Need opinion on my antenna results

[shiloh]

Hello All,

I'm still pretty new at this hobby and would like some opinion on the results I'm having with my brend new antenna installation.

I've installed an "Antenni.net" 5dbi omni on my rooftop (this antenna : http://www.anteni.net/adsb/index.html#!/~/product/category=3647502&id=15504149)

I have a 50ft run of LMR-400-Ultraflex to my receiver (currently a dongle).

According to the Times Microwave loss calculator this is the loss I'm having with my run:

Code Select Expand


Product: LMR-400-UltraFlex
Frequency (MHz): 1090
Run Length (Feet): 50
Attenuation (db/100 feet): 5.184
Attenuation (db/100 mtrs): 17.011
Average Power (kW): 0.43
Total Run Attenuation(dB): 2.6
Efficiency (%): 55.0


The typical contact range I'm having with this setup is around 100NM. I see very sporadic contact above that range but within 100NM I get good coverage.

I must admit that I was expecting a greater coverage range than what I am currently getting.

So, what do you think?

I'm wondering if I have too much loss with my coax run.

Anyone knows if this antenna has a good reptutation?

thanks a lot in advance for your input, it's much appreciated.

[Bethsalem]

Hi Shiloh

I'm getting about 75nm with an indoor 1090MHz antenna with my R820T dongle, so your range isn't too bad.

I've no experience with your antenna or cable, but regardless of your antenna and cable setup, you're very unlikely to get 200 plus nm coverage with a dongle with costs a small fraction of a Beast or a SBS-3.

Regards

Stephen

[kered]

As Steven says you can't expect results from a 6 pound dongle as from a 300-450 pound purpose built receiver, but i would have thought you should get a bit more distance.
The attached screan capture is with an rtl dongle, home made colinear antenna and normal 75ohm satelite antenna cable with a run of about 18meters(59ft).
A bigger image can be seen here

http://i677.photobucket.com/albums/vv137/incubator_album/RTL-homemadecolinear-75ohmsatcable_zpsb68228e2.jpg

A good clear all round positioning of the antenna is a great help, my colinear is just clear of the house ridge and as you can see i get nearly 200nm on a regular basis to the NW which is the only clear direction, to the south only about 50nm as i'm half way up a hill. The greatest distance i have seen so far is 226nm but thats not normal.
If you have a good clear all round view of the horizon i would expect about 150nm at least.

Something to try is changing the tuner and rtl AGC on the dongle, i seam to get better results with tuner gain manual at 49.5db(max) and RTL AGC on. When a plane drops out try different combinations to try to get it back

Derek

Edit:- the program had been running less than half an hour when i took the screan capture.

[Attachment deleted by Admin to save file space]

[kered]

Another screen capture but using SDR# with ADSB pluggin  instead of rtl1090 software
http://i677.photobucket.com/albums/vv137/incubator_album/adsbscopeSDRanddongle_zps09734807.jpg

note the distance to NW

[IanH]

R820T dongle, Radarbox 1090 aerial in loft of house running Dump1090 on a Raspberry Pi.

On a slight hill so above some nearby houses but below those further up the hill.

Up into Scotland and over the North Sea I'm getting ranges of over 150nm.


Ran SBSPlotter this afternoon and got max of 194nm.

http://www.ihld.co.uk/sbsplotter_dongle_20130420.jpg

This shows maximum range.

I think that you should be getting better ranges.

[shiloh]

Thank all for your input. I understand that the performance of a dongle will not match a high end unit however your comments confirm me what I've seen elsewhere that dongle are capable of getting more range than what I get. I still think that my long run of coax is a factor with 45% of loss.

I'll try a few thing and report back. I like the idea of the Raspberry PI in the attic too.

[Anmer]

I still think that my long run of coax is a factor with 45% of loss.

That's a problem that no receiver can easily overcome.

My antenna has 10m Ecoflex10 that terminates at ceiling level in an upstairs room.

Expensive, but this gives me USB connectivity across my home network.  Works with SBS, RadarBox, microADSB and even GNS5890.  But not a dongle using RTL1090.

Silex SX-DS-3000WAN

[kered]

All the tables i have seen LMR400 is good low loss cable, half the loss of rg213, as long as its proper lmr400 and not a chinese copy.
most tables give about 14db loss over 100 meters  at 1ghz which is on par with westflex most use.

Check your connections, and antenna position.
Don't plug the dongle directly into a PC usb port, use a cable to separate it from the pc's interference
better still into a powered hub(that makes sure it gets the full voltage)
Try different tuner agc settings
Also it may be off frequency, check it out with sdr# or the likes against a known frequency ie a fixed beacon and see how far it is out
then try adsbsharp with the adjustment done and see if things improve(i don't know if you can adjust it in rtl1090)

A bit here and a bit there should improve things

good luck
Derek

[shiloh]

I tried a few things last night.

-Moved the dongle 10 feet away from computer using an active USB extender cable and a powered hub

No difference at all.

-turned off automatic gain on the dongle and set manual gain to max

It did help, no major improvement but I do see better coverage overall

-Switched from RTL1090 to ADS#

This did the most improvement. I would says 15 to 20% increase in range. ADSB# seems to decode weaker signals better however it does not feed raw data and cant be used in a ground station/mlat setup.

I'll try some more things and report back. When weather will allow I'll climb on the roof with a laptop and dongle connected directly to the antenna and see if the range is much better. if it is, then COAX loss is part of the issue. BTW, I do have genuine Times Microwaves LMR, bought it at a reputed local ham shop.

thanks again to all for your help! it's much appreciated.

[Anmer]

-Switched from RTL1090 to ADS#

This did the most improvement. I would says 15 to 20% increase in range. ADSB# seems to decode weaker signals better however it does not feed raw data and cant be used in a ground station/mlat setup.

Interesting article here with comments from Andy at Jetvision.de about RTL1090 vs ADSB# (ADS-B Sharp)

http://www.hamradioscience.com/ads-b-sharp-ads-b-decoder-for-windows/

[shiloh]

I didnt noticed the message rate they are talking about. For comparision purpose I compared an 8 hours range plot form RTL1090 vs another 8 hours range plot with ADSB#. this is how I saw the range increase. Anyhow, it's good to have options