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Author Topic: Yes, the Antenna!  (Read 5554 times)
MW1CFN
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Posts: 31




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« on: November 15, 2011, 01:10:18 AM »

I wish amateur radio wasn't quite so complex! 

I've been looking at G5RV antennas, mainly as they are fairly simple and cheap.  I see one on e-bay, made in the US, but then wonder why a wire that needs to be at least 16 feet up in the air (as recommended by the maker) only has 16 feet of ladder line, which then seems to need coax to make it to the tx.  Then there's the argument about baluns and chokes, about which nobody seems to agree!  And anyway, I've never put up an antenna before!

So, although it's a worn-out question, for someone on a budget and would like to make some DX contacts using a simple antenna where there is maybe no more than 40-45 metres available in total, firstly which bands would be best to focus on for long distance contacts, and then what kind of wire antenna would be best?  Verticals are interesting, but seem more complex to erect in a very windy area (and my area is exceptionally windy!), and to tune.  I quite like the magentic loop by MFJ, but it's a little costly for the moment.

I can only apologise for my ignorance, but at least I'm trying to do something about it by learning from others, rather than reinventing the wheel as a square!


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N2EY
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Posts: 3835




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« Reply #1 on: November 15, 2011, 05:49:02 AM »

There is no short or easy answer to your questions. It all depends on what's available.

Some things to remember:

1) On HF, the waves are pretty big. So the antennas have to be big and high off the ground. There's no cheating the laws of physics.

2) Progress in electronics has made possible small, relatively-inexpensive transceivers that cover multiple bands and modes from MF to UHF and work flawlessly right out of the box. But due to 1), the same cannot be said for antennas. You have to do a bit of planning, putting-up and adjusting.

3) HF propagation is predictably unpredictable. That's what makes it fun. If we knew exactly when a particular path would be open it would be no different from the telephone. The thing to do is to get some sort of antenna and rig and listen. Then make some QSOs. There is no substitute for on-the-air experience.

4) Wire antennas are easy to make. I don't know why hams buy them.

5) ZS6BKW. Google is your friend.

73 de Jim, N2EY

"If it were easy, everybody would do it."

- paraphrase of Tom Hanks in "A League Of Their Own"
« Last Edit: November 15, 2011, 05:51:04 AM by N2EY » Logged
W7ETA
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Posts: 2528




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« Reply #2 on: November 15, 2011, 05:57:49 AM »

You are in luck.

This site has tons of info for hams: http://www.w8ji.com/
This site has tons of info on all sorts of antennas: http://www.cebik.com/

And this link will explain how the antenna works: http://www.qsl.net/aa3px/g5rv.htm

At the top of that page you will see that the antenna has a "special" feed line arrangement, the ladder line.

Further down the page it explains how the ladder line works.

Antennas are fascinating.

Consider making your own G5RV.

What is nice about wire antennas is that we can make a lot of different ones.

If you have limited space you can have different wire antennas for different purposes, like one for close stuff on one or two bands and other antennas for "long-haul" contacts.  Just lower one antenna and hoist up the other one you want to use.

Best from gorham ME
Bob
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W7ETA
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« Reply #3 on: November 15, 2011, 06:06:42 AM »

Oh.
The most important thing about your first wire antenna is that you get it up and have FUN with it!  Its sorta nice if it will stay up until you want to take it down.

My first antenna was a trapped inverted Vee for 80 and 40 meters.  I held the center up with the mast for the TV antenna was and spread the legs over the two story house I was in.  It also loaded on 15 meters.

My next antenna was a home made dipole for 20 meters.

Personally, I'm a big fan of delta loop antennas, they are self contained.  As a result one does not have to lay down radials.

Have FUN.  I'm on my third sunspot cycle now.
Bob
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NA4IT
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Posts: 870


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« Reply #4 on: November 15, 2011, 06:59:14 AM »

G5RV Description - An amateur radio antenna made of varying types of wire and feed line, that radiates equally poorly in all directions.....

In my talking with other hams, about 1 of every 5 G5RV antennas work right. The rest don't, RF feedback problems, high SWR, etc. etc.
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K8AG
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Posts: 349




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« Reply #5 on: November 15, 2011, 09:34:11 AM »

I have used a ZS6BKW for years as my primary antenna.  It is a bit shorter than the G5RV with a bit more window line in the transformer section.  I have about  dozen turns of coax around 8" in diameter just at the end of the transformer ladder line and have no RF problems inside the house.  I run 100W max so I can't speak for 1KW+ power levels.

The BKW matches more bands better than the G5RV.  And I get DX.  I normally have no problem making contacts at QRP power levels, including DX.  I have been stretching (compressing?) the limits of late and my current record is Pamplona Spain with 100mw (that's 0.1 watt).  Works out to about 49,000 miles per watt.  Not bad for a wire in the trees.

My 2 cents.

73, JP, K8AG
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W1JKA
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Posts: 1618




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« Reply #6 on: November 18, 2011, 04:42:35 PM »

  Keep it simple:make two cheap and easy to build dipole antennas,coax fed, (I use cheap electric fence wire) one for 20m,one for 40m Cut to center frequency of your cw/phone preference, no tuner or balun necessary.Experiment with height 20 to 40 ft.and different directions,learn your day/night propagation on these bands and you will have all the local/dx contacts that you can handle.Just get on the air with the basics,experiment,have fun and the rest will all fall into place.


73,Jim

 
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MAGNUM257
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Posts: 159




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« Reply #7 on: November 18, 2011, 06:05:44 PM »

G5RV Description - An amateur radio antenna made of varying types of wire and feed line, that radiates equally poorly in all directions.....

In my talking with other hams, about 1 of every 5 G5RV antennas work right. The rest don't, RF feedback problems, high SWR, etc. etc.

Interesting facts, thanks.  However, in the small group of exactly five hams in my community (coincidence), all of which operate a g5rv, none of us have the problems you describe above.
We have all earned DXCC, WAS, and fill our log books with contacts using the g5rv. Also intersting...
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STAYVERTICAL
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Posts: 854




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« Reply #8 on: November 22, 2011, 02:04:14 PM »

I totally agree with you!

Antenna's over the years have taken on mythological status, and much of ham radio lore is involved with maintaining this situation.

Lets get brutal.

An antenna is simply a way of losing radio frequency energy to the environment, which is why it has a term called radiation RESISTANCE.
A resistor loses energy in the form of heat, an antenna loses energy in the form of electromagnetic radiation at radio frequencies.

It is basic engineering that a source of energy, such as a radio transmitter, is designed to transfer this energy optimally at a particular impedance.
For the maximum transmission of energy from the source (transmitter) to the load (antenna) the impedance of the antenna should match the impedance of the transmitter.
This impedance is normally 50 ohms, due only to the production and use of 50 ohm coaxial cable, this impedance has become standard in ham radio transmitters, but it was not always so.

In pre-coax days, open wire feedline was the status quo, and this feedline was usually around 450 to 600 ohms impedance, so the transmitters used tuners which were appropriate for this impedance.
After world war two, when lots of surplus coax became cheaply available, it made its way into ham hands where its simplicity of use made it become ubiquitous, and open wire feedline declined in use.
50 ohms came to rule the world.

But there was a problem - open wire lines usually operated with high SWR and it did not make much difference because these type of feedlines have extremely small losses, but 50 ohm coax with high SWR is a disaster for losses.
So came the need to design matching circuits to try to keep the impedance at 50 ohms where it joined the feedline.

This was done through use of "matching sections" which are basically bits of feedline acting as impedance transformers, but keeping 50 ohms at varying frequencies was extremely difficult, so hybrid setups such as the G5RV developed with specific antenna lengths, open wire sections and coax sections. The whole point of the exercise was to provide 50 ohms for the coax at as many frequencies as possible.

Now enter the modern age.

All of this sectioning and matching is not necessary in these times, but due to antenna's being mythological not science, many hams have not noticed.
What is the antenna giant killer which arrived on the scene?

Yes you guessed it, the remote ATU.
This device is like having a whole department of bureaucrats at the junction of your antenna and feedline who's entire purpose in life is to monitor the frequency of the radio energy coming down the feedline and adjust coils and capacitors until the antenna provides a 50 ohm match to the feedline.
Some of these magic boxes are just left out in the rain and work autonomously, some have a control line back to the shack or into your transceiver, where you press a button to tune your antenna perfectly, but they all do the same thing, and do it well.

Now notice I said the REMOTE ATU, not the atu built into your rig or on your desk in the shack.
These units work great for their purpose, which is to match the coax feedline to the rig, rather than the antenna to the feedline.
What is the difference?
In the case of the in-shack ATU, the coax and antenna may not be matched and a high SWR may exist on the coax feedline, while with the remote ATU the coax will not have a high SWR.

Coaxial cable losses increase with high SWR because coaxial cable has losses!
This circular argument is appropriate, because having a high SWR means that your radio energy is going to the antenna, losing a bit on the way in the coax, then some is radiated by the antenna, and the rest is reflected back to the transmitter end tuner.
When it gets to the transmitter tuner it is turned around, synced and added to the energy going to the antenna (yes, you actually have more power going to the antenna than you are sending, because the the reflected energy is added).

Every time the energy does this "bouncing" back and forth, some of the reflected energy is lost in the coax, the poorer quality the coax the worse the loss.
This is why open wire line can be used with high SWR, its losses are miniscule.

In the modern era we don't need magic lengths of antenna anymore if we have a remote ATU - we just throw up some wire where it fits and where our whimsy decides and press the button - instant match making.
Yesterday I decided to try a classic windom (single wire feed) with a counterpoise, total construction time 20 minutes, total cost a dollars worth of wire.
Time to tune - 2 seconds with the ATU. Frequency range 40m to 6m with an SWR of 1:1.
How does it work - amazingly well!

So the moral of the whole story is:
- Antennas consist of two parts, the radiating part and the matching part.
- Most of the complexity is in the matching part, open wire feedline sections, coax sections etc.
  For a G5RV, the radiating part is the wire, all the other bits are just for matching and do nothing for the radiation characteristics.
- A remote ATU will replace the complex matching sections and release you from the slavery of cumbersome antique matching methods.

73s
« Last Edit: November 22, 2011, 03:21:37 PM by STAYVERTICAL » Logged
AD7C
Member

Posts: 81




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« Reply #9 on: November 22, 2011, 02:10:30 PM »

I'll answer your questions as everyone seems to have avoided doing so.

There are  a lot of manufacturers who make a G5RV.  The "REAL" G5RV is approx 102' from end to end with 31' of ladder line (feed line).  You need to use about 70' of coax cable to attach your transceiver to the end of the ladder line.  Most manufactures place a SO-239 connector at the end of the ladder line for you to do so.  The antenna should be about 30' in the air and as flat as possible.  The ladder line should run straight down.   Think big "T".  All this is required to make the antenna work in the way it was designed.

You will see different versions of this antenna everywhere.  If the dimension are not close to the above then it is a 'type' of G5RV and not the original design. Nothing wrong with them, just not really a true G5RV.  Things like G5RV mini, G5RV junior, etc.

Can you make your own G5RV? Yes.  Should you? Depends.  The cost of making your own and the cost of some manufactures pre-built versions are so close there is little argument to making your own... unless you really want to learn how.  I suggest buying your 1st then making your 2nd, 3rd, or hybrid version yourself.

Does the original G5RV need a choke and/or balun  I say NO.  The original designer also said NO. Experiment with and without one and see what happens IN YOUR CASE.  That's the best answer. Just use the 'loop of coax' method for a balun.   Cheap and easy.

Does the G5RV work? Yes.  Does it work well? Depends. Any antenna is better than no antenna.  If you install it the way it was designed (or the way the manufacturer intended) then you'll make contacts.  It's definitely not the greatest and not the worst.  You'll hear tales of amazing DX about the G5RV nd others lament that it couldn't talk down the street.  My recommendation is "TRY IT".  I have talked to numerous people and hundreds of DX stations on antennas that many said would never, ever, ever work. That's the fun of Ham Radio.  Experiment and try for yourself.

Beware!  Although the G5RV can work o 10-80m... it most likely will need an antenna tuner to work correctly.  If you install it just right (as mentioned in my 1st paragraph) then you may get a good match on most of the bands.

As some other mentioned.  A simple, single band dipole is always a good option for a 1st antenna.  Simple, cheap, and almost always a performer if done right.  That would be my 1st antenna to try. 

73,

Rich
AD7C










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WB6BYU
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Posts: 13015




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« Reply #10 on: November 22, 2011, 03:26:53 PM »

Quote from: MW1CFN
I wish amateur radio wasn't quite so complex!...

Well, it is by nature, and it doesn't have to be in practice.

A simple dipole antenna will get you on one band quickly with a minimum of effort.
You can make it yourself with a bit of wire.

You can add a dipole for a second band to the original antenna  so it works two
bands - say 20m and 15m.  By starting with the wires a bit long and trimming the
ends you can get the SWR down to where you don't need a tuner.

Where things tend to get complicated is when someone wants a single antenna
that has good performance on all the bands their radio covers - such as 160m to 6m.
That sounds convenient, but the radiation pattern likely won't be optimum for all
the bands.  That, and other tradeoffs, is why there are so many multi-band options,
and they all have their pros and cons.

But you aren't limited to one antenna - often it makes more sense to have several
that are optimized for different bands or paths rather than try to make one do all
jobs.




Quote
And anyway, I've never put up an antenna before!

Let's start there.  Every ham starts out not having put up an antenna.  Then most of them
do.  There is a lot of practical knowledge involved, but it is mostly a matter of mechanics.
A good way to start is to join the local radio club and ask for assistance.  The "antenna
party" used to be a great ham tradition:  you get several hams together to help put up
your antennas (or you go along to help others) and then have lunch or drinks afterwards.
You make some friends and learn a lot, your antenna gets put up and you get some help
on how to operate the rig, tuner, etc.  You may even find a local with a pile of scrap
wire for building antennas.

Not that you can't get started all by yourself - many of use did that.  But if there is a
local club it makes life easier.


Quote
...would like to make some DX contacts using a simple antenna..., firstly which bands would be best to focus on for long distance contacts...

I'd start with 20m.  It is THE band for DX.  Not that other bands aren't often as good, or better,
at times, but if you only had one band, that probably is the best choice.

Conditions change over time.  We've just come out of an extended dip with low sunspot numbers,
where propagation was nearly non-existant on the higher bands.  But things are getting much
better, and we're even seeing openings on 10m.  The higher bands -when they are open - give
better signal strengths for DX.  So 15m and 10m are good second choices, as well as 17m
(which has less activity, and isn't as full of contests), though just a year ago there wouldn't
have been nearly as much activity.  A single antenna that you can use on 20m through 10m
isn't difficult.

40m is different in Europe than on this side of the Pond, where the band is 300kHz wide and
we don't have to contend with nearby SW BC stations.  You'll have to try it and see if it is
to your liking.  80m provides a lot of local contacts.  DX is possible on both bands, but takes
more work.  The same goes for Top Band (even more work.)

Quote
and then what kind of wire antenna would be best? 

There are two basic approaches to wire antennas.

The first is to tune the antenna to give a good match to common coax cable.  The dipole
antenna I recommended above is an example.  Once you've done that, the antenna will
work without a tuner on the design band, and sometimes the 3rd harmonic (typically
using a 40m dipole on 15m.)  You can add additional wires to the feedpoint to give you
coverage of more bands - I've often set up my portable antenna kit to cover 80, 40, 20,
15 and 10m at the same time.  This approach is convenient because you don't have
to bother with the antenna when you change bands.  There are several different ways
you can make an antenna work on multiple bands, such as adding traps, etc.

The other approach is to put up a wire antenna and use a tuner to match it on all
bands of interest.  This requires a tuner, but simplifies antenna construction.  The
most common example is to put up a dipole of any convenient length fed with
ladder line or twin lead to the tuner in the shack.  That allows you to use a simple
antenna on multiple bands, with the added cost of a tuner.  (Which you can also
build yourself if you want.)

Both approaches work.  Some people find one more convenient for their preferred
operating style than the other.  The main problem comes when people try to combine
the two methods by feeding an untuned antenna with a tuner through a coax line - the
line losses can be very high.  Not that you won't still make some contacts, but you may
be losing 50% to 90% of your power in the feedline before it reaches the antenna.
That's why the untuned antenna uses ladder line - it can operate over a wide range
of impedances with low losses.

Unfortunately, many antennas sold as working "all bands" don't necessarily do so very well.

You'll get a lot of different responses on this matter.  The standard (31m) G5RV with coax feed to
a section of twinlead should work reasonably well on 80m, 40m, 20m and 12m.  It will tuner on
some other bands, but losses may be higher, depending on your choice of feedline and the length.
There are variants of the Off-Center Fed Dipole ("OCFD", sometimes mistakenly called a "Windom")
that are also advertised to cover all bands.  They may do a good job on several of them.  With both
of these you most likely will need a tuner.

Another option is a horizontal loop - one for 40m and up will be 10m on a side.  This makes a nice
all-band antenna, though it requires more support points than a simple dipole.  When fed with a
4 : 1 balun at the feedpoint you can get 40, 20, 15 and 10m with usable SWR, or you can use
open wire line to a tuner in the shack for all-band coverage.


But I'd still recommend starting simple to get on the air while you read more about other options
and plan your next antenna.


One other thing to remember is that, with horizontal antennas for working DX, they will work
better the higher in the air you can install them.  So give some thought to what you have
available for antenna supports.  A good target would be to get your antenna up 10m, but
if you can't manage that, just do the best you can.


Quote
Verticals are interesting, but seem more complex to erect in a very windy area (and my area is exceptionally windy!), and to tune.

Not necessarily any worse than other antennas.  They can be self-supporting, which comes
in handy if you have no local trees to string wires from.  They typically require a good earth
radial system for high efficiency, but you can use some lengths of dural tubing or a wire hanging
from a fishing pole or tree branch.  Much of the discussion you have read about tuning them
is related to the multi-band versions with traps, but again you can put up your own simple
vertical for one or two bands with much less effort.


Quote
I can only apologise for my ignorance, but at least I'm trying to do something about it by learning from others, rather than reinventing the wheel as a square!


Not a problem - we all started from that point at some point in our lives.  (And some have
never moved on from there.)  Once you get a feel for the mechanics of putting up an antenna
(such as throwing a rope over a tree branch, or installing a mast of some sort, tying knots, etc.)
then putting up an antenna doesn't need to be a lot of work.  If you use halyards at each end
it becomes simple to take one antenna down and try another to see which works better.
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AA4PB
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« Reply #11 on: November 22, 2011, 06:03:53 PM »

I highly recommend that you start out with a simple single-band 1/2 wave, coax fed, dipole. They are inexpensive, easy to put up, easy to understand, and work as well as most any wire antenna on the band they are cut for. There is plenty of time to experiment with other antennas after you get some experience with the dipole.
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M6GOM
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Posts: 875




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« Reply #12 on: November 23, 2011, 07:05:01 AM »

Another here for halfwave dipoles. Cheap to build, work well and don't need a tuner unlike a G5RV. You will find using a G5RV with a manual tuner a frustrating experience after a while. Going on your PSU thread, you're a bit short on cash. The money you save on a tuner would go a long way towards a PSU.
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W5DQ
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« Reply #13 on: November 23, 2011, 10:51:24 AM »

I'm not sure what your looking at that's being called a G5RV with the dimension you descibed?

By definition as described by Louis Varney G5RV, the original antenna is a 20M 1.5 wavelength dipole with a span of 102 feet (51 feet either side of the center insulator) and a 20M 1/4 wave ladder line matching stub (appx 34 feet long) before the lead in coax. There are all kinds of posers out in the market and you have to wonder if the person/company selling them ever even read about the original or saw one given some of the dimensions passing off as a G5RV antenna??

Why not just build one yourself and save the money. I build them all the time and they work just fine. Use some #16 or #14 stranded copper coated antenna wire, a piece of fiberglass rod or tubing for the insulators. Ladder line is available at most ham stores or online. I would recommend that you get stranded wire type ladder line as it is a bit more flexible. I have used both types of ladder line (stranded and solid wire). Solid tends to break if flexed too much and we live in a windy area.

Good Luck in your antenna building,

Gene W5DQ
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
N3JJB
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Posts: 36




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« Reply #14 on: November 25, 2011, 07:57:46 AM »

I'll be the third to recommend this.  ZS6BKW.  No turner needed on 5 bands.
If you are looking for a G5RV type of antenna, make one of these.  You won't be sorry.
Terry
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