Mobile antenna broke and it still works?

[Danny37]

I had a 5/8 30 inch UHF antenna mounted on my car. Its a 5.5 db gain antenna with two coils and I just noticed as I got home that the top part is missing. It must've gotten loose and detached from the top coil while I was driving.

This antenna is used for recieve only, no transmiting and noticed no change at all with the signal across the board. I measured the antenna now as it only has one coil in the middle with the spring and its around 12 inches.

Does it make it a 1/2 wave antenna now? Should I replace it?

 

[mmckenna]

Depends on the original antenna design. What brand/model is it? Sounds like a colinear design if it had matching coils on the whip. If you lost everything other than the bottom section of whip, it's going to work just fine.

You are probably not hearing any difference since the original gain of the antenna wasn't necessary to receive what you wanted to. If the current antenna is working fine, even though it's missing parts, and you don't care about the looks, then roll with it.

 

[Danny37]

Depends on the original antenna design. What brand/model is it? Sounds like a colinear design if it had matching coils on the whip. If you lost everything other than the bottom section of whip, it's going to work just fine.

You are probably not hearing any difference since the original gain of the antenna wasn't necessary to receive what you wanted to. If the current antenna is working fine, even though it's missing parts, and you don't care about the looks, then roll with it.

It's a browning br-1713-b-s antenna. The coils looked abit different from each other. The bottom one was more square and the top one was more rounded.

I'm fine with the way it looks. Would you happen to know what gain it would be considered now? 2.4?

 

[mmckenna]

Looks like it was designed as a 5/8th's over 5/8th's. The upper coil was for phasing the two sections together. Not sure what the lower "C coil" did, maybe something to stretch the bandwidth.

So, if the top coil broke off and you just have the lower 12" or so section (with the "C coil), then it's now just a single 5/8th's wave antenna. That'll give you about 3dB over a 1/4 wave in a perfect install.

If you are just receiving with it, and you hear everything you want to, then it's good to go. If you plan on transmitting, then you'd want to check the SWR at minimum.

 

[mmckenna]

Sorry, not C-coil, the Amazon page shows it as "C-load"

BROWNING BR-1713-B-S 406MHz-490MHz UHF Pretuned 5.5dBd Gain Land Mobile NMO Antenna (35"")​

35"" tall ; No tuning ; Wideband ; 84MHz bandwidth; Low SWR ; 5/8 over 5/8 wave with C-Ioad ; 160W; Black, chrome-plated stainless steel spring; Premium-quality heavy-duty black chrome-plated solid brass NMO base; Black, chrome-plated stainless steel whip ; Gold plunger-type contact pin; NMO mounting ; Mount sold separately; SWR​

 

[Danny37]

Looks like it was designed as a 5/8th's over 5/8th's. The upper coil was for phasing the two sections together. Not sure what the lower "C coil" did, maybe something to stretch the bandwidth.

So, if the top coil broke off and you just have the lower 12" or so section (with the "C coil), then it's now just a single 5/8th's wave antenna. That'll give you about 3dB over a 1/4 wave in a perfect install.

If you are just receiving with it, and you hear everything you want to, then it's good to go. If you plan on transmitting, then you'd want to check the SWR at minimum.

Good to know, thank you for your help as always. One thing I noticed is that the tip of the antenna is bare and pointy. I wonder if this could be hazardous or may rust since the paint is chipped off. Any thoughts on what I should do to combat this?

 

[mmckenna]

One thing I noticed is that the tip of the antenna is bare and pointy. I wonder if this could be hazardous or may rust since the paint is chipped off. Any thoughts on what I should do to combat this?

I don't know what Tram makes their whips out of, but if it's like other antennas, it should be OK and should not rust.
You can buy replacement corona balls/"don't poke your eyeball out balls" and put it on top, but you'd need to know the diameter of the whip.
Or, just get one of those Jack in the Box antenna toppers and shove it down over it.

 

[FFPM571]

That thing is huge. There are better UHF gain antennas that are shorter and probably better. The Laird comes to mind its 5/8 3db and just a bit smaller than a 1/4 Wave VHF with a spring

 

[merlin]

Like I have been saying all along. For receiving, it hardly matters. The only advantage to single band antennas is they tend to be resonant within that single band. that may help reduce 'out of band' signals except multiples of frequencies.
You will probably pick up any signals that get to the antenna. Low band may fall off a little
Gain only matters with transmitting, same with SWR.
Your antenna was designed with transmitting in mind also. ( I have one, decent antenna)
My brothers scanner antenna is an FM mirror mount antenna, and gets everything 80 Mhz and up.
He gets 700/800 Mhz as well as my CelWave gain antenna. He gets UHF just as well as my MaxRad (Motorola) 5.5 Db UHF antenna.
ACE hardware, if you can find small enough rubber cap-plug, that will fix the broken whip.

 

[Danny37]

Like I have been saying all along. For receiving, it hardly matters. The only advantage to single band antennas is they tend to be resonant within that single band. that may help reduce 'out of band' signals except multiples of frequencies.
You will probably pick up any signals that get to the antenna. Low band may fall off a little
Gain only matters with transmitting, same with SWR.
Your antenna was designed with transmitting in mind also. ( I have one, decent antenna)
My brothers scanner antenna is an FM mirror mount antenna, and gets everything 80 Mhz and up.
He gets 700/800 Mhz as well as my CelWave gain antenna. He gets UHF just as well as my MaxRad (Motorola) 5.5 Db UHF antenna.
ACE hardware, if you can find small enough rubber cap-plug, that will fix the broken whip.

I thought gain mattered when it came to recieving as well. I replaced my rg174 cable with lmr200 and noticed a significant difference.