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Author Topic: Elmer Advice on Which To Choose  (Read 3623 times)
AC2EU
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« Reply #15 on: March 25, 2013, 08:03:50 PM »

My vote for best answer goes to: ... K0ZN!
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W1JKA
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« Reply #16 on: March 26, 2013, 04:20:03 AM »

   As mentioned above K0ZN's post is step #1.As you are new to HF you will then have to devote time deciding the following: favorite band(s),operating style i.e. dx/local,casual/contest,qrp/qro etc. along with antenna considerations as space/height available,aesthetics,cost etc.By understanding basic antenna design and theory you will realize that no one antenna will do it all and each has its own good and bad points depending on your expectations.A previously mentioned simple homebrew tuneable dipole will get you on the air for some fun while sorting this all out .
   To date my last three year antenna journey has resulted in this:favorite bands 20/30/40 meters,niche  qrp cw/dx, casual operation, small lot with restricted height.Rigs K-1 20/40M,SW30+,IC-7200.Antennas: 20m single element hex beam @23 FT. hand rotated for K-1,switchable 30M inverted Vee @25 ft. for SW30+, 66 ft.new Carolina windom @25 ft. for 40m with K-1 and back up for all three rigs and with tuner for 30m.IC-7200 used for spotting and SWL.All antennas are homebrewed as I prefer to experiment and spend little money on antennas that will fit my needs in lieu of one disappointing costly magic do all antenna.Experiment and have fun.
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W5DXP
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« Reply #17 on: March 26, 2013, 06:21:39 AM »

How does the 88 ohms stack up with a 50 ohm TX?

Some transmitters are designed to drive a 50 ohm load but do not have a source impedance of 50 ohms so strictly speaking, maximum power transfer doesn't occur. The maximum power transfer theorem only applies when all losses are limited to the source impedance and the load impedance, i.e. the rest of the system is lossless which is never the case in the real world. When we prohibit reflected energy from reaching the source through a piece of 50 ohm coax, we have established a 50 ohm Z0-match which can be considered to imply a 50 ohm source. The truth is that some transmitters would overheat if they were actually delivering maximum power. One cannot tell the source impedance difference between two 100v sources driving a 50 ohm load unless one makes some complicated measurements. Often, source efficiency is more important than maximum power transfer. That is certainly the case for the generators at a power generating plant.

88+j0 ohms is resonant, by definition, and my IC-756PRO faithfully delivers 100 watts into that resonant load just as easily as it does into a 50 ohm load. When driving a 50 ohm load, my 50 ohm wattmeter reads 100w forward and 0w reflected. When driving an 88 ohm load, it reads 108w forward and 8w reflected. It only starts folding back at about 10w reflected.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KD2CJJ
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Posts: 368




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« Reply #18 on: March 29, 2013, 12:05:05 PM »

I own a IC 7000 whereby my shack is on the 2nd floor 25 feet from where my antenna is located.  Im using an AlphaDelta DXEE with a LDG tuner at the operating position.  I had significant near field issues and common mode current issues.  I resolved these two issues by grounding my equipment to a water pipe and adding a balun midway to the shack.  Because of the near field issues (the way my feed line was running in my attic parallel to the antenna, how close the operating station was to my antenna, on the second floor, etc.) this approach was recommended and worked.  Neither approach worked without the other (grounding and balun)

With that said, I suspect you will have similar problems with any antenna you get.  I would suggest from staying away from OCF as they are notorious to have common mode current.  The G5RV is a great antenna but again, there are caveats and issues (like how the anteanna AND FEEDLINE must be positioned)... Personally I would stick to the Fan Dipole of the AlphaDelta.  Of course like the others I would suggest building one but if your pressed for time and not money then buy it....  I ended up adding a 1/2 wave End Fed for 40 meters (The DXEE did not perform well at all on 40 meters compared to the end fed its about 5S points higher) which has worked out well ...

Get the center portion as high as you can! By increasing 7 feet it made a HUGE difference for me on 20m.
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73

Mike
KD2CJJ
PA1ZP
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« Reply #19 on: March 29, 2013, 04:36:49 PM »

Hi Chuck

Congrats about your nice set of rigs.
Both the IC7000 and YS590 are excellent rigs.

On good rigs belong good antennas.
In the past I have build about 100 antennas for HF.
And tried about 50 or more different designs.
They ranged from 5 el monoband yagi to 2 element halfwave verticals phased array on 40 mtrs.

The reason for homebrewing all my antennas was that my first OCF dipole from Fritzel was such a great disappointment, that I chose never to buy an HF antenna again.
Allmost all my humble and cheap homebrew antennas outperformed this Fritzel OCF dipole very easily.

The best advice I can give you is learn antenna theory and learn and study propagation on HF.

Good books are the ARRL antenna hand book and Rothhamel antenna book.

I read a load of articles here and reactions.
And i read a lot of different opinions.

If you ask 20 questions again on HF antennas you will get probably the same responses, all different opinions.

My advice is study on what bands you want to work and study what propagation there is.
Look at your space and room for an antenna and then make your choice.

My personal favourite antenna is a balanced dipole with open line feeders.

I use 2 of these.
One homebrew rotary V-dipole 2 x 22 feet with abt 10 mtrs of 600 ohm homebrew openlines.
Feedpoint is about 35 feet high.
( the V configuration is just cosmetic )

One homebrew wire dipole inverted of 2 x 38 feet with spiderweb coils of 25 feet at each end.
Also fed with 600 ohm homebrew open wire.
Feedpoint of this dipole is about 34 feet.

( I didn't have enough space so used the spider coils to lengthen the antenna)
   
The Dipole is perfect for use from 10-40 mtrs
The wire dipole is used on 40 and 80 mtrs

But most of the time I use the Dipole on 40 mtrs.

One absolute must to use balanced line fed dipoles is a good quality balanced tuner.
And these are very rare things.
Most tuners are just unbalanced tuners with an 1:4 balun at the antenna side.

And only a few balanced tuners are around to be bought that are really quality made.
I find the number one is PA0LL  double-L tuners.
A good other balanced tuner is Palstar 1500 double L tuner.
But these tuners are costly and even then you will have to learn and operate them.
But a good tuner will last about a lifetime.

Most hams using open feeders here use one of these 2 tuners or use a homebrew tuner like me.

If you have the money to spare and the place to set up a tower of course a big Stepp-IR  beam
Or other big beams and performers at about 60 feet high.
.
But these systems are very expensive, but there performance is super.

One of the biggest tips I can give you if you are making wire antennas please use copper wires.
Do not use steel wires.
Steel wires will lead to great losses.

My advice for all is.
A good antenna doesn't have to be expensive
An expensive antenna doesn't have to be good..
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AA5WG
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Posts: 493




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« Reply #20 on: March 29, 2013, 07:14:05 PM »

Chuck,

K0ZN has the great advice.  Get yourself a RSGB hand book or an ARRL antenna handbook.  The older ARRL antenna books from the sixties are invaluable books. 

Others above have given good advice. To sumerize a simple, efficient and capable antenna for all the high frequency ham bands would be the center fed doublet using
open wire feeders.

This "antenna system" incorporates a home brew link antenna coupler, ladder line (home brew ladder line is the best) and a random length dipole.  Some  say the minumum
length for this antenna should be no shorter than 1.25  x  the lowest band to use in meters.  i.e. if 80 meters is the lowest band that will be used then 1.25 x 80 = 100 feet.
100 feet is a "recommended" minimum length for 80-10 meters.  A zillion other lengths could be used because this "system" can be tuned. 

73,
Chuck - AA5WG

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W5DXP
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« Reply #21 on: March 30, 2013, 09:16:36 AM »

1.25 x 80 = 100 feet.

Seemed like a mistake until I realized that 1.25 is feet of antenna per meter of wavelength. The formula is very close to what Walter Maxwell recommended, i.e. a minimum length of 3/8WL at the lowest frequency of operation = 370/freq in Mhz = 100 feet for 3.7 MHz.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K4NMO
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Posts: 16




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« Reply #22 on: March 30, 2013, 06:35:30 PM »

Thanks for everyone's feedback and ideas.

 Wink
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NJ5G
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Posts: 5




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« Reply #23 on: April 30, 2013, 03:38:33 PM »

Just a little detail/amplification of some previous good advice.  Don't use steel wire EXCEPT copper or aluminum coated steel wire.  The skin effect limits the penetration of RF energy into the antenna wire. At higher frequencies like HF the RF energy does not penetrate very deep at all and doesn't know the steel is there.  Look up the formulas and you'll see most copper or aluminum coated steel wire will provide the same RF conductivity as "pure" copper or aluminum.  Copper coated steel is stronger and can be stretched tighter with no problems than copper wire.

The lower in frequency you go the deeper the penetration of the RF energy into the wire. This isn't much of an issue above 160 meters.  At 2 meters copper coated steel filler rods for oxy-acetylene welding make good antennas with no observable RF losses in excess of pure copper and the welding material is way stronger and damage resistant.

I second the advice given regarding building your own antennas.  You can save a serious chunk of green stamps to spend on other aspects of the hobby or your significant other.  It is a serious FEEL GOOD to talk on sky wire you built with your own hands. I have a mix of store bought and home brew antennae and I can assure you I get way better bang for my buck from the home brewed ones.

73 and welcome to the club,

Patrick AF5CK
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