Hi guys,
I want to share with you a schematic of a 70cm antenna, designed by PCTel, built in Russia and sold by a business in UK. More about the model here :
http://www.saraelektronik.com/pdf/204_SIGMA Antene catc-datasheet-v1.pdf
Although it performs well, it has a design flaw which makes the fiberglass rod come out of its base due to vibrations. Also, PCTel confirmed that it has been discontinued.
Among many types of collinear designs I've seen, this ones looks and performs great for repeater installations.
Because I collected the "remains" of the dead antennas, I opened one up and measured the elements then drew the schematic available here :
http://www.xpander.ro/Sigma_Collinear_Design_draft1.pdf
Now, I could build it on my own and correct the flaws but I was wondering if any of you can answer a few questions :
1. If somebody knows or understands, how does the matching works? I believe it is made by tuning A2+B+C1 elements? The upper element looks like λ/2 @ 439Mhz
2. How can I adapt the schematic for 2m band?
3. If the gain is 5.2dBd, a 0dBd version can be obtained by using only two λ/2 elements and keeping the end-fed the same?
I will start my experiments in the spring and will get back with details, but for now I just want to understand how it works and how can I adapt the same design to different frequencies and gains.
Thank you.
Regards,
Razvan
I want to share with you a schematic of a 70cm antenna, designed by PCTel, built in Russia and sold by a business in UK. More about the model here :
http://www.saraelektronik.com/pdf/204_SIGMA Antene catc-datasheet-v1.pdf
Although it performs well, it has a design flaw which makes the fiberglass rod come out of its base due to vibrations. Also, PCTel confirmed that it has been discontinued.
Among many types of collinear designs I've seen, this ones looks and performs great for repeater installations.
Because I collected the "remains" of the dead antennas, I opened one up and measured the elements then drew the schematic available here :
http://www.xpander.ro/Sigma_Collinear_Design_draft1.pdf
Now, I could build it on my own and correct the flaws but I was wondering if any of you can answer a few questions :
1. If somebody knows or understands, how does the matching works? I believe it is made by tuning A2+B+C1 elements? The upper element looks like λ/2 @ 439Mhz
2. How can I adapt the schematic for 2m band?
3. If the gain is 5.2dBd, a 0dBd version can be obtained by using only two λ/2 elements and keeping the end-fed the same?
I will start my experiments in the spring and will get back with details, but for now I just want to understand how it works and how can I adapt the same design to different frequencies and gains.
Thank you.
Regards,
Razvan