best antenna

[abcd567]

Well the aerial has been up for a day and a half now, its not what i was expecting.

I have had better range from a 8 element (to be expected) how ever i am actually seeing more aircraft in the range it has than i have from other aerials. So overall its actually very good.
[ATTACH=CONFIG]4019[/ATTACH]

Just out of curiosity i am going going to attach it to my radarcape, its currently on a rtl stick on a beaglebone just to see how much difference the input stage and bits actually makes. I will be keeping it in its current location (loft space) for a direct comparison, my normal aerial is on a mast well clear of the house and i wont be going up a ladder just for this

Please see below the "Radiation Pattern" of 3.5-element and 8-element CoCos.

The 3.5el CoCo has a fatter horizontal lobe + extra slanting (35 deg from vertical) lobes which get you more nearby planes. That is why you see more planes.
The 8el CoCo has a very high gain horizontal lobe, which picks far away planes, increasing maximum range. However it's horizontal lobe being leaner than 3.5's horizontal lobe, plus the absence of slanting upward lobes, results in reduction of the number of nearby planes, so you see less nearby planes.

coco 3.5 element shorted at top simulation output.png .. coco 8 element simulation output.png

[lutorm]

I finally got my antenna up on the roof:


I'm now getting 500+ km tracks out over the ocean and wider coverage compared to having it in the window.

[Ressy]

So I'm puzzled why people are getting such bad ranges. I plugged my RTL2832 into the raspberry pi, hooked a 1/4-wave dipole up to a short length of coax, and started dump1090, and was immediately getting detections out to 450km away. Changing out the dipole for a 4-element Franklin gave me out to 475km, and with a preamp I'm now getting slightly over 500km. But this is looking out over open ocean. When I see people getting 100-150km range, I can't but think that it must be a line of sight issue, not an antenna problem.

Absolutely is the LOS problem would be killing it off for almost evgeryone, I dont live all that high, and have limited low level coverage even locally, but high level distances are about 100nm in all but one direction where it was only 7, yes, thats not a typo, I said seven nm, due to N/W neighbours palms, I raised my ant about 1m and now get 90nm in that direction, but unless I blow up the neighbours double story house S/E of me, not much I will ever do about that direction even though I still get down to 2K feet, 30 K's away in that direction.

Using a home made 8 element coco inside 110cm pvc pipe with the base about 4 meters AGL, with 10 mtrs rg6 into a dongle attached to my linux file server (well its always on, so no point getting an RPi just for it)

[abcd567]

I finally got my antenna up on the roof:


I'm now getting 500+ km tracks out over the ocean and wider coverage compared to having it in the window.

Wow! A 2m band J-Pole + 4 element Franklin, all nicely & professionally built & installed in clear open space... I wish I also lived in a house instead of an apartment.
P.S. I think I see an in-Line amplifier installed on the horizontal arm supporting Franklin. What are summer tempratures at your place? Is the amplifier rated for outdoor installation (rain/humidity/temrature etc)?

EDIT dated Sept 15, 2023:
Added below the missing picture of user lutorm's 2m J-Pole + 1090 MHz Franklin Antenna

1090 MHz Franklin and 2-meter J-pole by lortum.jpg

[abcd567]

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Abstracts from another book (Antenna Theory & Design by Stutzman & Thiele) about sleeved antennas:

Sleeve Antennas-1.jpg . Sleeve Antennas-2.jpg

[lutorm]

Wow! A 2m band J-Pole + 4 element Franklin, all nicely & professionally built & installed in clear open space... I wish I also lived in a house instead of an apartment.
P.S. I think I see an in-Line amplifier installed on the horizontal arm supporting Franklin. What are summer tempratures at your place? Is the amplifier rated for outdoor installation (rain/humidity/temrature etc)?

Thanks! I'm pretty happy with how it turned out. Not professional by any means though -- strictly amateur!

Not sure about the amplifier. It looks pretty well sealed, but in any case it was 6 bucks, including shipping from China, so if it gives up it's not a big deal. Given that I live in one of the rainiest towns in the US, we should find out soon. The picture is from this post, which has some more info. Nothing that people here doesn't already know, though.

[F-EGLF1]

Thanks! I'm pretty happy with how it turned out. Not professional by any means though -- strictly amateur!

Not sure about the amplifier. It looks pretty well sealed, but in any case it was 6 bucks, including shipping from China, so if it gives up it's not a big deal. Given that I live in one of the rainiest towns in the US, we should find out soon. The picture is from this post, which has some more info. Nothing that people here doesn't already know, though.

Looks very nice, however there does not appear to be any weather proofing on the connectors to the amplifier, some self amalgamating tape over them might be a good idea to stop the rain getting in and wrecking your cable.

[abcd567]

The image below shows Radiation Patterns for collinear antennas, 1-element to 8-elements.
Source: Radio Antenna Engineering by Edmund A. Laport, former Chief Engineer RCA.

Collinear Patterns.jpg

[peterhr]

Thanks! I'm pretty happy with how it turned out. Not professional by any means though -- strictly amateur!

Not sure about the amplifier. It looks pretty well sealed, but in any case it was 6 bucks, including shipping from China, so if it gives up it's not a big deal. Given that I live in one of the rainiest towns in the US, we should find out soon. The picture is from this post, which has some more info. Nothing that people here doesn't already know, though.

I would wrap the amp and the connectors in self amalgamating tape and shade the (wrapped) amp from the sun so it doesn't bake (especially if wrapped in black tape).

[lutorm]

Looks very nice, however there does not appear to be any weather proofing on the connectors to the amplifier, some self amalgamating tape over them might be a good idea to stop the rain getting in and wrecking your cable.

The connectors have internal o-rings so (supposedly) they are weather proof. Like I said, we'll see.

[abcd567]

The connectors have internal o-rings so (supposedly) they are weather proof. Like I said, we'll see.

Better order one more amplifier in case.......It takes couple of weeks to ship from china. Better to keep a spare handy.

[peterhr]

Better order one more amplifier in case.......It takes couple of weeks to ship from china. Better to keep a spare handy.

I'm wondering if it's worth taking the mast down to insert an amplifier at the antenna base before it gets to the co-ax ... I have all the bits to do it.

[abcd567]

I'm wondering if it's worth taking the mast down to insert an amplifier at the antenna base before it gets to the co-ax ... I have all the bits to do it.

The advantage gained may be subdtantial if you have long & lossy cable, otherwise advantage may not be worth the effort in many cases.

Calculte coax loss using length attenuation figures of your coax. This will help you make a decision.

Finally it all depends on your zeal to attain the optimum.

[charan]

Today i made a discovery of my coax ! while i removed 1 element in 8.5 coax and i kept it on my table.. today i kept my mobile over it and when i took mobile the element came with the mobile (attached to speaker).. is this common or i have a cheap coax? will this have any effect on range of my antenna?
i ordered RG402 yesterday.! IMG_20140506_081140.jpg

[F-EGLF1]

Today i made a discovery of my coax ! while i removed 1 element in 8.5 coax and i kept it on my table.. today i kept my mobile over it and when i took mobile the element came with the mobile (attached to speaker).. is this common or i have a cheap coax? will this have any effect on range of my antenna?
i ordered RG402 yesterday.! [ATTACH=CONFIG]4030[/ATTACH]

This is common with cheaper coax, the better ones are pure copper, the cheaper ones are copper plated steel, provided the screening is good then it should not have much impact on your range.
Ben.