My first collinear antenna

[SpaxmoidJAm]

@SpaxmoidJAm
So, how much will it impact my setup? 3-4 meters coax from spider antenna to DVB-dongle, and a FA bandpass Filter in between?

i'm guessing at your using something like rg-6 with a run that short probably around a fifth of a db (next to nothing) for the cable alone. i can find numbers for the filter (flight aware one) at around 1.65db insertion loss. So lets say 1.85db (a ratio of 1.5).

When your dealing with small power levels this can have a big effect, which why an LNA at the mast head is always a good idea.

@abcd to be fair when i read several i may have miss read read that as seven, but even so you found some ropey filters http://194.75.38.69/pdfs/CBP-1062C+.pdf has insertion of 0.5db around where we want it.

[abcd567]

The CPB-1062C is a ceramic filter with very low insertion loss. It is very costly also. Generally SAW filters are used as these are very cheap, but have insertion loss of 2.5 to 4 dB.

See the Uputronics LNA which has a built-in filter. The standard version is fitted with a SAW filter and costs £35.99. Same LNA is available with Ceramic filter instead of SAW at £83.99, an extra payment of £48.00 just for Ceramic filter.

https://store.uputronics.com/index.php?route=product/product&product_id=50

.....

[SpaxmoidJAm]

i see where your coming from, but when your dealing with marginal signals being cheap doesn't pay off.

that minicircuits ceramic filter is 26 US dollars and only £29 (i actually live new mini circuits Europe so i can at least save on shipping).

edit:apologies for the thread over take

[FR24-BB8]

I have now tested some more with a new spider made of a F-connector and bare copper wire. I recieved the FA bandpass filter some days ago and installed it and got a very large decrease in range, around 50 nm at most, due to the db loss from the filter i guess.
I then installed an amplifier for test, it is actually an amplifier for TV 40-862 Mhz 18 Db, but i figured it probably would amplify signals at 1090 Mhz to, but not at 18Db probably a lot lower figure. Anyway, below is some range plots, with spider only and then with spider + filter + amp. I do not have a range plot for the setup with only spider and filter cause i immediately noticed the drop in range and removed the filter. I will try to get an amplifier for higher frequencies and try to mount it more close to the antenna. For testing now i have it in this order: filter then the amplifier and then the reciever.

The number of aircrafts tracked have gone from around 70-80 per day to 120-130, and the range is slightly better.

Spider only (outer red line 200 nm):
SPIDER_COPPER.PNG

Spider with filter and amp (outer red line 200 nm):
SPIDER_COPPER_WITH_FILTER_AMP.PNG

[FR24-BB8]

My third bare copper spider sealed with melted glue and measured real carefully with calipers going up tonight.

[abcd567]

@FR24-BB8
Looks great! Hope it performs well. Waiting for results.

Edit:
How much is:
1) length of horizontal part (measured from whip to bending down point)

2) length of slanting part (measured from bending point to tip of radial)

[FR24-BB8]

@abcd567

1: It´s half the length of the diagonal of the SO 239, sqrt(25*25+25*25)/2= 17,7 mm

2: The slanting part is 69 mm

And the center whip is also 69 mm from the f-connector.

[FR24-BB8]

@abcd567

I already get readings from 170 nm.

Edit:
So the first impression is that it is at least not performing worse than the one before.

[abcd567]

@FR24-BB8

"It´s half the length of the diagonal of the SO 239, sqrt(25*25+25*25)/2= 17,7 mm"

Your brain works like mine

[FR24-BB8]

@abcd567

Haha.. Yeah, i´m trying..

[SpaxmoidJAm]

it looks like you pretty competent have a go at a coco antenna.

[FR24-BB8]

@SpaxmoidJAm

Thx.

I've already made a coco, but did not get as good results as with the spiders. But I will for sure try to make another one and be more precise with the section lengths than I was with the first one.

[abcd567]

@FR24-BB8
The very first step in being precise is to use a coax for which manufaturer's data sheet / specification is available, so that you precisely know the value of Velocity Factor, and determine the accurate length of elements.

[SpaxmoidJAm]

some time ago i made a little how-to on making a soldered 5 element coco, you can ignore the comments about connectors, but it does illustrate a technique for joining sections together reliably (often the problem with push together ones) i cant find the vna plot for this one but iremember it not being to far off.

http://forum.flightradar24.com/threa...5-element-coco

[FR24-BB8]

My first collinear antenna

@abcd567

I'm thinking of buying RG58C/U 50 ohm, and what I can find online is that the velocity factor is 0.659. Is this correct? I can't get the data sheet for the cable.

Edit:
I'll try to get hold of the specs at the hardware store, at least cable manufacturer.

Edit:
I found another 75ohm cable at another store, and got a hold of the velocity factor 0.85. So let's start building then.