Antenna Analyzers/Old QST magazines
Hang Kim Yam
-----------------
I was browsing through the CQ Amateur Radio magazine (August 94) and noticed
the following products for analyzing antennae:
SWR-121 Antenna Analyzers by AEA, Inc.
RF Analyst by Autek Research
I would like to lay my hands on one of them, but would like to find out more from
those who have used them. The only antenna analyzing tool I have is MFJ's
antenna bridge bought about four years ago. Together with one of
Optoelectronics' frequency counters, I am quite happy using it except that
the antenna bridge does not provide me with information about an antenna's
inductance or capacitance.
Information on these and other analyzers (which I am not aware of) would be
greatly appreciated.
Old QST magazines
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I read in the ARRL antenna handbook that there used to be some articles on
constructing coaxial traps in the QST magazine (probably some issues in
1981). It would be greatly appreciated if someone could advise me if it is
still possible to find these articles. Are there any CD-ROMs which are
compilation of past QST and/or CQ magazines?
Lastly, I would also like to find out if ARRL membership is opened to
foreign radio amateurs.
Thank you for your time in reading this posting.
73s de 9V1WI (Hang)
Gary Coffman
>In article <37j4df$c...@nova.np.ac.sg>, h...@np.ac.sg (Hang Kim Yam) writes:
>
>>SWR-121 Antenna Analyzers by AEA, Inc.
>>RF Analyst by Autek Research
>
>tuning our field day antenna. Sure makes it easy. The Autek is fairly
>new but have heard good things about it and I like the price. I am leaning
>toward the Autek because of that and the size (very small).
I have the AEA (the VHF/UHF version). It's an excellent tool, but it
does have some limitations. The primary problem is that it can't deal
with VSWRs over 10:1, IE 50 db return loss. That limits its usefulness
for fine tweaking cavities and stubs. It does make rough tuning of
duplexers really quick and easy though.
All it displays is a sweep of VSWR vs frequency, there is no direct
readout of complex vector impedance. To derive those you need some
additional parts (L or C components), and the ever popular Smith
Chart. The center frequency and swept span can be entered from the
keyboard. A zero span can be entered which allows spot VSWR reading
or use as a signal source. The unit outputs 1 mW, and is nicely
accurate and stable. In zero span mode it puts a "chirp" FM modulated
tone on the carrier. That is absent in swept mode.
The unit has a computer interface that allows it to operate under
computer control. I haven't tried this out yet, but it should allow
you to do automated proof of performance testing on antenna systems
and record the results to disk.
Like all broadband bridge based VSWR instruments, the Antenna Analyst
can be fooled by high RF fields from nearby transmitters. When another
transmitter on the site keys up, a general rise in the VSWR curve
displayed on the LCD will be noted. The mins and maxs are still in
the same places, but their absolute values will be altered. This
can be a nuisance, but usually isn't a serious limitation.
In short, this is a specialized instrument for doing swept VSWR
plots in quasi-realtime. With the proper accessory equipment, and
access to the Smith Chart, many of the things you want to know
about antennas, transmission lines, stubs, and cavities can be
determined. It's no HP vector impedance analyzer, but then it
doesn't cost like one either. Recomended for those who know how
to use the capabilities offered.
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | emory!kd4nc!ke4zv!gary
534 Shannon Way | Guaranteed! | ga...@ke4zv.atl.ga.us
Lawrenceville, GA 30244 | |
Gary Coffman
>Gary Coffman KE4ZV (ga...@ke4zv.atl.ga.us) wrote:
>
>: I have the AEA (the VHF/UHF version). It's an excellent tool, but it
>: does have some limitations. The primary problem is that it can't deal
>: with VSWRs over 10:1, IE 50 db return loss. That limits its usefulness
>: for fine tweaking cavities and stubs. It does make rough tuning of
>: duplexers really quick and easy though.
>
Not me. :-)
What I *meant* to say was that it can't display VSWR over 10:1 *or*
return losses > 50db. The former is more of a limitation than the
latter.
JimKD0AV
>SWR-121 Antenna Analyzers by AEA, Inc.
>RF Analyst by Autek Research
I have heard great things about both of them. We used the AEA version for
tuning our field day antenna. Sure makes it easy. The Autek is fairly
new but have heard good things about it and I like the price. I am leaning
toward the Autek because of that and the size (very small).
73 es GL,
Jim KD0AV
mor...@ipers1.e-technik.uni-stuttgart.de
Zack, I bet its a typo. Moritz DL5UH
Zack Lau (KH6CP)
: I have the AEA (the VHF/UHF version). It's an excellent tool, but it
: does have some limitations. The primary problem is that it can't deal
: with VSWRs over 10:1, IE 50 db return loss. That limits its usefulness
: for fine tweaking cavities and stubs. It does make rough tuning of
: duplexers really quick and easy though.
I wonder if anyone understood this?
Useful Return loss to SWR Table
Return loss SWR
20 dB 1.222
10 dB 1.925
6 dB 3.00
3 dB 5.83
Notice that 50 dB isn't on the chart. Most directional couplers aren't
able to separate forward and reverse power that accurately, so I don't
consider it useful. You can measure it by hooking an accurate 50 ohm
reference loading and seeing what reflected power is measured. My
guess is that a directivity of 15 to 30 dB is typical for amateur
equipment. Note that 15 dB isn't very good. A plot of a good design
appears in January 1987 QST, p. 20. The directivity is better than
35 dB in the HF/MF bands and 26 dB on 6 meters.
SWR is useful for talking about really large mismatches, while return
loss is better suited for talking about small ones.
--
Zack Lau KH6CP/1 2 way QRP WAS
8 States on 10 GHz
Internet: zl...@arrl.org 10 grids on 2304 MHz
Ian G3SEK
writes about the AEA version:
> What I *meant* to say was that it can't display VSWR over 10:1 *or*
> return losses > 50db. The former is more of a limitation than the
> latter.
Since the errors in VSWR/return loss measurements increase rapidly at
both low and high VSWRs (high and low return losses, respectively)
it seems very likely that the readings are unreliable long before they
hit the limits built into the display software.
After all, it needs precision lab equipment to measure *real* return
losses better than 35-40dB, and the same applies at the opposite end of
the scale too.
Question is: what kind of bridge or other vector impedance sensor circuit
is inside the Autek and AEA instruments? Maybe it's different at HF
and VHF, but the RF circuit is the interesting part - the rest is just an
ADC and software.
Come on, Gary, let's see your company break one open!
73 from Ian G3SEK | Editor, _The_VHF/UHF_DX_Book_
Abingdon, England |
g3...@ifwtech.demon.co.uk | "In Practice" columnist for RadCom (RSGB)
Ronald Miranda
>Antenna Analyzers
>-----------------
>I was browsing through the CQ Amateur Radio magazine (August 94) and noticed
>the following products for analyzing antennae:
>
>SWR-121 Antenna Analyzers by AEA, Inc.
analyzer, rather it's a swr analyzer, now if it could plot r+jx or r-jx i'd buy
it in a hot second but at $400 dollars its difficult to justify, but he who dies
with the most toys wins so I will probably get one. if/when I do I will post a
report on it. I just ordered the new aea dm1 deviation meter interested in a
user report on that? you mentioned a mfj antenna bridge but not the model. I
have and use a mfj 249, it works well to analyze swr. and a palomar noise
bridge to get r+jx but only
works to 100mhz. and I do mostly vhf and uhf. if I could find one that worked
above 100 mhz I would be satisfied.
73 Ron n6tft
Ronald Miranda
and advertisment
what mag and issue! or does autek list a phone number.
73 Ron n6tft
Ronald Miranda
>Zack Lau KH6CP/1 2 way QRP WAS
> 8 States on 10 GHz
>Internet: zl...@arrl.org 10 grids on 2304 MHz
and wondered if you could give any equip. recomendations and why. what would you
buy if you could afford it. I am also interested in using it on point to point
packet.
73 Ron n6tft