FM Tx antenna options
 

I'm relatively new to this--pardon any vernacular errors. I've a 50mW
veronica transmitter that I'm using around the house and yard. 9/12V DC
power source. It currently has two flexible wire leads serving as the
antenna and ground--each is 70cm in length and is directly soldered to
the PCB. I usually coil them up to keep the range at a minimum.

Is there anything I can do to change the existing antenna setup? I'd
like to be able to switch antennas to attain different coverages. I was
told the impedance on such a unit is different than that of common
connectors (BNC, F, etc). Is there any way to change this configuration
to accept a whip antenna or a rubber duck antenna? I tried wrapping the
existing wires around rabbit ears arranged vertically which seemed to
give me an option for increased range.

Thanks.

erichmadison wrote:

I'm relatively new to this--pardon any vernacular errors. I've a 50mW
veronica transmitter that I'm using around the house and yard. 9/12V DC
power source. It currently has two flexible wire leads serving as the
antenna and ground--each is 70cm in length and is directly soldered to
the PCB. I usually coil them up to keep the range at a minimum.

Is there anything I can do to change the existing antenna setup? I'd
like to be able to switch antennas to attain different coverages. I was
told the impedance on such a unit is different than that of common
connectors (BNC, F, etc). Is there any way to change this configuration
to accept a whip antenna or a rubber duck antenna? I tried wrapping the
existing wires around rabbit ears arranged vertically which seemed to
give me an option for increased range.

Thanks.


I'm guessing here.
It seems to me that if you have 140cm total antenna fed at the middle,
then you have a full size dipole (or close enough) at the FM-BC band.
That further suggests a 75 ohm output impedance.

It would take some work to match a rubber-duck antenna - and it wouldn't
be very efficient. However, you should be able to use a whip of about
70cm and not suffer too much for lack of the ground plane.

If increased range is the goal then 75-ohm cable to an outdoor antenna
(dipole, etc) would seem to be ideal. All would need to be done within
the regulations of your country, of course. :)

There's zillions of folks using the Veronica gear...keep asking around
and I'm sure you'll find something more definitive than my guesswork.

My 2c,

Bill

Bill,

One of the wires is a ground, the other is the antenna. Would this
still be a dipole? Thanks for your previous post!

Yes Bill.
It sounds like that is serving as a dipole.
I too would strongly suspect that is a 75 ohm BALANCED output.
You should be able to remove the wires which are serving as the "dipole" and
run them to a 1:1 balun and the other side of the balun to a 50-75 ohm
unbalanced antenna. Or, to the input of a FM power amp....

Warmest regards,
John

"erichmadison" wrote in message
oups.com...
| Bill,
|
| One of the wires is a ground, the other is the antenna. Would this
| still be a dipole? Thanks for your previous post!
|

erichmadison wrote:

Bill,

One of the wires is a ground, the other is the antenna. Would this
still be a dipole? Thanks for your previous post!

'Ground' has various implications when it comes to rf. If they tell you
to attach it to a water pipe or ground rod then it may be a true dc
ground. If they tell you to extend it just like the antenna side and
not connect it to anything, then its an RF ground plane...which can be
compared to rabbit ears, dipole, etc.

Is it balanced or not? Hard to guess.

-Bill

An "Unbalanced Dipole", interesting concept...

Regards,
John

"Bill" wrote in message
...
| erichmadison wrote:
|
| Bill,
|
| One of the wires is a ground, the other is the antenna. Would this
| still be a dipole? Thanks for your previous post!
|
| 'Ground' has various implications when it comes to rf. If they tell you
| to attach it to a water pipe or ground rod then it may be a true dc
| ground. If they tell you to extend it just like the antenna side and
| not connect it to anything, then its an RF ground plane...which can be
| compared to rabbit ears, dipole, etc.
|
| Is it balanced or not? Hard to guess.
|
| -Bill

What would happen if he didn't use a balun?

Roy Lewallen, W7EL

John Smith wrote:
Yes Bill.
It sounds like that is serving as a dipole.
I too would strongly suspect that is a 75 ohm BALANCED output.
You should be able to remove the wires which are serving as the "dipole" and
run them to a 1:1 balun and the other side of the balun to a 50-75 ohm
unbalanced antenna. Or, to the input of a FM power amp....

Warmest regards,
John

"erichmadison" wrote in message
oups.com...
| Bill,
|
| One of the wires is a ground, the other is the antenna. Would this
| still be a dipole? Thanks for your previous post!
|

What exactly do you mean by "balanced"?

If you put a balun between a "balanced" radio and a "balanced" antenna,
what would happen? What would happen if you put it between an
"unbalanced" radio and an "unbalanced" antenna? What would happen if you
connected an "unbalanced" radio to a "balanced" antenna without a balun?

Roy Lewallen, W7EL

John Smith wrote:
An "Unbalanced Dipole", interesting concept...

Regards,
John

"Bill" wrote in message
...
| erichmadison wrote:
|
| Bill,
|
| One of the wires is a ground, the other is the antenna. Would this
| still be a dipole? Thanks for your previous post!
|
| 'Ground' has various implications when it comes to rf. If they tell you
| to attach it to a water pipe or ground rod then it may be a true dc
| ground. If they tell you to extend it just like the antenna side and
| not connect it to anything, then its an RF ground plane...which can be
| compared to rabbit ears, dipole, etc.
|
| Is it balanced or not? Hard to guess.
|
| -Bill

John Smith wrote:

An "Unbalanced Dipole", interesting concept...

Regards,
John

Yeah, then its a quarter-wave vertical w/ground plane laying on its side :-)


-Bill

If the output is really Unbalanced, and he fed an unbalanced ant of 50
ohms--nothing--as likely a 1.5:1 (75/50) match as not...

Or, depending on the type of ant he picks (75 ohm bal/unbal), and taking for
granted the output of the rig is balanced--probably just a distortion of the
radiation field of the ant (won't EXACTLY perform as modeled)...

Even if he feeds a bal ant of 200 ohms (folded dipole, and output is
balanced, all he sees is a high (200/75) SWR, and distance is reduced...

But, hey, I am a newbie... that is only my best guess(s)...

Warmest regards,
John

"Roy Lewallen" wrote in message
...
| What would happen if he didn't use a balun?
|
| Roy Lewallen, W7EL
|
| John Smith wrote:
| Yes Bill.
| It sounds like that is serving as a dipole.
| I too would strongly suspect that is a 75 ohm BALANCED output.
| You should be able to remove the wires which are serving as the "dipole"
and
| run them to a 1:1 balun and the other side of the balun to a 50-75 ohm
| unbalanced antenna. Or, to the input of a FM power amp....
|
| Warmest regards,
| John
|
| "erichmadison" wrote in message
| oups.com...
| | Bill,
| |
| | One of the wires is a ground, the other is the antenna. Would this
| | still be a dipole? Thanks for your previous post!
| |
|
|

That is why I mentioned "UnUn." It is taken for granted he will ask, or use
the correct one (Balun/UnUn)...

A balanced "supplies its own ground." A ground or "counterpoise" is NOT
required for the ant to work against...

Warmest regards,
John

"Roy Lewallen" wrote in message
...
| What exactly do you mean by "balanced"?
|
| If you put a balun between a "balanced" radio and a "balanced" antenna,
| what would happen? What would happen if you put it between an
| "unbalanced" radio and an "unbalanced" antenna? What would happen if you
| connected an "unbalanced" radio to a "balanced" antenna without a balun?
|
| Roy Lewallen, W7EL
|
| John Smith wrote:
| An "Unbalanced Dipole", interesting concept...
|
| Regards,
| John
|
| "Bill" wrote in message
| ...
| | erichmadison wrote:
| |
| | Bill,
| |
| | One of the wires is a ground, the other is the antenna. Would this
| | still be a dipole? Thanks for your previous post!
| |
| | 'Ground' has various implications when it comes to rf. If they tell
you
| | to attach it to a water pipe or ground rod then it may be a true dc
| | ground. If they tell you to extend it just like the antenna side and
| | not connect it to anything, then its an RF ground plane...which can be
| | compared to rabbit ears, dipole, etc.
| |
| | Is it balanced or not? Hard to guess.
| |
| | -Bill
|
|

ROFLOL!!!

Warmest regards,
John

"Bill" wrote in message
...
| John Smith wrote:
|
| An "Unbalanced Dipole", interesting concept...
|
| Regards,
| John
|
| Yeah, then its a quarter-wave vertical w/ground plane laying on its side
:-)
|
|
| -Bill

So then a dipole with one leg 5 times as long as the other would be a
"balanced" antenna. I see.

Tell me, how is this "ground" "supplied"? What exactly is a "ground",
say 50 feet up in the air?

Roy Lewallen, W7EL

John Smith wrote:
. . .
A balanced "supplies its own ground." A ground or "counterpoise" is NOT
required for the ant to work against...

Warmest regards,
John

Well, "di" = two, so in that sense, "dipole" would not necessarly be
balanced--however, that is not what I expect when someone tells me they have
a "dipole."

Although, quite well granted, it qualifies (my groundplane ant is a
"dipole", but I think I would mislead if I stated that in some circles! (as
it does have a few extra "legs" on one side.) However, it (the radials)
could be viewed as one single conductor, in the sense a tophat might be a
sheet, or a set of multiple wires, or the bottom cone of a "discone"
composed of many "legs" as compared to one solid sheet of conductor...

Semantics: retarded person = mentally disabled = special needs =
handicapped, etc... don't ya just love it!

"Gound" at 1000 ft in the air is a counterpoise (body of an aircraft, most
likely what the neg lead of the power source is hooked to), could be one
long wire to ground too--most likely in need of "tuning" to function
optimally....

If I someone stuck a 1K resistor (or diode-anode towards +) between my
chasis of the radio and the negative lead (probably best to bypass it with a
cap at rf in question), the top of that 1K resistor (or cathode of diode) is
"real ground"--in the sense of "time" being real... they "ground" every
telephone pole now and then, because across distances "earth ground" is not
"equal ground."

If your point is that "ground" is relative--I know a guy who claimed that of
the whole universe....

That guys ground could well be the chasis (even though a 1k resistor!), or
the other side of coil with its center at "ground", or not... etc.

But, those two wires he described are two wires of equal length, so, suggest
themselves as a "conventional dipole", with nothing else to go on--I am
willing to accept that...

I have been wrong before, is so this time--I learn something...

Warmest regards,
John

"Roy Lewallen" wrote in message
...
| So then a dipole with one leg 5 times as long as the other would be a
| "balanced" antenna. I see.
|
| Tell me, how is this "ground" "supplied"? What exactly is a "ground",
| say 50 feet up in the air?
|
| Roy Lewallen, W7EL
|
| John Smith wrote:
| . . .
| A balanced "supplies its own ground." A ground or "counterpoise" is NOT
| required for the ant to work against...
|
| Warmest regards,
| John

My intent was to spur some thought about the meaning of the terms you've
so liberally and seemingly authoritatively tossed about. These
"explanations" show that your understanding is, indeed, very muddled and
vague. I suggest you do a bit of study to gain a clearer grasp of these
concepts before you give too much advice about how to apply them.

Roy Lewallen, W7EL

John Smith wrote:
Well, "di" = two, so in that sense, "dipole" would not necessarly be
balanced--however, that is not what I expect when someone tells me they have
a "dipole."

Although, quite well granted, it qualifies (my groundplane ant is a
"dipole", but I think I would mislead if I stated that in some circles! (as
it does have a few extra "legs" on one side.) However, it (the radials)
could be viewed as one single conductor, in the sense a tophat might be a
sheet, or a set of multiple wires, or the bottom cone of a "discone"
composed of many "legs" as compared to one solid sheet of conductor...

Semantics: retarded person = mentally disabled = special needs =
handicapped, etc... don't ya just love it!

"Gound" at 1000 ft in the air is a counterpoise (body of an aircraft, most
likely what the neg lead of the power source is hooked to), could be one
long wire to ground too--most likely in need of "tuning" to function
optimally....

If I someone stuck a 1K resistor (or diode-anode towards +) between my
chasis of the radio and the negative lead (probably best to bypass it with a
cap at rf in question), the top of that 1K resistor (or cathode of diode) is
"real ground"--in the sense of "time" being real... they "ground" every
telephone pole now and then, because across distances "earth ground" is not
"equal ground."

If your point is that "ground" is relative--I know a guy who claimed that of
the whole universe....

That guys ground could well be the chasis (even though a 1k resistor!), or
the other side of coil with its center at "ground", or not... etc.

But, those two wires he described are two wires of equal length, so, suggest
themselves as a "conventional dipole", with nothing else to go on--I am
willing to accept that...

I have been wrong before, is so this time--I learn something...

Warmest regards,
John

"Roy Lewallen" wrote in message
...
| So then a dipole with one leg 5 times as long as the other would be a
| "balanced" antenna. I see.
|
| Tell me, how is this "ground" "supplied"? What exactly is a "ground",
| say 50 feet up in the air?
|
| Roy Lewallen, W7EL
|
| John Smith wrote:
| . . .
| A balanced "supplies its own ground." A ground or "counterpoise" is NOT
| required for the ant to work against...
|
| Warmest regards,
| John

Suck it up old man--that ego will heal!

John

"Roy Lewallen" wrote in message
...
| My intent was to spur some thought about the meaning of the terms you've
| so liberally and seemingly authoritatively tossed about. These
| "explanations" show that your understanding is, indeed, very muddled and
| vague. I suggest you do a bit of study to gain a clearer grasp of these
| concepts before you give too much advice about how to apply them.
|
| Roy Lewallen, W7EL
|
| John Smith wrote:
| Well, "di" = two, so in that sense, "dipole" would not necessarly be
| balanced--however, that is not what I expect when someone tells me they
have
| a "dipole."
|
| Although, quite well granted, it qualifies (my groundplane ant is a
| "dipole", but I think I would mislead if I stated that in some circles!
(as
| it does have a few extra "legs" on one side.) However, it (the radials)
| could be viewed as one single conductor, in the sense a tophat might be
a
| sheet, or a set of multiple wires, or the bottom cone of a "discone"
| composed of many "legs" as compared to one solid sheet of conductor...
|
| Semantics: retarded person = mentally disabled = special needs =
| handicapped, etc... don't ya just love it!
|
| "Gound" at 1000 ft in the air is a counterpoise (body of an aircraft,
most
| likely what the neg lead of the power source is hooked to), could be one
| long wire to ground too--most likely in need of "tuning" to function
| optimally....
|
| If I someone stuck a 1K resistor (or diode-anode towards +) between my
| chasis of the radio and the negative lead (probably best to bypass it
with a
| cap at rf in question), the top of that 1K resistor (or cathode of
diode) is
| "real ground"--in the sense of "time" being real... they "ground" every
| telephone pole now and then, because across distances "earth ground" is
not
| "equal ground."
|
| If your point is that "ground" is relative--I know a guy who claimed
that of
| the whole universe....
|
| That guys ground could well be the chasis (even though a 1k resistor!),
or
| the other side of coil with its center at "ground", or not... etc.
|
| But, those two wires he described are two wires of equal length, so,
suggest
| themselves as a "conventional dipole", with nothing else to go on--I am
| willing to accept that...
|
| I have been wrong before, is so this time--I learn something...
|
| Warmest regards,
| John
|
| "Roy Lewallen" wrote in message
| ...
| | So then a dipole with one leg 5 times as long as the other would be a
| | "balanced" antenna. I see.
| |
| | Tell me, how is this "ground" "supplied"? What exactly is a "ground",
| | say 50 feet up in the air?
| |
| | Roy Lewallen, W7EL
| |
| | John Smith wrote:
| | . . .
| | A balanced "supplies its own ground." A ground or "counterpoise" is
NOT
| | required for the ant to work against...
| |
| | Warmest regards,
| | John
|
|