Slim Jim antenna practical?

[galenthurber]

just thinking of the very low projection Slim Jim and was wondering could one be made or is it too impractical and too precise

 

[derbysatellite]

sorry its an old post but thought i'd knock one up for testing.
Its on first floor level, at a window....
N-type with just some scrap copper wire.

 

[derbysatellite]

Above pic is J-Pole, Below is slim Jim. from first tests J-Pole seems to be better. Made to this data.

 

[derbysatellite]

after 12 hours using cheap'o ebay DVB stick un-amped un filtered
I'll leave it running till 8pm tonight (another 12 Hours) then switch over and leave the Slim-Jim running for same time.
I'm impressed with its performance so far, might run a test in a few days with it up a mast.

 

[galenthurber]

welcome to homebuilt antennas, my best is a horseshoe

Horseshoe antenna works, bi-directional beam. stay tuned. 225nm

Just built an ugly horseshoe antenna; it works. it's a smaller version of a 145Mhz one. each arm (L shape) has 1/4wave horizontal & 1/2wave vertical. The antenna is fed where the open end of the horizontal element arms almost touch; 10mm apart. The feed line must come in at 90degrees to the...

forum.planefinder.net

 

[derbysatellite]

Ok,so after 25 hours of testing the J-Pole.

 

[derbysatellite]

tried to edit /etc/rbfeeder.ini via SSH

sudo nano /etc/rbfeeder.ini

but doesn't open the file??? comes up with new file....any ideas as to why?

 

[wiedehopf]

rbfeeder is for radarbox.
maybe rbfeeder isn't installed, pretty much the only explanation i can think of.

Are you looking for planefinder settings?

 

[derbysatellite]

Ooooh lol, yeah sorry i am looking for planefinder settings.
I wanted to start a fresh aircraft plot for this test

 

[ab cd]

sudo nano /etc/pfclient-config.json

Above command will open file pfclient-config.json whose contents are:

{ 
"tcp_address":"127.0.0.1", 
"tcp_port":"30005", 
"select_timeout":"10", 
"data_upload_interval":"10", 
"connection_type":"1", 
"aircraft_timeout":"30", 
"data_format":"1", 
"latitude":"xx.xxxx", 
"longitude":"yy.yyyy", 
"sharecode":"zzzzzzzzzzzz" 
}

After making changes, save the file Ctrl+o and close Ctrl+x.

Restart pfclient

sudo systemctl restart pfclient

 

[derbysatellite]

Thanks, worked. Now plotting on clean slate

 

[wiedehopf]

The restart should be enough for the clean slate.

And you pretty much should only change settings via the web interface.

 

[derbysatellite]

oh right... thanks for letting me know.

 

[derbysatellite]

Slim Jim after 2 days

 

[derbysatellite]

Flightradar Antenna @ 30ft, Flightradar Pro Plus Stick VS USB DVB Unamped unfiltered Slim Jim @ First Floor level behind window.

 

[derbysatellite]

so to finalize this test i also built the well know 8 legged spider to compare against the J-Pole and Slim Jim. All element lengths are 69mm as per tutorial on this forum.
They all show very very similar reception range, but in my opinion the J-pole wins as its far simpler to build and just as effective as the spider.
I don't have an F-plug to SMA adapter to make a solder-less J-pole however i think it should be a recommended easy make solder-less antenna for beginners. The last picture is a quick knock-up of a solder-less J-Pole. Once i have my new antenna analyzer I'll give the true size for each antenna.

 

[Janos Konya]

Above pic is J-Pole, Below is slim Jim. from first tests J-Pole seems to be better. Made to this data.View attachment 2878
View attachment 2877

Using the calculator above, the Velocity Factor should be set to 0.95 - since this is for the copper wire. the 0.83 (83%) is for coax cables with this specification...

 

[Janos Konya]

sorry its an old post but thought i'd knock one up for testing.
Its on first floor level, at a window....
N-type with just some scrap copper wire.


View attachment 2875
View attachment 2874
View attachment 2876

Just to be more exact, it is an open stub J-pole or Arrow antenna. The original J-pole is a DC short antenna. The latest is less noisy and does not tend to gather the dangerous static voltage.