Childs Low Band Base Antenna

[HappilyRetired]

about a year ago or maybe a little longer I came across an excellent VHF low band base station antenna that looks like a fiberglass CB radio base antenna but it's shorter. It kicks butt. I had included it in a post discussing other topics and I'm not sure if it was stripped out or if I screwed up adding the url. The price is reasonable especially if you are a CHP affectionionado or other area that uses VHF low band. This is a similar and tuna used by CHP offices and repeater sites but they use a $900 Kreco antenna. I don't see any rules saying I can't post this so here goes.

Low Band VHF Base antenna, 30-88 mhz, omni-directional, 1/2 wave, so239 | eBay

30-88 Mhz, Unity gain, 1/2 wave, 2 piece antenna. Fiberglass Omni-directional Base Antenna.

www.ebay.com

 

[prcguy]

Both the Childs and the Kreco are tuned to a specific frequency and cover about 1MHz of bandwidth before performance starts dropping off. An antenna for CHP needs about 7Mhz of bandwidth. I have a Kreco coaxial dipole and its nice but very narrow bandwidth. There are two versions of the Kreco, one has a basic vertical element and one with a folded element which does cover a little more BW, maybe 2MHz or so. Mine is the simple version.

 

[merlin]

What I know about the design is these are a center fed vertical dipole.
The CB version was a popular "Big Stick"
Any of these I tested did well across a 10 Mhz bandwidth. less than 2.0:1.
They are intended for a transceiver/transmitter up to 500 Watt.
If they are like Shakespear, they come in 4 lengths to cover low VHF.
Probably excellent for scanners or receiving, but I would get the lowest
bandplit. (longest of 4)

@ prcguy.
These have no 'tuned section so they have a broad bandwidth.
A folded dipole would be narrower and built with tuned sections may be down to a couple of Mhz.

 

[prcguy]

What I know about the design is these are a center fed vertical dipole.
The CB version was a popular "Big Stick"
Any of these I tested did well across a 10 Mhz bandwidth. less than 2.0:1.
They are intended for a transceiver/transmitter up to 500 Watt.
If they are like Shakespear, they come in 4 lengths to cover low VHF.
Probably excellent for scanners or receiving, but I would get the lowest
bandplit. (longest of 4)

@ prcguy.
These have no 'tuned section so they have a broad bandwidth.
A folded dipole would be narrower and built with tuned sections may be down to a couple of Mhz.

I just checked out and painted an actual original Shakespeare 176 Big Stick for an install next week and it won't even do 1MHz BW, more like 500KHz for 1.5:1 and 10MHz is impossible. Its very common to use a shorter whip on them for CB freeband or 10m amateur and they are still very narrow band up there.

Shakespeare never made them for the 30-50MHz VHF lo band unless your talking about their broad band military vehicle models, but they are not coaxial dipoles. My Kreco 1/2 wave coaxial dipole cut for 51MHz is about 1MHz for 1.5:1 and 10MHz is impossible on that one. I have not come across a coaxial dipole with the BW you mentioned.

 

[HappilyRetired]

What I know about the design is these are a center fed vertical dipole.
The CB version was a popular "Big Stick"
Any of these I tested did well across a 10 Mhz bandwidth. less than 2.0:1.
They are intended for a transceiver/transmitter up to 500 Watt.
If they are like Shakespear, they come in 4 lengths to cover low VHF.
Probably excellent for scanners or receiving, but I would get the lowest
bandplit. (longest of 4)

@ prcguy.
These have no 'tuned section so they have a broad bandwidth.
A folded dipole would be narrower and built with tuned sections may be down to a couple of Mhz.

It is a coaxial sleeve antenna. Yes, it is center fed but if you want to make one at home without all the fuss, you simply measure I think it's 4 and 1/2 ft of the center conductor up and then take four and a 1/2 ft of the braid down over the remaining coax and tape it in place. If your ceiling is tall enough you can then tack it to the wall. Obviously the outside version works far better. I found the design on a website and then I found Bruce Childs selling them. They are a solid antenna. They are broadband to a certain extent but I got mine cut at 42 MHz so that it covers CHP 39-45 mhz. I do this by adding the highest and the lowest frequency together and then dividing by two for the center point. My Elmer taught me this.