Antenna Newsgroup Denizens:

Apart from the professional 'lab grade' (and undoubtedly very expensive)
devices made by the likes of Agilent, there are on the amateur market
several antenna analyzers that are more reasonably priced.

I'm currently considering the purchase of such a device, and so...

I'm interested in hearing opinions, pro-con arguments, and/or receiving
pointers to reviews of such devices.

All thoughts and comments will be appreciated, unbiased or not.

Thanks!

-- Pete k1po
-- Indialantic By-the-Sea, FL

I have only one comment which applies to most if not all of the amateur
level products, as well as a very high quality HP impedance meter I used
years ago.

I live about 15 miles from hilltops where the local AM, FM, and TV
broadcast towers are. The signals from those stations are strong enough
to overwhelm the broad bandwidth detection circuitry in the analyzers
(and HP vector impedance meter) I've used, resulting in meaningless
readings when connected to an antenna. I find that I grab my MFJ antenna
analyzer for a host of jobs like measuring a ferrite core impedance,
checking the length of a piece of coax, and so forth. But for me it's
just about useless for the job of analyzing actual antennas. When I need
to measure antenna impedance I dust off an old GR bridge and use a
portable receiver for the detector in order to reject the strong ambient
signals.

Of course this isn't a problem for everyone, but it sure is for me and I
don't think my situation is unusual for an urban environment. I've had
to put common mode chokes on my thermometer thermocouple wire, my light
meter connecting wire, scope leads, and even in audio circuitry to keep
the RF out. But even one strong local station might be enough to upset a
typical antenna analyzer.

Roy Lewallen, W7EL

On 8/23/2010 11:15 AM, Peter O. Brackett wrote:
Antenna Newsgroup Denizens:

Apart from the professional 'lab grade' (and undoubtedly very expensive)
devices made by the likes of Agilent, there are on the amateur market
several antenna analyzers that are more reasonably priced.

I'm currently considering the purchase of such a device, and so...

I'm interested in hearing opinions, pro-con arguments, and/or receiving
pointers to reviews of such devices.

All thoughts and comments will be appreciated, unbiased or not.

Thanks!

-- Pete k1po
-- Indialantic By-the-Sea, FL

Roy:

Thanks for your input on the effects of interference from other
transmitters, especially BC transmitters, point well taken.

I suppose one might add some kind of carefully designed passive filtering to
the devices to 'notch' out offending BC stations, etc...

But... that would be messy and complicated.

Using a bridge with a tuned detector seems a much better approach. I do
have an old MFJ Rx resistance bridge at hand, but I was looking for a little
bit better accuracy. I must check e-bay, etc... for prices for a used
bridge of the GR class you have.

My current problem could likly be solved by using one of my (so-called) VSWR
meters, but I felt I might like to get a little more metrological capability
for a few bucks.

I've never had a vertical antenna before and currently I'm laying out a
radial field under a new vertical antenna. I just wanted to know when to
stop laying down radials.

I figure that I just need to measure the input impedance of the antenna Zin
at my frequencies of interest and record the (hopefully decreasing)
impedance values as I lay down more radials. My assumption is that Zin =
Zant + Rg. where Zant includes the reactance and radiation resistance of
the radiator element at my frequency of interest and Rg is the ground
resistance. Hopefully Rg should decrease as I add raials. I intend to quit
adding radials when the impedance decrease becomes 'negligible' ( In the
sense of received S units [smile]).

Thanks again!

-- Pete k1po
-- Indialantic By-the-Sea, FL


"Roy Lewallen" wrote in message
...
I have only one comment which applies to most if not all of the amateur
level products, as well as a very high quality HP impedance meter I used
years ago.

I live about 15 miles from hilltops where the local AM, FM, and TV
broadcast towers are. The signals from those stations are strong enough to
overwhelm the broad bandwidth detection circuitry in the analyzers (and HP
vector impedance meter) I've used, resulting in meaningless readings when
connected to an antenna. I find that I grab my MFJ antenna analyzer for a
host of jobs like measuring a ferrite core impedance, checking the length
of a piece of coax, and so forth. But for me it's just about useless for
the job of analyzing actual antennas. When I need to measure antenna
impedance I dust off an old GR bridge and use a portable receiver for the
detector in order to reject the strong ambient signals.

Of course this isn't a problem for everyone, but it sure is for me and I
don't think my situation is unusual for an urban environment. I've had to
put common mode chokes on my thermometer thermocouple wire, my light meter
connecting wire, scope leads, and even in audio circuitry to keep the RF
out. But even one strong local station might be enough to upset a typical
antenna analyzer.

Roy Lewallen, W7EL

On 8/23/2010 11:15 AM, Peter O. Brackett wrote:
Antenna Newsgroup Denizens:

Apart from the professional 'lab grade' (and undoubtedly very expensive)
devices made by the likes of Agilent, there are on the amateur market
several antenna analyzers that are more reasonably priced.

I'm currently considering the purchase of such a device, and so...

I'm interested in hearing opinions, pro-con arguments, and/or receiving
pointers to reviews of such devices.

All thoughts and comments will be appreciated, unbiased or not.

Thanks!

-- Pete k1po
-- Indialantic By-the-Sea, FL

On 8/23/2010 2:53 PM, Peter O. Brackett wrote:
Roy:

Thanks for your input on the effects of interference from other
transmitters, especially BC transmitters, point well taken.

I suppose one might add some kind of carefully designed passive
filtering to the devices to 'notch' out offending BC stations, etc...

But... that would be messy and complicated.
. . .

Yes, it is. I've done it, but a lot of care has to be taken that the
filter doesn't have a significant effect on the impedance being
measured. At best, it usually also restricts you to a relatively narrow
bandwidth. It might be adequate for your particular purpose, however.
But for the job you describe of evaluating a radial system, a simple
homebrew resistance bridge is perfectly adequate. _Solid State Design
for the Radio Amateur_ had some examples, and I assume its successor
_Experimental Methods in RF Design_ does also.

Roy Lewallen, W7EL

On Aug 23, 4:53*pm, "Peter O. Brackett"
wrote:
Roy:

Thanks for your *input on the effects of interference from other
transmitters, especially BC transmitters, point well taken.

I suppose one might add some kind of carefully designed passive filtering to
the devices to 'notch' out offending BC stations, etc...

But... that would be messy and complicated.

Using a bridge with a tuned detector seems a much better approach. *I do
have an old MFJ Rx resistance bridge at hand, but I was looking for a little
bit better accuracy. *I must check e-bay, etc... for prices for a used
bridge of the GR class you have.

My current problem could likly be solved by using one of my (so-called) VSWR
meters, but I felt I might like to get a little more metrological capability
for a few bucks.

I've never had a vertical antenna before and currently I'm laying out a
radial field under a new vertical antenna. *I just wanted to know when to
stop laying down radials.

I figure that I just need to measure the input impedance of the antenna Zin
at my frequencies of interest and record the (hopefully decreasing)
impedance values as I lay down more radials. * My assumption is that Zin =
Zant + Rg. *where Zant includes the reactance and radiation resistance of
the radiator element at my frequency of interest and Rg is the ground
resistance. *Hopefully Rg should decrease as I add raials. I intend to quit
adding radials when the impedance decrease becomes 'negligible' ( In the
sense of received S units [smile]).

Thanks again!

-- Pete k1po
-- Indialantic By-the-Sea, FL

"Roy Lewallen" wrote in message

...



I have only one comment which applies to most if not all of the amateur
level products, as well as a very high quality HP impedance meter I used
years ago.

I live about 15 miles from hilltops where the local AM, FM, and TV
broadcast towers are. The signals from those stations are strong enough to
overwhelm the broad bandwidth detection circuitry in the analyzers (and HP
vector impedance meter) I've used, resulting in meaningless readings when
connected to an antenna. I find that I grab my MFJ antenna analyzer for a
host of jobs like measuring a ferrite core impedance, checking the length
of a piece of coax, and so forth. But for me it's just about useless for
the job of analyzing actual antennas. When I need to measure antenna
impedance I dust off an old GR bridge and use a portable receiver for the
detector in order to reject the strong ambient signals.

Of course this isn't a problem for everyone, but it sure is for me and I
don't think my situation is unusual for an urban environment. I've had to
put common mode chokes on my thermometer thermocouple wire, my light meter
connecting wire, scope leads, and even in audio circuitry to keep the RF
out. But even one strong local station might be enough to upset a typical
antenna analyzer.

Roy Lewallen, W7EL

On 8/23/2010 11:15 AM, Peter O. Brackett wrote:
Antenna Newsgroup Denizens:

Apart from the professional 'lab grade' (and undoubtedly very expensive)
devices made by the likes of Agilent, there are on the amateur market
several antenna analyzers that are more reasonably priced.

I'm currently considering the purchase of such a device, and so...

I'm interested in hearing opinions, pro-con arguments, and/or receiving
pointers to reviews of such devices.

All thoughts and comments will be appreciated, unbiased or not.

Thanks!

-- Pete k1po
-- Indialantic By-the-Sea, FL- Hide quoted text -

- Show quoted text -

Hi Pete, If you are evaluating a radial field for a vertical, then
the value you should be shooting for is 30-35 ohms, with no
reactance. As you know this is 1/2 the impedance of a 1/2 wave
dipole-70 ohms in free space. I have never done this, but an
impedance below 40 ohms with little reactance should provide you with
an efficient vertical. Once you get around this value, I guess there
is nothing to be gained by adding more radials. What your analyzer
tells you, as others have mentioned, depends on the rf in the area.

Gary N4AST

On 8/23/2010 5:38 PM, Gary wrote:

Hi Pete, If you are evaluating a radial field for a vertical, then
the value you should be shooting for is 30-35 ohms, with no
reactance. As you know this is 1/2 the impedance of a 1/2 wave
dipole-70 ohms in free space. I have never done this, but an
impedance below 40 ohms with little reactance should provide you with
an efficient vertical. Once you get around this value, I guess there
is nothing to be gained by adding more radials. What your analyzer
tells you, as others have mentioned, depends on the rf in the area.

Gary N4AST

The actual value you get when the radial system loss is minimal depends
on a number of factors, including the height and diameter of the
vertical. I've also seen convergence to other resistance values when the
ground was dry on the surface but apparently wet at some depth below. In
that case, radial current can be significant at quite a distance from
the antenna (as opposed to the exponential-looking decay you see in the
current on radials buried in moist ground), making the system act more
like a system of elevated radials. In those systems, radial length also
plays a role in determining the feedpoint resistance value.

The bottom line is that I don't trust a single value or its comparison
to 36 or 40 ohms as being a reliable indication of efficiency. You
either need to look for convergence of the feedpoint resistance as Peter
proposed, or even better yet, look for convergence of field strength
values at a fixed location as you increase the number of radials.

Roy Lewallen, W7EL

Roy:

[snip]
"Roy Lewallen" wrote in message
...
..
..
..
The bottom line is that I don't trust a single value or its comparison to
36 or 40 ohms as being a reliable indication of efficiency. You either
need to look for convergence of the feedpoint resistance as Peter
proposed, or even better yet, look for convergence of field strength
values at a fixed location as you increase the number of radials.

Roy Lewallen, W7EL
[snip]

That's exactly what I thought.

Since; (a) I don't know my soil characteristics and (b) because of property
limitations that dictate a non-uniform radial field, I felt that all I can
do is to lay down radials in the property area I have avaliable until I see
the change in Zin due to adding more radials become insignificant, then...
I'm done!

I don't really care what the exact value of Zin = Rin + jXin ends up to be,
since there is nothing I can do about it anyway. When I reach the point in
laying down radials to where I can't reduce Zin much by adding more radials,
I will then have the most efficient radial field with the lowest ground
resistance Rg that I can get for my money and effort [smile].

Heh, heh... Money is only money, the effort, hmmm... well that's me crawling
on my hands and knees for hours digging in the dirt (sand) in the blazing
hot Florida sunshine, heat and humidity!

When I arrive at that point in burying radials, I believe that I can then
tune out any reactive part of Zin with my 'tuner' and and end up feeding
power into the remaining resistance Rin which then should be the sum of the
vertical element radiation resistance Rr and whatever value I have ended up
with for ground resistance Rg.

I just won't know what the value of Rr and Rg is, but I will know that I
have achieved the most efficient radial field I could put down here at my
place.

Is this right?

-- Pete k1po
-- Indialantic By-the-Sea, FL

PS: I took your advice and did some reading on simple impedance bridges,
and I saw one that you had designed in one of my ARRL pubs. Cool!

Another idea I came upon that allow the use of those antenna analyzers in a
situation where they can be somewhat immune to BC interference involved a
two step process that went as follows...

(1) Hook up a transmitter through an antenna tuner to the antenna and ground
systems under test and tune the tuner for zero reflected power with a 50 Ohm
reflectometer (VSWR meter). Then (2) disconnect the tuner from the antenna,
and without disturbing the tuner settings, hook a 50 Ohm load to the input
side where the transmitter was connected, and then use the antenna analyzer
to measure the impedance looking back into the output, or antenna terminals,
of the tuner. This impedance should be the conjugate of Zin. Here the
analyzer may not be as affected by potentially strong BC RF signals picked
up by the lengthy antenna element.

On Aug 23, 8:09*pm, Roy Lewallen wrote:
On 8/23/2010 5:38 PM, Gary wrote:



Hi Pete, *If you are evaluating a radial field for a vertical, then
the value you should be shooting for is 30-35 ohms, with no
reactance. *As you know this is 1/2 the impedance of a 1/2 wave
dipole-70 ohms in free space. *I have never done this, but an
impedance below 40 ohms with little reactance should provide you with
an efficient vertical. *Once you get around this value, I guess there
is nothing to be gained by adding more radials. *What your analyzer
tells you, as others have mentioned, depends on the rf in the area.

Gary N4AST

The actual value you get when the radial system loss is minimal depends
on a number of factors, including the height and diameter of the
vertical. I've also seen convergence to other resistance values when the
ground was dry on the surface but apparently wet at some depth below. In
that case, radial current can be significant at quite a distance from
the antenna (as opposed to the exponential-looking decay you see in the
current on radials buried in moist ground), making the system act more
like a system of elevated radials. In those systems, radial length also
plays a role in determining the feedpoint resistance value.

The bottom line is that I don't trust a single value or its comparison
to 36 or 40 ohms as being a reliable indication of efficiency. You
either need to look for convergence of the feedpoint resistance as Peter
proposed, or even better yet, look for convergence of field strength
values at a fixed location as you increase the number of radials.

Roy Lewallen, W7EL

Hi Roy, I agree that field strength would be the best indicator of
efficiency as additional radials are laid down. However, for the
average Joe Ham trying to figure out how many radials is enough, and
all he has is an antenna anlyzer, what do you recommend?

Seems to me, with a 1/4 wave vertical of diameter large enough to
minimize I^2*R losses over average ground, if you add enough radials
to get the impedance to 35+/-j0 ohms as measured by the antenna
analyzer, you should be good to go. An additional check with the
analyzer could be the SWR bandwidth. If the swr was 1.7 across a
broad range then the 35 ohms is all ground losses. If the 1.7 swr
bandwidth is very narrow then you have a high Q antenna, and very
efficient at the operating frequency. Does this make sense?

Gary N4AST

On Aug 23, 8:38*pm, Gary wrote:
On Aug 23, 4:53*pm, "Peter O. Brackett"
wrote:



Roy:

Thanks for your *input on the effects of interference from other
transmitters, especially BC transmitters, point well taken.

I suppose one might add some kind of carefully designed passive filtering to
the devices to 'notch' out offending BC stations, etc...

But... that would be messy and complicated.

Using a bridge with a tuned detector seems a much better approach. *I do
have an old MFJ Rx resistance bridge at hand, but I was looking for a little
bit better accuracy. *I must check e-bay, etc... for prices for a used
bridge of the GR class you have.

My current problem could likly be solved by using one of my (so-called) VSWR
meters, but I felt I might like to get a little more metrological capability
for a few bucks.

I've never had a vertical antenna before and currently I'm laying out a
radial field under a new vertical antenna. *I just wanted to know when to
stop laying down radials.

I figure that I just need to measure the input impedance of the antenna Zin
at my frequencies of interest and record the (hopefully decreasing)
impedance values as I lay down more radials. * My assumption is that Zin =
Zant + Rg. *where Zant includes the reactance and radiation resistance of
the radiator element at my frequency of interest and Rg is the ground
resistance. *Hopefully Rg should decrease as I add raials. I intend to quit
adding radials when the impedance decrease becomes 'negligible' ( In the
sense of received S units [smile]).

Thanks again!

-- Pete k1po
-- Indialantic By-the-Sea, FL

"Roy Lewallen" wrote in message

...

I have only one comment which applies to most if not all of the amateur
level products, as well as a very high quality HP impedance meter I used
years ago.

I live about 15 miles from hilltops where the local AM, FM, and TV
broadcast towers are. The signals from those stations are strong enough to
overwhelm the broad bandwidth detection circuitry in the analyzers (and HP
vector impedance meter) I've used, resulting in meaningless readings when
connected to an antenna. I find that I grab my MFJ antenna analyzer for a
host of jobs like measuring a ferrite core impedance, checking the length
of a piece of coax, and so forth. But for me it's just about useless for
the job of analyzing actual antennas. When I need to measure antenna
impedance I dust off an old GR bridge and use a portable receiver for the
detector in order to reject the strong ambient signals.

Of course this isn't a problem for everyone, but it sure is for me and I
don't think my situation is unusual for an urban environment. I've had to
put common mode chokes on my thermometer thermocouple wire, my light meter
connecting wire, scope leads, and even in audio circuitry to keep the RF
out. But even one strong local station might be enough to upset a typical
antenna analyzer.

Roy Lewallen, W7EL

On 8/23/2010 11:15 AM, Peter O. Brackett wrote:
Antenna Newsgroup Denizens:

Apart from the professional 'lab grade' (and undoubtedly very expensive)
devices made by the likes of Agilent, there are on the amateur market
several antenna analyzers that are more reasonably priced.

I'm currently considering the purchase of such a device, and so...

I'm interested in hearing opinions, pro-con arguments, and/or receiving
pointers to reviews of such devices.

All thoughts and comments will be appreciated, unbiased or not.

Thanks!

-- Pete k1po
-- Indialantic By-the-Sea, FL- Hide quoted text -

- Show quoted text -

Hi Pete, *If you are evaluating a radial field for a vertical, then
the value you should be shooting for is 30-35 ohms, with no
reactance. *As you know this is 1/2 the impedance of a 1/2 wave
dipole-70 ohms in free space. *I have never done this, but an
impedance below 40 ohms with little reactance should provide you with
an efficient vertical. *Once you get around this value, I guess there
is nothing to be gained by adding more radials. *What your analyzer
tells you, as others have mentioned, depends on the rf in the area.

Gary N4AST

Hi Pete, long time since I've seen a post from you on this NG!

Pete, I'd take Roy's route and use a GR impedance bridge. I've used
the GR-1606A and the 1606B for the last 50 years. If you're not
familiar with it it's been the standard impedance-measuring device for
AM BC antennas for more than 50 years. It's accuracy cannot be beaten.
These bridges were expensive when new, but they are available rather
inexpensively now, and are stable as a rock. And as Roy said, they use
either a millivolt meter or a tunable receiver as the detector. Using
the receiver, interfering signals picked up with the antenna being
measured are eliminated, thus not degrading the accuracy of the
impedance measurement.

The GR-1606A measures from below 500 kHz up to 60 MHz. The GR-1602
measures well into the VHF range. If you should try one I know you'll
like it.

Walt, W2DU

PS--If you'd like to see the results of measuring W2DU's antenna
impedances, I refer you to Reflections, Chapter 15, Tables 15-4, 15-5,
and Fig 15-1, which is a graph of the data in the Tables. If you don't
have a copy of Reflections you can see this data on my web page at
www.w2du.com. Just select 'Read Chapters from Reflections 2'.

Thanks Walt!

"walt" wrote in message
...
On Aug 23, 8:38 pm, Gary wrote:
On Aug 23, 4:53 pm, "Peter O. Brackett"
wrote:



Roy:

Thanks for your input on the effects of interference from other
transmitters, especially BC transmitters, point well taken.

I suppose one might add some kind of carefully designed passive
filtering to
the devices to 'notch' out offending BC stations, etc...

But... that would be messy and complicated.

Using a bridge with a tuned detector seems a much better approach. I do
have an old MFJ Rx resistance bridge at hand, but I was looking for a
little
bit better accuracy. I must check e-bay, etc... for prices for a used
bridge of the GR class you have.

My current problem could likly be solved by using one of my (so-called)
VSWR
meters, but I felt I might like to get a little more metrological
capability
for a few bucks.

I've never had a vertical antenna before and currently I'm laying out a
radial field under a new vertical antenna. I just wanted to know when to
stop laying down radials.

I figure that I just need to measure the input impedance of the antenna
Zin
at my frequencies of interest and record the (hopefully decreasing)
impedance values as I lay down more radials. My assumption is that Zin =
Zant + Rg. where Zant includes the reactance and radiation resistance of
the radiator element at my frequency of interest and Rg is the ground
resistance. Hopefully Rg should decrease as I add raials. I intend to
quit
adding radials when the impedance decrease becomes 'negligible' ( In the
sense of received S units [smile]).

Thanks again!

-- Pete k1po
-- Indialantic By-the-Sea, FL

"Roy Lewallen" wrote in message

...

I have only one comment which applies to most if not all of the amateur
level products, as well as a very high quality HP impedance meter I
used
years ago.

I live about 15 miles from hilltops where the local AM, FM, and TV
broadcast towers are. The signals from those stations are strong
enough to
overwhelm the broad bandwidth detection circuitry in the analyzers
(and HP
vector impedance meter) I've used, resulting in meaningless readings
when
connected to an antenna. I find that I grab my MFJ antenna analyzer
for a
host of jobs like measuring a ferrite core impedance, checking the
length
of a piece of coax, and so forth. But for me it's just about useless
for
the job of analyzing actual antennas. When I need to measure antenna
impedance I dust off an old GR bridge and use a portable receiver for
the
detector in order to reject the strong ambient signals.

Of course this isn't a problem for everyone, but it sure is for me and
I
don't think my situation is unusual for an urban environment. I've had
to
put common mode chokes on my thermometer thermocouple wire, my light
meter
connecting wire, scope leads, and even in audio circuitry to keep the
RF
out. But even one strong local station might be enough to upset a
typical
antenna analyzer.

Roy Lewallen, W7EL

On 8/23/2010 11:15 AM, Peter O. Brackett wrote:
Antenna Newsgroup Denizens:

Apart from the professional 'lab grade' (and undoubtedly very
expensive)
devices made by the likes of Agilent, there are on the amateur market
several antenna analyzers that are more reasonably priced.

I'm currently considering the purchase of such a device, and so...

I'm interested in hearing opinions, pro-con arguments, and/or
receiving
pointers to reviews of such devices.

All thoughts and comments will be appreciated, unbiased or not.

Thanks!

-- Pete k1po
-- Indialantic By-the-Sea, FL- Hide quoted text -

- Show quoted text -

Hi Pete, If you are evaluating a radial field for a vertical, then
the value you should be shooting for is 30-35 ohms, with no
reactance. As you know this is 1/2 the impedance of a 1/2 wave
dipole-70 ohms in free space. I have never done this, but an
impedance below 40 ohms with little reactance should provide you with
an efficient vertical. Once you get around this value, I guess there
is nothing to be gained by adding more radials. What your analyzer
tells you, as others have mentioned, depends on the rf in the area.

Gary N4AST

Hi Pete, long time since I've seen a post from you on this NG!

Pete, I'd take Roy's route and use a GR impedance bridge. I've used
the GR-1606A and the 1606B for the last 50 years. If you're not
familiar with it it's been the standard impedance-measuring device for
AM BC antennas for more than 50 years. It's accuracy cannot be beaten.
These bridges were expensive when new, but they are available rather
inexpensively now, and are stable as a rock. And as Roy said, they use
either a millivolt meter or a tunable receiver as the detector. Using
the receiver, interfering signals picked up with the antenna being
measured are eliminated, thus not degrading the accuracy of the
impedance measurement.

The GR-1606A measures from below 500 kHz up to 60 MHz. The GR-1602
measures well into the VHF range. If you should try one I know you'll
like it.

Walt, W2DU

PS--If you'd like to see the results of measuring W2DU's antenna
impedances, I refer you to Reflections, Chapter 15, Tables 15-4, 15-5,
and Fig 15-1, which is a graph of the data in the Tables. If you don't
have a copy of Reflections you can see this data on my web page at
www.w2du.com. Just select 'Read Chapters from Reflections 2'.