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Author Topic: Need Help Understanding Hypothetical Situation  (Read 1776 times)
KG4KLV
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Posts: 5




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« on: February 22, 2011, 07:58:34 AM »

First, let me say, I'm a licensed General, but I need help putting theory into practice. This will be my first foray into HF. Let's say I want to participate in a local slow CW net on 40 meters. Now, let's say I purchase a Yaesu FT-897D.

If I want to setup an antenna in my backyard, how do I know which kind of antenna is best for my purpose? Furthermore, if I make my own antenna out of wire or something (maybe an inverted-V dipole), must I also have an automatic antenna tuner? I'm thinking I should be able to trim and measure its performance without an auto tuner, but I just don't know how. I can pretty much figure out that if I do that, then that antenna is only good for 40 meters from then on. How can I figure out how to construct this inverted-V (if that's even the best option)? I'm very afraid of damaging my transceiver (that I don't even own yet). Is the choice to either have an auto-tuner or have a bunch of antennas erected for various bands?

I know there are a lot of newbie questions strewn about in my post, but I hope some wise Elmer will pick them out and help teach a new dog old tricks.
« Last Edit: February 22, 2011, 08:02:05 AM by KG4KLV » Logged
W7ETA
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Posts: 2527




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« Reply #1 on: February 22, 2011, 08:15:11 AM »

Here you go:

http://www.kd5om.com/build-an-inverted-vee.htm
http://hf-antenna.com/004/


Modern rigs, those without tubes, have a fold back circuit that reduces output as SWR increases.

As long as you get your antenna close to where it should be, your rig will load into it and show you the SWR.  You can them trim the antenna to less than 2:!, full output on your rig.

With an antenna system presenting  2:1 or less, you won't need a tuner.

Your rig an probably load into your antenna system on 15 meters.

Best From Tucson
Bob
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N1UKX
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Posts: 38




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« Reply #2 on: February 22, 2011, 08:24:22 AM »

At my last three homes, to easily get on the air, I have used a manual tuner w/4-1 balun, 400 ohm Window/Ladder line to dipole antenna cut for whatever room I had (both sides being equal length) and go for it down to the lowest band the tuner could handle.  Just saying, ya don't have to be fancy to get on the air....LL
« Last Edit: February 22, 2011, 02:41:12 PM by N1UKX » Logged
K8AXW
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Posts: 3827




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« Reply #3 on: February 22, 2011, 08:34:30 AM »

Since your immediate interest is the slow speed CW net on 40m, you could build a 40m dipole, cut for the CW portion of the band.  Once you get the correct length the transceiver will load into it fine, without a tuner of any kind.

THEN, at a later date, if your interests moves to other bands, you can drop the dipole and add additional 'elements' drooping down from the original (to go the higher bands) or add an 80m dipole  and let the original 40m dipole droop below it.

The name of the game is to Keep It Simple.  Calculating and cutting an antenna is really a fun project.  Watching the SWR change with lengthening or shorting the wires is very interesting.  The dipole is very inexpensive and a proven performer.  Tip: If you decide on a dipole and you calculate the lengths of the two sides, add 2 more feet to each end of the wire and run the ends through the end insulators and fold back this extra 2 feet of wire onto itself and clamp it or wrap it around the antenna.  This way you can lengthen the antenna.  When you get it where you want it, then cut off the excess.

After 55 years of hamming, I can tell you the PLANNING is the most fun!  If you don't have the money, planning is a great mind exercise.  If you don't know which way to go, planning is the only correct option.  Planning is another word for thinking!  Thinking leads to understanding.  Have fun!
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WB6BYU
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Posts: 13238




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« Reply #4 on: February 22, 2011, 08:53:45 AM »

It wasn't that long ago when auto-tuners were virtually unknown in ham circles and we just
built wire antennas and got on the air without them.  Some of use still prefer to adjust our
antennas so we don't need to use a tuner.

A dipole or inverted vee (they are essentially the same thing) is simple to build and, once
the length is adjusted, shouldn't need a tuner of any sort.  While there are many other
options one might consider, it is an excellent choice to start with.  RG-58 coax is quite
sufficient for feedline as the losses on 40m are low.
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KE4JOY
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Posts: 1377




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« Reply #5 on: February 22, 2011, 08:55:09 AM »

No you don't have to have a tuner. You can cut a dipole for the desired frequency band and have a lot of fun.

However a tuner as mentioned will make both you and your rig a lot happier and open up greater sections of the bands for you.

Good luck and have fun !
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KG4KLV
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Posts: 5




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« Reply #6 on: February 22, 2011, 09:05:23 AM »

What is the absolute cheapest way I could get on 40 meters? In other words, the cheapest radio I could reasonably buy, new or used, that would accomplish the purpose? Forget kits or homebrew, I'm terrible with soldering and have no patience for tiny electronic parts.
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WB6BYU
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Posts: 13238




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« Reply #7 on: February 22, 2011, 09:13:34 AM »

The cheapest rig is whatever is for sale locally, or even better what a local ham may have
back in a closet to loan out.

Used equipment isn't a bad deal, especially if you have a local ham to help check it out.
I've seen a number of quite usable rigs sell for $250 or less in the last few years - the
venerable TS-520 series, for example, the solid-state TS-120/130, some of the older
Icoms, etc.  My personal favorites are some of the Ten-Tec rigs, though they are not
all that common.  (The Century 21, for example, is a good entry-level CW rig.)

Your best best it to list your interest with the local club and/or check out a hamfest
to see what is on offer.
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2E0OZI
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Posts: 270




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« Reply #8 on: February 22, 2011, 10:31:40 AM »

If you know CW you are way ahead of the game in some ways! I second all those saying build a simple dipole cut for the band, that way no tuner is required.

However if you are a CW guy you could build a W3EDP, which is what I have, and it will work from 40 to 15 reasonably well with a simple tuner like the MFJ901B. The CW will get you contacts all over the world with 10w.

I'm SSB only at the moment, and have 10w, not got all over the world but got as far as Macedonia, Poland, Serbia.

As AXW says - experimenting is half of the fun. I just folded my dipole over and secured it with clothes pegs until it was the right length, then used cable ties. I was up and down the stairs 10 times to get it right, but over the whole of 20 it worked well.

all the best

Scotty 
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Men can only be happy when they do not assume that the object of life is happiness.
George Orwell
KG6AF
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Posts: 355




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« Reply #9 on: February 22, 2011, 10:57:20 AM »

I'd probably go with a simple dipole or inverted vee, too.  But if you want to delve into this a little more deeply, the ARRL puts out a nifty book called Simple and Fun Antennas for Hams that's worth a read.  Here's a link to the ARRL store:

http://www.arrl.org/shop/Simple-and-Fun-Antennas-for-Hams/

By the way, if you do stumble upon the perfect antenna on the first try, you'll be the first person in the history of ham radio to do so.


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WX7G
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Posts: 6035




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« Reply #10 on: February 22, 2011, 11:19:18 AM »

A good and cheap manual tuner such as the MFJ-901B at $99 will enable you to turn just about any piece of wire into an antenna.
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N4KC
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Posts: 288


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« Reply #11 on: February 22, 2011, 11:57:45 AM »

Here's an article that might help in your planning:

http://www.eham.net/articles/21270

It is also available at my web site...along with several others that might be of interest to newcomers to the hobby:

http://www.n4kc.com

Good luck, and see you "on the wind!"

Don N4KC
www.n4kc.com
www.donkeith.com
http://n4kc.blogspot.com
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VA7CPC
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Posts: 2386




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« Reply #12 on: February 23, 2011, 12:42:34 AM »

Find a copy -- it doesn't have to be the newest edition -- of the "ARRL Antenna Book".

There's more information in that book than you need -- but _everything_ you need is there.

I agree with a previous post -- since manual antenna tuners are simple and inexpensive (see MFJ 901B, for example), don't be afraid to use one.

               Charles
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