Broomstick

[simoneb]

Hello:

I'm very new to radios and know nothing about antenna theory. Go easy, I'm learning. I recently ordered a windom antenna and a tuner, but in the mean time, while waiting for it to get here, I thought I'd try my hand at a DIY project - the broomstick antenna.

I spent $45.00 on the parts (including a Dremmel bit to cut the aluminum). I'm sad to report that it does absolutely nothing better than five feet of speaker wire jammed into the Hi-Z.

The instructions provided online claim that I should terminate the bottom end, which I feel I did somewhat adequately. I "spliced" the multiple loops of speaker wire at the bottom of the broom to the feed line to the radio and connected it at the broom bottom with a screw and nuts, as you can see in the picture.

If time permits, would someone please tell me where I went wrong. It's academic at this point, as once the windom arrives, this thing will go on "display" in the garage anyhow.

 

[kf5qgf]

Well as far as I can tell you have 1/2 an antenna. generally an antenna consists of two conductors, one connected to the center conductor of coax, the other connected to the shield of the coax. Now this antenna does hold potential, come up with a way to insulate that aluminum plate from another vertical on top of the plate, then connect the vertical to the center of the coax, and the shield to the plate, and viola, a 1/4 wave ground plane antenna. (for 2 meters that's 19 1/2" vertical) However having that aluminum plate, or plane as we'll refer to it, completely vertical like that will result in a higher impedence, so beating it down diagonally, as close to 45 degrees as possible, will lower the impedence and match it at the beloved 50 ohms.

I made an antenna with coat hangers as such that worked well for me transmit and receive, take a so-239 with the 4 holes drilled into it, cut a coat hanger at 19 1/2 inches, straighten it out and solder it to the center conductor, take 4 more cut a smidgen longer, say 21 inches, and put a loop in the end smaller then a pencil, then find some nuts and bolts that will go through those little holes and bolt one hanger on each corner. Now bend the hangers down to a 45 degree angle. Hang it from the ceiling (just put a small loop in the vertical and hang it with some rubber bands, or so I did) connect the coax to the bottom, and key up! If you're scared stick an swr meter on it and check it. I never did but the math added up and well, what's the fun in living safely? Hope this helps.

KF5QGF

BTW: I swear by j pole antennas, give one of those a try.

 

[kf5qgf]

You know what might've been smarter for me to start with asking, are you transmitting or receive only? And what frequencies?

 

[simoneb]

Thank you for replying. I'm using it only to receive. Apparently, it should work well as is - at least according to articles I've read. I might have a go at modifying it at this point just to see what the end result will be, because as it is, it does nothing.

Thanks again. Was thoughtful for you to reply.

 

[LtDoc]

I'm not sure how you may be connecting that antenna to your radio, so, this may sound a bit dumb. I would suggest using only one of the conductors coming from the antenna connected to the input of your receiver. That should give you at least as good reception as your 'wire' antenna. In effect, you have a much longer wire 'lumped' into a smaller space (not really, but sort of). The 'key' in that is the "longer wire" thingy. Depending on your situation/circumstances, using the same length(s) of wire connected to the end of your 'other' wire antenna and thrown over the top of your house/building would produce about the same (better?) result.
In general, antennas are length dependent. The lower in frequency the longer they get. Specific lengths work 'better' at particular frequencies. From there it starts to get 'technical', and requires some electrical knowledge to understand the 'why' of it.
Have fun.
- 'Doc

 

[k9rzz]

It's all a learning process. If all you have room for is a broom handle, then you'd probably be pretty happy with it. When it comes to wire antennas, size does matter I'm afraid.

 

[wtp]

so close

looks like you were trying to make a discone antenna --- its a disk and a cone get it
ok the disk is the antenna so connect one wire to it . the ground is below it so thays your other connection point. check at radioshack for the idea of how it works.
____
^
/ \

 

[LtDoc]

A discone antenna for HF is huge by definition. I seriously doubt if anyone will have enough room (in town) to put one up. That broom-handle antenna may have a disk at the top but it's also not large enough to make a practical 'top-hat'/'cap-hat'.
So what it amounts to is a shortened, loaded, antenna with a 'too small' cap-hat. It -can- be a usable antenna but that just depends on what you make the comparison with and the frequency(s) of interest. As the man said, it don't do as well as his short length of wire.
Try that antenna on VHF/UHF, it may do very nicely...
- 'Doc

 

[majoco]

What a load of cr*p you guys are giving. It's obviously an antenna for HF bands - not VHF, not scanning, not 800MHz.

I guess the original poster got his instructions from the Arne Coro site...

Broomstick Special, easy-to-build shortwave antenna -- on hard-core-dx.com

and I think hes done a great job of it,

.....but the important bit is at the bottom of the article....

8.
The antenna works best near a window. Or better yet, you can install it in your balcony or garden... but do keep the connections to the tuner short.

9.
The antenna is resonated with your antenna tuner.... you may use it without a tuner, but results are not going to be as good as when the antenna is connected to the receiver via a well-designed antenna tuner

The important bit is "TUNER". That's avery high impedance atenna you've made and you are feeding it into a much lower impedance radio (even if it does say "Hi-Z or something) so you need a tuner to match the antenna to the radio. You'll get a vast improvement in performance.

Available on FleaBay occasionalyy for a few dollars and will always come in handy later.

 

[nanZor]

I spent $45.00 on the parts (including a Dremmel bit to cut the aluminum). I'm sad to report that it does absolutely nothing better than five feet of speaker wire jammed into the Hi-Z.

Don't feel bad - I built a "helical" vertical like this 2 decades ago and came to the same conclusion. There are a number of reasons why this is bad - if you want you can research the helical stubby hf antenna with the top hat if you like. These are single-banded affairs too with incredibly narrow bandwidth.

But with the expense of what you've purchased, how about some slight modifications to get you near 15 mhz or so? Like this with some pics at the bottom:

A Two Dollar Helical HF Portable Antenna

Toss the capacity hat for a small single wire extension. With the existing coil taped in place, carefully remove ONE of the windings to have some separation between them. Use coax and attach the center conductor to the bottom of the coil, and at least one radial wire to the shield.