hole in antenna affects performance?

[unclebabar]

let's say you have a simple antenna consisting of a bar of metal 1 cm wide and however long, if you drill a hole (0.5 cm diameter) in the bar near where it attaches to the balun, is that going to affect the performance of the antenna significantly? Intuitively I would have thought that less conducting pathways = less signal strength.

The reason I ask is because I just bought an antenna, and there is a hole, perhaps drilled by an overzealous factory worker where no hole should be.

 

[ScottMac]

How big is the hole, physically and relative to the size of the antenna element?

Where is the hole relative to the energizing contact of the element?

Is this the driven element (is it the part the cable connects to)?

What frequency or purpose is this antenna built for?

It is a receive-only or does it also transmit?

 

[unclebabar]

the hole is 0.5 cm diameter and is part of a 1 cm wide bar that connects 2 halves of a total size 29" H x 42 " W x 4" Deep structure (it's actually the Terrestrial Digital DB8 antenna that I'm refering to). There is another same sized bar on the other side, connected with a screw and a bolt. The side I am concerned about just has a screw and an empty (no metal, no nothing) hole.

These 3 contact points (2 screws and bolt) are the only electrical contacts that penetrate the plastic housing of the balun/transformer. I don't know if the bolt (or any of the screws for that matter) is actually connected inside.

The screws/bolt are approximately 1 inch away from the f-connector for signal out.

The antenna is for receiving ATSC tv signals.

 

[bobdole369]

You won't have a problem. You can pick up ATSC (as well as any RF transmission) with just a random length of wire. A hole would only slightly modify the SWR and radiation pattern of the antenna if you were transmitting with it - and would do so very slightly (depending on frequency). You are looking at only a 0.05% difference in performance on receive (just pulling numbers out of my ass - meaning to say you won't notice a difference).

It sounds like the ground side is what has just a hole - not a big deal as neither side of a dipole antenna doesn't need to be connected - just there, it's capacitively coupled if it isn't directly connected. You still get an E and M field around that side, it just needs to be a conductor in the general area. If you were transmitting it would still work too.

 

[unclebabar]

thanks that makes sense.

the reception is pretty good with the antenna mounted inside compared to a different powered antenna rated with 2db more gain (RCA 24769) . I get 3 more channels but lost one, well maybe if I mount the antenna outside or higher up I'll get it back.

 

[Jabbernyx]

Depends on how it was designed. Lots of patch antennas have weird slots in seemingly random locations. Have to look at the far field distribution in a (preferrably fullwave) simulator.