I would like to be able to determine if antenna is present at the end of a
piece of coax. In some case antennas of type ?? would have a DC resistance
across the coax and that makes it easy. But..., how would you easily
determine if a coax shows an infinite DC resistance (NO RETURN PATH) no
current flow - like simple did-poke.

Trying to spare the group all the details of what I am doing but I will
gladly answer any questions. Thank you in advance for your help.

Don

Don Baker wrote:
I would like to be able to determine if antenna is present at the end of a
piece of coax. In some case antennas of type ?? would have a DC resistance
across the coax and that makes it easy. But..., how would you easily
determine if a coax shows an infinite DC resistance (NO RETURN PATH) no
current flow - like simple did-poke.

You can never be sure that someone hasn't swapped your
antenna for equivalent circuit components but the
MFJ-259B antenna analyzer works for me.
--
73, Cecil, http://www.qsl.net/w5dxp

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I would do a frequency sweep with an MFJ-259 or similar to cover the
frequencies of interest. A noise bridge and a receiver would be another
approach.

A few specifics would aid in pointing you in the right direction.

"Don Baker" wrote in message
...
I would like to be able to determine if antenna is present at the end of a
piece of coax. In some case antennas of type ?? would have a DC
resistance
across the coax and that makes it easy. But..., how would you easily
determine if a coax shows an infinite DC resistance (NO RETURN PATH) no
current flow - like simple did-poke.

Trying to spare the group all the details of what I am doing but I will
gladly answer any questions. Thank you in advance for your help.

Don

If you have an antenna present the receiver noise level should
increase when you connect the coax. If there is no antenna there
should be no or much less increase in the noise level. This assumes
you are using good low leakage coax.

Ron, W4TQT

Don Baker wrote:
I would like to be able to determine if antenna is present at the end of a
piece of coax. In some case antennas of type ?? would have a DC resistance
across the coax and that makes it easy. But..., how would you easily
determine if a coax shows an infinite DC resistance (NO RETURN PATH) no
current flow - like simple did-poke.

Trying to spare the group all the details of what I am doing but I will
gladly answer any questions. Thank you in advance for your help.

Don

Either use a TDR, or something that measures RF impedance - an SWR
meter, an impedance bridge, an antenna analyzer, or even a signal
generator and a scope. Sure there's a path for current flow, but only
for sure at RF, so that's where you have to detect it.

Roy Lewallen, W7EL

Don Baker wrote:
I would like to be able to determine if antenna is present at the end of a
piece of coax. In some case antennas of type ?? would have a DC resistance
across the coax and that makes it easy. But..., how would you easily
determine if a coax shows an infinite DC resistance (NO RETURN PATH) no
current flow - like simple did-poke.

Trying to spare the group all the details of what I am doing but I will
gladly answer any questions. Thank you in advance for your help.

Don

In article ,
Roy Lewallen wrote:

Either use a TDR, or something that measures RF impedance - an SWR
meter, an impedance bridge, an antenna analyzer, or even a signal
generator and a scope. Sure there's a path for current flow, but only
for sure at RF, so that's where you have to detect it.

Or, modify the antenna very slightly - put an RF choke or a
large-value resistor across its feedpoint. This will give you
something to probe for at DC, without affecting the antenna's
performance at RF.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Go and take a look.

"Don Baker" wrote in message
...
I would like to be able to determine if antenna is present at the end of a
piece of coax.

Excellent!

"Polymath" wrote in message
...
Go and take a look.

"Don Baker" wrote in message
...
I would like to be able to determine if antenna is present at the end of a
piece of coax.

On Fri, 15 Jul 2005 16:27:17 +0100, "Polymath"
wrote:

Go and take a look.

That could be a dangerous suggestion, as seen at
http://www.lhup.edu/~dsimanek/horse.htm which contains a few
additional comments as to the source.


In part, it reads:

In the year of our Lord 1432, there arose a grievous quarrel among the
brethren over the number of teeth in the mouth of a horse. For
thirteen days the disputation raged without ceasing. All the ancient
books and chronicles were fetched out, and wonderful and ponderous
erudition such as was never before heard of in this region was made
manifest. At the beginning of the fourteenth day, a youthful friar of
goodly bearing asked his learned superiors for permission to add a
word, and straightway, to the wonderment of the disputants, whose deep
wisdom he sore vexed, he beseeched them to unbend in a manner coarse
and unheard-of and to look in the open mouth of a horse and find
answer to their questionings. At this, their dignity being grievously
hurt, they waxed exceeding wroth; and, joining in a mighty uproar,
they flew upon him and smote him, hip and thigh, and cast him out
forthwith. For, said they, surely Satan hath tempted this bold
neophyte to declare unholy and unheard-of ways of finding truth,
contrary to all the teachings of the fathers. After many days more of
grievous strife, the dove of peace sat on the assembly, and they as
one man declaring the problem to be an everlasting mystery because of
a grievous dearth of historical and theological evidence thereof, so
ordered the same writ down.

Francis Bacon, 1592.






"Don Baker" wrote in message
...
I would like to be able to determine if antenna is present at the end of a
piece of coax.

Do you know Silvia Brown?

John

"Don Baker" wrote in message
...
I would like to be able to determine if antenna is present at the end
of a
piece of coax. In some case antennas of type ?? would have a DC
resistance
across the coax and that makes it easy. But..., how would you
easily
determine if a coax shows an infinite DC resistance (NO RETURN PATH)
no
current flow - like simple did-poke.

Trying to spare the group all the details of what I am doing but I
will
gladly answer any questions. Thank you in advance for your help.

Don