The nitrogen was for the transmission line.

Regards
Gary

On Fri, 30 Jan 2004 22:03:22 -0500, "Doug Dotson"
wrote:

Thanks for the clarification Larry. I was pretty sure that modern
transmitter technology wasn't something I had in a dream. I was up
in Fairbanks a couple years ago and I suspect that keeping
the finals cool isn't much of a problem there My father was
the engineer for a UHF station back in the late 50's. He told
stories of having to run out and get bottles of Nitrogen to keep
the finals going. Life is much simpler now.

Doug, k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
Er, ah, Bruce? There are no "finals" any more. The 50KW transmitter
is just a switching power supply from Harris.....take a look at:
http://www.geocities.com/aaron_white/inside.html
It's all done by that big board switching the modules on and off at
the audio rate, in sequence. See those two little powertab
transistors on the copper heat sink? THOSE ARE THE FINALS!

If a module fails, the computer simply bypasses it and uses another
module (there are spares) until someone shows up at the transmitter to
look for the failure lights. They don't even shut down the
transmitter to swap them out, any more. Hot swaps just like a
computer...(c;

The two PC boards on the door are the "modulator", the drivers for the
modules creating the RF. It's so efficient it's cooled with small
FANS! To produce a 50,000 watt carrier, it requires only 55,000 watts
of AC power from the power company, not the 120KW we were accustomed
to. No massive filament power, no blood-red plates being cooled with
water, no cooling pond.

The RF modules (there are 144 of them in a Harris DX-50, 50KW
transmitter) look like:
http://www.geocities.com/aaron_white/dxmod.html
Some are 100W, 500W, 1KW, 2KW. The audio is simply converted into how
many modules run at this instant in time. The modules, themselves are
switching on and off at the carrier rate. The output filter takes out
the 3rd harmonic caused by the square wave switching up. Nothing
analog to make heat. It's a RF synthesized sinewave just like your
boat inverter.

You'll be glad to know from the Harris out it's still RF....(c;
Here's the ATU at WFAN:
http://www.geocities.com/aaron_white/atu1.html
75KW dummy load:
http://www.geocities.com/aaron_white/load.html

50KW isn't what it used to be...(sigh).
http://www.geocities.com/aaron_white/maintx.html
The modulator and final are inside the right doors. The other end is
the power supply. Kinda a non-event unless the RF output flashes
over, which my friends in broadcasting says is also a non-event for
the digital transmitter. It simply clears it, resets and tries again.
If it continues to flash over, the transmitter comes up in low power
(10KW) until the techies show up.....

The computer that operates the transmitter is in that rack to the left
of the Harris at WFAN. The whole thing is in a corner of the
transmitter shack which is mostly taken up by the darkened old 50KW
monster you're thinking about.

Tom Ray, Director of Engineering over at WOR in NYC, sent me some cool
pictures of their IBOC Digital AM experiments on their Harris DX-50.
If you listen to WOR or WLW's IBOC on a regular AM radio you hear a
faint hissing sound that is the digital subcarriers. The two
stations, 10 Khz apart, are experimenting with interference caused by
the IBOC carriers. Most interesting.....AM that sounds like mono-FM
but at great distances.



On Fri, 30 Jan 2004 21:20:46 GMT, Bruce in Alaska
wrote:

In article ,
"Doug Dotson" wrote:

and dispatches licensed techs

Nope Doug, no License Required anymore. Knowledgable Tech's recomeended
but not even required. That's why I got out of the Broadcast Business
35 years ago. To many Carneigie, and Elkins, First Phone's showing up,
and getting OTJ Training on my license as Chief Engineer. There's no
such thing as an Automated 50,000 Watt AM Transmitter. When those
puppy's decide to melt down, they do it in a hurry, and usually with
lots of sparks and steam from the liquid cooling systems. Usually
the finals are pulled at 50% of rated time, but nowdays with skimpy
maintaince money, owners are pushing that out to 80% and catastophic
failure is happen a lot more often. Reminds me of a very cold January
Night when KRAB-FM's antenna took a hell of a wet snow load, and
unbalanced the two 5Kw finals explosivly. I came around the corner
and the DJ on duty was out in the street with a bunch of steaming holes
in the snow where hot final Parts had melted down through the snow.
Took the consulting engineer and I, 8 hours to rebuild the final cage
(Lots of plumbing parts) and get it back on the air.

Bruce in alaska
--
add a 2 before @


Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

Ok guys,, what's your comments on the 2m homebrew antenna? Anyone build one
and had a particular preference or reasons why one over the other?

Thanks






"Gary Schafer" wrote in message
news
Yes the top hat would help out on 2 and 4 mhz frequencies. Problem is
where to put it where it is not in the way.

A loading coil on the stay would also help out but it would work even
better if it was up high nearer to the top of the stay.
Problem is that usually only one antenna is available for all bands on
a boat. At the higher frequencies that loading coil would act as a
choke and effectively disconnect the upper portion of the antenna.
Which may not be all that bad if there is sufficient length below the
coil for the higher frequencies.

The other problem that you may run into is that the auto tuner may not
like the impedance it sees. Most auto tuners do not like to see a
resonant antenna near 50 ohms. But on 2 mhz it would probably help a
lot.

Regards
Gary


On Thu, 29 Jan 2004 12:20:07 -0500, "Vito" wrote:

Tests of mobile antennae in the Amateur Radio 75 meter band (4MHz)
yielded
the following results:

* Well-designed Bugcatcher or Screwdriver with top hat 0 dB reference
* Bugcatcher or Screwdriver with no top hat -3 dB
* Hustler or Outbacker -9 dB
* Hamstick -12 dB
* Whip with autotuner -14 dB

This suggests that the common insulated-backstay-with-autotuner used on
sailboats could be improved by adding a capacitive top hat immediately
below
the upper insulator and/or a tapped coil in parallel (ie around) the
lower
insulator to tune whatever length of antenna one can physically
accomodate
to resonate on or near the Marine frequencies of interest, such as 2182
MHz.
Has anyone any experience doing so?

On Sat, 31 Jan 2004 04:04:29 GMT, Gary Schafer
wrote:

The nitrogen was for the transmission line.

Regards
Gary

Channel 24, WTAT-TV, runs 180KW into nitrogen-pressurized, rigid
transmission line. ERP is 5 megawatts at 1900 ft. It's the FOX
affiliate, here.

Exciting things happen when 180KW of 500 Mhz RF flashes over inside 6
1/2" hardline if the nitrogen goes away.......some of it involving
$30,000 4-cavity klystrons taller than a man.

It's not pretty.....

I have some friends in Charleston running only 1000 watts on Channel
12 from a little solid state Taylor (English) transmitter at 380'
broadcasting Telefutura and local Spanish programs. The whole TV
station is about the size of your refridgerator...(c; They used to
have a remote studio, of sorts, about 9 miles away linked with 10
watts on Channel 26 UHF pointed at the transmitter with a dish. The
"custom" receiver for this TV station, down at the transmitter
building shared with pagers, businessband, etc., was a genuine
Panasonic VHS tape deck tuned to Channel 26. If things at the studio
went awry, one only punched PLAY on the link receiver to get the
canned spanish movie on the air. The VHS cart would give you 4 hours
of canned programming to get whatever blew up fixed....hee hee.

Low Power TV is a lot of fun. I work for them for nothing because
they run on the bleeding edge of bankruptcy. That's why they don't
have a "studio" any more. Something about "rent payments"....(c;
Panasonic link receivers are $59 at Circuit City, if you need one for
you broadcast station. Ask for Mike and tell him you want one like
WJEA-TV uses....(c;



Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

On Sat, 31 Jan 2004 01:41:00 GMT, Larry wrote:

I had a 1st as well, but frankly thought the 2d was a good deal harder. If
nothing else, it was a lot longer! I recall the 1st was 50 questions (and
it seems like it was mostly law) and the 2d was 200 questions. I passed
them both, but I recall spending a long time on the 2d. Never did the
GMDSS/M or radar.

2nd was MUCH harder. I was a 3rd for too long...(c;

Go to the FCC website and download the tests for GMDSS operator and
servicer. Local ham radio volunteer examiners are also volunteer
commercial testers, now. Our commercial tester used to be the "Mud
Duck" on CB running 10KW into twin Telrex beams at 80'......(big
grin). Times change. I helped him pass his Advanced ham ticket.

I thought that after the FCC went to General Commercial that NABER or
someone like that handled endorsements for a while, but then they gave that
up. Do you remember what happened to that stuff?

I had all mine long before FCC stopped doing the testing. All the
testing is now done with volunteer examiners, mostly the VEs that test
for ham radio. Sea School has a GMDSS testing site, but you have to
go to Florida to take it. It's not offered in our Sea School in
Charleston.

73, DE W4CSC


Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

All I remember is that dad said he had to run out and get the
nitrogen to prevent the finals from melting down. Otherwise the
the station would have to shut down.

Doug, k3qt
s/v Callista

"Gary Schafer" wrote in message
...
The nitrogen was for the transmission line.

Regards
Gary

On Fri, 30 Jan 2004 22:03:22 -0500, "Doug Dotson"
wrote:

Thanks for the clarification Larry. I was pretty sure that modern
transmitter technology wasn't something I had in a dream. I was up
in Fairbanks a couple years ago and I suspect that keeping
the finals cool isn't much of a problem there My father was
the engineer for a UHF station back in the late 50's. He told
stories of having to run out and get bottles of Nitrogen to keep
the finals going. Life is much simpler now.

Doug, k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
Er, ah, Bruce? There are no "finals" any more. The 50KW transmitter
is just a switching power supply from Harris.....take a look at:
http://www.geocities.com/aaron_white/inside.html
It's all done by that big board switching the modules on and off at
the audio rate, in sequence. See those two little powertab
transistors on the copper heat sink? THOSE ARE THE FINALS!

If a module fails, the computer simply bypasses it and uses another
module (there are spares) until someone shows up at the transmitter to
look for the failure lights. They don't even shut down the
transmitter to swap them out, any more. Hot swaps just like a
computer...(c;

The two PC boards on the door are the "modulator", the drivers for the
modules creating the RF. It's so efficient it's cooled with small
FANS! To produce a 50,000 watt carrier, it requires only 55,000 watts
of AC power from the power company, not the 120KW we were accustomed
to. No massive filament power, no blood-red plates being cooled with
water, no cooling pond.

The RF modules (there are 144 of them in a Harris DX-50, 50KW
transmitter) look like:
http://www.geocities.com/aaron_white/dxmod.html
Some are 100W, 500W, 1KW, 2KW. The audio is simply converted into how
many modules run at this instant in time. The modules, themselves are
switching on and off at the carrier rate. The output filter takes out
the 3rd harmonic caused by the square wave switching up. Nothing
analog to make heat. It's a RF synthesized sinewave just like your
boat inverter.

You'll be glad to know from the Harris out it's still RF....(c;
Here's the ATU at WFAN:
http://www.geocities.com/aaron_white/atu1.html
75KW dummy load:
http://www.geocities.com/aaron_white/load.html

50KW isn't what it used to be...(sigh).
http://www.geocities.com/aaron_white/maintx.html
The modulator and final are inside the right doors. The other end is
the power supply. Kinda a non-event unless the RF output flashes
over, which my friends in broadcasting says is also a non-event for
the digital transmitter. It simply clears it, resets and tries again.
If it continues to flash over, the transmitter comes up in low power
(10KW) until the techies show up.....

The computer that operates the transmitter is in that rack to the left
of the Harris at WFAN. The whole thing is in a corner of the
transmitter shack which is mostly taken up by the darkened old 50KW
monster you're thinking about.

Tom Ray, Director of Engineering over at WOR in NYC, sent me some cool
pictures of their IBOC Digital AM experiments on their Harris DX-50.
If you listen to WOR or WLW's IBOC on a regular AM radio you hear a
faint hissing sound that is the digital subcarriers. The two
stations, 10 Khz apart, are experimenting with interference caused by
the IBOC carriers. Most interesting.....AM that sounds like mono-FM
but at great distances.



On Fri, 30 Jan 2004 21:20:46 GMT, Bruce in Alaska
wrote:

In article ,
"Doug Dotson" wrote:

and dispatches licensed techs

Nope Doug, no License Required anymore. Knowledgable Tech's
recomeended
but not even required. That's why I got out of the Broadcast Business
35 years ago. To many Carneigie, and Elkins, First Phone's showing
up,
and getting OTJ Training on my license as Chief Engineer. There's no
such thing as an Automated 50,000 Watt AM Transmitter. When those
puppy's decide to melt down, they do it in a hurry, and usually with
lots of sparks and steam from the liquid cooling systems. Usually
the finals are pulled at 50% of rated time, but nowdays with skimpy
maintaince money, owners are pushing that out to 80% and catastophic
failure is happen a lot more often. Reminds me of a very cold January
Night when KRAB-FM's antenna took a hell of a wet snow load, and
unbalanced the two 5Kw finals explosivly. I came around the corner
and the DJ on duty was out in the street with a bunch of steaming
holes
in the snow where hot final Parts had melted down through the snow.
Took the consulting engineer and I, 8 hours to rebuild the final cage
(Lots of plumbing parts) and get it back on the air.

Bruce in alaska
--
add a 2 before @


Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

That must be a recent change. I had to take my test at a
Sylvan Learning Center testing site. I registered as a VE
but haven't been called upon to exersize it. I'm not
currently active in a local club.

Doug, k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
On Sat, 31 Jan 2004 01:41:00 GMT, Larry wrote:

I had a 1st as well, but frankly thought the 2d was a good deal harder.
If
nothing else, it was a lot longer! I recall the 1st was 50 questions
(and
it seems like it was mostly law) and the 2d was 200 questions. I passed
them both, but I recall spending a long time on the 2d. Never did the
GMDSS/M or radar.

2nd was MUCH harder. I was a 3rd for too long...(c;

Go to the FCC website and download the tests for GMDSS operator and
servicer. Local ham radio volunteer examiners are also volunteer
commercial testers, now. Our commercial tester used to be the "Mud
Duck" on CB running 10KW into twin Telrex beams at 80'......(big
grin). Times change. I helped him pass his Advanced ham ticket.

I thought that after the FCC went to General Commercial that NABER or
someone like that handled endorsements for a while, but then they gave
that
up. Do you remember what happened to that stuff?

I had all mine long before FCC stopped doing the testing. All the
testing is now done with volunteer examiners, mostly the VEs that test
for ham radio. Sea School has a GMDSS testing site, but you have to
go to Florida to take it. It's not offered in our Sea School in
Charleston.

73, DE W4CSC


Larry W4CSC

No, no, Scotty! I said, "Beam me a wrench.", not a WENCH!
Kirk Out.....

Last one I built was just a rod soldered into a SO-259 chassis mount
connector. Radials were bolted into the 4 mounting holes along with
a mounting bracket. Worked good. Hardly worth doing homebrew
for something so common these days.

Doug, k3qt
s/v Callista

" Tuuk" wrote in message
...
Ok guys,, what's your comments on the 2m homebrew antenna? Anyone build
one
and had a particular preference or reasons why one over the other?

Thanks






"Gary Schafer" wrote in message
news
Yes the top hat would help out on 2 and 4 mhz frequencies. Problem is
where to put it where it is not in the way.

A loading coil on the stay would also help out but it would work even
better if it was up high nearer to the top of the stay.
Problem is that usually only one antenna is available for all bands on
a boat. At the higher frequencies that loading coil would act as a
choke and effectively disconnect the upper portion of the antenna.
Which may not be all that bad if there is sufficient length below the
coil for the higher frequencies.

The other problem that you may run into is that the auto tuner may not
like the impedance it sees. Most auto tuners do not like to see a
resonant antenna near 50 ohms. But on 2 mhz it would probably help a
lot.

Regards
Gary


On Thu, 29 Jan 2004 12:20:07 -0500, "Vito" wrote:

Tests of mobile antennae in the Amateur Radio 75 meter band (4MHz)
yielded
the following results:

* Well-designed Bugcatcher or Screwdriver with top hat 0 dB reference
* Bugcatcher or Screwdriver with no top hat -3 dB
* Hustler or Outbacker -9 dB
* Hamstick -12 dB
* Whip with autotuner -14 dB

This suggests that the common insulated-backstay-with-autotuner used on
sailboats could be improved by adding a capacitive top hat immediately
below
the upper insulator and/or a tapped coil in parallel (ie around) the
lower
insulator to tune whatever length of antenna one can physically
accomodate
to resonate on or near the Marine frequencies of interest, such as 2182
MHz.
Has anyone any experience doing so?

In article ,
"Doug Dotson" wrote:

"Bruce in Alaska" wrote in message
...
In article ,
"Doug Dotson" wrote:

and dispatches licensed techs

Nope Doug, no License Required anymore.

I misstated my thought. I mean't "qualified techs" since a license is
no longer required.
The question was as to the reason that a license is no
longer required. Larry seems to suggest that it is because very
few blacks are able to get a 1st Phone. My recollection is that
it is because detailed technical knowledge is not required to safely
and legally operate a transmitter these days.

There's no
such thing as an Automated 50,000 Watt AM Transmitter.

Maybe up in Alaska. But I'm pretty sure that is not the case in general.

When those
puppy's decide to melt down, they do it in a hurry, and usually with
lots of sparks and steam from the liquid cooling systems.

My years in the process control industry make me pretty confident that
the computer can sense and react to pretty much anything unusual faster
than the most skilled engineer/tech. Not to say that an on-site person is
not an asset because once the computer has either shut things down or
reduced power to save the transmitter, someone has to diagnose and
fixed the problem.

Usually
the finals are pulled at 50% of rated time, but nowdays with skimpy
maintaince money, owners are pushing that out to 80% and catastophic
failure is happen a lot more often. Reminds me of a very cold January
Night when KRAB-FM's antenna took a hell of a wet snow load, and
unbalanced the two 5Kw finals explosivly. I came around the corner
and the DJ on duty was out in the street with a bunch of steaming holes
in the snow where hot final Parts had melted down through the snow.
Took the consulting engineer and I, 8 hours to rebuild the final cage
(Lots of plumbing parts) and get it back on the air.

A good SCADA system should have sensed the impending problem and
may have been able to save the day. But, as you say, some failures are
so sudden that there is no way out.

Bruce in alaska
--
add a 2 before @



Well I have now been updated on Broadcast Transmitters...... thanks
Larry. It has been a few years since I inspected an AM Broadcast Station
and the one's I did do were out in the small communities of alaska.
I got out of the Broadcast Industry as an Engineer, many years ago,
so it isn't to suprising that I am a bit out of date on the technology.
Oh well, age gets us all eventually. Thank goodness Marine Radios
are still using 1990 technology, cause I still have a bit of a handle on
them.

I also talked to my buddies at SEA, and they are just coming back
into production on their SEA157 VHF Radio's and even a few of the SEA235
MF/HF Radio's. This is very good news for the thousands of folks who
have SEA Products onboard. I also had a chance to talk to Mark Johnson
of ShineMicro about AIS. He is really big into this new (to me) Position
Reporting System now being mandated for ships of 65Ft in the US.
Way cool stuff if you got the money, and still way cool when the ClassB
stuff for Volitary Compliance comes out later this year.


Bruce in alaska
--
add a 2 before @

In article ,
"Doug Dotson" wrote:

"Bruce in Alaska" wrote in message
...
In article ,
"Doug Dotson" wrote:

Not familiar with a Marine Radio Tech License? I have a GROL
with radar Endorsement and a GMDSS/M, but I'm not aware
that is what you are referring to. The NMEA has a certification
process but that's not really a "license" per se.

Doug, k3qt
s/v Callista

Licensed Marine Radio Tech is a person who has an FCC GROL/w
RADAR/GMDSS-M and is licensed to maintain Maritime Mobile Radio Service
licensed systems aboard US flagged Vessels.

Then I guess I R 1. But what is the second part of your statement? The part
that
reads "and is licensed to maintain Maritime Mobile Radio Service
licensed systems aboard US flagged Vessels"? What is this license? Who
issues it?

The SOLAS Requires that
Title III Part II, and title III Part I Vessels be inspected on an annual
basis and that inspection by a Licensed Marine Radio Tech, be logged in
the Vessel Station Log and a renewed SOLAS Certificate be Issued and
Posted for Public Inspection. In the passed, these inspections were
done by FCC Field Agents, and the SOLAS Certificates, Bridge to Bridge
RadioTelephone Certificates, were issued by the FCC Field Agents, on
completion of the inspection. A similar inspection of Title IIi Part
IIi Vessels needs to be completed every 5 years for those class vessels,
and is done, now, through the same method.

I remember all the mumbo-jumbo from the GMDSS license. So is the GMDSS/M
license what makes one all of these fancy titles or is there some other
authority that grants these lofty titles.

Bruce in alaska
--
add a 2 before @



Yep, your R one, and with this little slip of paper, you can now LEGALLY
adjust Marine & Aircraft Radio Systems so as to make them compliant with
Parts 80 & 87 of the FCC Rules and Regulations. Oh yea, you need an FAA
Certificate if you mess with Aircraft systems in actual Aircraft, or you
need someone who has an FAA Certificate to sign off on any work on
Aircraft Radio's.

All that said, there really isn't much to adjust anymore unless your
working with some of the older MF/HF Radio's around. Mostly just
setting the Master Osc. on frequency, and then setting the power output,
and your done these days.

Bruce in alaska
--
add a 2 before @

Maybe someday I'll look into the FAA stuff. If ever I decide to get
current on my pilot's license I can fix my own radios!

Doug, k3qt
s/v Callista

"Bruce in Alaska" wrote in message
...
In article ,
"Doug Dotson" wrote:

"Bruce in Alaska" wrote in message
...
In article ,
"Doug Dotson" wrote:

Not familiar with a Marine Radio Tech License? I have a GROL
with radar Endorsement and a GMDSS/M, but I'm not aware
that is what you are referring to. The NMEA has a certification
process but that's not really a "license" per se.

Doug, k3qt
s/v Callista

Licensed Marine Radio Tech is a person who has an FCC GROL/w
RADAR/GMDSS-M and is licensed to maintain Maritime Mobile Radio
Service
licensed systems aboard US flagged Vessels.

Then I guess I R 1. But what is the second part of your statement? The
part
that
reads "and is licensed to maintain Maritime Mobile Radio Service
licensed systems aboard US flagged Vessels"? What is this license? Who
issues it?

The SOLAS Requires that
Title III Part II, and title III Part I Vessels be inspected on an
annual
basis and that inspection by a Licensed Marine Radio Tech, be logged
in
the Vessel Station Log and a renewed SOLAS Certificate be Issued and
Posted for Public Inspection. In the passed, these inspections were
done by FCC Field Agents, and the SOLAS Certificates, Bridge to Bridge
RadioTelephone Certificates, were issued by the FCC Field Agents, on
completion of the inspection. A similar inspection of Title IIi Part
IIi Vessels needs to be completed every 5 years for those class
vessels,
and is done, now, through the same method.

I remember all the mumbo-jumbo from the GMDSS license. So is the GMDSS/M
license what makes one all of these fancy titles or is there some other
authority that grants these lofty titles.

Bruce in alaska
--
add a 2 before @



Yep, your R one, and with this little slip of paper, you can now LEGALLY
adjust Marine & Aircraft Radio Systems so as to make them compliant with
Parts 80 & 87 of the FCC Rules and Regulations. Oh yea, you need an FAA
Certificate if you mess with Aircraft systems in actual Aircraft, or you
need someone who has an FAA Certificate to sign off on any work on
Aircraft Radio's.

All that said, there really isn't much to adjust anymore unless your
working with some of the older MF/HF Radio's around. Mostly just
setting the Master Osc. on frequency, and then setting the power output,
and your done these days.

Bruce in alaska
--
add a 2 before @