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It’s Time

Get your antenna in tip-top shape to survive the long winter
Time to:

Fix any weather damage
Put up that new antenna
Improve your 2 meter and 70 cm signal range
Get started on the HF bands

To do these, you will need to use an antenna analyzer

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What is an Antenna Analyzer?

Antenna Analyzer:

A device for measuring the impedance, Standing Wave Ratio (SWR), and other properties of an antenna or RF circuit versus frequency

Analyzers range from simple SWR only meters, to complex impedance meters, and 2-port vector network analyzers
Antenna analyzers are an important tool for any Ham putting up a new antenna or checking an old one
They have many other uses around your shack

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Range of Capabilities

Basic Analyzers (measure just impedance or SWR)

Measure antenna resonant frequency
Check antenna SWR at desired frequency

Advanced Analyzers (also measure impedance, reactance)

Z, R, X_C, and X_L help you know how to trim antenna including off-center fed ant.
Measure capacitors and inductors by X_C and X_L and frequency
Make a Dip-meter to check resonant circuits on PC board

2-Port Vector Network Analyzers

All the above plus direct measure of Z, R, C, L
Measure 2-port devices for gain, return loss, reflection coefficient, etc.
Can use to see filter passband, insertion loss, and out-of-band rejection
Find cable flaws (time-domain reflectometry)

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Three Views of the Same Thing

RL has greater resolution near low SWR.

See Nov 2022 QST

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Basic Antenna Analyzer

SWR Impedance Bridge

Frequency Generator

SWR display

Frequency Display

Tune

Freq Display

SWR Display

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Why use an antenna analyzer?

– Tune antenna
– Avoid “costly” mistakes when pruning antenna length
– Check your antenna against mfg. published specs
– Tune feedline
– Tune phasing “stubs”
– Troubleshoot problems
– Education – “demystify” your antenna system
– See if an antenna tuner will have the range you need

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Effects of High SWR

SWR at Antenna	Reflected RF Power Can Turn to Heat	RF Power Radiated
1:1	0%	100%
2:1	10%	90%
3:1	25%	75%
4:1	36%	64%
5:1	44%	56%

Turns precious RF power into heat in the transmission line or transmitter
Antenna tuner in the shack only satisfies the transmitter electronics,

RF power still heats the transmission line

To get all of the radiated RF power you paid for, tune and match your antenna

Table of possible power loss with lossy transmission line

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Antenna Tuner Only Partial Solution

Transceiver

Antenna Tuner

1:1

SWR 5:1

Transmitter happy, outputs 100W

Antenna tuner finds a match, outputs <90W

Up to 40W heats the cable

~50W radiated

Low loss transmission line helps ensure most of the RF power eventually gets radiated

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Other Uses for an Antenna Analyzer

Antenna bandwidth (SWR across frequency)
Feedpoint impedance
Coax cable loss
Ground loss
Adjust tuners and amplifier circuits and measure loss
Make a Dip meter to find circuit resonances
Measure phasing lines
Impedance of transmission lines
Measure balun loss
Inductor Q
TDR (Time Domain Reflectometry) cable shorts, opens, damage (VNA only)

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Many Analyzers Available

MFJ 269C - $399

MFJ 226 - $359

Rig Expert AA55 - $378

NanoVNA - $49 to $125

Advanced Analyzers

True 2-Port Vector Network Analyzer

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What to Buy

CARA has a couple of analyzers that can be borrowed, with/without technical assistance
If you find a working traditional analyzer (MFJ, Comet, …) at a hamfest for ~$25, that would be a good choice
Graphing analyzers are very desirable to see across the band
The NanoVNA full vector analyzer is only ~$50 to $125,

Comes in 2 sizes (2.8 and 4 inch screens)
Has a small learning curve for its use

R&L Electronics sells the 4-inch NanoVNA-H4 was $60, now $90

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