Finally found my next antenna project..a collinear dipole array for the 70cm US ham band.

The general idea:

enter image description here

(image courtesy https://link.springer.com/referenceworkentry/10.1007%2F978-981-4560-75-7_52-1)

I don't have enough RG58 or LMR240 on hand to use for this, but I have a ton of RG8...would that be suitable?


Good RG8 such as Belden 9913 has less loss than RG58 or LMR240, so as long as the thicker diameter doesn't cause you trouble, then it should work fine for your project.

  • $\begingroup$ Not sure, but would a slightly different velocity factor not require the lengths of the individual pieces to be altered? I believe that in theory the bigger diameter would lead to a slightly bigger bandwidth but the difference likely won't be noticeable unless with specialist measuring equipment. $\endgroup$ Jul 16 '20 at 16:43
  • $\begingroup$ @Dieter there's so much unsubstantiated and downright conflicting information presented online by ham enthusiasts, and a mysterious absence of scientific validation...It does indeed stand to reason that there would be a relationship between the velocity factor of the cable and the ideal length of each section. But at some point I just jave to stop reading random blogs and such and start building and analyzing. $\endgroup$
    – user14945
    Jul 16 '20 at 17:07
  • $\begingroup$ Case in point: the guy who gave me the RG8 last summer said it wouldn't be any good for UHF...I took this at face value and never actually looked at the datasheet until this morning...and it is indeed Belden 9913. $\endgroup$
    – user14945
    Jul 16 '20 at 17:09
  • $\begingroup$ Not arguing with that. Hence "not sure..." and "I believe in theory... ". If you're looking for scientific evidence (whatever that is), I'd think you're better buying measurement equipment and trying it out. $\endgroup$ Jul 16 '20 at 17:59
  • $\begingroup$ Although I can wholeheartedly recommend "Reflections, Transmission lines and antennas" by Walter Maxwell. He goes over a lot of "common knowledge" in the ar community, explaining why some of them are misconceptions and what's really going on. A refreshing read. $\endgroup$ Jul 16 '20 at 18:04

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