Antenna question on the wrong website

I know this isn't a radio forum but a lot of you have experience in HAM and other radio circuits I've learned.

My question is based on previous experience producing good results.
If I use an antenna promoted by the manufacturer for 2.4ghz, to receive 260mhz, will it really be an issue?

I've done this in the past with various devices. I used an automotive car stereo whip antenna on my radio controlled RC car and it gave me the furthest range I've ever achieved. A prime example of manufacturer rated spec not hindering performance. In this scenario, I'm replacing a crappy, broken metal telescopic antenna for the wireless receiver in my wirless guitar system that transmits at 260mhz. The choice being between a near frequency CB whip antenna or, a small wireless LAN whip type antenna.

I understand the issue of wavelengths but will it REALLY create THAT much of an issue?
I've used hunks of wire for some of the best antennas I've ever owned!
 
Yes, I build tube amps here in this forum, but in real life I am an RF engineer. Your wireless mic antenna works at 260 MHz. THe wierless LAN antenna is made for 2400MHz. This is just too different to work very well.

Any telescopic antenna of about the same length would work much better. One intended for a portable TV would be a good choice. And yes a piece of wire about 1 1/2 to 2 feet long should be OK too.
 
Radio frequencies radiating thru the air is a real cool thing! All around us are frequencies bouncing off walls, coming thru the windows...& all of it has their own wave-length. Quite the thing..if only we could SEE these frequencies...we would all be astounded!
You have one frequency at 2400000000 Hz(2.4Ghz) another at 260000000 Hz(260Mhz)....or 260Mhz and 2400Mhz, or one is nine and a quarter times higher than the other. When one designs an antenna......size of elements is everything...when a frequency is too long to be practical for say...handheld use, you cheat, or fool the receiver, or transmitter into thinking the antenna is bigger than it is.
Ever wonder why there are these large incredibly tall "radio towers"?
A common 1/4 wavelength hertz antenna in the AM band would have an element hundreds of feet high........This same 1/4 wavelength at 2.4Ghz, would be only about Forty Millimeters high(Appx, ONE inch). These are the scales we are talking about...
For your "piece of wire" antenna....imagine this wire is probably not straight....you body just holding onto it is redirecting radio waves in all different directions, and at a great wide swath of frequencies. Recall the poor guy long ago twisting & turning with an old pair of TV "rabbit ears" trying to get a good reception....with the onlookers saying "Freeze, thats it...now just hold it there" The poor guy contorted in some goofy pose.
He was acting as an antenna himself....directing and reflecting radio waves with his body.
Yes it will be an issue with this great a mismatch of frequencies.

_____________________________________________________Rick.........
 
It all depends on range. A very poor antenna will still give enough signal if the transmitter is close to the receiver. As you move it away you will find a much shorter range than with the correct antenna. Roughly speaking, an antenna only a tenth of the correct size will pick up only a tenth of the voltage but will then lose most of that in an impedance mismatch so you will get maybe 1% of the correct voltage into the receiver.

Antenna performance depends on physics, not manufacturer specs. Hopefully the two are related, though.
 
Thanks for all the very informative answers which expanded the basic understanding of antennas I already had. I suppose I've been lucky in using antennas with boldly different ratings in contrast to the applications I've used them for. At 99 cents shipped to the door, I figured I can't lose by testing a couple of these antennas out. If all else fails, I'll just build my own and cannibalize the housing of one of these cheap antennas which is largely the reason I seek to use one.

Many years ago I built a dish antenna. Looked like a mini satellite dish by the time I was done. Coat hanger framing, aluminum foil sheeting and was about 2.5-3 feet across at the open end.
Man that thing could pull in stations from Canada and sometimes Tennessee! It was mighty finicky though and I often found myself running outside to fuss with it.
With the internet being such a good source of information, I learned about wavelengths and antenna design. Bought myself a couple large steel hoops from the craft store then ran copper wire across them which created varying lengths. With it sensitive to wavelengths of a massive bandwidth range, totally blew my "trailer park satellite dish" away.

I suppose an antenna of this design might actually be applicable to multiple bandwidth applications?
 
Fun stuff antenna. There are a lot of ways to make an antenna and many antennas work at octave intervals of the their intended frequency...though maybe not optimally. At least not without a little modification. Would really like to see an image of the antenna with the hoops you described. Receiving antenna have one job- to convert the electric (and/or the magnetic) wave into an electrical signal. Make some images and put them up. We will claim it is for audio because it receives music! HAHA
 
A test!

Kudos to the first one who can tell me what this is & what its for...........

_______________________________________________________Rick........
 

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And the prize goes to George .......with the first runner up to Abrax...for recognizing it somewhat. By now I'm sure there are countless programs that make this "old tech"....but when I learned it, thats all we had. Who knows how to work a slide rule????? What happens when your prized HP calculator gets stepped on?? What-cha gonna do?
Slide rules were a little before my time....I recall drooling over the new HP 15C calculators when I was in school........reeling at the $395 price-tag.

________________________________________________________Rick....
 
We still used slide rules in high school. Obsolete right after that, tho. All those headaches for nothin'.

I was at school when calculators superceded sliderules. But I wouldn't say the headaches from using a sliderule were for nothing. Being taught to use a sliderule also taught me the very useful skill of making the sanity check about what order of magnitude the result was going to be. Those who didn't acquire that skill were subject to keying errors... I did notice amongst some of my peers an over-reliance on the apparent precision of the answers which came out of the magic electronic box:eek:
 

infinia

Member
2005-05-15 9:51 am
SoCal
Nahh Smith charts aren't obsolete, you need both software and a plan obtained from looking at a Smith chart. All good RF design software and Network Analyzers still plots things on a Smith chart. For example there are many solutions to a matching problem. You can devolop the best matching topology from looking at a Smith Chart, software will hand you a solution that may not be an optimum solution.
My profs always said you should have an idea what the answer is before you start punching in the numbers. I would NOT trust an RF engineer that proclaims that using a Smith chart as a visualization tool in design or measurement is dead.
 
I don't have the software for RF. Or I should say I have lots of software but have not verified any of it works correctly. Of the 20 or so programs I have 18 don't work right so kind of quit trying. Smith charts are in arms reach when needed. Very handy to "stack" multiple devices quickly and see where it ends up. Smith chart is very intuitive making it east to see trends and so on. Gotta love em!

=SUM
 

wakibaki

Banned
2008-01-08 11:51 pm
The size of the antenna is pretty much irrelevant on receive except that it won't be optimal. Just try it and see, it's a question of range. There's not much lost if it doesn't work. 'Course you won't get it to radiate very much if you wanted to use it to transmit.

What is it? A vertical whip? A stub? A trailing wire?

About 30cms of something metallic. You can definitely make something at these wavelengths, you can even tune it crudely by trimming or with a sliding section. A piece of bamboo with a wire taped to it?

w