[Lowfer] Ultimate LOWFER Transmitter?

[W2MXW]

At 03:28 AM 3/12/02 -0500, you wrote:
>At the risk of being a spoilsport (but at least I'll try not to be a wordy
>one)...
>
>For most serious LowFERs, the _first_ requirement of an "ultimate"
>transmitter these days is frequency agility, and ideally FSK ability as
>well.
Those requirements are certainly possible and reasonable.

>Type Acceptance on a unit is not a magic talisman.  It possesses no juju.
>It's not going to carry much more weight during a station inspection for a
>suspected violation than having a police association bumper sticker on your
>car does if you're stopped for doing 90 in a school zone.

That may certainly be true if someone is grossly in violation. That is bad 
karma! :-) Cert. isn't going to help if you're doing 10 watts or have a 
100' Beverage!  But there have been  cases I know of where an inspection 
was averted in the first place because the operator was using a Certified 
rig; basically a situation where they were called, the agent stating 
something to the effect of: "We heard you were transmitting on such-and 
such. What is the ID number of your transmitter...?" Upon furnishing the 
information the operators were never called back or visited. That can give 
peace of mind. Plus it is a mark of quality, because it means it meets 
FCC's basic requirements. Kind of like UL listing. And, if we want to sell 
it we have to get it Type Accepted anyway...you can't (legally) sell a Part 
15 intentional radiator in the US without it. Which means those "other 
guys" out there who haven't done so are skating on thin ice...


>Furthermore, the FCC equipment authorization will be invalidated anyway by
>many of the suggested features.  Remember, for manufactured equipment, no
>antenna substitutions are permitted!  Only one of the exact same type
>provided with the unit (the same type TESTED with the unit for
>certification, that is) may be attached.  Therefore, discussions of output
>coupling options are moot.

You're right about this. This is a toughie. However I think it's solvable 
with some thought. I have it on good authority that if a substitute antenna 
used is substantially electrically identical to the type with which it was 
approved it can be used without voiding the Certification; for example, if 
it was approved for use with a pipe 50 feet tall you could substitute any 
pipe of the same dimensions, it doesn't have to be a specific brand of pipe 
and I doubt that small changes in dimensions are an issue (as long as the 
length isn't exceeded). With the AM rig as it is we've had issues like 
suppliers of the original antenna discontinuing same and having to 
substitute another which was similar but not identical and there was no 
problem with doing so.
I suggest a method which might be to get the unit certified thus: mount the 
unit atop a 49 foot grounded mast to which it in turn is grounded ('inverse 
feed" as I call it) and with nothing but a capacity hat attached to the 
"antenna" terminal. (Whip antennas as used in the original version really 
are more of a capacitance than anything else anyway). So you get a sort of 
"top loaded" system (assuming we were to use the present design having the 
coil internal to the transmitter which performs the function of a loading 
coil but is legal because it's part of the transmitter) which is very 
efficient system since the mast carries current up it thus does more of the 
radiating than a typical 'base loaded' system. If it can be tested and 
approved in this manner then it could be used atop any mast of similar 
height and diameter and could be either supplied with a capacity hat as a 
standard item, or a homebrew one essentially the same as the original (in 
terms of capacitance and physical dimensions both of which are 
interrelated) could be used in accordance with the above rule 
interpretation that it's okay if it's substantially the same.
I know that some Lowfers may not want to be wedded to a specific antenna 
design but I don't think many would mind because it is a simple yet 
efficient design. Whaddya think?

>As for the multiple amplifier concept, I also call your attention to Section
>15.204, External radio frequency power amplifiers and antenna modifications,
>paragraph (b):
>
>"A transmission system consisting of an intentional radiator, an external
>radio frequency power amplifier, and an antenna, may be authorized, marketed
>and used under this part. However, when a transmission system is authorized
>as a system, IT MUST ALWAYS BE MARKETED AS A COMPLETE SYSTEM AND MUST ALWAYS
>BE USED IN THE CONFIGURATION IN WHICH IT WAS AUTHORIZED.  An external radio
>frequency power amplifier shall be marketed ONLY IN THE SYSTEM CONFIGURATION
>with which the amplifier is authorized and shall not be marketed as a
>separate product."  (emphasis mine)
>
>In other words, if he wants to market it various such versions, he will have
>to test it in EACH such a configuration, and sell it in exactly the
>configurations as tested.  Sell a two-output version, get Type Acceptance
>for a two-output version; sell a four-output version, get Type Acceptance on
>the four-output version; etc.

I think you misunderstood although this is good information cogent to an 
ongoing argument we've been having on another forum, so thanks! :-)
The system as-is is Certified to be used in the manner I described but each 
unit has only one output, and each is a standalone unit not just an RF 
power amp. They can share carrier from a master unit (or not, each can have 
it's own xtal and can be trimmed to exact freq.) but that master when used 
as such is also a standalone unit not just an oscillator. These things are 
whole transmitters in other words, not piece parts of a system.
I assumed that most Lowfers wouldn't want this option but only mentioned it 
anyway just-in-case.

>Now, don't anybody go writing about getting out your flame-retardant suits!
>:-)
>
>There's no putdown here, just a healthy dose of reality.  It simply sounds
>like a very costly project to me, given the number of active or potentially
>active LowFERs; and, given what would have to be incorporated in such a unit
>to be considered "ultimate" by most any current LowFER's standards.

Again, I think you misunderstood, or maybe I was not as clear as I could've 
been (hey, it was late at night, whaddya want?... :-)
There doesn't have to be all these options, but just those which most 
Lowfers agree on as necessary for a good rig. In other words, there 
wouldn't be like 27 different models but just one, which incorporates all 
the desired features (within reason). Mutually exclusive features like 
conflicting antenna output circuits would be decided upon by whichever had 
the most support; only that one would appear in the finished product. For 
example, we wouldn't be making a model with a pi-net output plus a model 
with the present hi-Z transformer output plus a low-Z direct output, no 
way. That'd be WAY too costly. We'd be making one model which incorporates 
the design which by democratic 'vote' proved most popular (the most people 
wanted it).
I realize it can't be all things to all people so maybe the term "Ultimate" 
is inappropriate but I should say "relatively complete and satisfactory for 
the majority".

73, Jon W2MXW