question on R/S scanner antenna

[oldcb]

i scored an NOS 20-013 antenna at a yard sale last weekend for a whole dollar!, i just mounted it up yesterday afternoon, my question is, from what i,ve read, by removing the rubber cap on top of the antenna and adding a whip, you'll improve reception, true?, if so what's the best whip to use?, a 102" or maybe even a loaded whip?, any input would be great, thanks ahead of time...........

 

[oldcb]

here's a pic of the antenna in question..............

 

[DickH]

i scored an NOS 20-013 antenna at a yard sale last weekend for a whole dollar!, i just mounted it up yesterday afternoon, my question is, from what i,ve read, by removing the rubber cap on top of the antenna and adding a whip, you'll improve reception, true?, if so what's the best whip to use?, a 102" or maybe even a loaded whip?, any input would be great, thanks ahead of time...........

It depends on which frequencies you want best.
33MHz = 84"
46MHz = 60"
150MHz = 18"
460MHz = 6"
850MHz = 3-1/4"

 

[N8IAA]

The whip that came with the antenna was for 50MHz. Check the threads to see if they are 3/8x24. I put a 102" whip on the antenna and used it for CB 20 years ago.
DickH gave you the measurements for other bands. The antenna is tuned for 120-460MHz. Depends on whether or not you want to improve your reception on 25-60MHz.
Larry

 

[ko6jw_2]

The original antenna had a loading coil and a whip. It centered at about 44Mhz, but tunes very sharply. The whip has nothing to do with reception above 50Mhz. The discone itself can receive and transmit from about 100Mhz to 1.3Ghz. If you don't need low band, then the whip is not needed. RS used to sell them with and without the whip. The image you posted shows that the antenna is missing a piece of tubing that attached to the bottom of the antenna. The tube also had the mast mounting hardware. The coax ran up the center of the tube to the SO-239 connector on the base of the antenna and had a bracket to attach it to the mast. I don't think that this will affect the antenna very much or at all, but it will make mounting it more difficult.

For 25-50Mhz reception the antenna functions as a based loaded ground plane. It is only a discone above 100Mhz.

I have use these antennas for years. They work well. The only problem is that they are not very rugged. The discones made by Diamond are much better constructed and can be ordered with N type connectors.

 

[iMONITOR]

The discones made by Diamond are much better constructed and can be ordered with N type connectors.

The Diamond can be ordered two ways:

DJ130J (SO239 connector)
DJ130NJ (Type N connector)

Diamond D-130J D-130NJ Discone Antenna

 

[oldcb]

The original antenna had a loading coil and a whip. It centered at about 44Mhz, but tunes very sharply. The whip has nothing to do with reception above 50Mhz. The discone itself can receive and transmit from about 100Mhz to 1.3Ghz. If you don't need low band, then the whip is not needed. RS used to sell them with and without the whip. The image you posted shows that the antenna is missing a piece of tubing that attached to the bottom of the antenna. The tube also had the mast mounting hardware. The coax ran up the center of the tube to the SO-239 connector on the base of the antenna and had a bracket to attach it to the mast. I don't think that this will affect the antenna very much or at all, but it will make mounting it more difficult.

For 25-50Mhz reception the antenna functions as a based loaded ground plane. It is only a discone above 100Mhz.

I have use these antennas for years. They work well. The only problem is that they are not very rugged. The discones made by Diamond are much better constructed and can be ordered with N type connectors.

yes, mine came complete with the mounting tube and brackets, though mine did not come with a whip of any sort, hence my question about adding a whip, one last question, if i do want to try even lower frequencies, what would be the best length?

 

[iMONITOR]

yes, mine came complete with the mounting tube and brackets, though mine did not come with a whip of any sort, hence my question about adding a whip, one last question, if i do want to try even lower frequencies, what would be the best length?

See post #3

 

[oldcb]

See post #3

i guess what i meant was, down to 25 mhz

 

[ko6jw_2]

As I said before, this antenna does not offer broadband performance on the 25 to 50Mhz band. The one I have has the stock loading coil and whip. The SWR is 1.2:1 at 44.44 Mhz. The bandwidth for 3:1 SWR is 43.9 to 45.3 Mhz. I need to lengthen the whip a little to have it resonate at 42Mhz for the CHP here. There is about a 1.6:1 SWR at 33Mhz, but the impedance is about 30 ohms. At 50Mhz the SWR is greater than 6:1. As you can see this is not a good antenna for broadband reception at lower frequencies. The discone is quite flat throughout its range of 100-1300Mhz.

 

[N8IAA]

i guess what i meant was, down to 25 mhz

See post #4.
Larry

 

[n5ims]

A dollar is a fair price for that antenna. The design with the hollow rods that are poorly crimped to the screw connectors cause it to not last. A picture of what mine looks like after last winter's ice storm is here --> http://forums.radioreference.com/sc...s/280159-increasing-distance.html#post2114921

 

[kc2kth]

I had one of these in the 90s, it worked but like others have said it was cheaply constructed. So many people modded these by attaching a CB whip to them to gain some VHF lo coverage RS came out with on that included the whip later, but it was still cheaply made compared to the D130J. I've now had the D130j in my attic for close to 15 years and it is a great performer.