1
$\begingroup$

Is it possible to combine 2 antennas, each being half the length of a normal antenna for a given band. To be connected to 1 mobile radio. Giving you 2 shorter antennas rather than 1 long antenna, for a better clearance height of the vehicle. How would this be done?

$\endgroup$
4
  • 1
    $\begingroup$ What is a "normal" antenna in this context? Generally, you can combine antennas, but two inefficient antennas do not make one efficient one. You can build a single antenna that spans a longer distance, but that can't be done by connecting "complete" antennas via coax. I think you have some specific band, some specific type of antenna and some specific multi-antenna setup in mind, but we really don't know what you think of - please describe! $\endgroup$ Commented Aug 15, 2023 at 0:08
  • $\begingroup$ Marcus, by normal size I mean a properly sized antenna for any given band of any wave length that you prefer. Those specifics aren’t my question. I’m asking if I took the measure meant for the properly sized antenna for a band or dual band. And then divided that in 2 and made 2 antennas with that length could I then use those 2 antennas work as one and be electrically the proper length. $\endgroup$ Commented Aug 15, 2023 at 3:09
  • 2
    $\begingroup$ I think you may be experiencing the XY Problem... I've certainly experienced it myself many times! The short answer to your question is, "no." A longer answer is below. I think the real solution can be uncovered if you share the problem you're trying to solve instead of asking about a seemingly ill-conceived solution to a mystery problem. $\endgroup$
    – webmarc
    Commented Aug 15, 2023 at 12:58
  • $\begingroup$ @JakeKoenig you'll have to be more specific. I'm an electrical engineer from the field, and I have no clue what a "properly size antenna" would be - you design your antennas to fulfill a specific requirement, and there is always the trade-off between large antennas having more effective area and thus better reception, and smaller antennas being more practical. So, what is a properly sized antenna to you? You are the one that needs to come up with specifics, we can't generalize something that we don't even know the roughest corner data about. $\endgroup$ Commented Aug 16, 2023 at 0:51

1 Answer 1

2
$\begingroup$

I think you may be experiencing the XY Problem... I've certainly experienced it myself many times!

I think you're asking:

My goal is to keep my vehicle hight relatively low, and I'd like to do this by breaking my antenna in half and mounting each of the resulting 2 pieces to get back to "full size."

IF that's your question, then the answer is, "no, not really."

BUT, good news, you can still keep a low profile by using a properly designed antenna. It will have worse performance than a typical antenna, BUT this is the necessary compromise required to achieve your height goal.

For example, here is a compact antenna for 2m / 70cm. I don't endorse this product as I have no experience with it, and just offer it as an example in the category you seem to be looking for.

Understanding that the inspiration for your question is a dual CB antenna kits, they solve a different problem: the trailer can block the signal from an antenna installed near it, and so a second antenna is installed on the other side of the blockage to get full coverage. You're correct that they're installed in parallel and both transmit & receive at the same time. There's a tradeoff of course and that is the radiation pattern of the antenna system is no longer a circle, but rather is very eccentric with the specifics being dependent upon the ratio between the frequency used and the sparation distance of the 2 antennas.

In order for an antenna to radiate efficiently, it needs to be resonant. Resonance is dependent upon electrical length which largely means physical length. Simply cutting a simple antenna in two results in two elements that will now work on a frequency approximately double the original. With proper phasing, you can feed them in series BUT they will NOT work on the same frequency as the original uncut antenna.

In order to get these 2 half size antennas to radiate on the original frequency, they'll each need a base coil or other impedance matching mechanism to achieve resonance AND they'll end up with an eccentric ration pattern as above.

If your goal is to achieve omnidirectional communication AND keep antenna height to a minimum, I don't see a more practical solution than a single shortened antenna....

But since you haven't yet shared why you're trying to cut an antenna in half and get the two pieces to radiate, I have no idea if any of the above is helpful... would love to have that information!

$\endgroup$
5
  • $\begingroup$ I know CB sometimes uses 2 Antennas for trucker radios. I believe that these would be called in parallel. Is there a way to do it in series instead so the RF would get properly transmitted out without crazy SWR $\endgroup$ Commented Aug 15, 2023 at 3:05
  • $\begingroup$ I've updated the answer with more info based on your comment. $\endgroup$
    – webmarc
    Commented Aug 15, 2023 at 12:52
  • 1
    $\begingroup$ I have that compact antenna regularly mounted on my truck. It works quite well. Is it as good as a longer whip antenna? No, I have a 6' whip for far-off-road hilly situations. But I certainly don't need two of the compact antennas 99% of the time. $\endgroup$
    – Jon Custer
    Commented Aug 15, 2023 at 14:47
  • 1
    $\begingroup$ @JakeKoenig Even then, those mirrors on big trucks were not far enough apart for the best pattern and efficiency. $\endgroup$ Commented Aug 15, 2023 at 15:46
  • 1
    $\begingroup$ @JakeKoenig ah so you do have a mental model of what you want to do? Could you please expand that a bit in your question. The trick here is getting specific at first. We can generalize after. But we can't look into your brain and hit exactly what you wanted to know. $\endgroup$ Commented Aug 16, 2023 at 0:54

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .