Here is a intetesting Antenna to think about

[Big Kahuna]

Since many RV's have fiberglass or non-metal roofs that why I thought it might not need the ground to work effectively. Something like this could work really well in a neighborhood with HOA's against antennas. If it sits only 2 feet off the roof and is 5 x 6 it could easily sit on the backside of a roof peak. If it does provide some vertical and horizontal than might work slightly better than a dipole.

 

[The DB]

Could you post an image of your antenna?

Sure.

[photo=medium]5883[/photo]

The blue dots is the capacitor in the gamma, and the pointy ends are pointing away from us in this image. This was built based on the image shown and the info on the linked web site in previous posts.

I am not sure why Jo-Gun designed the antenna this way, I would have used just one of the two dipoles, the only technical reason I can see for using two of them is to attempt to increase the antennas bandwidth, but this will only add so much, especially with a gamma match in the mix. As far as the technical aspects go, I think such as addition, if anything, would do more harm than good. I guess, knowing the company involved, looks were most likely the reason...


The DB

 

[Mustang 131]

131, do you know why your buddy has his still in the box instead of using it? Do you guys have any goof pictures of this fire breathing antenna?

I checked out MMM's DDRR mobile antenna as noted in the link below.

No..he owns two of them. We used one on Dodge Caravan back in the '90's. The reason was stealth. By that time law enforcement was well aware of cb interference and the problems it could cause. And me driving a vehicle with a CB type antenna in certain area's would surely get me in trouble. The reason he got two is that we where sure we would blow one up, then attempt to figure out what went wrong with the match.
With beefed up suspension a 32 pill and boatload of Lee batteries are goal was not dx..but causing problems, for our enjoyment. However we did learn it actually got out pretty good.
Anyway..I saw still sitting in his rafters in his garage last time I visited...yep..new in box. I'll ask for a pic.

 

[Shadetree Mechanic]

No..he owns two of them. We used one on Dodge Caravan back in the '90's. The reason was stealth. By that time law enforcement was well aware of cb interference and the problems it could cause. And me driving a vehicle with a CB type antenna in certain area's would surely get me in trouble. The reason he got two is that we where sure we would blow one up, then attempt to figure out what went wrong with the match.
With beefed up suspension a 32 pill and boatload of Lee batteries are goal was not dx..but causing problems, for our enjoyment. However we did learn it actually got out pretty good.
Anyway..I saw still sitting in his rafters in his garage last time I visited...yep..new in box. I'll ask for a pic.

Wow, the young police officers now days probably have no idea what CB radio is....

 

[Marconi]

Looks like it has to be sitting on metal and the feed end is grounded to it. This might be good for the top of my golf cart with a thin sheet of aluminum added.
View attachment 30387

ShadetreeM, there are probably some good reasons we don't see this DDRR design in use in the CB world.

Below are some detailed specs for the real DDRR in case you want to build one for your golf cart.

 

[Marconi]

I asked this question earlier in my post #21 above and here is some evidence for why.

Is it possible a user of this mobile design might not perceive enough difference in a mobile setup to really tell during typical mobile use?

Below are two models at only 10' feet high with color overlays to compare the patterns.

1. a 1/4 wave 102" whip radiator over 4 x 102" radial whips.
2. a JoGunn Super Sinner RV 1/2 wave bent dipole with a gamma match.

These are not mobiles but they should give us comparisons for these two radiators low to the Earth similar to a mobile. This also supports my claim above...not much difference in signal, but there is a difference in polarity that has to be considered at higher angles.

 

[Marconi]

I thought this wasn't the case until I modeled an antenna similar to this one. This similar antenna model mounted 10 feet high has close to 5 dBi gain to the front and back, horizontally polarized, and about 2.3 dBi vertically polarized gain the the sides. Its the first time I've seen a (mostly) horizontally mounted antenna with any real vertically polarized gain...

DB, you told us some results for your 1st model of the Jo Gunn idea above, suggesting you were surprised at seeing good gain for both vertical and horizontal polarities.

Doing some more work, and modeling the actual antenna (as opposed to the similar antenna mentioned above),

In this follow-up post you tell us you modeled the actual antenna. I take this as though your model changed.

I too have redone my first model (post #11) several times, but I've not seen much if any vertical gain among all of the iterations I've done for this Jo Gunn Super Sinner RV bent 1/2 wave dipole.

In your re-model, do you still see vertical gain to the sides like you reported earlier?

BTW, have your tried to model the original Boyer 1/4 wave DDRR? Shadetree Mechanic posted an image above, and I posted the spec noted by Joseph Carr in his book "Practical Antenna Handbook, Fourth Edition, pages 424-427?
http://www.ok1mjo.com/all/ostatni/HAM/Practical_Antenna_Handbook.pdf

 

[The DB]

In this follow-up post you tell us you modeled the actual antenna. I take this as though your model changed.

Yes. The first one was a quick and dirty test model that was essentially one of the two antennas and center fed. I just wanted to see if I got vertical gain on that one. I later reproduced the antenna design and posted those results.

In your re-model, do you still see vertical gain to the sides like you reported earlier?

Yes, and I posted said results... Look at my models from above that represent the X axis, the blue line represents vertical gain. As the antenna was pointed along the Y axis, the X axis is showing what is radiating off of the sides.

TW, have your tried to model the original Boyer 1/4 wave DDRR?

I haven't recently but I have attempted to model ddrr antennas in the past. I am not really happy with any of the models I have made of it thus far.


The DB

 

[Marconi]

Now a look at the X axis.

[photo="medium"]5880[/photo]
This is where we are seeing our vertical gain. With the metal sheet under the antenna, we have less vertical gain then without. In both situations, this gain peaks straight up.

The DB

DB the first PDF file below is my JG SSRV model with a gamma. The 3 pattern overlays show the Total Field plus the Horizontal and Vertical polarities and looks similar to your overlays above. They do show a little less gain than your model overlays.

As you note above "In both situations, this gain peaks straight up." IMO, I think it is not so obvious that the high gains we're both reporting with our models...all peak at very high angles. I made this point in my post #38 in the link below. Here, I only considered the models with the gains as close to the Earth as practical and where these two patterns intersect.

Here is a intetesting Antenna to think about

 

[Marconi]

I haven't recently but I have attempted to model ddrr antennas in the past. I am not really happy with any of the models I have made of it thus far.

Below is my DDRR model with a ground plane that seems to work. However, it does not show all the magical high vertical and horizontal gains reported...with it just 12" inches above the Earth.

I still see mostly horizontal gain 1.89 dbi at 0* degrees, with way less vertical gain at -16.36 dbi at -5* degrees, and Total Field gain at 1.96 dbi at 0 degrees. These gain numbers and angles seem more realistic for a 1/4 antenna antenna that is set low to the Earth.

 

[W4KVW]

Several companies have had this design over the years & they pretty much went away.I think if they really were so good they would have taken off & still be sold by other companies.Just my own opinion.

SIX-SHOOTER

 

[Slowmover]

That it’s low in height is attractive. Yet it’s large, overall. As it’s also “expensive” these would seem to dampen enthusiasm.

Especially, if afterwards, performance wasn’t what one hoped for.

Still, . . . .

.

 

[Marconi]

Several companies have had this design over the years & they pretty much went away.I think if they really were so good they would have taken off & still be sold by other companies.Just my own opinion.

SIX-SHOOTER

I agree SIX-SHOOTER, especially with all the high gain values for vertical and horizontal polarities that have been reported for this mobile or ground mounted 1/4 wave antenna.

Can you recall the name of the antenna or the company you referred to above? I can check "Way Back" database and see if something shows up there.

 

[Marconi]

Here is an old ad for a low profile antenna like the Jo Gunn RV. It's in CB Tricks.

http://www.cbtricks.com/ant_manuals/bill_owen_inc/rv_269/ad/index.htm

Below is a another old ad.

The DDRR is also referenced in detail in the ARRL Antenna Handbook.

 

[W4KVW]

I agree SIX-SHOOTER, especially with all the high gain values for vertical and horizontal polarities that have been reported for this mobile or ground mounted 1/4 wave antenna.

Can you recall the name of the antenna or the company you referred to above? I can check "Way Back" database and see if something shows up there.

I will do some research but I think I can find it .

SIX-SHOOTER