Diamond D-130J Discone Whip Diameter

[Fast1eddie]

Hello, does anyone know the whip diameter?? I'm into low bad dx, and I want to find a longer whip to replace the original. Don't use it to transmit, just receive so the length isn't critical.

Thank you and happy dx

 

[Whiskey3JMC]

Tech specs are here

Diamond D-130J Super Discone Antenna

Check out this Diamond Antenna D130J at www.WalcottRadio.com

www.walcottradio.com

 

[merlin]

One thing I did to improve 6 meter reception is added a legth of 14 gage antenna wire from a top element lock nut extended out as horizontal as I could get. the lenght I recall was 55 inches.
Not perfect but a vast improvement at 6 meters and 11 meters.
I would think adding the same to a lower element would be more like a dipole and better yet.
You could always homebrew your own 6 meter discone. there is math for that in ARRLs antenna book, and how to in old QST magazine.
Try youtube search also.

 

[merlin]

That Diamond D-130J Super Discone under an analyzer doesn't do well below 80 Mhz by reason the ground radials are too short for lower frequencies. It does do better with the top whip than without, but lossy compared to a dipole.

 

[Fast1eddie]

Thank you all for replying. I should have mentioned I live in a second floor apartment (small building, only 2 floors and I am on second) mounted on my deck. Guessing I am maybe 30 some feet high.

You want a good low band antenna, the old Antenna Specialists Monr-31 was great and wish I still had it.

Ed

 

[Ubbe]

It's a shortening coil at the base that makes the whip 0,6 meters shorter. A 1/4 of 52Mhz are 1.4 meters but the whip are 0.8 meters long so the coil reduces the length by 0.6 meters. If you want to improve 35Mhz then that are 2 meters at 1/4 wave and the whip needs to be extended 1.2 meters. It could be done with electrical wire that you fasten to the top of the whip with some sort of screw clamp. If you can't fastened the other end of the wire into something above you then let a PVC pipe go down a bit over the whip and tape it secure or use a stop like a hose clamp.

/Ubbe

 

[W8HDU]

You want a good low band antenna, the old Antenna Specialists Monr-31 was great and wish I still had it.

Ed

Diamond CP62, Hy-Gain SPT-500, or make your own from a discarded CB ground plane.

 

[ko6jw_2]

The whip diameter is 0.10 inches. I have replaced the stock whip with a longer one the receive CHP at 42 MHz. The stock whip is intended for 6 meters.
A few points about discones:

1. The theoretical bandwidth is about 10:1. About 100-1000 MHz for the Diamond.
2. The coil and whip are not part of the discone. They function as a base loaded ground plane.
3. Although they are advertised as covering 25-1300Mhz this simply not true.
4. The frequency coverage has three variables The disc diameter, skirt length and the spacing between the disc and skirt.
5. Modifying one dimension will not be beneficial.
6. If you are serious about low band get a ground plane cut for the desired frequency. Efficiency will be greatly improved.

 

[W8HDU]

Anything is an antenna. Efficiency is what separates it from a metal rod and useful tool.

 

[Fast1eddie]

Understand and thanks for the information. I realize a Discone is not optimal for low band DX, but I am space restricted and my old Antenna Specialists has 3 foot radials. Just won't fit.

 

[W8HDU]

@Fast1eddie ... Get creative with a design. It doesn't have to be a conventional antenna. Can you take two CB whips and put them back to back vertically for LB dipole? Could you get around the 3' by drooping the radials? Keep in mind, your goal is closer to being achieved if you think strategically on what you can do, rather than the physics of transmitting antennas or quibbling over dBs. Do what is possible rather than saying you can't.

 

[W8HDU]

@Fast1eddie ... Just thought of something as I was having morning coffee. I friend in Upper Michigan (Lake Superior region), used two "Tornado stinger" CB Antennas back to back for scanner monitoring of low band. Simple build. (2) antennas (2) threaded bumper mounts and a piece of aluminum as a bracket. The antennas are the type you see on trucker's mirrors with the open coil and about 32" of whip. Signal wise, worked better than a Diamond base antenna for 6, 2, and 70cm. Just a thought if you're not opposed to building.

 

[Fast1eddie]

Thanks! I will take a look at it.

 

[Alain]

The whip diameter is 0.10 inches. I have replaced the stock whip with a longer one the receive CHP at 42 MHz. The stock whip is intended for 6 meters.
A few points about discones:

1. The theoretical bandwidth is about 10:1. About 100-1000 MHz for the Diamond.
2. The coil and whip are not part of the discone. They function as a base loaded ground plane.
3. Although they are advertised as covering 25-1300Mhz this simply not true.
4. The frequency coverage has three variables The disc diameter, skirt length and the spacing between the disc and skirt.
5. Modifying one dimension will not be beneficial.
6. If you are serious about low band get a ground plane cut for the desired frequency. Efficiency will be greatly improved.

Great thread! I have had my Diamond D-130J up about 30' for the past thirteen years or so, being fed by 100' of LMR400. I can monitor the CHP into Santa Barbara and as far as Ojai [some 200 miles to my NW] with 4-5 bar consistency on my SDS200. I also use it occasionally for 220 MHz FM ham nets. Granted, I am up about 2,500 feet elevation, but I do have a 100' hill to my south and can monitor much of local San Diego 700 MHz from here, as well as 150-170 MHz with good results. I had a RS discone that died when the 2007 wildfires kicked up 70+ MPH winds here in NE San Diego; tossed the radials all over my property! I've got nothing but praise for the Diamond. It rocks for me...