• To anyone looking to acquire commercial radio programming software:

    Please do not make requests for copies of radio programming software which is sold (or was sold) by the manufacturer for any monetary value. All requests will be deleted and a forum infraction issued. Making a request such as this is attempting to engage in software piracy and this forum cannot be involved or associated with this activity. The same goes for any private transaction via Private Message. Even if you attempt to engage in this activity in PM's we will still enforce the forum rules. Your PM's are not private and the administration has the right to read them if there's a hint to criminal activity.

    If you are having trouble legally obtaining software please state so. We do not want any hurt feelings when your vague post is mistaken for a free request. It is YOUR responsibility to properly word your request.

    To obtain Motorola software see the Sticky in the Motorola forum.

    The various other vendors often permit their dealers to sell the software online (i.e., Kenwood). Please use Google or some other search engine to find a dealer that sells the software. Typically each series or individual radio requires its own software package. Often the Kenwood software is less than $100 so don't be a cheapskate; just purchase it.

    For M/A Com/Harris/GE, etc: there are two software packages that program all current and past radios. One package is for conventional programming and the other for trunked programming. The trunked package is in upwards of $2,500. The conventional package is more reasonable though is still several hundred dollars. The benefit is you do not need multiple versions for each radio (unlike Motorola).

    This is a large and very visible forum. We cannot jeopardize the ability to provide the RadioReference services by allowing this activity to occur. Please respect this.

Coaxial Dipole?

Status
Not open for further replies.

sflmonitor

Member
Premium Subscriber
Joined
Jan 10, 2003
Messages
741
Location
Sunny South Florida
Does anyone have any experience with these type of antennas? I haven't worked with them but after some quick searching, I guess they are coaxial dipoles? I've seen them on national park office buildings, military bases, etc. Does anyone have any experience with them? Just curious what the benefits are when compared to other commercial base antennas such as fiberglass colinear or folded dipole?
 

Attachments

  • IMG_8432.jpg
    IMG_8432.jpg
    30.8 KB · Views: 444

ko6jw_2

Member
Premium Subscriber
Joined
May 18, 2008
Messages
1,448
Location
Santa Ynez, CA
They are vertical half wave antennas. A j-pole is another example of a vertical half wave. Coaxial antennas are difficult to construct for diy. They have the advantage that the sleeve decouples the antenna from the support mast and they do not need a ground plane. Other than that they are not that exotic. While they will exhibit gain over a quarter wave, they don't have any greater gain than any other half wave vertical antenna.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
23,618
Location
Hiding in a coffee shop.
Broad banded, really durable, nice omni-directional radiation pattern.

I used to have one here at work, it had been up for decades and still worked very well.
 

prcguy

Member
Joined
Jun 30, 2006
Messages
15,233
Location
So Cal - Richardson, TX - Tewksbury, MA
The one in the picture appears to be a Kreco and I have aluminum and brass versions I use on 2m. It is difficult to make one correctly because you need a dielectric "plug" inserted between the skirt and mast or skirt and feedline to make the inside surface of the skirt appear longer than the outside and size/placement of the plug can be critical. Kreco uses a large thick Plexiglass doughnut about an inch up inside the skirt for this.

As mentioned, they are just a half wave center fed dipole, nothing special but they are rugged and have reasonable band width. There is a version with a folded/grounded vertical element and that should have more band width.

I also have a Kreco 3 element Yagi that has a coaxial dipole as the driven element, very unusual.
prcguy
 

NC1

Member
Joined
Feb 8, 2014
Messages
733
Location
Surry County, North Carolina
If you want to build something similar, try the link below. I built one tuned to the 2m Amateur Radio band and it works great for both RX and TX.

All the formulas and tables are there to make what you want, along with instructions for the PVC enclosure and mounting instructions.

My cost was $0 because I had all the parts laying around. Give it a try, you might be surprised with how well it works.

The Vertical Bazooka Antenna - Ham Radio Library
 

prcguy

Member
Joined
Jun 30, 2006
Messages
15,233
Location
So Cal - Richardson, TX - Tewksbury, MA
These types of coaxial dipoles have some loss due to the folded back braid laying against the plastic outer covering of the coax and most outer coverings are a lousy dialectic with loss. If you use Teflon insulated coax it will work better but you really need to keep the feedline away and isolated from the inside skirt of the coaxial dipole and keep it centered as it exits the skirt.
prcguy

If you want to build something similar, try the link below. I built one tuned to the 2m Amateur Radio band and it works great for both RX and TX.

All the formulas and tables are there to make what you want, along with instructions for the PVC enclosure and mounting instructions.

My cost was $0 because I had all the parts laying around. Give it a try, you might be surprised with how well it works.

The Vertical Bazooka Antenna - Ham Radio Library
 

NC1

Member
Joined
Feb 8, 2014
Messages
733
Location
Surry County, North Carolina
These types of coaxial dipoles have some loss due to the folded back braid laying against the plastic outer covering of the coax and most outer coverings are a lousy dialectic with loss. If you use Teflon insulated coax it will work better but you really need to keep the feedline away and isolated from the inside skirt of the coaxial dipole and keep it centered as it exits the skirt.
prcguy

Agreed, but didn't want to get too technical.

I figure start with the basics and adjust from there. It's all about experimentation and having fun with it.
 

sflmonitor

Member
Premium Subscriber
Joined
Jan 10, 2003
Messages
741
Location
Sunny South Florida
Great info guys. Just when you think you know about antennas, there is always something new. thanks for the great detailed information.
 

K9DAK

Active Member
Premium Subscriber
Joined
Dec 16, 2010
Messages
688
Location
Wauconda, IL
I've been making these antennae out of leftover coax for quite a while. Made a 154 MHz version for the scanner that supplies my Broadcastify feed, and a 162 MHz version for the weather radio at my work. Didn't pay much attention to the shield length for receive only, and both work great... for zero cost.
 

NC1

Member
Joined
Feb 8, 2014
Messages
733
Location
Surry County, North Carolina
I've been making these antennae out of leftover coax for quite a while. Made a 154 MHz version for the scanner that supplies my Broadcastify feed, and a 162 MHz version for the weather radio at my work. Didn't pay much attention to the shield length for receive only, and both work great... for zero cost.

You got that right. These make an excellent receive antenna for scanning, and you can make them to target the frequency or band you desire. For the price it really can't be beat. Of course the antenna manufacturers will disagree ;)

For transmit, just use a meter to get the lowest SWR and it is just fine without getting into the murky details. I have one for use indoor when there are storms in the area that make me run around disconnecting cables going into the house.

If anything, they sure do beat a rubber duck antenna.
 

phask

Member
Premium Subscriber
Joined
Dec 19, 2002
Messages
3,670
Location
KZZV - SE Ohio
Anyone want to build me one for 800mhz? If so PM me. My skills are just not as good as in the old days.
 

Golay

Member
Joined
Apr 28, 2016
Messages
494
The Vertical Bazooka link pretty much shows the antenna I have made at work. Have put dozens of these at 460 for forklifts and at 153 for remote control locomotives that want to go thru a roll up door that isn't quite all the way up. Make the antenna as the link says, cover it with heat shrink, and it's basically a rubber duckie. I myself make the shield about 10% longer than the center conductor. Then put the heat shrink over everything. The resonant will always be lower than what I want. Then I nip the end about a 1/4" at a time until I get where I want, fold a piece of 3M Super 88 over the top and heat shrink in place.
 
Status
Not open for further replies.
Top