HELICAL UPS N DOWNS

[scudGB]

HI ALL
following a flurry of posts from baldgeek and james west i decided to do some quick tests of my rtl v2 patch, 8 turn helix and 26turn helix
very basic have a line of site to 54W just on tree line from attic window ,so using airspy and sdr# tuned to 10500 acars
the patch gave me 5.4 ish snr
8 turn helix gave me 7.4 ish snr
and the 26 turn just about hit 6 snr woefull result as i used to be so happy with this ant as i could do ok on alphasat with it from within roof space
the 8 turn helix was made to tighter tollarence than 26 turn as 8 turn on 3d printed former with correct coil pitch all the way up also exact diamater former from online calculator ,,
where as the 26 turn was coil spaced with lines on masking tape
tests quick n dirty as was pointing each antenna with left hand and trying so watch laptop in a sunlit room
so message to james west size does matter mate especialy the mm scud

 

[thebaldgeek]

The tight tolerance of the 3D printed helix is the key as you so well point out.
The 'more is always better' plagues us from gain to antenna sizes.... Not always true.

Slight rant, people build 16 element co-linear antennas for their ADSB antennas and think they have amazing range. At 1090Mhz, you need mm precision and they just cant build it like that. A well built 1.4 wave vertical always out performs them.
Off to have coffee before I really get started <grin>

 

[scudGB]

LOL
so true my best adsb is standard 1/4 wave with 8 radials cable tied to a fibreglass pole out of attic skylight it sways a bit but can build up a decent count ,,not bad considering am in a vally
mm precision and my nanova do me fine ,,had a spell of building basic patch antenna with double sided pcb then spending time to tune to aero section not bad results
allready thinking of printing something a bit longer and reducing infill on each section so it not to heavy at unsupported end
have you ever tryed combining two helicals ?? scud

 

[prcguy]

A properly designed 16 element colinear should greatly outperform a 1/4 wave ground plane when the aircraft is at great distance and near the horizon from the receiving antenna point of view. At high angles like straight above or 45 deg up or 60 deg up the aircraft is fairly close and anything should pick it up. A large colinear should show what it can do at 200+ miles. I test this and see this all the time. It sounds like the home brew crowd is not getting their antennas built right or the plans are flawed.

The tight tolerance of the 3D printed helix is the key as you so well point out.
The 'more is always better' plagues us from gain to antenna sizes.... Not always true.

Slight rant, people build 16 element co-linear antennas for their ADSB antennas and think they have amazing range. At 1090Mhz, you need mm precision and they just cant build it like that. A well built 1.4 wave vertical always out performs them.
Off to have coffee before I really get started <grin>

 

[scudGB]

probably true
but since am basicaly living in a egg cup 1300 ft absl but completly surrounded by hills 600 to 1000ft higher never gona build one,
thats why most of my radio play is about sats or high aircraft its all i can see ,,cant complain live in a nice part uk but worst location ever lived for radio play scud