Analyzer evaluation
Darrell Gordon W4CX
impressed with the knowledge here. I am shopping for an antenna
analyzer and am stymied by the choices (or lack thereof). In all of
hamdom (sub $600), I only find MFJ, Autek, AEA wireless, and Kuranishi
to choose from. I've checked eham reviews and found that the AEA VIA
(not Bravo) rates highest...and most expensive. Probably worth it.
Unfortunately, it's only good to 54Mhz, and I'd need up to 450Mhz. I
know this is impossible, and would be willing to go with separate
units (Autek), but they have awful reviews re: quality.
My question: What are you guys using for HF measurements? What about
V/UHF measurements? Do you recommend any particular model? How about
used HP gear from ebay (yes, I know the risks). V/UHF is my priority
since I'm building some copper loops for 6 and 2. What say you sage
antenna gurus?
Darrell W4CX
H. Adam Stevens, NQ5H
"Darrell Gordon W4CX" <w4cx....@arrl.net> wrote in message
news:7mnri09ar95859b0j...@4ax.com...
guru, schmuru
you will find the gamut of experience and education here, though
as well as some amazing flame wars
I have the MFJ with 450 and it works OK
Only measures SWR on 450.
It's not a laboratory instrument, but I have used it for years and it gets
the job done.
Priceless for setting up the HF mobile.
I have no comparative experience except with an old General Radio bridge in
my AM radio days decades ago.
73
H.
NQ5H
Richard Clark
<w4cx....@arrl.net> wrote:
>What are you guys using for HF measurements?
Hi Darrell,
General Radio 1606-A: 400KHz - 60MHz, Resistance 0 - 1000 Ohms ą1%,
Reactance 0 - 5000/F Ohms ą2%.
73's
Richard Clark, KB7QHC
Reg Edwards
> General Radio 1606-A: 400KHz - 60MHz, Resistance 0 - 1000 Ohms ą1%,
> Reactance 0 - 5000/F Ohms ą2%.
>
Is this recommendation of yours traceable directly to International
Measurement Standards or has it passed through the hands of a sales
department?
---
Punchinello.
Walter Maxwell
Hi Darrell,
I was just about to tell you what I use, but Richard, above, beat me to it. For
HF measurements this bridge, the General Radio 1606-A, is the Cadillac of all
bridges. It 's been the bridge of choice for nearly every AM broadcast engineer
in determining t he impedance of AM broadcast antennas since it came on the
market in 1955. It's very nearly the same as it's predecessor, the GR 916-A,
which came out in the 1940's. It's what the AM antenna engineers used prior to
the 1606.
You can find the 1606-A on eBay, and the price ranges from $200 to $1000.
However, you also need a signal generator to feed it the signal it needs to
operate, plus your receiver as the signal detector.
I also use more modern impedance measuring devices, such as Hewlett-Packard's
HP-4815 Vector Impedance Meter, and their HP 8405 Vector Voltmeter. These two
instruments are also laboratory grade quality. All of these instruments far
exceed the accuracy of the devices you listed.
Hope this helps,
Walt, W2DU
Walter Maxwell
Hi Reg,
I obtained my 1606-A in 1968, Ser # 924, directly after calibrated to IMS. I
have checked it periodically against some of my own standards, only to find the
calibration hasn't varied even the width of an engraved graduation mark on
either the reactance or resistance dial in all these years.
Walt
Richard Clark
<g4fgq...@ZZZbtinternet.com> wrote:
>Is this recommendation of yours traceable directly to International
>Measurement Standards or has it passed through the hands of a sales
>department?
Hi Punchinello,
Your hedged question belies an ignorance of premium equipment that has
been dominant in the field for 50 years. How is it you fail to
recommend what you use?
I have calibrated such in a Primary Electronic Standards Lab against
standards traceable to NBS at the time. [but you knew this already]
I did such work under contracts to Boeing, and the model I own was
acquired from Boeing complete with certificates of traceability(not my
own work, I have only on occasion found a piece of precision gear with
my stickers on it).
I have never encountered a GR 1606 that fell outside of its
specifications - except for one where someone apparently burnt out one
bridge component, a resistor. Undoubtedly this was accomplished by
applying a transmitter to the excitation port - one can only imagine
the fate of equipment connected to the detector port. This was very
simple to recover from (one resistor). The instrument is robust and
built like a Swiss precision watch. There are very few things that
could go wrong and only under physical duress (like dropping it down
three floors of stairs).
Roy Lewallen
At my location, about 10-15 miles from a hilltop with powerful TV, FM,
and I believe AM broadcast transmitters, the MFJ is pretty useless for
most antenna measurements. The impinging RF confuses it. It's great for
fiddling with circuits on the bench, quick measurements of coax length,
and checking the resonance of a 2 meter whip. I'm sure the RF problem
would be the same for the other analyzers. Years ago, I rented an HP
vector impedance meter for a consulting job, and it too was unable to
handle the RF environment. A friend lent me an ancient tube-type Z meter
that had a tunable detector, and I ended up making the measurements with
it. (That was before I got the 1606A.)
I use the 1606A when I need to make serious and accurate antenna
measurements. It's tedious to use, having to be calibrated at the
measurement frequency before making measurements. It only goes up to 60
MHz. And it requires an external signal generator and detector. The
external detector is really its strength, though, since by using a
narrowband detector (I use an old ICOM R1 portable receiver) I can make
good measurements in the RF environment I live in. It would be a real
nuisance to haul it up a tower, although you can put it on top of a
stepladder.
Sorry, I haven't used any of the other analyzers so can't help you out
with the comparison between them.
Roy Lewallen, W7EL
Walter Maxwell
>I have an MFJ 269 and a GR 1606A. Each has its place.
>
>At my location, about 10-15 miles from a hilltop with powerful TV, FM,
>and I believe AM broadcast transmitters, the MFJ is pretty useless for
>most antenna measurements. The impinging RF confuses it. It's great for
>fiddling with circuits on the bench, quick measurements of coax length,
>and checking the resonance of a 2 meter whip. I'm sure the RF problem
>would be the same for the other analyzers. Years ago, I rented an HP
>vector impedance meter for a consulting job, and it too was unable to
>handle the RF environment. A friend lent me an ancient tube-type Z meter
>that had a tunable detector, and I ended up making the measurements with
>it. (That was before I got the 1606A.)
>
>I use the 1606A when I need to make serious and accurate antenna
>measurements. It's tedious to use, having to be calibrated at the
>measurement frequency before making measurements. It only goes up to 60
>MHz. And it requires an external signal generator and detector. The
>external detector is really its strength, though, since by using a
>narrowband detector (I use an old ICOM R1 portable receiver) I can make
>good measurements in the RF environment I live in. It would be a real
>nuisance to haul it up a tower, although you can put it on top of a
>stepladder.
>
>Sorry, I haven't used any of the other analyzers so can't help you out
>with the comparison between them.
>
>Roy Lewallen, W7EL
>
It's gratifying to learn that the 'ole 1606 is still being used by people in the
group. About ten years ago I wondered what I'd do if anything happened to mine,
especially since General Radio was already out of business, so I found a 1606-B
for $400 as a backup. Son Rick, WB4GNR, is using it, but it's still my backup.
Walt, W2DU
Hal Rosser
"Darrell Gordon W4CX" <w4cx....@arrl.net> wrote in message
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H. Adam Stevens, NQ5H
;^)
"Hal Rosser" <hmro...@bellsouth.net> wrote in message
news:hcsXc.26092$cx.2...@bignews4.bellsouth.net...
John Moriarity
> My question: What are you guys using for HF measurements?
The original Autek. Limited accuracy,
but *very* portable and very useful.
I'm building the N2PK Vector Network
Analyzer, which is only good to 60Mhz,
with laboratory accuracy. Paul has hinted
at extensions to allow se to 450Mhz.
See www.n2pk.com .
The GR bridges suggested are very good,
but not too portable.
73, John - K6QQ
Wes Stewart
wrote:
|
|> My question: What are you guys using for HF measurements?
|
|The original Autek. Limited accuracy,
|but *very* portable and very useful.
|
|I'm building the N2PK Vector Network
|Analyzer, which is only good to 60Mhz,
|with laboratory accuracy. Paul has hinted
|at extensions to allow se to 450Mhz.
|See www.n2pk.com .
Me too. Well, let me rephrase... I have had the kit ($220) for about
8 months and have yet to start on it ;)
First I figured I needed a better, smaller soldering iron. $100.
Then I got that and realized I can't see the parts. Got a 10X
Optivisor. $35.
Depth of field is really marginal. Got a lighted magnifier. $50.
Ready to go... oops no anti-static mat and right in the middle of
building bathroom vanity cabinet. Figured I could save money by DIY.
New Delta Unisaw. $1500. Dovetail jig. $400. Better lighting in
garage $400. Hardwood $400. Misc router bits, finishing materials,
spray gun, screws, door and drawer hardware and my labor at $0.05/
hour... don't ask.
Other than that, I use a Boonton 250 or an HP 8405 for impedance
measurements.
9V1GO
Hi Darrell,
I have used the Autek VA1 and the MFJ 259B here in 9V for about a year.
Must have gotten a good Autek as it has performed well. All of the MFJ
series I have used in the past and they will do the job but as has been
said, high RF enviornments render it useless.
The MFJ that goes to UHF we used on a field day trip to a remote island just
off 9V and it also did a good job. YMMV but the VA1 goes into a pocket for
a tower climb, is a bit fiddley, but I find I use it more than the MFJ.
73
Bob 9V1GO
Hal Rosser
...and this analyzer post gives me an idea about the Stainless-steel wire
thread - hmmm
"Darrell Gordon W4CX" <w4cx....@arrl.net> wrote in message
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Reg Edwards
few microwatts output. And for the few components inside it, it is
overpriced.
---
Reg
J. McLaughlin
another from being scraped so I have a back-up.
However, for most tasks, I find that the AEA VIA is the cat's meow.
For instance, when trying to tune a Matchbox to strange frequencies, the
VIA tells one which way things are going.
I have not tried to use the VIA in the presence of strong broadcast
transmitters. At work, we have HP (Agelent) network analyzers and
standards to use as comparisons.
AEA also makes, and I use, a modest TDR that is good enough to be
used to keep track of transmission lines, connectors, and in-line
protection devices.
As Roy, and others, have said: when you need a GR, you need a GR.
Before I bought a 1606, I was once loaned the 900 something predecessor
to the 1606. This instrument is inside of a small, copper lined
suitcase and the particular instrument had been used by the military
since about WW2. The outside showed use. It was spot on with my
standards and, when I opened up the case, the insides were still bright
and shinny. GR made quality instruments.
Though I have not used it, somewhere I have a Delta bridge that was
given to me.
Go for the VIA for HF. You will not be disappointed.
73, Mac N8TT
--
J. Mc Laughlin - Michigan USA
Home: J...@Power-Net.Net
"Roy Lewallen" <w7...@eznec.com> wrote in message
news:10isec4...@corp.supernews.com...
Richard Harrison
"V/UHF is my priority since I`m building some copper loops for 6 and 2."
In the U.S., General Radio is champion. But, in Europe we used a British
Wayne Kerr UHF admittance bridge on lines and antennas in the middle of
a high frequency broadcast plant with a dozen or more competing
transmitters on the air at full power, as they always were.
The secret of success is the bridge detector used. A Collins 51-J was
useless, solid noise across the H-F bands. A Hammarlund SP-600 worked
like a champ.
Best regards, Richard Harrison, KB5WZI
Walter Maxwell
>snip
>
> As Roy, and others, have said: when you need a GR, you need a GR.
>Before I bought a 1606, I was once loaned the 900 something predecessor
>to the 1606. This instrument is inside of a small, copper lined
>suitcase and the particular instrument had been used by the military
>since about WW2. The outside showed use. It was spot on with my
>standards and, when I opened up the case, the insides were still bright
>and shinny. GR made quality instruments.
>
> 73, Mac N8TT
Hi Mac,
The predecessor to the GR-1606A was the GR-916A, which was the cadillac of
professional bridges prior to the GR-1606A, which came out in 1955. I used the
916A to adjust the tower resistance of WCEN, 1150 kHz, the station I engineered
and built in 1948. The National HRO receiver was used as the detector.
Walt, W2DU
Walter Maxwell
wrote:
Hi Richard,
Interesting you mentioned the Wayne Kerr UHF bridge. In my impedance-measuring
arsenal is the Wayne Kerr B108 admittance bridge. The beautiful aspect of this
bridge is that it's unknown terminals are balanced, thus allowing direct
measurement of balanced lines.
My arsenal also includes: 2 HP 8405 Vector Voltmeters with HP-778D dual
directional coupler.
HP-4815 Vector Impedance Meter
GR-1606A
GR-1606B
Boonton 250A Impedance Meter
PRD-219 Complex Reflection Coefficient Meter, 20 to 1000 MHz
What would you like me to measure?
Walt
Roy Lewallen
an AEA he had purchased worked very well except for one thing -- the
reference point appeared to be inside the instrument. He said it was as
though there were another length of line (about 5 cm as I recall)
inside. For example, measurement of a short circuit would indicate the
amount of positive reactance you'd expect from such a line. This might
not be too important for general purpose HF use, but would be a problem
with some measurements, especially at high frequencies. It could be
removed by mathematical adjustment of the measurement results, of course.
I mentioned this problem to the AEA folks at Dayton, not long after it
changed hands, and they might have fixed it. Do you see this phenomenon?
I saw a similar thing when I spent a few minutes playing with the very
first model of Autek. I don't see this with my MFJ.
Again, the problem might have been fixed, but it's something to look
for, particularly on an older used unit.
Roy Lewallen, W7EL
J. McLaughlin
As I remember, and this was a long time ago, the 916's unknown port
was less convenient to use than was the case with the 1606. As several
have pointed out, one needs a competent detector.
For VHF/UHF work, GR had an "admittance" bridge that worked very
well. Used one to tune a 400 MHz feed (of an 85 foot dish) so that the
feed was resonant at two frequency bands 60 MHz apart (30 MHz IF strip).
Thanks for the memories.
A correction to what I wrote: I have a CIA-HF from AEA, not a VIA.
73 Mac N8TT
--
J. Mc Laughlin - Michigan USA
Home: J...@Power-Net.Net
"Walter Maxwell" <w2...@iag.net> wrote in message
news:g0vui0pt4i6580ujj...@4ax.com...
Dale Parfitt
> A very capable engineering colleage of mine mentioned some time ago that
> an AEA he had purchased worked very well except for one thing -- the
> reference point appeared to be inside the instrument. He said it was as
> though there were another length of line (about 5 cm as I recall)
> inside. For example, measurement of a short circuit would indicate the
> amount of positive reactance you'd expect from such a line. This might
> not be too important for general purpose HF use, but would be a problem
> with some measurements, especially at high frequencies. It could be
> removed by mathematical adjustment of the measurement results, of course.
>
> I mentioned this problem to the AEA folks at Dayton, not long after it
> changed hands, and they might have fixed it. Do you see this phenomenon?
>
> I saw a similar thing when I spent a few minutes playing with the very
> first model of Autek. I don't see this with my MFJ.
>
> Again, the problem might have been fixed, but it's something to look
> for, particularly on an older used unit.
>
> Roy Lewallen, W7EL
>
I briefly owned the AEA V/U model- probably in 1999. Using my HP precision
termination set, it appeared that the best VHF return loss was indicated
when the analyzer was terminated in around 60 Ohms and for UHF it was 75
Ohms. When I called AEA to inquire, I was told "that's about the accuracy
you should expect for $500". The Autek V/U instrument was in excellent
agreement with an HP 8711B.
Dale W4OP
Darrell Gordon W4CX
to your reputation.
Has anyone had any experience with an HP 8754? They seem to be
around, and with a b/w of 4-1300Mhz might be an excellent choice???
Darrell
J. McLaughlin
Very interesting!
It just did not occur to me to test. Now that the EMC book I have
been helping with is finally being printed (over ten years in the
crafting) I shall put an appraisal of the AEA on our list of activities.
It occurs to me that almost all of my use of the instrument has been
below about 10 MHz. At those frequencies, my suspicions probably were
not tripped by a discrepancy of half a degree (or smaller).
I did buy the instrument after at least one change of hands.
Thank you very much for the heads-up. I am shaking my head in
wonder that that property I never thought to check.
Warm regards, Mac N8TT
--
J. Mc Laughlin - Michigan USA
Home: J...@Power-Net.Net
"Roy Lewallen" <w7...@eznec.com> wrote in message
news:10iv9fn...@corp.supernews.com...
Ian White, G3SEK
>
>"Roy Lewallen" <w7...@eznec.com> wrote in message
>news:10iv9fn...@corp.supernews.com...
>> A very capable engineering colleage of mine mentioned some time ago
>that
>> an AEA he had purchased worked very well except for one thing -- the
>> reference point appeared to be inside the instrument. He said it was
>as
>> though there were another length of line (about 5 cm as I recall)
>> inside. For example, measurement of a short circuit would indicate the
>> amount of positive reactance you'd expect from such a line. This might
>> not be too important for general purpose HF use, but would be a
>problem
>> with some measurements, especially at high frequencies. It could be
>> removed by mathematical adjustment of the measurement results, of
>course.
>>
>> I mentioned this problem to the AEA folks at Dayton, not long after it
>> changed hands, and they might have fixed it. Do you see this
>phenomenon?
>>
>> I saw a similar thing when I spent a few minutes playing with the very
>> first model of Autek. I don't see this with my MFJ.
>>
>> Again, the problem might have been fixed, but it's something to look
>> for, particularly on an older used unit.
>Dear Roy:
> Very interesting!
> It just did not occur to me to test. Now that the EMC book I have
>been helping with is finally being printed (over ten years in the
>crafting) I shall put an appraisal of the AEA on our list of activities.
> It occurs to me that almost all of my use of the instrument has been
>below about 10 MHz. At those frequencies, my suspicions probably were
>not tripped by a discrepancy of half a degree (or smaller).
> I did buy the instrument after at least one change of hands.
> Thank you very much for the heads-up. I am shaking my head in
>wonder that that property I never thought to check.
> Warm regards, Mac N8TT
A few years ago, I was evaluating an AEA-CIA for a possible magazine
review. One of the tests involved a load consisting of some metres of 50
ohm coax terminated in three paralleled 50 ohm chip resistors. When the
frequency is swept, this load walks around the SWR=3 circle on a Smith
chart, giving |Z| values ranging between 16 ohms and 150 ohms with a
progressively rotating phase; or equivalent results in terms of
(R+/-jX). In other words, the test involves only moderately high or low
impedances with no nasty surprises.
The AEA-CIA gave good results as a frequency-sweeping SWR meter, and the
graphical display is unique in this price range; but unfortunately but
it did not give sensible results in the R-X mode (the mode that gives
the "Complex Impedance Analyser" its name). In a frequency range where
the true value of X was falling progressively through zero, the
indicated value came down correctly to about 30 ohms - and then suddenly
jumped to 0.0. The R readings continued to change with frequency exactly
as expected, but the X reading stayed 'stuck' at precisely 0.0 until the
sweep reached the frequency at which X changed sign, whereupon the X
readings started to make sense again. This behaviour was totally
reproducible. Also, the AEA-CIA is also supposed to be able to resolve
the sign of the complex impedance (which it presumably does by changing
frequency and noting what happens to X), but perhaps not surprisingly
this didn't work reliably either. At a constant frequency where the
value of X was nowhere close to zero, the instrument was often unable to
make up its mind about the correct sign.
All these symptoms looked like firmware problems to me. Since R and X
are both computed from the same analog voltage readings, and R was
correct while X was not, the problem had to be in the computation. The
AEA management at the time were quick to respond through the UK dealer.
They sent me schematics, and analog-type mods to try, and even replaced
the entire instrument... which behaved exactly like the one before.
However, they didn't seem to understand what I just wrote above, and
didn't want to go anywhere near the firmware.
In the end, I abandoned the effort and the UK dealer didn't import the
instrument. The magazine decided we should review the MFJ-269 instead -
which handled the same test load with good accuracy.
Sorry, I don't recall what specific firmware versions gave these
problems with the AEA-CIA, and have no information whether they have
been fixed in later versions. As Roy said:
>> the problem might have been fixed, but it's something to look
>> for, particularly on an older used unit.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
J. McLaughlin
Most interesting. Thanks.
I have not used the AEA-CIA for R-X measurements. I always assumed
that firmware was used to guess at the sign of X, and it is not too
surprising (though disappointing) that the chap who wrote the software
might blank out small values of X altogether. [In a spherical
navigation program that I wrote long ago for a slow computer, I flagged
results that would have been in the noise because of round-off error.
It took some effort to know when the results were bad. Others ignored
error analysis, being enamored of many random digits, with disastrous
results. Sometimes, with computers, no answer is the best one can do.
As an example: Cramer's rule just does not work to solve some systems of
linear equations using a computer! Even the HP48 uses an iterative
technique, which computers are real good at and people are not.]
The most interesting use that I made of the AEA-CIA, which would
have been difficult to do with a GR bridge, was measuring the apparent
surge impedance of a split boom to be used with a LPDA (prior to the
elements being attached). Leaving out the appropriate lecture: I
terminated the split-boom with a series of resistors 'till the variation
in SWR (seen at the other end of the split-boom) with frequency was
minimal. [This is another example of SWR on a line depending on which
way one is looking.]
The strong suit of the AEA-CIA is in giving one repeatable data over
a wide frequency range. Most of the antennas that I deal with have
functional bandwidths of at least an octave. The value of the AEA-CIA
is much reduced if one is only interested in what is going on in a
narrow bandwidth.
Thanks very much for sharing your experience. We have once again
benefited from your experience and Roy's experience. 73 Mac N8TT
--
J. Mc Laughlin - Michigan USA
Home: J...@Power-Net.Net
"Ian White, G3SEK" <G3...@ifwtech.co.uk> wrote in message
news:3YyBLxCI...@ifwtech.co.uk...
<snip>
Ian White, G3SEK
> Most interesting. Thanks.
You're welcome. Just one small point, though:
> I have not used the AEA-CIA for R-X measurements. I always assumed
>that firmware was used to guess at the sign of X, and it is not too
>surprising (though disappointing) that the chap who wrote the software
>might blank out small values of X altogether.
In case anyone's not following this closely, I had been writing about
the AEA-CIA blanking out values of X less than about 30 ohms. That is
not "small" by any standard, and it only happened on one side of zero.
It could not possibly have been a deliberate feature of the programming.
In contrast, the MFJ-269 (and probably the 259B) does deliberately blank
out small values - truly small values, that is - as X passes through
zero. This occurs exactly as explained in the manual, and is exactly as
it should be.
Richard Harrison
measuring devices. He`s prepared. Walter also wrote:
"In my impedance-measuring arsenal is the Wayne Kerr B108 admittance
terminals are balanced, thus allowing direct measurement of balanced
lines."
Yes. Balanced unknown terminals are convenient for a commercial
shortwave operator located away from the seashore. Horizontal wave
polarization with balanced feedlines is economical as compared with coax
for high power.
Unbalanced vertical antennas are convenient for groundwaves to extend
beyond the horizon for the mediumwave broadcaster. These antennas are
conveniently fed by coax of the concentric pipe or skeletal types. All
groundwaves are vertically polarized. These can travel very far at low
and medium frequencies. Attenuation of high frequency groundwaves is
severe. There is no propagation of horizontally polarized groundwaves at
all. The low-angle reflected wave is out of phase with the incident
wave.
Bottom line is that shortwave broadcasters transmit from horizontal
antennas and mediumwave broadcasters transmit from vertical antennas.
For shortwave, the target is reached via the ionosphere. For mediumwave,
the target is reached via the earth`s surface which is involved in
reaching beyond the line of sight.
For a dipole, you are likely to prefer a balanced bridge. For a
monopole, you are likely to prefer an unbalanced bridge.
Reg Edwards
"Richard Harrison" wrote -
> There is no propagation of horizontally polarized groundwaves at
> all. The low-angle reflected wave is out of phase with the incident
> wave.
>
--------------------------------------------------------------
With a groundwaves there is no reflected wave and incident wave to get out
of phase with each other. By definition, it is all in the ground down to
one skin depth.
Very simply, a horizontally polarised groundwave, with its horizontal
current, suffers great attenuation in the loss resistance of the horizontal
ground. It gets launched but after one or two wavelengths it is many
decibels down.
This is the reason why horizontally polarised noise, relatively locally
generated, is smaller than the vertically polarised variety although, on the
average, both are randomly generated with equal amplitudes.
Half of the total noise power is dissipated in the ground except that which
is generated immediately adjacent to your receiving antenna.
----
Reg, G4FGQ
Walter Maxwell
<g4fgq...@ZZZbtinternet.com> wrote:
>
>"Richard Harrison" wrote -
>
>> There is no propagation of horizontally polarized groundwaves at
>> all. The low-angle reflected wave is out of phase with the incident
>> wave.
>>
>--------------------------------------------------------------
>
>With a groundwaves there is no reflected wave and incident wave to get out
>of phase with each other. By definition, it is all in the ground down to
>one skin depth.
Reg, you are correct, of course, but Richard H. said above, "There is no
propagation of horizontally polarized groundwaves at all. The low-angle
reflected wave is out of phase with the incident wave."
What Richard mean't concerning the 'reflected' wave is that the energy radiated
downward from a horizontal antenna is reflected by the ground, and that
reflected wave is out of phase with the incident wave.
Walt, W2DU
Walter Maxwell
wrote:
> snip
>Unbalanced vertical antennas are convenient for groundwaves to extend
>beyond the horizon for the mediumwave broadcaster. These antennas are
>conveniently fed by coax of the concentric pipe or skeletal types. All
>groundwaves are vertically polarized. These can travel very far at low
>and medium frequencies. Attenuation of high frequency groundwaves is
>severe. There is no propagation of horizontally polarized groundwaves at
>all. The low-angle reflected wave is out of phase with the incident
>wave.
>
>Bottom line is that shortwave broadcasters transmit from horizontal
>antennas and mediumwave broadcasters transmit from vertical antennas.
>For shortwave, the target is reached via the ionosphere. For mediumwave,
>the target is reached via the earth`s surface which is involved in
>reaching beyond the line of sight.
Richard, when I was doing AM BC consulting more than 50 years ago I made the
observation from FCC ground-wave distance vs frequency propagation charts that
with the same ground conductivity and 1/4 wl antennas for both frequencies, the
1mv/m contour attained by 100 w at 540 kHz would require slightly less than 50
Kw at 1500 kHz,
Proves your point, doesn't it?
Walt, W2DU
Roy Lewallen
the incident wave, and this explains the zero far field strength you get
with horizontally polarized waves, I'm not sure this is the relevant
explanation for the lack of ground wave propagation. The reason I doubt
it is that if you do the same analysis for vertically polarized waves,
you find that the net field strength is also zero at zero elevation
angle, except for the special case where ground is perfectly conducting.
So using the same analysis, you'd have to conclude that vertically
polarized waves can't propagate by ground wave, either.
Roy Lewallen, W7EL
Richard Harrison
"So using the same analysis, you`d have to conclude that vertically
I`ll turn to the authors for a source of my contention.
Terman says in his 1955 edition on page 803:
"The ground wave is vertically polarized, because any horizontal
component of electric field in contact with the earth is short-circuited
by the earth."
And on page 808, Terman says:
"Examination of these vector diagrams shows that with a perfect
reflector the horizontal components of electric field will exactly
cancel each other at the surface of the perfect conductor. In contrast,
the vertical components of the electric field of the incident and
reflected waves do not cancel, but rather add at the reflector surface
with small values of earth reflection angle."
Richard Harrison
"So using the same analysis, you`d have to conclude that vertically
Earth isn`t perfectly conductive but even so permits propagation of
vertically polarized waves.
Another expert, Kraus says on page 412 of his 1950 edition of
"Antennas":
"The electric field of a wave traveling along a perfectly conducting
surface is perpendicular to the surface....However, if the surface is an
imperfect conductor, such as the earth`s surface or ground, the
electric-field lines have a forward tilt near the surface.... Hence, the
field at the surface has a vertical component Ey and a horizontal
component Ex. The component Ex is associated with that part of the wave
that enters the surface and is dissipated in heat. The Ey component
continues to travel along the surface.
Tim Perry
> On Thu, 26 Aug 2004 15:28:36 GMT, Richard Clark <kb7...@comcast.net>
wrote:
>
> >On Thu, 26 Aug 2004 13:16:07 GMT, Darrell Gordon W4CX
> ><w4cx....@arrl.net> wrote:
> >
> >>What are you guys using for HF measurements?
> >
> >
> >General Radio 1606-A: 400KHz - 60MHz, Resistance 0 - 1000 Ohms ą1%,
> >Reactance 0 - 5000/F Ohms ą2%.
> >
> >73's
> >Richard Clark, KB7QHC
>
> Hi Darrell,
>
> I was just about to tell you what I use, but Richard, above, beat me to
it. For
> HF measurements this bridge, the General Radio 1606-A, is the Cadillac of
all
> bridges. It 's been the bridge of choice for nearly every AM broadcast
engineer
> in determining t he impedance of AM broadcast antennas since it came on
the
> market in 1955.
i have yet to see one at a US broadcast station. the meter that is usually
found, and used is the delta OIB-1 or OIB-3
http://www.deltaelectronics.com/data/oib1&3.htm
It's very nearly the same as it's predecessor, the GR 916-A,
> which came out in the 1940's. It's what the AM antenna engineers used
prior to
> the 1606.
>
> You can find the 1606-A on eBay, and the price ranges from $200 to $1000.
> However, you also need a signal generator to feed it the signal it needs
to
> operate, plus your receiver as the signal detector.
>
> I also use more modern impedance measuring devices, such as
Hewlett-Packard's
> HP-4815 Vector Impedance Meter, and their HP 8405 Vector Voltmeter. These
two
> instruments are also laboratory grade quality. All of these instruments
far
> exceed the accuracy of the devices you listed.
>
> Hope this helps,
>
> Walt, W2DU
Roy Lewallen
analysis than the first one you put forth.
Roy Lewallen
Richard Harrison
"That`s a much better explanation of the phenomenon of ground wave
analysis than the first one you put forth."
True! Kraus was a much better explainer than I will ever be, I fear.
Walter Maxwell
wrote:
>
>"Walter Maxwell" <w2...@iag.net> wrote in message
>news:2g6si0519vch9jeeq...@4ax.com...
>snip
>> I was just about to tell you what I use, but Richard, above, beat me to
>it. For
>> HF measurements this bridge, the General Radio 1606-A, is the Cadillac of
>all
>> bridges. It 's been the bridge of choice for nearly every AM broadcast
>engineer
>> in determining t he impedance of AM broadcast antennas since it came on
>the
>> market in 1955.
>
>i have yet to see one at a US broadcast station. the meter that is usually
>found, and used is the delta OIB-1 or OIB-3
>http://www.deltaelectronics.com/data/oib1&3.htm
>
Hi Tim,
I can't disagree with you here, because my knowledge is from several years back.
I'm not familiar the Delta except by reputation--all I've heard is that it's a
good instrument. The demise of General Radio is probably one reason the GR
instrument is no longer the instrument of choice, so the dividing line between
use of the GR and the Delta probably defines the end of one era and the
beginning of another.
Walt, W2DU
Steve Nosko
> http://www.ifwtech.co.uk/g3sek
Ian, and others,
I have the 269 HF VHF UHF analyzer and noticed something strange. In
the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an
otherwise good 75 ohm load (please assume I know how to tell and I used a
low frequency to reduce errors) shows something like a 1.3 : 1 SWR. When I
called to ask about it, the first tech at MFJ seemed confused and clearly
did not understand. Another call, on another day resulted in a better tech,
but the response was to send it in for re-calibration. This also seems to
be a calculation rather than an adjustment, no?
Once you know Z it is a simple calculation to get to SWR for another Zo. Or
have I been smoking a bad brand...?
Woha! I see they have on line calibration manual for the 259B & 269 on
line!
http://www.mfjenterprises.com/MFJ-259Bcalibration.php
http://www.mfjenterprises.com/man/pdf/MFJ-269_Calibration.pdf
I don't see anything other than "watch the blinking SWR" .(sounds like a
British insult) for the Advance 3 "calibration".
--
Steve N, K,9;d, c. i My email has no u's.
Roy Lewallen
to 77 MHz when Z0 is set to 75 ohms.
Roy Lewallen, W7EL
Tim Perry
transmitter is the (usual) frequency source and interruptions to
transmissions can be brief or non-existent.
in typical use the bridge is inserted using a hot jack or J plug.
the engineer must be careful at all time to avoid touching exposed RF as the
resulting burns are painful and long lasting.
the meter itself has some effect on the circuit tuning: sometimes a
permanent version is installed at the common point of a phased array.
sometimes special jacks are employed that add a bit of inductance when the
meter is removed.
Ian White, G3SEK
>
> I have the 269 HF VHF UHF analyzer and noticed something strange.
>In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms,
>an otherwise good 75 ohm load (please assume I know how to tell and I
>used a low frequency to reduce errors) shows something like a 1.3 : 1
>SWR.
And it had correctly showed SWR=1.5 when Zo was set to 50 ohms?
>When I called to ask about it, the first tech at MFJ seemed confused
>and clearly did not understand. Another call, on another day resulted
>in a better tech, but the response was to send it in for
>re-calibration. This also seems to be a calculation rather than an
>adjustment, no?
>
>Once you know Z it is a simple calculation to get to SWR for another
>Zo. Or have I been smoking a bad brand...?
>
I didn't check this feature as part of the review, but it should be
simply the inverse ratio of whatever resistances you choose to define as
your Zo values.
>Woha! I see they have on line calibration manual for the 259B & 269
>on line!
>http://www.mfjenterprises.com/MFJ-259Bcalibration.php
>http://www.mfjenterprises.com/man/pdf/MFJ-269_Calibration.pdf
>
>I don't see anything other than "watch the blinking SWR" .(sounds like
>a British insult) for the Advance 3 "calibration".
>
The MFJ-269 had to go back after the review (which itself was a few
years ago) so unfortunately I'm no longer able to check your findings,
Steve.
But don't recalibrate it yet, because that would be stirring-in
additional variables which will muddy the waters right now. After the
present question has been resolved, you may be able to give the
calibration procedure a little more TLC than there was time for on the
production-line - but you'll need some precision standards to do it.
--
Walter Maxwell
wrote:
>snip
>> Hi Tim,
>>
>> I can't disagree with you here, because my knowledge is from several years
>back.
>> I'm not familiar the Delta except by reputation--all I've heard is that
>it's a
>> good instrument. The demise of General Radio is probably one reason the GR
>> instrument is no longer the instrument of choice, so the dividing line
>between
>> use of the GR and the Delta probably defines the end of one era and the
>> beginning of another.
>>
>> Walt, W2DU
>>
>in part, the OIB (Operating Impedance Bridge) is popular because the normal
>transmitter is the (usual) frequency source and interruptions to
>transmissions can be brief or non-existent.
>in typical use the bridge is inserted using a hot jack or J plug.
>the engineer must be careful at all time to avoid touching exposed RF as the
>resulting burns are painful and long lasting.
>the meter itself has some effect on the circuit tuning: sometimes a
>permanent version is installed at the common point of a phased array.
>sometimes special jacks are employed that add a bit of inductance when the
>meter is removed.
>
Thanks, Tim, for the update on the OIB. It did refresh my memory concerning the
meter being used while the transmitter is on the air. That I now recall.
Walt, W2DU
j...@power-net.net
I sent you an E-mail message (in response to a message you sent to me)
and received an automated message by return indicating that my message had
been placed in a "bad" folder.
Sorry for the post here.
73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Steve Nosko
3 @75 ohms. Either I better change my brand of smokes or the Micro forgot
how to do the calculation... Better go back and try again to see it I
goofed somewhere...but I've done that several times...... . . . . .
. .
Am I correct about this being simply a calculation?
--
Steve N, K,9;d, c. i My email has no u's.
"Roy Lewallen" <w7...@eznec.com> wrote in message
news:10j7i84...@corp.supernews.com...
Steve Nosko
> Steve Nosko wrote:
> >
> > I have the 269 HF VHF UHF analyzer and noticed something strange.
> >In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms,
> >an otherwise good 75 ohm load (please assume I know how to tell and I
> >used a low frequency to reduce errors) shows something like a 1.3 : 1
> >SWR.
>
> And it had correctly showed SWR=1.5 when Zo was set to 50 ohms?
Yep! An extensive sheck of known good loads showed that the MFJ was
working as expected with reasonable accuracy. I don't have numbers, but 50
ohm loads looked ok and SWR, Z etc all appeared to be reasonable. Just this
one problem. (I have access to Agilent "N" cal kits)
The problem is the I found nothing wrong when measuring in all the other
modes. Only this one problem and I believe this is a calculation in the
microprocessor, not anything that can be "calibrated" to correct. I was
asking if this is correct. I also see nothing in the MFJ cal procedure for
the 269 for this mode other than "watch the blinkin' SWR symbol" (I
indicates you have set a Zo other than 50.
Roy Lewallen
once you know the Z, you can calculate the SWR for any Z0. And you don't
need to know the sign of the reactance in order to do it. So that's
surely the way it's done.
Can't imagine that yours does the calculation different than mine. . .
hm, maybe it does. . .mine says "Ver. 1.24" when it starts up. What does
yours say?
Steve Nosko
past 1 year old. oops.
Steve
--
Steve N, K,9;d, c. i My email has no u's.
"Roy Lewallen" <w7...@eznec.com> wrote in message
news:10j9m66...@corp.supernews.com...