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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Feb 24, 2012 9:38 am Post subject: Dipole antenna fabrication

At 09:39 AM 2/24/2012, you wrote:




Etienne drew a T-antenna on his discussion of the servo problem. This 

incluced stripping back the insulation on a coax, separating the 

shield and core, and stretching out each to form a Tee.



Clever. Actually too-clever-by-half. Would that it could be so easy! 

The problem lies in the termination, since the core and shield do not 

share the signal. In fact neither the core nor the shield even CARRY 

the signal.



See: periheliondesign.com/downloads/Dabbling%20with%20electricity.pdf



Then grab your SWR meter and Google any of the ham radio sites and 

see how to design a T-antenna.



Might it work the way Etienne shows? A little probably, but let's do it right.

   Can you cite a website specific to the

   fabrication of VHF dipoles fed with

   coax?



   Bob . . .

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Fri Feb 24, 2012 10:44 am Post subject: Re: Dipole antenna fabrication

Bob,



I see that there are thousands of sites when you Google them. But here a general purpose one that will get one started and discusses the issues (sorry for all the equations...):

http://en.wikipedia.org/wiki/Dipole_antenna



But Bob, in your vast experience, have you seen many dipoles per Etienne's drawing?

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

deej(at)deej.net
Guest

Posted: Fri Feb 24, 2012 10:57 am Post subject: Dipole antenna fabrication

On 2/24/2012 1:44 PM, Eric M. Jones wrote:

 	  Quote: 	
		   http://en.wikipedia.org/wiki/Dipole_antenna



 But Bob, in your vast experience, have you seen many dipoles per Etienne's drawing?


	


     I'm not Bob, but his diagram looks like the one at the top right of 

the page on that link you sent, and looks normal to me.  I've made many 

of these types of antennas for ham equipment when a quick-n-dirty setup 

was needed.  In fact, I just made one a couple of weeks ago for an APRS 

setup.  They tend to work okay.  Not great, just okay.  Much better than 

the flexible antennas that come on a handheld radio.



     What specifically are you seeing wrong with it?



-Dj



-- 

Dj Merrill - N1JOV

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Feb 24, 2012 7:14 pm Post subject: Dipole antenna fabrication

At 12:44 PM 2/24/2012, you wrote:

 --> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net>



 Bob,



 I see that there are thousands of sites when you Google them. But here a general purpose one that will get one started and discusses the issues (sorry for all the equations...):

  http://en.wikipedia.org/wiki/Dipole_antenna



 But Bob, in your vast experience, have you seen many dipoles per Etienne's drawing?



    Oh yeah . . . tens of thousands. For many years during

    the vacuum tube days of aviation radio, tens of thousands

    of single engine Cessna's went out the door with VOR whiskers

    in the vertical fin cap that were nothing more sophisticated

    than Etienne's coax fed dipole.



    Granted, the whiskers were stuck out in the breeze and

    assembled to the end of the coax but electrically, no

    different. I think we had a brief romance with adding

    BALUNS to these antennas. But without spending money

    to do really scientific tests on the antenna range,

    we generally relied on the anecdotal observations of

    production and flight test pilots. Cessna was putting

    10,000 airplanes a year out the door on 5 production

    lines.



    Some years later, Jim Weir suggested adding ferrite

    toroidal cores the coax right at the junction with

    the antenna. The idea was to reduce coax radiation

    depicted in the Wikipedia article



 [img]cid:.0[/img]



    . . . radiation caused by less than ideal termination

    of the feedline. I tested this work-around in the EMC

    lab at HBC about 15 years ago and found that an array

    of 10 cores had no appreciable effect on these stray

    shield currents.



    Years later I suffered this "hot-d(at)#n" moment. I saw

    an antenna product wherein the string of ferrites was

    replace with a single ferrite core. The coax was

    wound through it several times.



 [img]cid:.1[/img]



    But of course! Inductance in a single magnetic circuit

    varies with the SQUARE of turns. The picture seen here

    has 6 passes of the coax through the core. It is the

    electrical equivalent of 36 single cores. Now, having

    'discovered' that, it would still be interesting to

    go to the lab and see how effective it is.



    Had we possessed the knowledge and materials to

    duplicate this technique on a 1967 Cessna 172, I'll

    bet the pilots would have continued to report "no

    observable difference" in hearing the VORs.



    Of course, transmit is a different story. Energy

    levels are perhaps 130db higher (10 trillion

    stronger). The effects of poorly terminated coax

    don't have much to do with transmit/receive

    performance but MIGHT have an impact on how

    much energy is coupled into unwanted systems

    radiated from coax feed lines bundled in with

    other wires.



    But then, the potential for interfering signals

    radiated DIRECTLY from the antenna is already

    very high on a small airplane. If it's a plastic

    airplane, it's worse yet. And those 'el cheeso

    vertical dipoles tend to be really popular for

    installation in vertical fins of plastic airplanes.



    Admittedly, these antennas are not the best we

    know how to do . . . but they are easy to implement.

    They pose some risks for EMC issues. But the

    relative success with these installations suggests

    that the ship's 'other' appliances are reasonably

    designed immunity to strong external fields.



    The genesis thread discovered that making the servo

    more robust to the strong RFI environment was

    a good solution. But given that it's a plastic

    airplane, it's not clear that refining the

    antenna's feed point design would have made any

    difference at all.



 

    Bob . . .

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sun Feb 26, 2012 9:41 am Post subject: Re: Dipole antenna fabrication

The Wiki site shows a simple dipole and the caption says:



"A schematic of a half-wave dipole antenna connected to an unbalanced coaxial cable. Better practice is to connect the balanced dipole to the unbalanced line with a balun."



I've been thinking of putting aluminum foil on the TV rabbit ears....



Proper termination is the key to antenna efficiency. If Cessna didn't do it, that doesn't mean the homebuilder shouldn't do it right.



Bob et al. having flown extensively in the Western states and Mexico, I have plently of experience with being a zillion miles from a station. At those times I start to think that having a good radio and good antennas is a wise and cost effective thing to do. But do what you want.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

rhdudley1(at)bellsouth.ne
Guest

Posted: Sun Feb 26, 2012 10:38 am Post subject: Dipole antenna fabrication

A wise (and practical) person once said:



           "Perfection is the enemy of good enough."



                                                            Anymouse

RHDudley



On 2/26/2012 12:41 PM, Eric M. Jones wrote:

 	  Quote: 	
		   



 The Wiki site shows a simple dipole and the caption says:



 "A schematic of a half-wave dipole antenna connected to an unbalanced coaxial cable. Better practice is to connect the balanced dipole to the unbalanced line with a balun."



 I've been thinking of putting aluminum foil on the TV rabbit ears....



 Proper termination is the key to antenna efficiency. If Cessna didn't do it, that doesn't mean the homebuilder shouldn't do it right.



 Bob et al. having flown extensively in the Western states and Mexico, I have plently of experience with being a zillion miles from a station. At those times I start to think that having a good radio and good antennas is a wise and cost effective thing to do. But do what you want.



 --------

 Eric M. Jones

 www.PerihelionDesign.com

 113 Brentwood Drive

 Southbridge, MA 01550

 (508) 764-2072

 emjones(at)charter.net





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=367293#367293

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sun Feb 26, 2012 11:28 am Post subject: Re: Dipole antenna fabrication

A good job is sufficient. We disagree on what constitutes a good job.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

deej(at)deej.net
Guest

Posted: Sun Feb 26, 2012 12:13 pm Post subject: Dipole antenna fabrication

On 2/26/2012 2:28 PM, Eric M. Jones wrote:

 	  Quote: 	
		   



 A good job is sufficient. We disagree on what constitutes a good job.




	




     Having made and used at least a few dozen of these types of 

antennas, I can say they generally do perform a "good job".  They 

perform far better than a handheld antenna, and perhaps not as good as 

some other types of antennas, but overall they are okay, and of course, 

cheap to make!    Comparing $$ spent to value received they rank very 

high.



-Dj



-- 

Dj Merrill - N1JOV

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Feb 26, 2012 8:38 pm Post subject: Dipole antenna fabrication

At 11:41 AM 2/26/2012, you wrote:




The Wiki site shows a simple dipole and the caption says:



"A schematic of a half-wave dipole antenna connected to an unbalanced 

coaxial cable. Better practice is to connect the balanced dipole to 

the unbalanced line with a balun."



     . . . and I published instructions for adding this

     feature to a coax fed dipole at



http://aeroelectric.com/articles/BALUN/Balun_Fabrication.html



     . . . the same technique could be applied to a comm

    dipole.



I've been thinking of putting aluminum foil on the TV rabbit ears....



   Which will lower the resonant frequency of the antenna

   and perhaps lower the Q . . . wider bandwidth. But

   no benefit for relative efficiency compared to an "ideal"

   dipole at the same frequency.

Proper termination is the key to antenna efficiency. If Cessna didn't 

do it, that doesn't mean the homebuilder shouldn't do it right.



   I can assure you that Dr. Wood read the same books

   we've all read about antennas with professional

   attendance to "better practice." The point I endeavored to

   make was that after he came to understand all the

   deleterious effects over which we had no control on

   a C-172, adding baluns on the VOR antennas yielded very

   small gains compared the sum of other losses.



   Next time I can get into the test lab, I'll do some

   measurements on the difference between a balun-fed

   dipole and a bare foot, coax-fed dipole.



Bob et al. having flown extensively in the Western states and Mexico, 

I have plently of experience with being a zillion miles from a 

station. At those times I start to think that having a good radio and 

good antennas is a wise and cost effective thing to do. But do what you want.



   But you paint a picture suggesting that a balun would

   make the difference between communicating with some distant

   station . . . and not. Given the light of sight character

   of VHF+ frequencies, you're more likely not to have a useable

   path because you can't see the other station than because

   your effective radiated signal is down by a few db due

   to violations of feed point protocols. Further, it's

   insufficient to be able to see the other station

   peeking over the horizon (or mountaintop). The effects

   of intervening "roughness" in the "Fresnel zone" can

   have some profound effects on what might otherwise be

   considered a free-space, line of sight situation.



http://web.arundale.co.uk/docs/ais/PathlossCalculationsforAmateurs.pdf



   Mountain peaks and valleys intruding into the Fresnel

   zone can kick your free space performance predictions

   in the teeth.



   Currents flowing on the coax shield are but part of

   the 'violations' . . . the center impedance of a perfect

   dipole is on the order of 73 ohms. This means that the

   BEST SWR to be achieved without application of some

   impedance matching is on the order of 73/50 = 1.46:1

   So we've tossed off some efficiencies right out of the

   box. When we plot radiation patterns on VHF antennas

   on airplanes, one generally expects 10 db or greater

   'lumpiness' in the pattern due to geometry of the

   conductive elements around the antenna. So again,

   if one is at 'extreme range' for useful communications,

   it's more likely that you'll improve the path by turning

   the airplane a few degrees as opposed to optimizing

   feed point design.



   Yes, a BALUN can be "better" but experience on small

   aircraft has shown that the difference is so small

   compared to all other effects combined that the balun

   was not 'cost effective'. Further, it won't fix the

   fundamental mis-match so 1.46:1 is still the best

   we can expect. The textbooks are full of examples of

   data taken from the idealized antenna and feed line

   examined in the anechoic chamber with test equipment

   that can split a DB into small pieces.



   As soon as you put that same antenna is a real world

   environment, lots of things with potential for

   altering performance happen. This is why

   the guy flying 'around with a radio capable of

   talking to another one just like it 1000 miles

   away finds that the practical limits are much

   shorter for reasons mostly beyond control of

   the antenna designer.



   But just for grins, I've got some DIY antenna's I've

   used in my weekend seminars and articles. I'll

   fit one with a balun and leave the other barefoot.

   Then see if my buddy Don P can tell the

   difference without looking to see which one is

   hooked up.  Hmmmm . . . I think I know how to

   do the experiment with equipment I have. Need

   warmer weather though . . .



   Bob . . .

wynaire(at)citlink.net
Guest

Posted: Sun Feb 26, 2012 11:10 pm Post subject: Dipole antenna fabrication

Extremely educational dissection [of antenna logic] from bystander 

viewpoint. Many thanks Bob.

Mike W.

Moab, UT

****************8's

---

jan_de_jong(at)casema.nl
Guest

Posted: Mon Feb 27, 2012 3:09 am Post subject: Dipole antenna fabrication

Bob,



When you're at comparing I would be interested in the effectiveness of a 

Pawsey stub balun as it is so easy to make from scrap coax.

The following antenna gets good results using such, apparently:

http://chrusion.com/BJ7/InvVeeAntenna4ULs.pdf



I also wonder about the effectiveness of a coax air coil in the feedline 

(people use 10 turns of 2 or 3 " diameter or so). Also easy to make.



As I understand it the Pawsey stub works by compensating, the air coil 

(and ferrites) by choking.



Jan de Jong



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 11:41 AM 2/26/2012, you wrote:

 

 <emjones(at)charter.net>



 The Wiki site shows a simple dipole and the caption says:



 "A schematic of a half-wave dipole antenna connected to an unbalanced 

 coaxial cable. Better practice is to connect the balanced dipole to 

 the unbalanced line with a balun."



     . . . and I published instructions for adding this

     feature to a coax fed dipole at



 http://aeroelectric.com/articles/BALUN/Balun_Fabrication.html



     . . . the same technique could be applied to a comm

    dipole.



 I've been thinking of putting aluminum foil on the TV rabbit ears....



   Which will lower the resonant frequency of the antenna

   and perhaps lower the Q . . . wider bandwidth. But

   no benefit for relative efficiency compared to an "ideal"

   dipole at the same frequency.

 Proper termination is the key to antenna efficiency. If Cessna didn't 

 do it, that doesn't mean the homebuilder shouldn't do it right.



   I can assure you that Dr. Wood read the same books

   we've all read about antennas with professional

   attendance to "better practice." The point I endeavored to

   make was that after he came to understand all the

   deleterious effects over which we had no control on

   a C-172, adding baluns on the VOR antennas yielded very

   small gains compared the sum of other losses.



   Next time I can get into the test lab, I'll do some

   measurements on the difference between a balun-fed

   dipole and a bare foot, coax-fed dipole.



 Bob et al. having flown extensively in the Western states and Mexico, 

 I have plently of experience with being a zillion miles from a 

 station. At those times I start to think that having a good radio and 

 good antennas is a wise and cost effective thing to do. But do what 

 you want.



   But you paint a picture suggesting that a balun would

   make the difference between communicating with some distant

   station . . . and not. Given the light of sight character

   of VHF+ frequencies, you're more likely not to have a useable

   path because you can't see the other station than because

   your effective radiated signal is down by a few db due

   to violations of feed point protocols. Further, it's

   insufficient to be able to see the other station

   peeking over the horizon (or mountaintop). The effects

   of intervening "roughness" in the "Fresnel zone" can

   have some profound effects on what might otherwise be

   considered a free-space, line of sight situation.



 http://web.arundale.co.uk/docs/ais/PathlossCalculationsforAmateurs.pdf



   Mountain peaks and valleys intruding into the Fresnel

   zone can kick your free space performance predictions

   in the teeth.



   Currents flowing on the coax shield are but part of

   the 'violations' . . . the center impedance of a perfect

   dipole is on the order of 73 ohms. This means that the

   BEST SWR to be achieved without application of some

   impedance matching is on the order of 73/50 = 1.46:1

   So we've tossed off some efficiencies right out of the

   box. When we plot radiation patterns on VHF antennas

   on airplanes, one generally expects 10 db or greater

   'lumpiness' in the pattern due to geometry of the

   conductive elements around the antenna. So again,

   if one is at 'extreme range' for useful communications,

   it's more likely that you'll improve the path by turning

   the airplane a few degrees as opposed to optimizing

   feed point design.



   Yes, a BALUN can be "better" but experience on small

   aircraft has shown that the difference is so small

   compared to all other effects combined that the balun

   was not 'cost effective'. Further, it won't fix the

   fundamental mis-match so 1.46:1 is still the best

   we can expect. The textbooks are full of examples of

   data taken from the idealized antenna and feed line

   examined in the anechoic chamber with test equipment

   that can split a DB into small pieces.



   As soon as you put that same antenna is a real world

   environment, lots of things with potential for

   altering performance happen. This is why

   the guy flying 'around with a radio capable of

   talking to another one just like it 1000 miles

   away finds that the practical limits are much

   shorter for reasons mostly beyond control of

   the antenna designer.



   But just for grins, I've got some DIY antenna's I've

   used in my weekend seminars and articles. I'll

   fit one with a balun and leave the other barefoot.

   Then see if my buddy Don P can tell the

   difference without looking to see which one is

   hooked up.  Hmmmm . . . I think I know how to

   do the experiment with equipment I have. Need

   warmer weather though . . .



   Bob . . .

jan_de_jong(at)casema.nl
Guest

Posted: Mon Feb 27, 2012 3:13 am Post subject: Dipole antenna fabrication

Bob,



Sorry about this. The balun you describe making IS a Pawsey stub - 

should have taken a look before responding.

In any case - I'm interested in the comparison.



Jan

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Feb 27, 2012 7:55 am Post subject: Dipole antenna fabrication

At 05:12 AM 2/27/2012, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl>



 Bob,



 Sorry about this. The balun you describe making IS a Pawsey stub - should have taken a look before responding.

 In any case - I'm interested in the comparison. 	




 You are correct. If one compares the Pawsey stub with a

 1/4 wave, de-coupling sleeve  or "sleeve balun" as shown in Wikipedia:



 [img]cid:.0[/img]



   . . . we see that the top end of the sleeve is the open end

   of a shorted 1/4-wave transmission line. I.e., the

   impedance of the top rim of the sleeve looking at the

   shorted end is very high. Hence, connecting it to the

   center conductor adds no 'load' to purposeful energy

   but it would have the effect of collecting differential

   currents between coax shield and the center conductor

   and force them toward equivalency.



   The Pawsey stub functions in the same manner except that

   its behavior is more like a short piece of balanced

   transmission line as opposed to a piece of coax. This

   brings to light an error in my balun article cited

   earlier. Since the stub IS NOT operating as a free-space

   1/4-wave but instead as a transmission line, dielectric

   effects on velocity come into play. The velocity factor

   of this piece of transmission line is on the order of

   .95 to .97 which means that my 26" dimension for the

   stub would be closer to optimum were it shortened by

   an inch or so.



   The 'coiled coax ploy" has good foundations

   in physics.  Consider this image from the Wikipedia

   article:

 [img]cid:.1[/img]



   The current balun is a common mode choke which

   may be implemented by wires on a high-efficiency

   core (as in many TV couplers), a coil of coax

   immediately adjacent to the attach point on the

   dipole or consider this image also from Wikipedia

   article on baluns:



 [img]cid:.2[/img]



 

   As you can see here, the common mode choke effects

   are greatly enhanced by winding the coax onto

   the core. Inductance in these windings is proportional

   to the permeability of the magnetic path material.

   Air is 1.0, the ferrite may be 5-20 . . . thus 

   multiplying the beneficial effects by that factor.

   The neat thing about this balun is that it is not

   resonant or tuned; thus effective over a wider range

   of frequencies. The stubs in coax or balanced transmission

   lines are tuned and optimum at one frequency only.



   The 'hard' thing about the coax on core ploy is finding

   coax that will wind tightly through a relatively

   small core WITHOUT dropping below the recommended

   bend radius for that coax. Coaxes with solid center

   conductors are at risk for center conductor migration

   through the insulation over time and temperature

   cycles.  RG-141 wound through a core like that has

   potential for becoming a shorted feed line years from

   now. The commercial antenna I saw with this technique

   used a small diameter, very flexible coax and offered

   a BNC connector on the stub for extending the feed line

   to the appliance with more conventional coax.



   Bob . . .

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jan_de_jong(at)casema.nl
Guest

Posted: Mon Feb 27, 2012 9:38 am Post subject: Dipole antenna fabrication

Bob, thank you for the explanation.

There was some discussion on the web whether the velocity factor to be 

used for finding the length of the Pawsey stub was that for the coax 

insides (NO) or the coax outsides (YES). The latter would be the .97 to 

.99 then.



Jan

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Feb 27, 2012 2:26 pm Post subject: Dipole antenna fabrication

Dipole antenna erected vertically is similar to the 1/4 wave whip that we

now use.  The tricks are to make sure you have a large enough groundplane

(section of the aircraft skin).  When I first saw the talk of dipole

antennae I assumed incorrectly you wanted to be able to remove a radio and

take it with you and still have good range in case of a crash.



Aircraft radios are restricted to power.  Basically the powers to be don't

want you to be transmitting thousands of miles otherwise they would up the

power of transceivers and drop the frequency closer to six meters than to

two meters.  Main problem with that is you could end up with a lot of

crosstalk like they used to have on the CB band  (11 meters).



While flying in mountainous areas for safety I would not be without the new

400 mHz ELT.  There are lots of things about those ELTs I don't like but we

are stuck with it.



Noel

--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Feb 27, 2012 2:28 pm Post subject: Dipole antenna fabrication

"Good enough" is everyone's enemy when it comes to ceasing to operate at

3000' !

Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Feb 27, 2012 3:17 pm Post subject: Dipole antenna fabrication

Bob:



 Have you ever used a broadband windom antenna?



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Feb 27, 2012 8:39 pm Post subject: Dipole antenna fabrication

At 05:12 PM 2/27/2012, you wrote:

 	  Quote: 	
		  



Bob:



  Have you ever used a broadband windom antenna?


	


   No, I've known hams that did. Most of my activity

   for the past 40 years has been on 2M repeaters.



   In the picture at . . .



http://aeroelectric.com/Pictures/Misc/KTVH.jpg



   you can see the toes of my boots while peering

   down the center of KTVH tower east of Hutchinson

   KS. I was standing on the 1200' platform were

   the 22/82 repeater was quartered back then.



   Antennas to die for on that system were things

   like DB-228 arrays of 8 dipoles on a mast about

   40' long and weighing in at 75 pounds. Got to

   hang two of those off the leg of this tower

   about 100' apart.

   Bob . . .

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Tue Feb 28, 2012 5:39 am Post subject: Re: Dipole antenna fabrication

 	  Quote: 	
		  Bob N. said: But you paint a picture suggesting that a balun would make the difference between communicating with some distant 

station . . . and not. 	




No, I didn't. Not at all. But I've flown across western stretches (Try Bishop to Death Valley, pardner...). No Radar, no flight following, no radio communication of any kind. I've also flown all over Mexico, where radio relay from plane-to-plane-station is how it's done. In Baja, communications with the mainland is typical...and very hard...but HEY, it's line of sight!



I am glad to see others post good info. There are many Hams out there who are quite skilled in this area. Thanks Jan de Jong. I'll be building one of those for my Glastar's vertical stab.



If local ops and $100 hamburgers is all you do, Bob N. is right. If you want better performance for little extra effort, then I'm right.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)aeroelect
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Posted: Tue Feb 28, 2012 11:54 am Post subject: Dipole antenna fabrication

At 07:39 AM 2/28/2012, you wrote:


 > Bob N. said: But you paint a picture suggesting that a balun would 

make the difference between communicating with some distant station . 

. . and not.

No, I didn't. Not at all.



   . . . I'm confused . . .

But I've flown across western stretches (Try Bishop to Death Valley, 

pardner...). No Radar, no flight following, no radio communication of 

any kind. I've also flown all over Mexico, where radio relay from 

plane-to-plane-station is how it's done. In Baja, communications with 

the mainland is typical...and very hard...but HEY, it's line of sight!



   Okay, we're talking about fringe communications . . .



I am glad to see others post good info. There are many Hams out there 

who are quite skilled in this area. Thanks Jan de Jong. I'll be 

building one of those for my Glastar's vertical stab.



If local ops and $100 hamburgers is all you do, Bob N. is right. If 

you want better performance for little extra effort, then I'm right.



    I didn't know it was a right/wrong contest

    but an quantitative evaluation of return on

    investment. Did you agree that adding a balun

    is unlikely to produce any observable effect

    . . . yet hamburger runs makes Bob 'right'

    and 'extra performance' makes him wrong

    . . . ?????



    Just for grins I went to the bench and set up

    a receiver for 130MHz and turned on the HP

    generator set for 30% AM modulation. I opened

    the squelch and turned the radiated signal up

    until I could just barely tell that there was

    a modulated signal competing with the receiver's

    noise floor at (0.10 uV); a reasonable simulation

    of 'extreme fringe' communications.



    I turned the signal up until I was reasonably

    certain that I could deduce spoken words on

    a still very noisy signal. It took 0.2 to 0.33 uV

    (6 to 20 dB increase) to make that much difference.

    Were I trying to carry on meaningful conversation

    with cockpit ambients added in . . . maybe that

    wouldn't have been enough.



    If one compares balun vs. no-balun characteristics,

    what factor of 'better performance' would you expect?

   Bob . . .

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