can (the standard size has now been replaced for a 5cm diameter can - so I might have to actually buy something which is atleast 69mm in diameter).



In the meantime, what do you think of the following products:

1) https://www.aliexpress.com/item/32968513963.html
2) https://www.aliexpress.com/item/32951457619.html
personally i wouldn't bother with either of them items of aliexpress.
1 is a wideband satellite amp, so would imagine it will need the voltage from the satellite receiver to power it. (no voltage out of usb dongle)
2 i purchased 1 of these from ebay, didn't work for long so in the end i purchased the flightaware pro stick and pro stick plus. they both have built in amp, the plus also has a 1090 Mhz filter to. they work well for me.
Just my thoughts ;)
 
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derbysatellite

New Member
So I am facing an unrelated issue.

I recently modified my existing handy spider to Pi coax by putting in an F Connector so that the HDTV amplifier can be inserted in the existing setup. My existing antenna started picking up flights from a little further.

The issue starts when there is a power cut. Due to the heat, electricity sometimes goes off for a few mins. The Pi is not yet under any UPS.

When the power returns, the signal becomes zero. Both Graphs 1090 and pf client stats page show the same 0 kbps / no signal.

I thought the amp was overloading the DVB. But restarting does not seem to cure it really. Removing the amplifier did not stop the outage. In fact, I put the stock antenna directly to the dvbt. Even then the signal continued to be 0.

Could a power cut somehow affect the dvbt or the pi? Sometimes the pi works very slowly when the power returns and needs a manual forced reboot. But this problem has to be at either the dvbt or the pi since the rest of the circuit was changed.

Any ideas?

hi, i was having heat issues with my usb dongles cutting out, my dongle is connected directly to my antenna up the mast, i used a usb fan and put it all in a project box (including my PI Zero W) on my mast. works a treat now even in 30+ degs heat.
 

AnirbanSen

Member
BTW a cheap UPS device try a usb battery pack.

usb charger from 240v into battery bank then battery bank to you Pi
I'll will be using a switching power supply which stores power in a 12V 7ah battery and use a buck Converter to reduce voltage to 5V.

The unit is working fine now.
 

AnirbanSen

Member
personally i wouldn't bother with either of them items of aliexpress.
1 is a wideband satellite amp, so would imagine it will need the voltage from the satellite receiver to power it. (no voltage out of usb dongle)
2 i purchased 1 of these from ebay, didn't work for long so in the end i purchased the flightaware pro stick and pro stick plus. they both have built in amp, the plus also has a 1090 Mhz filter to. they work well for me.
Just my thoughts ;)
Well, the fun of building it also goes out with too much out of the box gear. That said, I haven't ruled out their stuff yet. And it will take time to acquire anyway.

The challenge is to obtain the best possible signal, amplify just the 1090 Mhz signal, and filter out the rest.
 

wiedehopf

Member
but not so bad for such an abysmal performance.
Well on the second picture you see the missing solder.
Those pads need soldering which is probably not too easy as you it has high heat capacity.
I'd recommend using a hot air gun to preheat everything and then complete the missing solder joints.
 
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