Co-phasing Puck-style Antennas

[AccuNut]

Hello all!

I’m new to radios in general but have poked around for a while gleaning what I can.

From what I have gathered, co-phasing antennas increases gain.

I am wondering if it is possible to co-phase puck style antennas? Not the 3+inch ghost antennas, more like the Larsen LP450NMO (1.5”). They are unity gain and I am hoping to achieve 3dB.

I understand that whip antennas offer better performance, and there are those who detest non-whip antennas. I’m not trying to start a debate about whether I SHOULD use a puck antenna, but I am trying to go “super-ghost” if you will with my antenna install.
I have a Jeep JKU (which I know is a difficult antenna platform) with a hard top. If co-phasing would give me 3dB I can mount them to my roll cage under the top. Unfortunately there is not enough room there for a standard ghost antenna, and I intend to avoid adding an antenna outside if it is at all possible.

Thank you all in advance for any info you can provide!

[Guest]

So putting aside all the other stuff you asked us to put aside…….
 do you have a steel or aluminum roof?   That is a ground plane antenna ground plane antennas will not work correctly both rx and tx.  Even if the swr is low with out it’s still not going to be right with out a 12-18” metal all around it.  Same with the midland ghost and many (most) others.  Notice ground plane not chassis ground.  

[Hoppyjr]

Unfortunately, if you have the hardtop the Larsen LP450NMO won’t work on the speaker bar. It does fit on the JLU, but won’t on my son’s JKU. Maybe the JKU soft top would clear, but just skip that and…..

The good news….. mount that sucker to the cowl panel under the windshield. It blends in well, works fantastic, and if you should ever decide to remove it, replacing that cowl panel is simple and relatively inexpensive.

Here’s photos of our install.

[nokones]

1 hour ago, AccuNut said:

Hello all!

I’m new to radios in general but have poked around for a while gleaning what I can.

From what I have gathered, co-phasing antennas increases gain.

I am wondering if it is possible to co-phase puck style antennas? Not the 3+inch ghost antennas, more like the Larsen LP450NMO (1.5”). They are unity gain and I am hoping to achieve 3dB.

I understand that whip antennas offer better performance, and there are those who detest non-whip antennas. I’m not trying to start a debate about whether I SHOULD use a puck antenna, but I am trying to go “super-ghost” if you will with my antenna install.
I have a Jeep JKU (which I know is a difficult antenna platform) with a hard top. If co-phasing would give me 3dB I can mount them to my roll cage under the top. Unfortunately there is not enough room there for a standard ghost antenna, and I intend to avoid adding an antenna outside if it is at all possible.

Thank you all in advance for any info you can provide!

You mean mount them like this? This was a temp. install that I used on my 23 Wrangler 2Dr "IZARUBICON" while I was waiting for my Larsen Glas-Mount to be delivered.

[nokones]

Thus is my Larsen Glass'Mount antenna. The antenna performs better than I thought it would.

 

[WRQC527]

31 minutes ago, nokones said:

Thus is my Larsen Glass'Mount antenna. The antenna performs better than I thought it would.

 

The folks who say they don't work are the folks who have probably never tried them. 

[nokones]

28 minutes ago, WRQC527 said:

The folks who say they don't work are the folks who have probably never tried them. 

I've used them before. I used them on two different C4 Corvettes. The ones I used before where the Antenna Specialist/Antenex Cellular Look-a-Likes. They were also great antennae and had the trimming adjustment Pot. I never had any difficulty in communicating with them at least I couldn't tell and was never disappointed in their performance.

[AccuNut]

4 hours ago, WRXP381 said:

So putting aside all the other stuff you asked us to put aside…….
 do you have a steel or aluminum roof?   That is a ground plane antenna ground plane antennas will not work correctly both rx and tx.

The roof is fiberglass. Kinda a good thing/bad thing since I can’t use it as a ground plane on top, but conversely it shouldn’t affect internal antennas as much.

As for the ground plane, I should be able to cook up something for that. The cab above the rear rollbar is basically invisible unless I have the hatch open, so a piece of sheet metal would virtually disappear up there.

3 hours ago, Hoppyjr said:

Unfortunately, if you have the hardtop the Larsen LP450NMO won’t work on the speaker bar.

I was actually thinking the rear rollbar. There is enough clearance for it there if I found/built a mount to account for the backward slope of the bar itself. (Turns out the rear bar is not round).

That cowl mount is pretty slick! If I can’t find a good solution inside I might just give that a shot!

3 hours ago, nokones said:

You mean mount them like this? This was a temp. install that I used on my 23 Wrangler 2Dr "IZARUBICON" while I was waiting for my Larsen Glas-Mount to be delivered.

Similar yes! Except the JKU has a second crossbar in the back due to the longer body. I am hoping to mount it to that.

I am still curious if it is possible to co-phase them to achieve a 3dB gain. Even if I do end up with an exterior mount it would be nice to have the extra range from such a low-profile antenna.

Is there any reason they couldn’t be co-phased? I’m not entirely familiar with how ghost antennas achieve adequate transmission to start with, so I’m wondering if the design inherently hinders co-phasing.

[gortex2]

You will will not gain anything by trying to cophase the antenna. In all reality the correct way is to use a power divder which just cuts your power in half to each antenna. I tried to use the Larsen on my JK but its a bit too tight for the hard top. Fine on the soft toft. I run a 1/4 wave on the front fender and it works just fine. Many use the cowl and on the JK its a good spot as well. 

[AccuNut]

10 hours ago, gortex2 said:

You will will not gain anything by trying to cophase the antenna.

Could you explain why please? This is exactly what I am trying to get a better understanding of so any info about why it would/wouldn’t work would be appreciated.

10 hours ago, gortex2 said:

In all reality the correct way is to use a power divder which just cuts your power in half to each antenna.

Good point. Is this the main reason you wouldn’t recommend trying it? Would the transmit power be so far reduced that any transmission pattern improvement would be lost?

For example, would a 30W radio transmitting on a unity gain antenna generally outperform a 15W with a 3dB antenna in terms of range? (Flat terrain, minimal obstructions).

[AccuNut]

Oops.

Edited June 1 by AccuNut
Deleted due to accidental duplicate post.

[gortex2]

I dont recomend it cause thats not how this works. Have you ever seen a police car, fire truck or ambulance with cophased antennas ? GMRS falls right in the middle of the commericla LMR world. Antennas built for LMR are built to be used as that antenna only. This isn't HF or lowband. There is really no need to do what yolur talking about. Buy the proper antenna and install it. 

[SteveShannon]

15 hours ago, AccuNut said:

Could you explain why please? This is exactly what I am trying to get a better understanding of so any info about why it would/wouldn’t work would be appreciated.

Good point. Is this the main reason you wouldn’t recommend trying it? Would the transmit power be so far reduced that any transmission pattern improvement would be lost?

For example, would a 30W radio transmitting on a unity gain antenna generally outperform a 15W with a 3dB antenna in terms of range? (Flat terrain, minimal obstructions).

If you really want to get more gain, pick a different antenna.  All phasing would do is change the pattern of the antenna.  That’s what gain is, a change in the propagation pattern that favors certain directions at the expense of others.. Usually you would use antennas that are designed to take advantage of it.  But if they aren’t designed for it, you might be surprised at the effects. 

Using two antennas in parallel without doing anything else drops the impedance in half, which causes a change in SWR. That’s great if the antennas were a high impedance type tuned for phasing in the first place, but if they’re tuned to present 50 ohms each to a connected radio, like most antennas are, now you have a 25 ohm antenna system and an SWR of 2.0:1 if it was perfect in the first place.

There’s much more that goes into phasing two antennas than just hooking two or more in parallel.  What kind of pattern are you looking for?  Phasing two antennas by placing two on the same horizontal plane can increase signal strength forward and back, but it does so at the cost of sideways propagation.  That might be what you want if you’re driving on a long piece of interstate, but might be bad if you’re on a jeep trail. 

[AccuNut]

@SteveShannon thank you that explanation helps a lot!

My curiosity is now satisfied. Looks like if I want to go 3dB gain I’ll be getting an antenna built that way.

Now to decide between trying a 3dB behind the rear rollbar or putting the puck antenna up there.

Then again, that cowl mount is still an option.

@nokones was that a gain antenna you had mag mounted to the rollbar? What kind of performance did you get?

Also, @Hoppyjr what kind of range are you getting with the cowl setup? I’m curious since it’s a 0dB antenna.

Lastly for both of you fine folk: is there a noticeable difference between performance in front vs behind your Jeeps with those respective setups?

Still kickin’ around the idea of maybe a single puck mounted high with a custom ground plane mount…but I like options!

Thanks to everyone else who chimed in too! I appreciate all the input!

[Hoppyjr]

[mention=6309]SteveShannon[/mention] thank you that explanation helps a lot!
My curiosity is now satisfied. Looks like if I want to go 3dB gain I’ll be getting an antenna built that way.
Now to decide between trying a 3dB behind the rear rollbar or putting the puck antenna up there.
Then again, that cowl mount is still an option.
[mention=10435]nokones[/mention] was that a gain antenna you had mag mounted to the rollbar? What kind of performance did you get?
Also, [mention=9524]Hoppyjr[/mention] what kind of range are you getting with the cowl setup? I’m curious since it’s a 0dB antenna.
Lastly for both of you fine folk: is there a noticeable difference between performance in front vs behind your Jeeps with those respective setups?
Still kickin’ around the idea of maybe a single puck mounted high with a custom ground plane mount…but I like options!
Thanks to everyone else who chimed in too! I appreciate all the input!

I’m not sure where you got “0 db” as the specs suggest about 2.4 but I think it varies. I initially had the Midland 3db “Ghost” antenna and I find the Larsen outperforms the Midland in actual use.

We were in my son’s Jeep in North Bend (Washington) and hit a repeater that is over 70 miles away (Gold Mountain). The terrain is not flat. We were quite pleased. I regularly hit the same repeater from about the same distance in the Toyota too.

[SteveShannon]

6 hours ago, Hoppyjr said:

I’m not sure where you got “0 db” as the specs suggest about 2.4 but I think it varies. I initially had the Midland 3db “Ghost” antenna and I find the Larsen outperforms the Midland in actual use.

I looked at several different sites that sell the antenna.  I found only one (https://www.tessco.com/product/450-470-mirage-antenna-black-68593) that actually gives the antenna gain using meaningful units. All the others said either “unity gain” which means the effective power is multiplied by one, which is mathematically the same as 0 dB added, or simply said 2 dB, which has no reference and is thus completely ambiguous.

Tessco properly expressed the gain referenced to an isentropic antenna (dBi).  They list the Larsen as having 2.15 dBi, which is exactly the same as 0 dBd (decibel referenced to a dipole), meaning it has the same gain as a dipole. A dipole always has 2.15 dBi.

Gain dBi (dBi)

2.15 dBi

[nokones]

8 hours ago, AccuNut said:

@SteveShannon thank you that explanation helps a lot!

My curiosity is now satisfied. Looks like if I want to go 3dB gain I’ll be getting an antenna built that way.

Now to decide between trying a 3dB behind the rear rollbar or putting the puck antenna up there.

Then again, that cowl mount is still an option.

@nokones was that a gain antenna you had mag mounted to the rollbar? What kind of performance did you get?

Also, @Hoppyjr what kind of range are you getting with the cowl setup? I’m curious since it’s a 0dB antenna.

Lastly for both of you fine folk: is there a noticeable difference between performance in front vs behind your Jeeps with those respective setups?

Still kickin’ around the idea of maybe a single puck mounted high with a custom ground plane mount…but I like options!

Thanks to everyone else who chimed in too! I appreciate all the input!

Yes, it was the Laird 3 dB Phantom antenna I used on the rollbar. As for the performance, it is very difficult to evaluate because in the Phoenix Area, we are very fortunate to have great repeater coverage from various high elevated repeaters. 

The simplex communications was not a problem but the simplex was within a close group of approx. 17 Jeeps on a trail run. 

I used the the Phantom antenna last year on my Porsche during a National Porsche Club event in Palm Springs. I came across a severe head-on collision up in the mountains overlooking Palm Springs and I was using a Kenwood TK880 24-watt radio to call in the accident because of no cell service and a repeater station was about 20 or so miles away and I had no problem with going through the repeater. However, I have not done a comprehensive test comparison with the Phantom. 

Also, I have been using the non-groundplane version on a couple of my roadrace racecars over the years with composite body panels with no problem.

Also, I have a couple of the Midland Phantom antennae. I really can't tell the difference between the two antennae and again, we have excellent repeater coverage throughout most of the Valley area except for south of Phoenix until you get closer to Tucson.

[Hoppyjr]

I looked at several different sites that sell the antenna.  I found only one (https://www.tessco.com/product/450-470-mirage-antenna-black-68593) that actually gives the antenna gain using meaningful units. All the others said either “unity gain” which means the effective power is multiplied by one, which is mathematically the same as 0 dB added, or simply said 2 dB, which has no reference and is thus completely ambiguous.
Tessco properly expressed the gain referenced to an isentropic antenna (dBi).  They list the Larsen as having 2.15 dBi, which is exactly the same as 0 dBd (decibel referenced to a dipole), meaning it has the same gain as a dipole. A dipole always has 2.15 dBi.

Gain dBi (dBi)

2.15 dBi

OK Steve, good info but waaaaaay over my head.

The fact remains that it worked better for me than the Midland 3db.

[SteveShannon]

8 minutes ago, Hoppyjr said:

OK Steve, good info but waaaaaay over my head.

The fact remains that it worked better for me than the Midland 3db.

It’s not uncommon for antennas with less gain to work better over a wider variety of locations than a high gain antenna.

[SteveShannon]

24 minutes ago, Hoppyjr said:

OK Steve, good info but waaaaaay over my head

Maybe this will help:

When it comes to antennas, gain is a measure of concentrated RF emissions.  Antenna gain does not increase the power of the radio, but it focuses it so that it’s directed where you need it.  But there must be a reference of some sort.  The most basic reference is an isentropic antenna.  Think of a bare bulb which shines evenly in every direction.  That’s what an isentropic antenna represents, a theoretical reference antenna reduced to a single point that radiates RF in all directions evenly.  By definition, radiating in all directions adds nothing extra to any direction and so the gain in any direction is said to be 0 dB.  That 0 dB value is something that all other antennas can be compared against.  When other antennas are compared to that reference point, their gain values are listed in units of dBi, or decibel isentropic.

But nobody makes an isentropic antenna. It’s really hard to make a geometric point radiate.  The next simplest antenna design is a dipole, two equal length pieces of wire that are each a quarter wavelength long.  So, for a 2 meter wavelength radio, each pole would theoretically be 1/2 meter. 
A dipole radiates RF in a toroidal shape that surrounds the wire.  In the direction of greatest concentration it has 2.15 dBi of gain.  Towards the ends of the dipole the RF is much lower and sometimes nearly nil. The gain has to come from somewhere.

Because they are very common and exist in reality, the gain of a dipole is sometimes also used as a reference, called dBd, or decibel dipole.  dBd and dBi are mathematically tied together by the following equation: 2.15 dBi = 0 dBd.  You can convert from one to the other by simply adding or subtracting 2.15 dB.

So now here’s my beef.  Many vendors advertise gain as dB, without specifying dBi or dBd.  Without knowing which it is, you have no way of knowing if you’re comparing apples to apples or oranges.  Midland advertises their MXTA-26 as 6 dB gain, but that’s a meaningless, possibly even misleading figure. If that’s 6 db of gain referenced to the theoretical isentropic antenna, it’s really only 3.85 dB gain compared to a wire dipole.

You’re probably sorry you even commented on my previous post and @OffRoaderX now has one more example of a sad ham going into way too much detail, but I’m one of those people that thinks this stuff matters.
 

[AccuNut]

Well, I appreciate the detail, that’s the main reason I posted under the “Technical” forum.

For instance, I now understand dBi vs dBd better, and am more confident in going with the Larsen since it has some dBi gain which is what I was looking for to begin with.

Just snagged a used Midland MXT575 for a good price, next up the antenna, some research on installing, and put it together!