Collinear vs. J-Pole Antenna

[ASAD]

What's the difference between collinear, J-pole, and J-pole design antennas?

Are Antenex FG series collinear antennas? Are these good for ham repeaters?

FG4605 - Antenex Fiberglass Base Station Antenna (460-470MHz, 5Bd)

 

[ko6jw_2]

The Antenex appears to be a collinear. It is tuned for 465Mhz so it would not work well in the 70CM band.
The claimed gain is 5Dbd. If true, this is considerably more that a j-pole.

J-poles are actually end-fed half wave antennas. Gain is 3Dbi not Dbd.

Why not just buy a collinear designed for ham band?

 

[k9wkj]

collinear jpoles are a thing

 

[DisasterGuy]

It really depends on your application, desired coverage pattern, desired ERP, etc. My "go-to" antennas to cover that band are:
-CommScope DB420
-RFS Celwave PD10055-2

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[cmdrwill]

Antenex, Laird, UHF base antenna insides: Just a copper plated steel wire in sort of a J pole configuration. Not recommended for repeater applications.

 

[k9wkj]

Not recommended for repeater applications.

at the risk of sounding like a id10t
other than the fact it has the same gain as any other single section vertical (and on UHF a single section seems silly)
why isnt it recomended

 

[lmrtek]

These commercial FG single section antennas are fine for repeater use and I've used Laird, antennex, and maxrads on commercial repeaters for decades without issue

But for ham frequencies, the Hustler G6-440 is a better choice

 

[DisasterGuy]

Generally the Laird style are considered more appropriate for control station use than repeater use. For repeater service those mentioned above are most appropriate. There are several factors to consider including wind ratings, lightning handling and pattern. $1000 may sound like a lot for an antenna until you consider a few thousand dollars in feedline, a few thousand dollars for every tower climb, etc.

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[mrsvensven]

at the risk of sounding like a id10t
other than the fact it has the same gain as any other single section vertical (and on UHF a single section seems silly)
why isnt it recomended

For repeater applications you have to consider PIM specs. If an antenna will arc at all, it will generate noise that will effect the receiver. It's only a problem for repeaters where the antenna transmits and receives simultaneously. It's why you shouldn't use braided coax on a repeater. Hardline won't arc while coax can arc from one strand of the braid to another. While brand new coax may work ok, over time it can develop "the crunchies". Fiberglass antennas can do the same: they may be fine for years but after enough flexing in the wind the elements will develop very small cracks that will arc and you will get "the crunchies". The antenna will still sweep fine and work ok for a base station, but an repeater connected to it will hear a bit of noise. Many commercial PIM rated antennas are dipole arrays rather than fiberglass collinears.

 

[ASAD]

Antenex, Laird, UHF base antenna insides: Just a copper plated steel wire in sort of a J pole configuration. Not recommended for repeater applications.

So I spend $200 on a stupid J-pole (Antenex FG4405). Specs said it was collinear. I would rather use Diamond X-300.

Thanks for showing elements.

 

[k9wkj]

So I spend $200 on a stupid J-pole (Antenex FG4405). Specs said it was collinear

if you put another section on top its a collinear
how its fed doesnt make it not collinear

 

[ASAD]

After doing a little research, I found the following page. BC200 and BC205 come with cutting chart and could be cut to a specific frequency. Would you choose Diamond ground plane over Antenex J-pole?

V/UHF STATION ANTENNA/DIAMOND ANTENNA CORPORATION

I know PCTEL, Sinclair and DB are ideal but they are too expensive.