Helical help/suggestions


#1

I’m relatively new to Outernet/L-band and while waiting for APAC to come back online I have been attempting some of the helical designs elsewhere on the forum. However I’m not yet able to build one as good in terms of SNR as the active patch. Some pictures of my 8 turn attempt - suggestions welcome… is thicker wire a better option than the copper tape? how critical is the coil diameter (this example is 63mm)…

Also one question - I’m not 100% clear on the the first 1/4 turn. I understand this should be ~2mm above the ground plane but where does the first turn end - 50mm above he feed point, or 50mm above the end of the first 1/4 section (assuming 50mm between coils)… asked another way - does the top of the helix finish in line with the Feedpoint or the end of the 1/4 parallel turn section?


#2

Hi rack201, according to what I read about it looking for info on google and based on my experience with my helix antenna is that the top of the helix finish in line with the Feedpoint (one lap is completed when the top of the helix is aligned with the start or feedpoint) I made mine of copper wire and has a square bronze reflector, I have read that this type of antennas is ideal for experimenting.


#3

The parallel section is a 1/4 wave section to match the 50 Ohm feedline with the 150 Ohm Helix. The N (some integer number) turns ends at the same place the matching section ends, further up the tube.

Here is a nifty link to a [Helical Antenna Design Calculator] that someone shared with me (http://www.daycounter.com/Calculators/Helical-Antenna-Design-Calculator.phtml)