0
\$\begingroup\$

I am not really working in radio circuit design but I am mostly working on embedded systems sides of things. I recently build a system to listen AIS signals. I ordered these telescopic antennas to receive messages on 161.975MHz (https://www.amazon.se/gp/product/B08DKWYCXD/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1). However, I am a little bit surprised with the item arrived. Signal and ground connections are shorted. I ordered 3 of it and it is the same for all. Is this a common thing in radio world? As far as I know, good antenna should have a large ground plane and clean separation between signal and ground for better reception. What's your opinion on this? Thanks for your opinions and feedback! /Deniz

\$\endgroup\$
2
  • \$\begingroup\$ Are you using this whip-style antenna on a handheld radio? Consider your safety first. If that antenna should contact high voltage, your body might complete a current-path to ground, putting you at risk. Consider your radio safety second - a DC path to shell might divert that high voltage from destroying the radio circuit front-end (a good thing). I would hope that at 162 MHz, that path-to-shell is high impedance. \$\endgroup\$
    – glen_geek
    Jun 10, 2021 at 13:18
  • \$\begingroup\$ Thanks for the life saving tip Glen. The device I am working on is receive only, but it is always good to remember. However, I ordered these antennas to receive AIS messages on the device I am desiged, not on off-the-shelf handheld radio. \$\endgroup\$
    – dnz
    Jun 10, 2021 at 13:23

1 Answer 1

0
\$\begingroup\$

How are you measuring it - with an ohm meter?

While it's possible you have defective units, it's very common for there to be some kind of matching network at the input to the antenna.

You need to test with a VNA or other RF device to be sure.

\$\endgroup\$
3
  • 1
    \$\begingroup\$ I am measuring with simple multimeter in continuity mode. I have other antennas tuned different frequencies and signal and ground are not shorted. \$\endgroup\$
    – dnz
    Jun 10, 2021 at 12:53
  • 1
    \$\begingroup\$ yeah, but it's only a 0Ω impedance at a frequency of about 0 Hz. You want this antenna to work at ca 162 MHz, so that's the frequency at which the impedance matters. \$\endgroup\$ Jun 10, 2021 at 13:47
  • \$\begingroup\$ @dnz Different antennas have different designs. Yours might have a coil to ground...which at DC is just a piece of wire - AKA a short. \$\endgroup\$
    – mike65535
    Jun 10, 2021 at 17:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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