Perhaps the answer here is to only use the analyzer on bands that are
not in active use at the time, like say Noon on 75 meters. I'm
speaking of when propogation is dead on thise bands because of time of
day.

Would the legality of it change? Probably not, but by doing it that
way you would have minimized the possibility of intererfering with any
other users that could hear you.

On Sat, 25 Aug 2007 19:42:26 -0400, Walter Maxwell
wrote:

On Sat, 25 Aug 2007 08:31:08 -0500, Bob Miller wrote:

On Fri, 24 Aug 2007 18:50:30 -0700, Roy Lewallen
wrote:

Bob Miller wrote:

I have an Oak Hills Research WM-2 QRP Wattmeter, which includes a
0-100 milliwatt scale.

With an MFJ 269 Antenna Analyzer hooked to the transmitter side of the
wattmeter, and an MFJ dummy load hooked to the load side of the
wattmeter, I get a reading of 3 milliwatts forward, 0 milliwatts
reflected.

Not sure whether the FCC is concerned with signals at the 3 milliwatt
level...

Most if not all the part 15 rules are defined in terms of field
strength, not power. 3 mW is way, way more than enough to exceed some of
the limits on some frequencies, when connected to even a poor antenna.
For example, Part 15 shows, in 15.209, that intentional radiators aren't
allowed to produce a field strength greater than 100 uV/m (with
exceptions) at 3 meters from 30 - 88 Mhz. 3 milliwatts will produce
*1,000 times*, or 60 dB greater than, this amount when connected to an
isotropic antenna. Hook it to a dipole to get another few dB. The limit
for class A digital devices (one class of unintentional radiators) is
the same in that range, according to 15.109. So don't think that just
because you consider a signal to be QRP that it's legal.

FYI, I checked the MFJ-269 manual, and it claims: "a relatively pure
(harmonics better than -25dBc) signal of approximately 3 Vpp
(aproximately 20 milliwatts) into 50 ohms."

So my measurement of 3 milliwatts on the wattmeter could have been
low.

Bob
k5qwg



That said, I agree that chances of prosecution are zero for using these
devices unless serious and/or intentional interference results. And I
strongly agree with the folks who have said that the last thing you want
to do is force a specific ruling on the matter from the FCC.

Roy Lewallen, W7EL

During the 1960's I engineered the antenna systems that flew on the early TIROS weather satellites. The
antennas radiated both RHCP and LHCP. In the earthward direction the gain was approximately 3 dBi. At the
ground station I operated the antenna had a 16 dBd gain at the beacon frequency of 136 MHz The beacon xmtrs
output power was 5 mW. While the satellite was at maximum slant range (just over the horizon) of 1800 miles,
the signal level from the beacons was several dB over S9 on R-390 receivers with their associated frequency
down converters.

Walt,W2DU