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Author Topic: The MFJ analyzers look nice. They really do. I just don't have that money....  (Read 5858 times)
KB1TXK
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« on: May 31, 2011, 08:25:36 AM »

Any advice on an analyzer that is cheaper than MFJs?  At this point, all I really care about is resonant frequency.  I have an SWR/power meter already...and I'm not into phased arrays and all that jazz at the moment. I just want something that shows resonance to help me cut/adjust antennas
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VA3WXM
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« Reply #1 on: May 31, 2011, 08:33:43 AM »

A company called Autek made small, handheld analyzers at one point.  Not sure if they still do.  I recall them being cheaper than MFJ (is that possible?!)
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KB1TXK
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« Reply #2 on: May 31, 2011, 08:40:31 AM »

Thanks I'll check that out!

And yeah the MFJs are certainly cheaper than some of the other ones out there.   If I hadn't jsut spent $800 on a radio and tuner, I'd be getting one Sad

Plus I want something cheap I can hand down to someone someday Smiley
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AD4U
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« Reply #3 on: May 31, 2011, 09:17:27 AM »

You don't NEED an "antenna analyzer".  A decent SWR meter is really all you need. 

It is a wonder how all us "Old Timers" ever managed to radiate a signal before "antenna analyzers" came along.

HI!!

Dick  AD4U
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N1LO
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« Reply #4 on: May 31, 2011, 09:20:37 AM »

Think of it as a test instrument. The MFJ's do much more than just determine resonant frequency.

I got started inexpensively with a used mfj-249. It was immediately obvious that this device was completely indispensable! I've owned a 269 ever since they came out and have used it countless times for myself and to help friends. I also have Auteks, but find that the MFJ's analog meter is far faster and more intuitive to use when sweeping the frequencies/

Treat it with care, handle it like eggs, and it will last a long time and not become a cheap 'hand-me-down' that nobody wants. I don't loan it out for fear of damage or misuse, so I offer to bring it over to make measurements.

The cheapest way to go is to invite a friend who owns one to bring it over and provide them a meal in return!

Regards,

- - · · ·  M A R K · N 1 L O · · · - -
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KA5N
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« Reply #5 on: May 31, 2011, 09:50:21 AM »

If all you want is to find resonance then a noise bridge is the simplest thing going.  I thank Polomar (not the CB amp people) used to build them.  I homebrewed one back in the 60's that I still have from an article in 73 Magazine.  I am sure a web search will turn up a schematic.
Basically you need a tuning capacitor, a diode and a variable resistor and your tranceiver or receiver and away you go.  You can find the resonant frequency of an antenna and the impedance thereof.
Allen
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WB2EOD
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« Reply #6 on: May 31, 2011, 10:04:25 AM »

If you "into" antennas and are restricted to 1 piece of test equipment, this is probably the one to own. 
It is great for building, tuning and troubleshooting antennas. 
In addition it can be used to check coax for loss or faults such as shorts or opens.
It also has a frequency counter and a few other clever features
The manual is a free download from the MFJ website. 
You may want to look it over to get some idea of what this thing can do. 
If you end up using one, just remember DO NOT TRANSMIT INTO IT.

The big problem with mine is never remembering which of my friends has borrowed it.

73
WB2EOD
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WB6BYU
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« Reply #7 on: May 31, 2011, 10:48:32 AM »

On HF I used a dip meter to find the resonant frequency of an antenna - that would get me
close enough that I could use an SWR meter.  Between the two I tuned up lots of antennas.

Now I have one of the original MFJ-207(?) HF-only analyzers.  No fancy digital readout, just
allows me to read the SWR across the band.  You might find a used one for $50 or less.

True, such an SWR analyzer won't find a 5000 ohm resonant point on an antenna, but the
fancier analyzers won't, either.

In most cases simply finding the point of lowest SWR is adequate for antenna work.  The
advantage of an analyzer is that it can measure outside the ham bands.  They are also
convenient for taking measurements at the antenna, rather than through a long feedline
inside the shack, but I would just put a battery on my Argonaut to do that (or run a
wire from the key jack out to the antenna, put an SWR meter in line there, and ground
the key line to the coax shield to transmit.)

I do have a noise bridge around somewhere - they can be handy if you have a wide range
receiver and want to check out of band, but I've never found it particularly useful since
you need to use a receiver with it as a detector.
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K5LXP
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« Reply #8 on: May 31, 2011, 11:05:31 AM »

I bought my MFJ259B at a hamfest with nicads in it for $100.  I don't see a point in looking for anything cheaper for an instrument you can have and use for many years to come.


Mark K5LXP
Albuquerque, NM

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KG6MZS
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« Reply #9 on: May 31, 2011, 11:30:43 AM »

You don't NEED an "antenna analyzer".

Don't really "need" any radio gear.  I sure wouldn't want to be without my antenna analyzer.  Some of the best bucks I ever spent in the hobby.
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AC5UP
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« Reply #10 on: May 31, 2011, 12:05:38 PM »

If all you want is to find resonance then a noise bridge is the simplest thing going.

I'll vouch for that as I have one and the only problem I've had is in not using it often enough so each session is like a new learning experience. Aside from that, you can find resonance, impedance and reactance without much effort - but - you will need a portable all-band radio of some sort to work with it. Think in terms of a Grundig, SONY, Sangean, etc. It's also possible to use your transceiver's RX. Not as handy, but possible.

For more, click here: http://bama.edebris.com/manuals/palomar/bridge
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N3OX
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« Reply #11 on: May 31, 2011, 12:31:05 PM »

I think if you have a SWR meter and just need to tune a few HF antennas you probably should just stick with the SWR meter.  I think the analyzers have made people obsess a bit about true resonance, that is X=0, when the best adjustment for many antennas just needs to present low VSWR to the coax cable.

People will go on and on about how "low SWR doesn't mean it radiates," and that's true.  But getting the SWR as low as possible by trimming/tweaking for an antenna where you expect low SWR and for which you don't have HUGE coax cable losses is just fine, and almost always leads you to the optimum.  If you put up a dipole or a multiband vertical and stick to sane adjustments like trimming the dipole or adjusting the lengths of the vertical sections within their design range and a shunt matching coil, you will do just as well with a SWR meter.  There are only a few antennas where simply adjusting for low SWR is going to add lots of loss, and you won't necessarily be able to notice that even if you have an analyzer.  It's kind of a pathological weird situation.

It can be much FASTER to find the lowest SWR on mobile antennas, bigger shunt matched verticals, beta matched yagis, and other  antennas with shunt matching elements.  You can leave the shunt coil out, tune for a particular value of X (usually something like X= -j10 to X = -j20 for most situations) and put the shunt coil back in and only fiddle with that to get lowest SWR.  But if you juggle element length and coil stretching/compressing you can ALSO find the lowest SWR point.  It will just take longer.

For most HF antennas, especially simple direct-feed like dipoles or more complicated commercial antennas, a SWR meter is really all you need.  Even at VHF it's okay as long as you make sure you're shooting for very low SWR.  At VHF cable loss can mask extremely high SWR, but if you're unsure, measuring the SWR at the antenna can help there.  That isn't even necessary at HF.  IF you are putting up a dipole, hook the SWR meter up at the shack end, trim for the lowest SWR across the band, and get on the air. 

A MFJ analyzer is an incredibly versatile tool and a good value but I almost never use it to adjust anything for exact resonance Grin  It's just a good RF multimeter.  I would be lost without it, but that means I also kind of have a good idea what I NEED it for and what it's just nice for.  I use mine to measure coils, capacitors, transformers, and traps as much as I use it on actual antennas as finished.  In fact, with a combination of EZNEC, careful cutting, and the MFJ-259B for pre-tuning matching networks, I haven't had to trim an upper-HF antenna at all in a long time.

I still trim single element antennas like dipoles because it's faster than careful modeling.  It is nice to not have to run in and out of the house when trimming a dipole or adjusting a vertical, and it's nice to have the '259B when you need to set five matching networks for a multiband antenna (http://www.n3ox.net/projects/stepperswitch) but maybe you live with that while you're saving money a little at a time, or you borrow an analyzer if you're a set-and-forget kind of guy.

The analyzer can be a real time-saver if you're experimenting a lot, and allows a lot of room to grow by allowing you to measure coils and caps for homebrew matching networks and so forth.  But if you're just installing a few antennas and doing light experimentation with simpler types, the cost vs. usage tradeoff might not work out so well for you.  There are a few resonance zealots who will make you feel like you can get a better signal by knowing when X=0 but those people don't have a thorough understanding of the role of resonance in antenna systems and how VSWR relates to that in HF systems.
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KJ4FUU
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« Reply #12 on: May 31, 2011, 12:42:21 PM »

Because of money issues, I bought the MFJ-209, which works, but only because I had an old frequency counter I could connect to it. The dial wasn't all that close for the frequency under test.

You can check Hendricks out (qrpkits.com), and they have a deluxe antenna dipper, which will allow you to change the frequency and get an LED indicator (bright means no match, off means you are good). It's cheaper than the MFJ units. The only reason I don't have one is that it does have one SMT part, and while they claim it's not difficult to install, I can still see myself burning my fingers with it.

-- Tom
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VK2TIL
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« Reply #13 on: May 31, 2011, 01:52:17 PM »

A noise bridge is a very useful instrument; one can be home-brewed if you are so inclined.  See older editions of the Handbook for construction details.  I built my own version of the Handbook bridge many years ago.

VK3AQZ sells kits for a couple of very nice designs; if you had to buy the parts you would spend a substantial proportion of what he charges;

http://vk3aqzkits.com/

Even if you don't buy his product, Lou's site has a lot of information on noise bridges.

A kit for the VK5JST antenna analyser is also available here;

http://www.scarc.org.au/index.php?option=com_content&view=article&id=47&Itemid=27

I built one years ago and it's still working fine.
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KD8MJR
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« Reply #14 on: May 31, 2011, 04:40:41 PM »

If you mess around a lot with DIY stuff or help out a lot of friends it's a great tool to have but if your just stringing up a factory antenna for your own use, save the cash! You will use it for a few days and then it ends up in a drawer collecting dust.
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