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Wideband antennae for Spec Analyzer

I have just purchased a secondhand Advantest 3465, 100KHz to 8MHz spectrum analyzer.

Well, that was expensive, so I can't really afford any factory-made antennae at this time.

Can anyone please advise how I can make a wideband antenna, or limited series of same, that will work within this range for monitoring of environmental EMI?

Hopefully, a little more than just hanging a wire off the input. The relevant specs are below.

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Measurement range: +30 dBm to avg. display noise level Maximum safe input: Avg. continuous power (input ATT = 10 dB): +30 dBm (1 W) DC input: 0 V Display range: 10 × 10 div Log ;10, 5, 2, 1, 0.5/div Linear; 10% of reference range/div Reference level range: Log; ?105 dBm to +60 dBm (0.1 dB steps) Linear; 1.25 µV to 223 V (approx. 1% of full?scale steps) Input attenuator range: 0 to 70 dB (10 dB steps)

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Many thanks,

Jim Jeffery

Reply to
Jim Jeffery
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Me? I'd probably use a nonresonant shielded loop calibrated against a known good loop antenna (rented). If you need a preamp for it, dozens of opamps are good to 10 MHz. with a moderate voltage gain, run from a

9 volt battery inside of a cheap metal box.

If it is REALLY low cost you need, Altoids mint boxes make a pretty good shielded enclosure.

Jim

Reply to
RST Engineering

I think you meant 8Ghz.

These spectran antennas look good.

The problem is you need a calibrated/flat response from the antenna. I would rent, as Jim pointed out.

Cheers

Reply to
Martin Riddle

Here they show the internal configuration.

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Would this really be that difficult to approximate using some soldered brass rod?

Jim Jeffery

Reply to
Jim Jeffery

Really?

Antennas are easy. Calibrating them is not. You're going to need more than one for this range (assuming you meant 8GHz), though.

Reply to
krw

A log-periodic antenna is your best bet. They are relatively easy to make. Refer to these web pages for design info:

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Reply to
lektric.dan

Building a log periodic antenna isn't hard, see:

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However if your time is worth anything at all maybe you should buy one from the website you provided above.

Or, consider starting out with a simple dipole, with telescopic elements.

Additional useful info:

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-for-spectrum-analyzer

-- Joe

Reply to
J.A. Legris

Oh, that rather does make a difference in the answer, doesn't it?

Jim

Reply to
RST Engineering

OK, then the revised answer is to make a shielded loop to go up to 30 MHz. then a series of log-periodics from 30-100, 100-1000, and

1000-10G.

You *COULD* do 30-10G in one fell swoop, but the mechanicals get real hairy.

Jim

Reply to
RST Engineering

Great links. How about some less rigous methods for those who may not need calibration or directionality?

  1. A number of concentric circles glued on a piece of perspex. Each would have a gap so as not to be complete, and be oriented at 180 degress from the next one. Feed would be from one end of each, and wired in series.
  2. An array of a few dozen pieces of brass welding rod (different lengths) with one end of each soldered to a copper base plate. Or telescoping antennae if they need to be adjustable.

Worth a try or too simplistic?

Jim Jeffery

Reply to
Jim Jeffery

Another option, somewhat similar to (2), is a biconical antenna...

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has one description.

One of these would certainly serve for casual-RF-sniffing applications. Might even serve for crude measurement purposes, if you tested it against a well-calibrated antenna in a far-field or anechoic environment and drew up a conversion chart/graph.

--
Dave Platt                                    AE6EO
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Reply to
Dave Platt

Not to pick, but I admit it's a pet peeve of mine....

Antennas =3D useful things to transmit and receive radiofrequency energy Antennae =3D things you find on bugs!

Reply to
mpm

There are "fractal" antennas, but the only thing I know about them is that they're fractal. :-)

Good Luck! Rich

Reply to
Rich Grise

Can anyone elaborate upon the properties of this one ... tin foil "butterfly" antenna.

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If it is meant to be broadband, how are the attached LC components determined?

Thanks,

Jim Jeffery

Reply to
Jim Jeffery

Point it at the Sun. Nice white noise source, at least when it's high enough in the sky that the ionosphere doesn't mess you up.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
Reply to
Phil Hobbs

You might want to look at Wilmar Robert's measurement antennas.

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Kevin Gallimore

Reply to
axolotl

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