Oops.............that should have been maximum return loss. Touch
typing...........you know!

Pete

"Pete KE9OA" wrote in message
...

"Frank Gilliland" wrote in message
...
On Sun, 10 Apr 2005 19:58:28 GMT, "Pete KE9OA"
wrote in
:

Hey Vinnie............I can help you. The formula for a 1/4 wavelength
radiator is (234 / F) whereby F is the frequency in MHz. This will give
you
the length in feet. For the radials, (237 / F) will give you that length.
Always remember...multiply the radiator length by 1.05 and that is
another
way of calculating the 1/4 wavelength radials.


It should be noted that these formulas are only appoximations. Actual
sizes are dependent upon the conductivity and diameter of the
elements, and the quantity and angle of the radials. When building a
resonant antenna it's a good idea to make the elements a little long
and trim to resonance.

Very true..........I use a spectrum analyzer with a directional coupler
and trim for maximum return loww.


The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you
have
the radials at a 90 degree angle with respect to the radiator. If you
have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.


These are impedances for antennas in free space, and are practical
only if you can mount your antenna well above the ground and away from
any tall objects.

Also true, but a good starting point.


There was an article in RF Design magazine a few years back, explaining
why
certain impedances are used in the RF industry.
72 ohms was the impedance that produced minimum cable losses...........50
ohms is a happy medium.


Close. For lowest loss, the optimum characteristic impedance of coax
is 76.9 ohms. 70-73 ohm coax is used as a compromise between low loss
coax and coax optimized for minimization of flashover, the latter
having an impedance of about 60 ohms.

Good memory.

And while many people have many different ideas as to why 50 ohm coax
is made, it is just a compromise between low-loss/low-flashover coax
of 72 ohms and coax optimized for handling power (about 30 ohms, which
is too lossy for practical transmission lines).


On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect.
For a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.


.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I hope this helps.

Pete





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On Mon, 11 Apr 2005 08:03:21 GMT, "Pete KE9OA"
wrote in
:

snip
On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect. For
a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.


.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I understood that much. My point was that whenever an antenna/coax
mismatch occurs, tuning the output tank (as with a tube final) doesn't
cure the mismatch or the resulting signal loss. All it does is protect
the final from the reflected power. The output tank should be matched
to the characteristic impedance of the coax whether the final is a
tube or a transistor. If the coax shows standing waves, the mismatch
should be fixed at the point of mismatch, not at the radio. I realize
that this is not always practical, but people should know that such a
conjugate match just dissipates that reflected power somewhere else,
usually from the outside of the coax or the radio.

As for ALC, I thought you were referring to a different type of
limiting. My bad.





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Imax is a piece of garbage. Get a dipole.

Point taken..........it sounds like you are either also in the business, or
have quite a bit of interest. I understand that an output matching network
only tunes out the imaginary terms, and that matching the impedance at the
antenna feedpoint is the best approach.

"Frank Gilliland" wrote in message
...
On Mon, 11 Apr 2005 08:03:21 GMT, "Pete KE9OA"
wrote in
:

snip
On a final note...........at 37 ohms, you will have a VSWR of 1.3 to
1.................at 75 ohms, you will have a VSWR of
1.5 to 1. What is the difference here? For a transmitter with a tube
output
and an internal matching network, you wouldn't really see much effect.
For
a
typical solid state transmitter, there would be some difference between
the
two antenna impedances, because the broadband solid state transmitter
would
be called upon to deliver more current to the antenna. It probably
wouldn't
have any effect, unless the ALC circuit was aggressive in its operation.
In
this case, power foldback would occur into the 37 ohm load. Would it
happen?
Probably not.


.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I understood that much. My point was that whenever an antenna/coax
mismatch occurs, tuning the output tank (as with a tube final) doesn't
cure the mismatch or the resulting signal loss. All it does is protect
the final from the reflected power. The output tank should be matched
to the characteristic impedance of the coax whether the final is a
tube or a transistor. If the coax shows standing waves, the mismatch
should be fixed at the point of mismatch, not at the radio. I realize
that this is not always practical, but people should know that such a
conjugate match just dissipates that reflected power somewhere else,
usually from the outside of the coax or the radio.

As for ALC, I thought you were referring to a different type of
limiting. My bad.


That's ok............sometimes, I tend to think in Greek!

Pete Gianakopoulos

On Fri, 08 Apr 2005 19:31:47 GMT, Lancer wrote:

Dave;
I know this was directed to Frank, hope you don't mind if I
comment?

This is a public forum, comments from participants is what it's all
about.


A dipole is a dipole. It has 0 db of gain, and that assumes a resonant
dipole . If the dipole is non-resonant and requires a tuner to force
an impedance match, it will have further losses. It won't stand a
chance against a commercially produced (or home made if you are
so-inclined) 5/8th wave vertical (with proper radials, not an Imax).

Because a dipole/antenna is non-resonant it doesn't automatically mean
it will be a more "lossy" antenna. A non-resonant dipole fed with
ladder line can/will end up being a more efficient antenna than a
resonant dipole fed with coax and a balun.

In what way? If the length of the dipole is at a no resonant length,
you have to "force" it to a proper impedance match through the use of
a tuner. Standing waves will still be present after the tuner, and
efficiency will suffer as a result.

Why have a resonant antenna at all if a non-resonant antenna works
better? It doesn't make sense.

I've tried loading up different antennas that I've had to run on bands
they were not designed for, and while I could certainly get better
than a 1.5:1 SWR, they might as well be a load of bed springs for as
well as it worked.


I have built non-resonant antennas that beat a 5/8ths. A 5/8ths is
hard pressed achieve the claims for gain that it has.The only
commercial 5/8th that I seen that was properly decoupled was an
Isotron.

An Isopole maybe? IIRC, that's a 2 meter antenna. I never particularly
liked them. I've had better performance from a Hustler G7. Especially
on VHF, you don't see people running non-resonant dipoles. Gain is
particularly important there.

Proper decoupling can be achieved through the proper use of a radial
counterpoise, which is what is lacking in the "stick" style antennas
we're discussing on CB

I've done this type of
antenna myself and never had any problems with local contacts -- in
fact, it worked a lot better than the 9' whip on the truck.

I find that very hard to believe, assuming identical height and
conditions, as my own experiences prove otherwise.


I ran a home brewed wire dipole on CB years ago, and used it in
addition to my main 5/8th wave antenna. While the dipole worked well
when the skip was running, locally, the signal from the dipole was a
few "S" units less than the ground plane. With 4 watts of power, you
don't get much range on a horizontal wire dipole strung in a tree.


Well there's your problem, Dave -- I didn't say anything about
horizontal. On the contrary, it's better if it isn't.

Yea, if you're talking local. For DX, horizontal is usually better for
a number of reasons, most notably a lower noise floor and better take
off angle.

Horizontal antennas are dependant on height above ground and the
conductivity of the ground they are above. The closer to the ground
and more lossy the ground, the higher the take off angle.

That is correct. For best performance, a dipole needs to be at least
1/2 wave above the ground.



Since most
man made noise tends to be vertically polarized, a horizontal antenna
tends to quieter.

Also correct.


Like I said
before, just throw some wire up into the trees (or whatever tall
object happens to be available). Didn't you read the link I posted?

Of course. But a dipole is a basic antenna. It has no gain. A properly
made purpose built CB antenna will out perform it.

Let's look at this from a practical standpoint. If a non-resonant,
tuner fed dipole worked so well, then why aren't all CB'ers using one?
Why would people want huge 5/8th wave antennas then? Better tell Jay
to forget about selling his Interceptor, since a simple non-resonant
dipole will work just as well and for far less money.

A non-resonant dipole has ONE big advantage. It's a compromise antenna
that will work on all the HF bands. That's great if you don't have the
room to put up single band antennas for each band. But like any
compromise, it will not work as well as a dedicated antenna for each
band. Such a compromise is usually acceptable for a ham who has 1500
watts on tap. But for a 4 watt CB'er, who needs to squeeze every watt
of ERP he can for best local range, he needs a high gain efficient
antenna.


Again, non-resonant deosn't mean that its not efficient. Your looking
at a non-resonant antenna as a chunk of wire thats just tossed in a
tree. A resonant antenna doesn't have any magical gain over a
non-resonant antenna just because its resonant.

An antenna radiates most efficiently at its resonant frequency.
Practical experience with local communications pretty much supports my
observations (or more accurately is the basis for them). I've made
many dipoles over the years, and none of them have ever matched or
even came close to the 5/8th wave ground plane for local work on CB.
DX is another matter. Dipoles work very well there. Perhaps that's why
many H.F. hams have several different antennas to switch to, to take
advantage of varying DX conditions or groundwave, as their
communications dictate. When working 40 meter groundwave, a ground
mounted vertical is often a superior choice.


Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

On Sun, 10 Apr 2005 20:35:06 -0700, Frank Gilliland
wrote:

On Fri, 08 Apr 2005 17:02:43 -0400, Vinnie S.
wrote in :

On Fri, 08 Apr 2005 13:30:51 -0400, Dave Hall wrote:

Believe me. I have nothing to worry about.

Vinnie S.

You don't believe his callsign is WA3MOJ do you?

I don't know what to believe from him. But if some lardass steps foot on my
property, I will look thru his wallet for ID will I hold his face in the dirt.
And if he doesn't have a wallet, then I will get the info from the car.


.....oh brother, he's a crybaby -and- a tough-guy. This is just too
good to be true!


And it don't look like I am the only one !!!

I did a little search on you in the archives. This is precious.

http://groups-beta.google.com/group/... 2f3b40d85682


Don't you think it's time you quit with the killfile charade? You
aren't fooling anyone when you reply to half my posts via piggybacks
and swim through Google juice to read even more of them.


Maybe he is a true tough guy. Stranger things have happened.



It's a amazing what a little info you can get on a poster's history on Google,
Dave. My favorite about this info on Frank, it the imaginary McDonald's, and the
fishing trip he had at the lake in a storm !!!!


It's amazing how quickly some people resort to digging up the past
when they can't deal with the present.

But the past is what sets a pattern of behavior. Look at what they're
digging up from Mikey Jackson's past. Looks like Vinnie has exposed
some hypocrisy from you. So maybe you should be a little less zealous
to call other people hypocrites in the future.


Heck, even Dave agrees with me
on this one -- every time I bring up Bush's DUI or business failures,
Dave says they are irrelevant. So Vinnie, are you calling Dave a liar?

You should leave the spin and deflection tactics to Twisty. He's had
way more experience.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

On Fri, 08 Apr 2005 18:27:15 -0700, Frank Gilliland
wrote:

On Fri, 08 Apr 2005 13:59:47 -0400, Dave Hall
wrote in :

snip
Maybe you had difficulty, but there are a very large number of hams
-and- CBers who don't share your ineptitude.

A dipole is a dipole. It has 0 db of gain,


Wrong. A 1/2-wave Hertzian dipole has a gain of roughly +3 dBi in free
space.

Isotropic is a theoretical spherical reference model which does not
exist in reality. A dipole is THE reference antenna, by which most
credible gain claims are based against.


It has 0 dB when referenced to itself.

Isn't that what I just said?


and that assumes a resonant
dipole .


That's an assumtion -you- made, and it's also wrong: A resonant dipole
can be any multiple of 1/2-wave, and has a gain that differs depending
upon the length and directionality.

Then it's no longer a half wave dipole. You are now talking double
ended zepp designs, which do exhibit gain over a 1/2 wave dipole



If the dipole is non-resonant and requires a tuner to force
an impedance match, it will have further losses.


Wrong again. A tuner only adds insertion loss, which is usually quite
small if it's built with quality components. The insertion loss is
easily overcome by slightly increasing the length of the elements,
which is no big deal since the antenna is already non-resonant.

You fail to consider the standing waves which will still be present in
the feedline due to the mismatch. A tuner only presents a proper match
to the transmitter. With a high mismatch in the feedline, losses
increase as well and creating a tendency to radiate from the feedline.
In order to compensate for this the tuner should be mounted at the
feedpoint of the 4:1 balun that is normally used to feed 450 Ohm
ladder line to such designs. But such is impractical for guys who
change bands and frequency often, unless the tuner is automatic.

But keeping with the original perspective, of a simple antenna system
for Vinnie, this falls far short of that objective.




It won't stand a
chance against a commercially produced (or home made if you are
so-inclined) 5/8th wave vertical (with proper radials, not an Imax).


Well guess what, Dave -- a 5/8-wave antenna is a non-resonant antenna
and requires some method of impedance matching. Thank you.

A 5/8 wave is most certainly resonant. It's just that the feedpoint
impedance is high and needs to be transformed. It's a different issue
than forcing a match from something that is not resonant naturally.

You can have a 1:1 SWR but not be 50 Ohms.

Time to read some more books. Or better yet, befriend an experienced
ham to show you.


I've done this type of
antenna myself and never had any problems with local contacts -- in
fact, it worked a lot better than the 9' whip on the truck.

I find that very hard to believe, assuming identical height and
conditions, as my own experiences prove otherwise.


Oh, the humanity.....

This coming from someone who looks at people who share healthy
relationships as being "co-dependant", and prefers instead the
isolation of "independence".


I ran a home brewed wire dipole on CB years ago, and used it in
addition to my main 5/8th wave antenna. While the dipole worked well
when the skip was running, locally, the signal from the dipole was a
few "S" units less than the ground plane. With 4 watts of power, you
don't get much range on a horizontal wire dipole strung in a tree.


Well there's your problem, Dave -- I didn't say anything about
horizontal. On the contrary, it's better if it isn't.

Yea, if you're talking local. For DX, horizontal is usually better for
a number of reasons, most notably a lower noise floor and better take
off angle.


A horizontal dipole can have a wide variation in take-off angle
depending on height above ground, ground resistance, proximity to
other structures or objects, etc.

Yea, so?

And the noise floor may be slightly
lower but that's a product of it's directivity, as compared to a
vertical which is omnidirectional.

No, it's a product of the fact that most atmospheric and man-made
noise tends to be vertically polarized.


A pair of phased verticals, as well
as any other directional antenna or antenna array, will also have the
effect of lowering the noise floor.

Not if the noise isn't concentrated in a single direction.


Like I said
before, just throw some wire up into the trees (or whatever tall
object happens to be available). Didn't you read the link I posted?

Of course. But a dipole is a basic antenna. It has no gain.


Wrong again. As I said before, a 1/2-wave Hertzian dipole in free
space has about 3 dB gain over an isotropic antenna; but a dipole is
merely an antenna with two elements and is not limited to a 1/2-wave
Hertzian configuration. Not only that, but a tuner isn't limited to
dipole antennas -- they can load up a long-wire just as easily.

Ah, so you're changing the parameters of the discussion. Long wires
are inefficient on CB as well. Been there, done that.





A properly
made purpose built CB antenna will out perform it.


Get a clue, Dave. You're an Extra, right? What's the name of that tech
school you claim to have attended?

What's your call sign Frank?

Frank, all the king's horses and all the books you read will not make
up for your glaring lack of experience. Get out from behind the table
and DO something, and then report back.




Let's look at this from a practical standpoint. If a non-resonant,
tuner fed dipole worked so well, then why aren't all CB'ers using one?
Why would people want huge 5/8th wave antennas then? Better tell Jay
to forget about selling his Interceptor, since a simple non-resonant
dipole will work just as well and for far less money.


This resounds back to your argument that roger-beeps were illegal
because most radios didn't include them. The problem is that a tuner
requires a little skill and practice to use, which is beyond the scope
of the intended purpose of the service (a plug-n-play radio service).

Antenna tuners were available as an accessory for CB for less than the
cost of a good SWR meter. Granted they were simple coaxial in and out
tuners.

A tuner requires readjustment when changing channels within the CB,
and most CBers don't want to deal with the hassle.

So you are now claiming that CB'ers are too "dumb" to handle that?

And to add further evidence to your lack of experience with CB, it was
common that "matchboxes" were often used by CB'ers to "correct" a
mismatch within their antennas. Instead of taking the time to properly
tune the antenna, they forced the match with the tuner. The radio was
happy, as it saw a 1:1 SWR, but the signal was not so good. When a
more knowledgable person would finally retune the antenna, and the
tuner was removed, signal improved considerably.


Regardless, there
are still many CBers that do indeed use a tuner, not just with prefab
antennas but also with homebrew and beverage-can hooks.

None of which are work a tinker's dam for local CB communications.


And just about
every CBer who runs a tube linear uses a tuner because it's built into
the amp, which by itself blows big holes in your "practical" argument.

Not at all. A tube amplifier requires a tuner because the impedance of
a tube is much higher than 50 ohms, and needs to be transformed. It's
not practicality, it's necessity.


Then there is the issue of the non-resonant 5/8-wave antenna..... oh,
Dave, when will you learn?

The question is Frank, when will you start?


A non-resonant dipole has ONE big advantage. It's a compromise antenna
that will work on all the HF bands. That's great if you don't have the
room to put up single band antennas for each band. But like any
compromise, it will not work as well as a dedicated antenna for each
band. Such a compromise is usually acceptable for a ham who has 1500
watts on tap. But for a 4 watt CB'er, who needs to squeeze every watt
of ERP he can for best local range, he needs a high gain efficient
antenna.


If that were the case then every CBer would have a 5-el yagi on a 30'
mast and a 9' whip on their vehicles.

Most high performance CB'ers do.


For ham band use, I agree with you, just not for CB.


What's the name of that tech school, Dave?

What's your call sign Frank?


I'm not a ham.

Yet you are trying to impart your opinion on a subject you have not
participated in?



I answered your question, now you answer mine: what's
the name of your tech school, Dave?

The fact that you keep asking, makes me all the less likely to tell
you.


Frank, your experience with both ham and CB radio is sorely lacking.
You read a few books and web sites and think you have all the answers.
OTOH, I've walked the walk for the last 30+ years and have played with
more antennas and equipment than I can remember. I have also been in
contact with people in the know when it comes to antennas. What I
know, I know through experience, and that's worth 10X what you read in
any book.


Which explains why your theory is severely lacking. If you took the
time to actually learn why these things work and -then- applied them
to your experiences, you could be the guru you think you already are.
But you don't and you're not. Instead you do things backwards: you
theorize about radio based on your own experience, then read only
enough to validate your own conclusions whether they are right or not.

If the evidence supports the theory, then it's valid. If not, then the
theory is wrong. You are a perfect example of someone who is
book-smart and street foolish. You will sit there and tell people, who
do these things every day, exactly why they can't possibly work. While
we sit here and laugh at you, because we've been there and done that.


Check this out, Dave: Education doesn't come from a textbook that some
geek sat down and wrote just for ****s and giggles. It's a compendium
of knowledge that has been collected from over a century of research,
experimentation and practical experience by experts in all aspects of
the field. Those experts didn't become experts simply by playing with
CB radios as a hobby for 30 years. And an education doesn't include a
couple textbooks, a few lectures and a test -- it also includes years
of experience with the practical application of that knowledge.

No kidding. You seemed to have failed the "practical application"
aspect. Hell, you never even heard of the term "drying out" in
reference to electrolytic capacitor aging, and you try to cover this
glaring hole by claiming a pompous, superior attitude as if this was
beneath you.

When
you mock those that have a formal education and extensive experience
in electronic communication then you mock the same people who made the
television set you watch way too much, the telephone and cell-phone
infrastructure that keeps this world talking, the NASA and JPL
engineers who communicate with space probes billions of miles away,
etc, etc, etc.

I'm not mocking them. They know what they are doing. And I work with
many of them on a daily basis. You probably have products in your home
(or will) that I have had a part to play in their development. I
work in the field every day. I am not mocking them, I am mocking you.
You who CLAIM to be educated, but evidence suggests you are sorely
lacking in practical application of whatever it is you might have
learned.

While I may not have participated in any world-changing
technology, I certainly have an education and the experience in the
field that puts you to shame.

While you tend bar and drive a 20+ year old truck......

Yet -you- try to teach -me- theory based
on your education from a third-rate vocational tech school, a few
years in a CB shop, and your experience in =amateur= radio.

As far as you know. But it is evidently light years ahead of those
internet websites you lift your information from while you sit at home
alone with no other people to "relate" to.


And here's the kicker: Do you have any idea where I came up with the
idea to just throw a couple wires in the air and load them up with a
tuner? A ham.

Not all hams are mensa candidates. And most hams know that one antenna
solution, which may be great in one application, is not necessarily
good in another. In ham radio, there is no "one size fits all" answer.
But then again, you wouldn't know that. You're not a ham (or CB'er).

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

On Fri, 08 Apr 2005 18:27:26 -0700, Frank Gilliland
wrote:

On Fri, 08 Apr 2005 13:28:53 -0400, Dave Hall
wrote in :

On Thu, 07 Apr 2005 16:44:59 -0700, Frank Gilliland
wrote:

On 07 Apr 2005 23:32:45 GMT, Steveo wrote in
:

snip
I suppose they drive like that everyplace..it's a matter of being in
the wrong place at the wrong time, or your truck is a magnet. I have
one of those too.


I think -I'm- the magnet. The Dart I drove in college was hit 5 times,
the LTD got hit twice before it was totalled, the S-15 was rear-ended
by an ambulance, the LeBaron was hit three times in two weeks, etc.
I've had the S-10 for two years and it's been hit twice -- both times
while it was parked! All in Spokane. Fortunately, I've only been hit
once when I had a passenger, and that was the ambulance wreck so at
least there was help available if someone got hurt.


There's something cosmic about that. I've had 2 major accidents in my
whole life, and both were in the same car. Neither were my fault.


Nothing is ever your fault, Dave. We discussed this problem in your
last therapy session.

What therapy session? The one where you exposed yet another
shortcoming in your insight?

I find it interesting that someone who shuns regular human contact
would attempt to pass themselves off as someone with some experience
at it.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

On Mon, 11 Apr 2005 13:46:07 -0700, Frank Gilliland
wrote:

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.


I understood that much. My point was that whenever an antenna/coax
mismatch occurs, tuning the output tank (as with a tube final) doesn't
cure the mismatch or the resulting signal loss. All it does is protect
the final from the reflected power. The output tank should be matched
to the characteristic impedance of the coax whether the final is a
tube or a transistor. If the coax shows standing waves, the mismatch
should be fixed at the point of mismatch, not at the radio.

So much for running a non-resonant length antenna through a tuner.


Sounds like you read a different book this time.


I realize
that this is not always practical, but people should know that such a
conjugate match just dissipates that reflected power somewhere else,
usually from the outside of the coax or the radio.

Which is the main reason why a non-resonant, tuner matched antenna is
less efficient than one that is resonant. But you'll argue that with
me just to argue.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

On Mon, 11 Apr 2005 08:03:21 GMT, "Pete KE9OA"
wrote:

It should be noted that these formulas are only appoximations. Actual
sizes are dependent upon the conductivity and diameter of the
elements, and the quantity and angle of the radials. When building a
resonant antenna it's a good idea to make the elements a little long
and trim to resonance.

Very true..........I use a spectrum analyzer with a directional coupler and
trim for maximum return loww.

So do I. It gives a much better picture than a simple SWR bridge.


The feedpoint impedance of a 1/4 wave ground plane is 37 ohms when you
have
the radials at a 90 degree angle with respect to the radiator. If you have
the radials drooped at a 45 degree angle, the impedance rises to
approximately 50 ohms.
If you have a single radial drooped at a 180 degree angle with respect to
the radiator, the impedance rises to 75 ohms.


These are impedances for antennas in free space, and are practical
only if you can mount your antenna well above the ground and away from
any tall objects.

Also true, but a good starting point.

Some people like to make the subtle conditions into much greater
points than they need to be.



.....uh, what?

Both tubes and transistors use matching networks, so I don't know what
distinction you are trying to make there. Power will be reflected from
an antenna/coax mismatch -regardless- of whether you have a tube or
transistor final. And what does an ALC circuit have to do with
transmission line propogation?

This pertains to solid state amateur transceivers that don't have an
adjustable output matching network.........most of today's units have
fixed-tuned bandpass filters after the output stage. I am not referring to
transmission line propagation; I am referring to the fact that, with a
fixed-tuned output network that expects to see a 50 ohm characteristic
impedance, the ALC can fold back the power. Usually, that doesn't occur
until a VSWR of 2 to 1 is reached. My explanation is for illustrative
purposes only.

Not only that, but the bandpass filter characteristics of the output
stages can change if the load impedance changes significantly,
increasing loss and broadening the cutoff points.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj