I'm trying to determine if using an antenna analyzer is technically a
violation of the telecommunications Code of Federal Regulations. Typical
antenna analyzers inject a incident CW or sweeping CW to the antenna and
measure its return loss (reflection). Very few frequency bands have a CW or
sweeping CW as their allowed modulation type. The way I see it is that by
using an antenna analyzer you are intentionally radiating an improper
modulation type that was allocated for the band and therefore you are in
violation of the Code of Federal Regulations.

Anyone have any thoughts on this topic?

By your logic a noise bridge would also be illegal. However in most places
there is a limit on the amount of power one can use before it requires
a license. Since an antenna analyzer puts out a few microwatts, if that,
no one seems to care.

My understanding is that the popular MFJ antenna analyzers generate
around 2 volts RMS of RF at their output port. This works out to
around 80 milliwatts into a 50-ohm load... comparable to what a small
QRP transmitter would deliver.

I do not have the capability to measure the power level of mine, but I
expect that it is less than a regenerative receiver.

I think that it's more than you might expect. These analyzers don't
use a tuned detector - they use a simple diode detector (admittedly
with low-threshold / "zero bias" Schottky diodes) and they need a
reasonably hefty signal. I've heard that there are some analyzers
which use some sort of mixer-and-filter arrangement to sample the RF
(thus allowing the analyzer to reject incidental off-frequency RF such
as the AM broadcast-band signals that render MFJ analyzers rather
useless on 80 and 160 meters) but I haven't seen one myself.

As to the issues of legality - IANAL, but I think that there's
probably a way to justify their use under the CFR.

For one thing: CW modulations are authorized under Part 97 on almost
all of the ham bands (everything other than 60 meters, I believe).
Stick to the bands on which you have operating privileges, and you're
probably safe there. Feel free to turn the analyzer on and off to
send your callsign in CW at the end of your test, if you're feeling
cautious :-)

For another: Part 97 specifically authorizes "test transmissions" on
any band authorized to the control operator (with restrictions on
pulse and spread-spectrum test transmissions).

For a third thing: it's quite possible that these devices would emit
a low-enough power level that they would qualify for use under Part 15
"intentional radiator" standards... and such devices are permitted to
operate in most frequency bands. Such devices to have maximum-power
limits, which are measured in microvolts-per-meter field strength at a
specified distance - limits and distances vary by frequency band.

For a fourth: they *might* also qualify for legal use under Part
18 (Industrial, Scientific, and Medical Equipment). These devices can
also operate in most frequency bands (although there are several
subbands which are specifically authorized for them and are thus
recommended), subject to maximum-field-strength limits similar to
those specified for Part 15 devices.

I doubt that the FCC has the inclination, desire, or resources to try
to forbid or limit the use of antenna analyzers. If they did, they'd
have to start raiding labs all over the country and confiscating
multi-thousand-dollar vector network analyzers, S-parameter test sets,
and so forth. The Benevolent Association of Agilent And Anritsu
Equipment Owners would no doubt start writing harsh letters to their
Congressmen :-)

In practice, I suspect that you're quite safe in using such devices as
long as you aren't causing harmful interference to licensed users of
the bands in question... and if you believe that you are, you should
of course cease transmission immijitly!

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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