.....I have built a few coaxial co-linears over the years for 430 MHz and 1296 MHz ham bands.
They work OK. just don't try too many segments as the law of diminishing returns comes into play
here's one on my www site that I that I used to play with ....
https://www.sydneystormcity.com/microwave.htm
cheers
Dave
Hi Dave!
Thanks for sharing the link for drawing of your 2400 MHz Coaxial Collinear antenna.
Nice design. Will give it a try.
The problem I was trying to solve pertains to DIY CoCo made using coaxial cable RG6 vastly used by TV & Satellite installations. This cable and its fittings are low-cost & commonly available. This cable has an Aluminum foil & braid, and soldering is not possible. The method used is "push-pin", i.e. the core of a piece is joined to braid of next piece by pushing the core wire between outer jacket & braid of the next piece. Hence the name push-pin method.
This originates from the relatively new hobby of ADS-B flight tracking using (or misusing) a DVB-T USB Receiver. This receiver is very cheap, $25 if purchased from USA, $10 if purchased from China. This was originally intended for receiving Digital Video Broadcast (Terrestrial) for European System. It has two chips, RTL2832 + R820T. Some wise guys discovered its tuner chip R820T has a wide frequency range (24 – 1766 MHz, can be improved to ~13 – 1864 MHz with experimental drivers), and can be used as Software Defined Radio (SDR). He wrote a driver software, and some others wrote Receiver Software, most popular being SDR# (SDR Sharp). Also one group wrote a software which tuned this tuner to 1090 MHz, and had a decoder to decode position, elevation, speed etc signals transmitted by aircrafts. RTL1090 by jetvison.de for Windows, and dump1090 for Linux/Raspberry Pi. another set of software also sprang which plotted the position data output from these receiver-dfecoder softwares on Google map in a web browser, making a live display of aircrafts flying around the receiver/antenna upto maximum distance of 500 km / 250 nautical miles.
The above development made this hobby tremedously popular, as it required less than $50 investment. Since most hobbyists wanted a low cost antenna as well, the Coaxial Collinear made of RG6 Coax, using push-pin method became very popular. However, as I have mentiond in my first post, majority of hobbyist ended in CoCo with poor performance, a result of lack of expertise, understanding, using cheap quality stuff etc.
My post was specifically for ADS-B hobbyist scenario.
One more problem with these hobbyist is they thing "bigger is better", so they try to make CoCo with 8 to 24 number of elements! they dont understand that every doubling the number of elements increases gain by 3 dB. So to increas gain by 6 dB, the number of elements have to be doubled twice, i.e. 4 times. As you said, the law of diminishing returns applies here.
Regards
abcd