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Old February 7th 06, 08:40 PM posted to rec.radio.amateur.antenna
chris
 
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Default Antenna analyzer- no MW?

I've been thinking about springing for an MFJ (or other) antenna
analyzer
to check on the myriad antenna's I've got around the place.
I noticed that most of the analyzers on the market (like the MFJ-269,
for ~$350.00)
only go down to 1.8 MHz. I do a lot of work with xtal radio's
(DX'ing), and have a lot of different AM (MW) antenna's strewn about
the property. I was wondering why they cut that portion out of their
instrument? No demand? Too exotic?
Does anyone know if the analyzer could be modified (add some
inductance, etc. somewhere) to bring it down to about 500kc? Thanks!
Chris, AI4MI

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Old February 7th 06, 09:42 PM posted to rec.radio.amateur.antenna
 
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Default Antenna analyzer- no MW?

instrument? No demand? Too exotic?
Does anyone know if the analyzer could be modified (add some
inductance, etc. somewhere) to bring it down to about 500kc? Thanks!


Another thing to think about: most of the analyzers around are pretty
much useless on low freqs anyway due to interference from AM broadcast
signals.

I recently finished shunt feeding my tower for 160m, and found that
my AEA CIA analyzer was completely useless trying to measure the feed
impedance. In the end I just used a regular swr meter to adjust the
shunt feed. I don't remember exactly how low the AEA goes, but it is
below 1.8 MHz.

Tor
N4OGW/5

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Old February 7th 06, 09:47 PM posted to rec.radio.amateur.antenna
Wes Stewart
 
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Default Antenna analyzer- no MW?

On 7 Feb 2006 11:40:57 -0800, "chris" wrote:

I've been thinking about springing for an MFJ (or other) antenna
analyzer
to check on the myriad antenna's I've got around the place.
I noticed that most of the analyzers on the market (like the MFJ-269,
for ~$350.00)
only go down to 1.8 MHz. I do a lot of work with xtal radio's
(DX'ing), and have a lot of different AM (MW) antenna's strewn about
the property. I was wondering why they cut that portion out of their
instrument? No demand? Too exotic?
Does anyone know if the analyzer could be modified (add some
inductance, etc. somewhere) to bring it down to about 500kc? Thanks!
Chris, AI4MI


If you are not adverse to building (I don't know why a ham would be)
look at the N2PK network analyzer. www.n2pk.com



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Old February 8th 06, 02:48 AM posted to rec.radio.amateur.antenna
Dan Andersson
 
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Default Antenna analyzer- no MW?

chris wrote:

I've been thinking about springing for an MFJ (or other) antenna
analyzer
to check on the myriad antenna's I've got around the place.
I noticed that most of the analyzers on the market (like the MFJ-269,
for ~$350.00)
only go down to 1.8 MHz. I do a lot of work with xtal radio's
(DX'ing), and have a lot of different AM (MW) antenna's strewn about
the property. I was wondering why they cut that portion out of their
instrument? No demand? Too exotic?
Does anyone know if the analyzer could be modified (add some
inductance, etc. somewhere) to bring it down to about 500kc? Thanks!
Chris, AI4MI




Don't panic!

There is an Italian analyzer, 0-60MHz for about 150€ ( 180 US $ ) which is
based on the AD9851 from analog devices.

You need a computer so it's not a handheld.

It's a "half VNA", giving +/- 90 degrees phase info but that is normally not
a problem as it's easy to find out the sign anyway.

A new version is coming soon and covers 0.1 Hz to 160 MHz. I think I saw a
price of 240€ on that one.

The TenTec TAPR VNA, 0-100 MHz is a "real" VNA with full quadrature 360
degree phase info.

However, you do still need a computer.



Cheers

Dan / M0DFI


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Old February 8th 06, 04:07 AM posted to rec.radio.amateur.antenna
Randall Gawtry
 
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Default Antenna analyzer- no MW?

In article . com, "chris" wrote:
I've been thinking about springing for an MFJ (or other) antenna
analyzer
to check on the myriad antenna's I've got around the place.
I noticed that most of the analyzers on the market (like the MFJ-269,
for ~$350.00)
only go down to 1.8 MHz. I do a lot of work with xtal radio's
(DX'ing), and have a lot of different AM (MW) antenna's strewn about
the property. I was wondering why they cut that portion out of their
instrument? No demand? Too exotic?
Does anyone know if the analyzer could be modified (add some
inductance, etc. somewhere) to bring it down to about 500kc? Thanks!
Chris, AI4MI


take a look at:
http://www.timewave.com/TZ-900.html

Randy, K0CBH
Timewave
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Old February 8th 06, 07:15 AM posted to rec.radio.amateur.antenna
 
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Default Antenna analyzer- no MW?

Chris,

The problem with low cost analyzers is that they use broadband detector
diodes. Strong local AM radio stations will cause an output from these
diodes and generate erroneus results. In fact, MFJ suggests a highpass
filter before the instrument in order to alleviate this problem (in
areas with strong local AM stations). MFJ discusses this issue in the
MFJ-259B manual which is a free download @
http://www.mfjenterprises.com/manuals.php.

However, a German ham has modified his unit for operation from 40 kHz
to 1.8 mHz. This is not a trivial mod and it is described on page 88
of his manual @
http://www.darc.de/distrikte/f/27/MF...andbuch1v4.pdf

Unfortunately it is all in German so you will have to use Google to
translate the appropriate sections. BTW - this is the most
comprehensive user manual for this analyzer available anywhere.
Includes testing, calibration, schematic diagram, numerous mods,
operating tips and techniques, and how to build accessories.

Hope this helps - Roger

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