Getting into amateur radio

My last towers set in 6 yards of re-barred concrete. Usually the antenna is more at risk than the tower.

I've had a variety of HF antennas; Tri-bander +WARC, bandpass log periodic yagi, and Quads. The Quad is my favorite; the bandpass LPY was one feed line instant satisfaction.

The story of the Quad is quite interesting also.
[Towertalk] The Quad antenna was developed by HCJB

Wire antennas work well; some offer low band gain and low angle of radiation. The pitch of a roof is a natural inverted V.

These are great getting an antenna up a tree.
http://www.wcerc.org/Projects/images/slingshot-antenna-helper-01.gif

I use a sling shot and a fishing pole.

 

too much going on here. You are wasting your time trying to make a long dipole work on shorter bands and using coax. Ladder line, twinlead, or open wire line has 'practically' zero loss even at very high SWR, but coax has very HIGH loss when not matched.
So put up your wire, and feed with coax, and use it only on 40. I think it may resonate on 15 also... something about odd harmonics.

I think what you're contemplating is not a dipole if you feed it at the end, and I don't think coax will work even for the resonant band fed at the end without some kind of matching network. Again I'm too new to be fluent but I do think it's not that simple.

Wire is cheap. set up a feed line to the outside and try different antennas. Something will work well for you.

Bringing ladder line down the roof from the center is common, I think. You're supposed to twist balanced line and that would keep it from laying flat at least, even if you didn't have it elevated. I'm not sure that's okay, but I have read of it being done. It just has to be kept several times the space between the connectors away from metal. I would suppose it could also be bad touching a wet roof.

 

Ladder line is ~420 ohms and a dipole at 1/4 wave above ground is ~70 ohms.

You want to match the impedance of the antenna and the feed line as closely as possible.

If you want to feed it with a form of ladder line; use 75 ohm TV twin lead to match the antenna.
That should get you a little less than 1.1 on swr. Antennas in free space are easy; in real life there are a lot of factors.

 

I just set an 80 meter Dipole in the tree tops. I used a fishing sinker attached to a rod and reel and a slingshot to shoot a messenger line into forks of trees and passed a para-cord, then the line that will support my antenna. I also placed a screen-door spring at each attachment point for a shock absorber when the wind get a bit brisk and trees don't tend to sway synchronized. No tree climbing involved, Ghrit.

 

a dipole connected to ladder line and run to either a tuner capable of tuning balanced line; or a balun with a short coax jumper to the tuner, does not need to be matched at the antenna. What freq would you match it for? It's purpose in life is to be used on mostly non-resonant freqs and the impedance would be all over the place. It simply isn't necessary when using balanced line on a balanced antenna; the loss is insignificant even when severely mismatched.

reminder- this is from reading, I have no experience yet.

 

I was a teaching VE but that was 23 years ago. So, it has been a very long time. LOL

"The matched method for coupling a line to an antenna consists is matching perfectly the antenna impedance to the characteristic impedance of the line. This method will gives a very low SWR, below 1.5:1, less than 1/20th of the input power is reflected, and the input impedance will be purely resistive, regardless the line length. In other terms the line will be "flat" or at least its lost by radiation are considered as negligible."
All about Transmission lines

I was a DX'er and the FCC created all DX'ers equal except if my antenna radiates more of my RF than yours; simply stated means more watts hit the antenna, more bandwidth with a low SWR.

ANTENNA TUNER MATCHING PROBLEMS AND SUGGESTED FEEDLINE LENGTHS

It can get a lot more techie when you don't consider from the radio to the tip of the antenna as one circuit. Antennas are both an art and a science.

I hoped that helped.

 

The $4 Special
"But beware: Marconi spins in his grave everytime a ham buys an aerial instead of building it."

 

I enjoy antennas, so I build them from wire because it is cheap fun. Play with them for a few months or more. Anyhow for me it is fun, lol.
When you buy an antenna; you assemble it and fine tune it. When you build an antenna, you do all the "math" and tuning. Direct match gets you the "most" out of an antenna.
Twin lead is balanced line and your radio is unbalanced. Although you don't need one; I personally use a balun.

Balun - Wikipedia, the free encyclopedia

More technical Baluns in theory

I prefer current baluns and the link is a source or you can build current baluns.

A high SWR produces heat. Radios with transistor finals do not tolerate heat for long. My rig has a built in tuner which is nice for mobile/field day etc.
My old TS530-SP has tube finals 2x 6146B which are much more forgiving than transistor rigs.
Tube final rigs have a load and plate control which matches the network load and plate tuning of the finals to the antenna. Sort of a built in tuner tuning the output to the load. Drive tunes the driver tube and some other things.

www.eham.net/data/classifieds/images/351754.jpg

If the wire runs 330 to 150 that is the nulls; peak rx/tx 60 and 240; however it will cover a lot more. My first DX was Europe, Africa, SA with a windom 20' up and part of the vertical section ran parallel to the ground.. (Think of a Novice building first antenna.... LOL)

 

When a dipole is horizontal the impedance is ~70. As it's ends are closer to the ground an inverted V's impedance is closer to 50.

The balun would connect the coax to the antenna.

 

An inverted Vee can be fed with 50 coax. I would recommend using a 1:1 balun at the antenna so both elements of the antenna will radiate alternatively. Baluns can also stop common mode currents (RF) on the feed line.

 

There is a website that just started up Prepared ham. Survival ham radio ops the entire site is about ham radio for preparedness, they help getting people licensed and on the air. You guys should check it out if your are into comms. They are building a group of a pretty experienced ops, and getting ready to setup an on air net to practice the skills once you get licensed.

 

Any downloadable study guides for technician and general? I just contacted the local club and have a couple weeks before they test again. If not then, it will be 6 weeks out. Maybe longer based on how much material I have to learn.

 

Here's some links that should get you going. There are books you can buy but I wouldn't recommend any of them over the free stuff.
AA9PW FCC Exam Practice » Amateur Radio Exam Practice
No-Nonsense Study Guides - KB6NU's Ham Radio Blog
HamExam.org: Free Amateur Radio Practice Tests with Flash Cards
Practice Amateur Radio Exams by QRZ.COM
eHam.net Ham Radio Practice Exams

You should attempt General while you're there. Much of the prep for Tech is also applicable. Doesn't hurt, nobody will know if you don't pass it, no harm in trying.

Take practice tests by the hundreds and if you're doing 90% on them after a while, you'll pass the test. The questions and answers that will be on the test are the exact same ones you can get from the internet. The only thing I remember is I had done so many practice tests, I was remembering which answer letter A) B) C) D) was correct, but on the real test they were not in the same order.

Take practice tests even though you don't have a clue as to the answer. Just guess. The practice test will tell you which ones are right and if they're wrong, it'll tell you which answer is correct.

I did a combination of the methods. I tried using the study guides that explain the answer, the ones that show only the correct answer, the ones the phrase the answer in the form of a sentence... I think for my brain it was most beneficial to answer tests that I didn't understand. I did get to remember which answer was right, even if I didn't know what it meant.

That, combined with learning the easy formulas for wavelength in meters/antenna in feet, wavelength to frequency, etc. Like Ohm's Law, you can draw yourself a little cheat sheet on the scratch paper. I'm not talking about cheating, you aren't bringing this in on paper, you take the scratch paper and before you start the test, draw the little helpers. They make it easy to remember what to calculate. Put your thumb over the value you need, and it tells you what to do with the values you have. Picture these with a circle around them, or I've seen some people use a triangle. For example if you have Volts and Ohms in this drawing,

E
------ where E=Potential in Volts, I=Current in Amps, R is Resistance in Ohms
I | R

cover the Amps and it shows Volts over Ohms, which is a division, Volts divided by Ohms to get Amps.
If you have Amps and Resistance, cover the E, and now you can see you multiply I times R.

Same idea with these:

300
-------- where the constant 300= the speed of light in km/sec, f=Frequency in MHz,
f | m and m=wavelength in meters.

468
------- 468 is a commonly used conversion factor
f | ft f=frequency in MHz, ft is length in feet of a halfwave dipole

I know I've seen the stupid thing somewhere but I can't find it now, so I drew it.
It was simpler for me to memorize this, to be able to draw it on the scratch paper, than to actually learn that stuff at the beginning.


Of course you want to learn what you need to be a proficient operator, I just don't see the need to do that first.