Looking for ideas on why amp kills performance by > half

I had a simple setup. I have this antenna " Outdoor omnidirectional antenna 1090 MHz ads-b 6 dBi for flightradar 24 r.ebay.com/A5Z7Om & I have it on a mast outside with a run of RG6. At some point I was going to throw on a grounding block - but I have not yet (probably next spring I will). Anyway, I used to feed FR24 but after meeting a FA user, I decided to try FA - I like it a lot. He had thrown an amp on his setup & got a HUGE performance increase. So I tried the same thing. I bought the following items:

DirecTV SWM Power Inserter Supply 21V PI21R1-03 SWIM LNB KaKu r.ebay.com/3PWg4F


DC power block F in-line coupler coaxial TV cable voltage blocking adapter r.ebay.com/aZ4OyV

This last weekend I put it all up. The Power Inserter Supply is inside the shack - I have the line leaving my USB Dongle to the ’ Signal to IRD ’ and the line then heads out to the antenna from the ’ Power to SWM ’ connector. The RG6 runs up to the mast & into the AMP from the amp to the antenna I placed the DC blocker then the line continues to the antenna.

I have 20-21v coming out of the power inserter. I don’t have the amp reversed/backwards. However, I went from over 100+ contacts throughout the day to a dozen or so… I killed all the auto gains in RTL1090 (Tuner AGC & RTL AGC are off) but I have the manual gain slider all the way up to 49.6 - anything lower & I lose everything. With any of the gains on it gets worse.

Anyone have any ideas? Before the amp I was getting catches at 200 to 250. Now, it’s not even close - totally bewildered how an AMP that does so much good for another could slaughter my setup. Hope this is detailed enough but if I missed some info you need, please ask. Any help appreciated!

I had similar result with an amp that I killed - it was working fine and I made the mistake of removing and reconnecting it with power supply turned on :frowning:

I can rule this out as I had everything set up but I had no power to the unit & I was getting nothing. I tried this deliberately to see how well it would work with no power. Answer: It doesn’t work at all.

How did you know you had the issue? What did you do to confirm what it was?

i think the biggest disadvantage is the concept itself.

today it makes no sense to transport analog datastraem via long, thick and expensive cables - amplifying these signals makes it even worse.

the way to go is - the shortest possible antenna-cable → transform analog to digital nearby antenna (e.g. via raspberry) → transport digital datastream via usb, ethernet, wifi or whatever …

just my 5 cent

It may come down to this, or close.

I’m at the point I just want to remove the amp, put a barrel connector on where the amp was & take off the power inserter & DC blocker and then just forget the whole thing.

I’m wishing I hadn’t cut into the line for the amp but maybe I could just put my grounding block there & make the best of that. I’m not sure a grounding block is even needed though.

don’t be sad - i also often buy things and spend money for nothing …
just sell it on ebay and life goes on :slight_smile:

btw. all you need is a raspberry pi, sd-card, power-adaptor, wifi dongle, dvb-t dongle - together about 100$

  • antenna e.g. the nice one from flightaware - about 50$
    => all inclusive 150$

All good, I just pulled everything and I’m back where I was 130+ A/C tracking, lots of messages, & back where I was. I put a gold plated barrel where the amp was taped it all up. Since I have now hacked into my RG6, anyone suggest a grounding block for this? If not, I’ll just run another straight piece of RG6 from dongle to antenna.

My setup is the NooElec R820T with a run of RG6 to my ADS-B omnidirectional, 6 dBi gain, collinear with 4 elements. Very simple. No wasted lengths & until a couple days ago, no unneeded cuts/connections. I use RTL1090 to PlanePlotter(FA), FR24, & VRS.

I guess if no one has any ideas on this, I’ll just remember - If it ain’t broke, don’t fix it.

I’m running the same kind of set up that you have. Except I don’t use a DC blocker and I’m using a home brew groundplane for antenna.
I was playing with the RTL1090 AGC settings and trying to find the best possible output. I used the Planeplotter message count meter (the
“m” key) to watch what effect changes on the RTL1090 Tuner AGC did to message count. I could NEVER get any positive results when using
RTL1090 Tuner AGC in the “OFF” position and manually adjusting the slider switch. Every time I tried the “OFF” position and moved the slider
either way, my message count dropped a bunch. I could never get the message count back up to match what the AGC mode gave me. So I’ve
put both Tuner AGC and RTL AGC in the on position and always operate that way. I realize the RTL1090 manual says to turn Tuner AGC off if
you’re using an outside antenna but that doesn’t work for me. The inline amp may have something to do with it.
Hope you get yours figured out.

I ordered this in-line amp http://smile.amazon.com/gp/product/B00EPHDPME which had positive reviews in another thread on this forum. The seller shipped a completely different brand with a crude label that looked like a black-and-white photocopy. When I first installed it I had similar results: my positions/second fell to almost zero. After some troubleshooting I discovered that the satellite diplexer I use as a high-pass filter for ADS-B (to keep my HF amateur radio transmitter from overloading the front-end of the RTL-SDR dongle) caused the in-line amp to become unstable. The problem occurred with the diplexer installed either before or after the amp. I had to move the diplexer between the RTL-SDR dongle and the power inserter to keep the amp happy. With the amp installed my positions/second increased by about 20%, but the number of aircraft seen increased by less than 10%: I see mostly the same aircraft, I just track them further away with the amp.

This is the inline amp I first tried. It worked as advertised. It worked so well that I ordered a second one to use as a back up as I’m likely
to someday forget to unplug the power inserted when I should.

amazon.com/Paladin-Tools-967 … B000X2D3E0

My first amplifier which I purchased 2 years ago, was unbranded, and frequency range 47 - 2400 MHz.
When I installed it, I ended up in same problem as you.
I removed it from my system.

My second amplifier, which I purchased 2 years ago (shortly after first one), was branded (RCA D903) and I got excellent results.

Nine months ago I found an amplifier on eBay, unbranded, frequency range 950-2150 MHz, and exactly like yours, for Canadian $3.66 + Free shipping from China.
Allured by price, I ordered it.

When it arrived, I replaced RCA D903 by the new unbranded one, and my system collapsed!

I removed unbranded amp, and and put back RCA amp.

I threw both unbranded amplifiers in garbage, and lived happily ever after :slight_smile:


Thanks guys, I think the amp is the problem - based a a well intentioned suggestion I bought a garbage amp. Well, now I know it’s garbage. I need to find a nice amp now, I’ll look for that RCA unit - unless there are other suggestions. Thank you all very much for your help & advice so far.

Never mind, I could see the RCA D903 was going to be a hard find (out of production?) - I bought 2 for 8$ ea. & free shipping.

RCA D903 amplifier is not the only make/model which is good. There are many other brands/models which are equally good or even better, available at reasonable price.

The reason I chose RCA is that I found it available in a electronics & hobby shop in my area for $4 (in store purchse, they dont sell on line).

However, if you are interested to buy RCA one, here are the links:

$9.95 + FreeShipping


RCA In-Line Satellite Amplifier
$7.95+$1.95 Shipping



when you put the amp on did you play with the gain of the DVB-T stick?

It maybe that everything is just to loud for it and its swamped.

When I use Windows machine with RTL1090 receiver/decoder software, I keep gain to 49.6 (maximum) and it is ok. Lowering the gain reduces number of planes & max range.

When I use Raspberry Pi with Dump1090 receiver/decoder software, I set gain to “max” (=49.6), and it is ok. Lowering the gain, or using agc reduces number of planes & max range.

Yeah, I tried every thing I could think of in regards to settings. It seemed like if I didn’t have RTL off & gain maxed at 49.6 I got little to nothing - even maxed it was still just terrible. I also now think its the amp, it looks exactly like the ones pictured above.

I’ll come back & let you all know how the RCA does, again - appreciate the help & advice. Thank you!

Those amps are supposed to be 14-18v at 20v you may be pushing it a bit.

You don’t need the DC blocker above the amp with that antenna - to verify do a continuity check between the center and outside connector … there should be no connection.

I’d try another amplifier - in case the one you have is a lemon.

Have a good look around for cell towers, etc - if you have one nearby, you might need the FA filter before the amplifier (more expense, though it would be good if someone would lend you one to try)

My Power supply is rated for 15V DC. When I measured, it gives 20V DC (it is a cheap unregulated power supply).
My 14-18V DC RCA Amplifier is working OK since last two years with this 20V DC supply :slight_smile:

His DIRECTV Power Inserter is rated for 21V DC.
Amplifiers rated for 14-18V DC may be slightly pushed, but will still work.

If he uses a PerfectVision Amplifier (Rated for 8 to 29 V DC), it will match with Directv power inserter rating (21V DC).


  • abcd567 -

Ohh boy, I really should have approached this better. The RCA is rated for 25-40 mA also… This DirecTV power supply pushes 1.2 A


I saw the Perfect Vision but I wasn’t sure how good it was & I had tunnel vision on the RCA.

  • PeterHR -

You wrote, " You don’t need the DC blocker above the amp with that antenna - to verify do a continuity check between the center and outside connector … there should be no connection. "

Are you certain of this. I’d hate to fry the thing out or something - Also, if I didn’t need it, could it be what was messing up the whole operation?