John W. Brosnahan
broz at csn.org
Tue Apr 13 23:13:47 EDT 1993
Been gone for a couple of weeks and just want to add a couple of comments
about previous discussions. (The launch (WSMR) was delayed for a few weeks.
Fortunately it has rescheduled to just after Dayton, rather than during.
I guess I don't have any excuse not to prepare my transparencies for my
talk at the antenna forum.
TRAPS: The traps for multi-band Yagis are parallel resonant circuits that
contain a coil but no separate capacitor (typically). The metal cover provides
the capacitance and on some kinds of antennas (Hustler 4-BTV for instance) can
be changed to affect resonance. So don't take them apart without marking it so
that it can reinstalled properly. The Hy-Gain ones are not adjustable so
should be no problem to reassemble, (as you discovered) as long as some care
TAPE: The best tape to use is not Scotch 33 but Scotch 88. 88 is the all-
weather version that doesn't get brittle in the cold and the adhesive seems to
last much longer outdoors. Scotch-Kote everything and it will stay
together much longer.
PLASTI-DIP: I have found that Black (more UV resistent) Plasti-Dip (the stuff
to coat tool handles with) provides a very good covering for things
that can be dipped in it. (Or it can be painted on, but the results are
not as good.) When you split the center and shield of coax to make the
connections to a vertical or a dipole (thru some beads for a current balun)
you can dip the thing in a diluted (with paint thinner) batch of plasti-dip
and it will soak in nicely into the braid. This helps prevent wicking of
moisture down the coax. Dip it a 2nd and maybe even a 3rd time in a
full strength batch for a nice "rubbery" covering. I use crimp-on (with
solder, too) lugs on the braid and center conductor and put some masking
tape over them before dipping in order to clean off the plasti-dip easily.
The plasti-dip over the polyethylene dielectric keeps it from discoloring
in the sunlight. You can always use Scotch 88 over or under the plasti-
dip (or both) if you are paranoid or live under water.
POLE MOUNTING: Be careful when using anything associated with water pipe.
The pipe itself is not specified for structural use and the pipe fittings
(elbows, etc) are typically cast iron and pretty brittle, especially in
BIG GAS: I wasn't proposing running more than 1500 watts in order to make
up for the coax losses, only mentioning the issue raised by W6QHS in his
book. It seems to me that within the last decade the FCC did some
de-regulating and may have obsoleted the following paragraphs, but if my
memory is wrong, then the following sheds some new light on the subject.
I received a nice letter with copies of the appropriate "Report and
Order" of the FCC from Bill Cross AA3DI. FCC 83-345 33549 adopted
July 18, 1983 (PR Docket No. 82-624) states in the Appendix that part 97
is ammended to read:
paragraph 97.3 Definitions.
(1) Transmitter Power. The peak envelope power (output) present at the
antenna terminals (where the antenna feedline, or if no feedline is used,
the antenna, would be connected) of the transmitter. The term "transmitter"
includes any external radio frequency power amplifier which may be used.
I believe this to mean the power is measured at the transmitter end of
the coax rather than at the antenna end, but the statement is poorly
worded and doesn't make it perfectly clear to me. It is typed above as
it appears in the Report and Order. I stumbled my way through it and I
assume all of you did also.
Something more disturbing is the revision of Subparagraph (d)(6)(ii) of
(ii) No amplifier shall be capable of amplifying the input RF driving signal
by more than 15 decibels. (This gain limitation is determined by the ratio
of the RF output power of the amplifier where both signals are expressed
in peak envelope power output of less than 1,500 watts, the gain allowance
is reduced accordingly. For example, an amplifier with a designed peak
envelop output power of 500 watts shall not be capable of amplifying the
input RF driving signal by more than 10 decibels.
This seems to make tetrodes illegal! In my case, with a long run to
my remote shack and the mandatory feedline losses, I will be using a
solid state amp to get the 10-20 watts up to a 100 watts in order to drive
my finals. If these two stages are in the same box, then does my amp
have more than 15 dB gain and therefore is it illegal? I don't think
the intent was to make innovation illegal, only limit high gain amps
that might be used in CB. Note: this may only apply to type-accepted
amplifiers. Guess I will have to get a complete copy of the current
FCC rules and read up on this. Thanks again to Bill Cross, AA3DI, for
giving me something to think/worry about. Remember, this may all
Hey Fred, if you read this far, do you still need a room at Dayton? If
so I will try to look around again.
73 John W0UN broz at csn.org
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