half wave antennas not needing ground elements?

[BOOTY MONSTER]

i was over at a friends how earlier today and hes in the HVAC business , i used to work with him in it 20 or so years ago . anyhow , i asked him if he ever had any left over small copper tubing in a 5 ft length if i could have it . he said sure . when i was leaving he called me over to the van and opened up a box of brand new 1/4 inch copper tubing and gave me half of it !! i told him i only needed 5 ft but he said i might wanna build another antenna later on .

guess ill be posting that coil thread tonight or tomorrow

 

[HomerBB]

 

[CDX-007]

i was over at a friends.... he... opened up a box of brand new 1/4 inch copper tubing and gave me half of it !! i told him i only needed 5 ft but he said i might wanna build another antenna later on .

guess ill be posting that coil thread tonight or tomorrow

Hey Booty, do you have an MFJ-259B analyzer available?

 

[BOOTY MONSTER]

nope , and i dont know any place that does . the local shop will let me "rent" their 259b for free , i just
have to leave them a ummmmmmm ............................ &400 deposit . im not real thrilled about that . they can be bought new here ......
HF/VHF Antenna/SWR/RF Analyzer w/ LCD, Counter & Meters
.........for almost half that price . but that's what they sell them for here .


BTW , i think im going to play hell trying to get that 1/4 inch tubing neatly around a 1 1/2 diameter form LOL
but ive got an idea .......

 

[CDX-007]

nope , and i dont know any place that does . the local shop will let me "rent" their 259b for free , i just
have to leave them a ummmmmmm ............................ &400 deposit . im not real thrilled about that . they can be bought new here ......
HF/VHF Antenna/SWR/RF Analyzer w/ LCD, Counter & Meters
.........for almost half that price . but that's what they sell them for here .

OK, and you do have to be very careful with those meters. I blew mine up by simply having it on, taking a reading of my ¼ wave mobile whip when someone with a big amp & 102" whip drove by and toasted the detector diodes before I even realized what was happening. Suddenly everything read X= 0, R = 0, all zeros.

Connect it to the antenna, turn it on, take the reading and turn it off/unhook it, and make certain there are no high power radios nearby.

It sure would help you to get that coveted X= 0 reading / tuning.

 

[Robb]

nope , and i dont know any place that does . the local shop will let me "rent" their 259b for free , i just
have to leave them a ummmmmmm ............................ &400 deposit . im not real thrilled about that . they can be bought new here ......
HF/VHF Antenna/SWR/RF Analyzer w/ LCD, Counter & Meters
.........for almost half that price . but that's what they sell them for here .

Do you know any local operators that will rent it to you; or help you with your project? There must be another way to skin an antenna...

I got one used -locally- but they aren't cheap unless you need to use it all of time I guess. Then it is practical to have. When I first got mine, I checked all of my antennas and even pieces of coax. I had to learn how to use it. Was kinda fun - really. They are not 'precision'; but they do work well enough to get a job done - be it tuning an antenna or perhaps building one.

 

[CDX-007]

Oh, that was good... so close! You could have written ...to skin effect an antenna! :laugh:

 

[BOOTY MONSTER]

having a perfect 1.1 and 50 ohms would make some nice bragging rights :

 

[Robb]

having a perfect 1.1 and 50 ohms would make some nice bragging rights :

I suppose. But it is more than that. Gives you the 'x' value for reactance. The lower; the better.

I also liked the way it showed me how wide a bandwidth my Wilson 1000, IMAX, and Sirio Z-180 had. I knew the IMAX had a very wide bandwidth, but I wasn't aware that the Wilson wasn't too shabby either. Better than I expected anyway. That antenna can work 38/CB/SSB and above - all the way to 28.300/Ham. SO I can use my Galaxy 99V on 10m/SSB with it. The Sirio was even better.

 

[W5LZ]

That wide SWR bandwidth does have a penalty though! That penalty is efficiency, how much actually get's radiated from that antenna. That efficiency is inversely proportional to the size of 'X', reactance. If you watch the SWR meter on that '259 along with the 'R' and 'X' values, you'll see that there can be quite a range of 'R' and 'X' values with the SWR still 'low'. As the SWR gets higher, those 'R' and 'X' values get really wide ranged. (That should also tell you that SWR isn't exactly the best indicator of how well the antenna is working.) 'Nasty' thought, huh?
Have you ever noticed that the 'wide banded' antennas all seem to have a lot of reactance present in some form or another? Their SWR width may be nice, but their efficiency isn't.
- 'Doc

 

[BOOTY MONSTER]

ive asked on air before , but i haven't asked recently , if anyone knew someone local with a 259b and didn't have any good leads . but ill start asking when i get my 6x6 post set up out back . i be able to set it up as is back there , with about a 10 - 14 foot max mast height . itll be very to fabricate a nice strong pivot for the bottom of the mast ...... anyhow .


old bastard , is the efficiency loss that's the penalty of wide SWR bandwidth detectable to the typical person ????
if my swr is say , 1.3 or 1.4 at the ends of my needed frequency usage , would the factors you mentioned be off enough that it would reduce performance enough that i would notice on tx or rx , or is it one of those .... a meter can see the difference , but our human ears cant hear a difference .... kinda things ?

i would like a broad banded antenna . one of the reasons i got such large diameter tubing when i got my aluminum was because larger diameter material is typically more broad banded than smaller . but i see folks in the forum posting about how happy they are with the range they get out of their copper wire imax . the main reason i got bigger stuff is that its stronger than smaller stuff and will stay more vertical in strong winds .

 

[W5LZ]

Booty M.',
The diameter of the conductor makes little practical difference until it get's quite large, as in feet, not inches. Sure, it can make the length of an antenna fractionally shorter, but at HF that difference in length/height isn't going to be much.
The diameter plays a part in how much reactance an antenna exhibits/has in and of it's self. So, how much of the opposite reactance is needed to make the thing resonant (zero reactance) will naturally change according to that size of diameter. It deals with resonance, not impedance matching. (One reason why this particular brand of antenna's size may be different than that particular brand of antenna's size.)
So is there a way for an average person to measure the efficiency of an antenna? Not a particularly accurate way unless that 'average person' is willing to do a lot of math, or spend some money. One way is by using a field strength meter. Measure the amount of radiation at a fixed distance, move frequency away from resonance and measure again. Small frequency excursions won't make much difference, but a few hundred Khz, or a Mhz frequency difference will certainly show up in that measuring (which is also going to be dependent on just how sensitive that field strength meter is). For the average person that isn't going to be all that easy, it does require some 'expertise' in using a really accurate meter to get any definite readings (uuV per foot, for instance). Antenna ranges do that sort of stuff regularly, wanna build an antenna range, or submit an antenna for examination? If so, you got more money than I do! Or, you can take someone else's word for it. I've seen such a test done on bazooka antennas in one of the ARRL's 'Antenna Compendium' books (vol-2 or 3 maybe). I can't remember the author's name, but he's well known, and does know what he's doing.

Range is a particularly silly way of 'measuring' any antenna's performance, it's just never going to be constant. The higher you go in frequency, the more propagation plays a part in 'range', so when at the higher end of the HF range, such as 10 or 11 meters, it's just not reliable at all. It can only be done in a very, very generalized way and is never accurate.
- 'Doc

 

[Beetle]

having a perfect 1.1 and 50 ohms would make some nice bragging rights :

Remember - you'd only have these "bragging rights", whatever that means, on ONE discrete frequency. Above or below that frequency, the antenna would appear a little too short or too long, introducing "imperfection".

But you can chase all of those little meaningless fractions, or you can get on the air and have fun. Your choice.

 

[hookedon6]

Remember - you'd only have these "bragging rights", whatever that means, on ONE discrete frequency. Above or below that frequency, the antenna would appear a little too short or too long, introducing "imperfection".

But you can chase all of those little meaningless fractions, or you can get on the air and have fun. Your choice.

well, i soldered a 50 ohm resister across a connector,.....( no "ground elements needed either,) and it don't care about any stinkin frequency


but then,...... it ain't much for radiating

 

[CDX-007]

well, i soldered a 50 ohm resister across a connector,.....( no "ground elements needed either,) and it don't care about any stinkin frequency


but then,...... it ain't much for radiating

Ya gotta add that 276" piece of wire, and change that to a 75ohm!