Hi,
Does anyone have a formula or know a technique for converting an 11 meter 3 element yagi antenna into a
10 meter yagi (beam antenna)?Thanks in advance, Brad
Before you type your password, credit card number, etc., be sure there is no active key logger (spyware) in your PC.
Brad wrote: > Hi, >
Well, wouldn't it be 10/11 length of each element? Get a big wire cutter and have at it.
GG
Don't forget to snip up the frame to pull the elements closer.
Brad -
First, What 11 meter beam is this? Manufacturer? Did you know that many manufacturers have this information in their assembly instructions?
Have your amateur radio license yet? I provide assistance for licensed amateurs.
Google will lead you to answer.
gb
Sure. Take your current antenna dimensions and plug them into an antenna modeling package such as:
4NEC2 (free)Eznec (free demo)
or any of those listed at:
Insert your current antenna dimensions into the program and make sure it works at 11 meters. Then, change the frequency to 10 meters and run the optimizer.
-- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 jeffl@comix.santa-cruz.ca.us # http://802.11junk.com jeffl@cruzio.com # http://www.LearnByDestroying.com AE6KS
Totally unnecessary on a 3-element with that % frequency shift. The characteristics are very insensitive to small spacing changes.
The frequency difference might be insignificant if your antenna tuner can accommodate the differences. The 10-meter band is lower in frequency than the
11-meter band, therefore all elements would have to be lengthened by a small amount to get it exactly right. Google around for yagi antenna design software. There are probably a number of freebies available.I Googled for yagi antenna design and the second hit came up with
Cheers!!
-- Dave M MasonDG44 at comcast dot net (Just substitute the appropriate characters in the address) Some days you're the dog, some days the hydrant.
Sorry, it's not. The eleven meter band, aka CB, is in the 27mHz range. The 10m Ham band is 28.0 to 29.7 mHz, but most people don't use the whole band. 28.0-28.3 is mostly CW (Morse code) because the U.S. prohibits usage of voice signals there.
SSB and AM voice signals are legal in the rest of the band, but most often they are found in the 28.5-29.0 range. FM voice is limited in the U.S. to 29.0 and up, and FM repeaters use 29.5 to 29.6 for TRANSMISSION.
While it would be best to shorten all of the elements, and move them closer together, it is really only necessary to shorten the driven element (where the radio connects) and the director (the one in front of it).
You can do it simply by measuring them and cuting off the ends to make them 27/28ths of the size they were.
Modeling the antenna with computer software would save you a lot of time and trouble, or carefully modifying it by cutting and trying it with an SWR meter or an antenna analyzer.
Keep in mind that you need a valid ham license in most countries to transmit on 10 meters. If you do not have a license and are planing to get one in the future, don't bother modifying it. The difference in reception is not really worth it.
Geoff.
-- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/
snipped-for-privacy@mendelson.com (Geoffrey S. Mendelson) hath wroth:
the
I don't think the original poster is interested in becoming a ham and using the 10 meter ham band allocations. My guess(tm) is that he's interested in "freeband" radio. Freeband is located in between the CB band and the 10 meter ham band from 27.410 to 28.000Mhz. Operation in this area is strictly illegal, but that doesn't seem to prevent Freeband operators from doing so, or seem to interest the FCC enforcement burro. For example:
In most cases, scaling the yagi antenna elements without changing the spacing is sufficient for such small changes in frequency. However, the gamma match should also be adjusted for minimum VSWR, especially if one is running an illegal high power amplifier. The pattern or gain won't be optimized but good enough to function as a directional antenna.
-- Jeff Liebermann jeffl@comix.santa-cruz.ca.us 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I assume nothing. Outside of the U.S. the bands are different, enforcement is different,e tc. For example in the E.U., you can use a regular ham radio on CB, no one seems to care about the power. FM and packet are also common on CB.
Since I've been here in Israel (almost 10 years), I've never met a person with a CB. I occasionaly scan through the bands, but I never hear anyone on 2m, 10m, and CB.
Geoff.
-- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/
the
small
software.
No, the higher the frequency, the shorter the wavelength.
You certainly can NOT legally use "a regular ham radio on CB" (at least not in the UK), even if you keep to the 4W power limit. CB radios have to be type approved to be legal.
If you are a licensed radio amateur, you can, of course, modify a legal CB radio for use on the 10m band (or, for that matter, any other amateur band). However, the authorities are (or were) a little difficult about modifying illegal CB radios for amateur use, on the grounds that they were not approved, so could not have been legally imported into the UK. No import duty could have been paid, so they must have been smuggled here.
Don't know why you've never heard anyone on 2m or 10m (but I can't speak for CB).
As for the original question, I don't see why an 11m beam can not be trimmed a little to move it up into the 10m band. I doubt if you will need to reduce the spacing between the elements.
Cheers. Ian.
snipped-for-privacy@mendelson.com (Geoffrey S. Mendelson) hath wroth:
You assumed that the original poster wanted to operate in the 10 meter ham band, and not between the ham band and CB.
True. World wide, the area between 27.410 to 28.000MHz is either meteorological, or commercial ISM service. See:
I do PSK31 on CB just to see if it can get through the interference. Seems to work quite well. Just because nobody cares, or nobody enforces the rules, doesn't make it legal.
See:
-- Jeff Liebermann jeffl@comix.santa-cruz.ca.us 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
The U.K.may be the exception. I have seen articles in radio magazines back when I could get them, showing ham radios used on CB in continental Europe, Spain, France, the Netherlands. If it was legal or not, the articles and pictures were there.
There is a 2m repeater here, but if it used more than an hour a week I'd be surprised. I've monitored it randomly and occasionaly for several days at a time, and it is unused. There may be more activity in the north, but not here. When I moved here in '96 the local repeater id'ed as "This is R1 Jerusalem open to all" in English and this is R1 Jerusalem in Hebrew. Now there is just an occasional high speed CW ID and often that's all I hear the entire day.
Ten meters is even less used. I can't hear any repeaters, maybe in a few years when the sunspots are back. On the SSB/CW end of the band nothing.
40 and 20 are busy sometimes. Propigation varies on 20, sometimes nothing, sometimes open. When it is open it's usually around sunrise/sunset and you can hear the band following the Sun.Geoff.
-- Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/
Yes, of course you are all correct, and I was totally wrong. I know better... just don't know what happened to my thinking before I started typing.
-- Dave M MasonDG44 at comcast dot net (Just substitute the appropriate characters in the address) Some days you're the dog, some days the hydrant.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.