I am trying to work a 700mhz LTE signal with a DB2 uhf bowtie television antenna. I find the cellular signal to be horizontally polarized. Can the bowties simply be twisted 45 degrees in both directions to obtain the correct polarity, or will the difference in element spacing defeat the attempt?

  • $\begingroup$ Hm, cellular sites these days usually are +-45° cross polarized, not horizontal (if anything, very old sites, think 2G, not 4G, were vertical). How do you know it's horizontal? $\endgroup$ – Marcus Müller Oct 4 '20 at 17:56
  • 1
    $\begingroup$ Hello Gary, and welcome to ham.stackexchange.com! $\endgroup$ – rclocher3 Oct 5 '20 at 15:06

Welcome to HamSE, Gary, and thanks for an interesting question.

We should be grateful to Russel Renaud, VA3RR, for posting his NEC2 simulation model of the DB2 antenna. Importing the model to the 4NEC2 simulator, we find that the antenna pattern is primarily horizontally polarized:

enter image description here

Assuming the antenna is "in the clear" - that is, no other conductive structures are present to affect the situation - simply rotate the entire antenna to achieve a different angle of polarization.

As you surmise, twisting only the elements will very probably disturb the overall pattern and the impedance of the antenna.

  • $\begingroup$ Thank you Brian. I was worried that twisting the bay would miss half the signal. Are the transmitted signals both + and - 45 degrees? Maybe adding a second antenna and turning both opposite? $\endgroup$ – Gary Oct 4 '20 at 11:01
  • 1
    $\begingroup$ I don't know the polarization of the transmitted signal, Gary. It could be horizontal, vertical, circular or cross-polarized. If it H or V, rotating the linearly-polarized DB2 to the "wrong" polarity will reduce the received signal strength by half (3-dB), a useful analysis technique. If the received signal strength doesn't change, the transmitted signal may be cross-polarized; i.e., the transmitting antenna my deliver some H and some V radiation. $\endgroup$ – Brian K1LI Oct 4 '20 at 11:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.