"Leland C. Scott" wrote:
If somebody says their amp is "clean" well the only sure way to know is
to test it with a spectrum analyzer. If you look at reviews for Ham
rigs, and power amplifiers in particular, you will see spectrum analyzer
screen shots so the buyers can see for themselves just how clean the
output happens to be. And I haven't seen a spectrum analyzer screen shot
for a 11m solid state amplifier yet. If you know of any it would be
interesting to see them.

While I've never used a spectrum analyzer on it, my tube type Collins
30L-1 amp seems to be very clean. It's the only amp I've had that
doesn't interfere with broadcast TV on channel five. So I agree with
you on the tube amp summary.

Leland wrote:
(Twist the amp doesn't have to be class "C" to cause problems. Even a
class "B" linear amp is not completely clean. In particular solid state
amps are a problem because many are push-pull designs with no filtering
on the output.)

_
I take your word for it.
I mentioned the class only because of the myriad of posts condemning the
class C amps.
What is push-pull design?


_



(A push-pull design has low levels of even harmonic output since the
even order signals cancel out in the output transformer. And that is
only for "well matched" power transistors.)

_
I guess that sort of answers my previous question.....but is something
that is not well matched better than a push-pull design, or am I
thoroughly lost here?


_
( The problem with the push-pull design is the odd order harmonics are
not attenuated at all! If you care to look at Ham rigs that use wide
band solid state push-pull amplifier output for HF operation you will
see band pass filters on the output.)

_
Ahhhh,,,,that explains it.

_

( In fact these filters are switched in and out depending on the band in
use. That's how the manufactures keep the output clean enough to meet
FCC specifications.
Tube amplifiers are another story. These amplifiers can be relativity
clean IF the output is designed correctly. The critical section is the
output matching circuit. This circuit performs two important functions;
load matching and harmonic filtering. Some of the posters on this board
in the past don't seem to grasp these two ideas well. They seem to think
that if the amp loads up OK then all is well - not true. If you go
through the math you will discover that there is no unique solution for
the value of the matching section component values. So how do the
designers pick the values they do? They pick an operation "Q" for the
matching section, that forces a particular value for the components. The
significance of the "Q" value is it is a measure of how frequency
selective the matching section becomes. The higher the "Q" the sharper
the response becomes, thus the less harmonic energy is coupled to the
output. Pick a "Q" too low and you have significant harmonic output from
the amplifier. Pick a value too high makes the amplifier a pain to use,
in other words the amplifier has to be retuned for small shifts in
operating frequency. From either experience, or through detailed and
complex calculations, acceptable values for "Q" have been determined
that would yield a tube amplifier matching circuit that is likely to
have acceptably low levels of harmonic output content. )
_
Hell, someone should have solicited your opinion long ago on this
matter,,,so here goes.....what type low power tube amp (say 100 to 250
watts), if any, would you recommend for 10 meter?
_

(If somebody says their amp is "clean" well the only sure way to know is
to test it with a spectrum analyzer.)
_
Yea,,,,guess so. When I first used an amp, I asked my neighbors if they
heard so much as an errant erratic noise anywhere, to let me know. Years
ago I had a neighbor tell me she could hear me on a cordless phone or pc
speakers (can't remember which) and she declined any action on by behalf
to rectify the situation. I think she enjoyed listening. Nevertheless, I
made some changes because I thought that if she could hear me, them
others could, too. A tower and new antenna changed everything.


-

( If you look at reviews for Ham rigs, and power amplifiers in
particular, you will see spectrum analyzer screen shots so the buyers
can see for themselves just how clean the output happens to be. And I
haven't seen a spectrum analyzer screen shot for a 11m solid state
amplifier yet. If you know of any it would be interesting to see them. )

-

I don't. There is no question some of those high drive competition amps
are dirty as hell. While I would never use one for dx, I admit a
fondness for a shoot-out.


--
Leland C. Scott
KC8LDO
Wireless Network
Mobile computing
on the go

"Dave Hall" wrote in message
...
On Mon, 20 Sep 2004 00:33:28 -0400, "Leland C. Scott"
wrote:


"Glenn S." wrote in message
.. .

Which omnidirectional base antenna will put out the least TV
and telephone interference in the neighborhood?

It doesn't depend on the antenna almost at all. The main cause of
interference is from three sources. One a dirty transmitter, the second
is
from receiver front end over load, and the third is from RF getting in to
the electronics directly.

That's not entirely true. The antenna DOES have a part to play in the
whole mess. Some of the "stick"-type antennas, such as the A-99, have
poor decoupling and this allows for significant coaxial shield
radiation. Some of these antennas also concentrate a good portion of
their near field radiation in places where it would exacerbate front
end overload or couple R.F. into house wiring.

An otherwise clean transmitter coupled to an antenna with the above
characteristics can cross the line between no RFI and significant RFI.
In some cases, this can be mitigated somewhat by moving the antenna
(usually raising it) to another area, where it's radiation will not
couple as much R.F. into neighboring premises. A better solution would
be to run an antenna with ground plane radials, such as a Sigma 5/8
wave or similar.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

That would be true of course for his own situation, the classic RF in the
shack problem, but he specifcaly asked about interference to the local
neighborhood if you re-read his post. In that case I doubt the antenna type
will have any significant impact.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft

That would be true of course for his own situation, the classic RF in the
shack problem, but he specifcaly asked about interference to the local
neighborhood if you re-read his post. In that case I doubt the antenna
type
will have any significant impact.

Rf on the feedline will be radiated through the whole path, and probably
much lower and closer to the neighbor. RF on the feedline is never a good
thing.

--
KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR

On Mon, 20 Sep 2004 23:01:30 -0400, "Leland C. Scott"
wrote:


"Dave Hall" wrote in message
.. .
On Mon, 20 Sep 2004 00:33:28 -0400, "Leland C. Scott"
wrote:


"Glenn S." wrote in message
.. .

Which omnidirectional base antenna will put out the least TV
and telephone interference in the neighborhood?

It doesn't depend on the antenna almost at all. The main cause of
interference is from three sources. One a dirty transmitter, the second
is
from receiver front end over load, and the third is from RF getting in to
the electronics directly.

That's not entirely true. The antenna DOES have a part to play in the
whole mess. Some of the "stick"-type antennas, such as the A-99, have
poor decoupling and this allows for significant coaxial shield
radiation. Some of these antennas also concentrate a good portion of
their near field radiation in places where it would exacerbate front
end overload or couple R.F. into house wiring.

An otherwise clean transmitter coupled to an antenna with the above
characteristics can cross the line between no RFI and significant RFI.
In some cases, this can be mitigated somewhat by moving the antenna
(usually raising it) to another area, where it's radiation will not
couple as much R.F. into neighboring premises. A better solution would
be to run an antenna with ground plane radials, such as a Sigma 5/8
wave or similar.

That would be true of course for his own situation, the classic RF in the
shack problem, but he specifcaly asked about interference to the local
neighborhood if you re-read his post. In that case I doubt the antenna type
will have any significant impact.

If you live in a fairly densely populated area (1/4 acre lots) the
near field will affect the neighbors as much as your own shack. I've
known people who have switched from an A-99 to a 5/8th wave ground
plane and have solved RFI problems. Nothing else changed, just the
antenna.

Antennas do not "create" harmonics or other spurious signals. But some
may be more "friendly" to radiating a second or third harmonic. Their
near field radiation pattern and coaxial decoupling contribute to the
near field strength of a signal. Due to the characteristics of some of
the most infamous antennas, they may radiate the same amount of R.F.
into nearby structures while running 4 watts, as another type of
antenna may do with 100 watts or more.

This just illustrates that there are many facets of a radio station
that need to be looked at when troubleshooting RFI. Everyone is aware
of "dirty" transmitters, and most people are aware that consumer
electronics are not particularly well designed with RF immunity in
mind. But once you've proven that the transmitter is "clean", and you
still have an RFI problem, you have to consider other options. Your
mission is to minimize the amount of RF which gets into neighboring
homes. If raising or moving the antenna to a place where it couples
less RF into a home may just do the trick. Changing the antenna to a
better design may accomplish the same thing. Good RF grounding may
also minimize RFI. There is no "one size fits all" solution.

Dave
"Sandbagger"
http://home.ptd.net/~n3cvj

Antennas do not "create" harmonics or other spurious signals. But some
may be more "friendly" to radiating a second or third harmonic. Their
near field radiation pattern and coaxial decoupling contribute to the
near field strength of a signal. Due to the characteristics of some of
the most infamous antennas, they may radiate the same amount of R.F.
into nearby structures while running 4 watts, as another type of
antenna may do with 100 watts or more.

Bingo.

First, don't make noise. (clean rig)
Second, don't radiate noise. (resonant antenna)
Third, use an antenna pattern and feedline decoupling, so that the radiated
energy is up and away from the vulnerable system.

Distance, because of the inverse square law, is your friend. Double the
distance between the radiator and the target, and the signal drops to 1/4 of
what it was.

If raising or moving the antenna to a place where it couples
less RF into a home may just do the trick. Changing the antenna to a
better design may accomplish the same thing. Good RF grounding may
also minimize RFI. There is no "one size fits all" solution.

Another less often appreciated point, fixing any one thing may make an
improvement, but not solve the problem. Then the perception is that the fix
"didn't help" or "was worthless".
Old engineering maxim, if you can't measure it, you can't improve it,
certainly applies.

--
KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR

Which omnidirectional base antenna will put out the least TV
and telephone interference in the neighborhood?

A resonant one, properly decoupled from the feedline.

Someone with an antenna analyzer can check this for you, you're not just
looking for low SWR, you're looking for little or no reactive component to
the impedance in that band.

As an extreme bad example, I saw a radio shack salesman explain to a
customer how he could use their discone antenna (the one without the top
element!) for CB.
That antenna is dramatically too small to be resonant on 11m, it would have
just been an efficient radiator for any VHF-UHF band harmonics and noise
that the rig might produce.



--
KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR

From: (itoldyouiamnotiamnotgeorge)
(Twistedhed) wrote in news:20940-41504213-125
@storefull-3252.bay.webtv.net:
Hey Twist, that's N8WWM you're responding to. _
Whoops,,,,,my sincere apologies to George. I caught it on the other post
where he addressed his arrest record via being a keyclown, but somehow
missed it here.

your apologizing to "george"



Yes, Mopar pointed out N8WWM is having problems again,,,his posts and
yours are remarkably similar at times..angry, hostile, insultive, and
remarkably delusional.



there is no

george



Landshark proved otherwise.


here never has been



See above.



but Ill give you time



Oh, thank you.


you

finally admit you have been falsely accusing

me of posting as Iam not george,



I said nothing of the sort. I apologized to you for honestly mistaking
one of Dogie's hostile posts as your own.


when I have told you It isn't me.


You have told many folks on this group many things. Nothing you say pans
out. That's Just The Way It Is (nod to Bruce Hornsby).