KFI transmitter off the air
 

Telamon wrote:
In article ,
Dave wrote:

Telamon wrote:
In article ,
"Bob Campbell" wrote:

"Telamon" wrote in message
.
..
KFI is having a lot of bad luck with transmitters and antennas.

So now that they have had two transmitters burn up anyone know why that
happened?
Because they were broadcasting in HD?

rimshot
I suppose that is possible.

I was thinking more along the lines of the cooling system failed or a
HV component failed shorting out the final stage.

There are protections for both of those. However I must point out that
solid state transmitters have no B+.

So what is the voltage out the finals on a solid state transmitter?


After the output matching network a little under 1,600 Volts.

KFI transmitter off the air
 

Telamon wrote:
In article ,
"David Eduardo" wrote:

"Telamon" wrote in message
...
In article ,

So what is the voltage out the finals on a solid state transmitter?

There are no finals. Just a bunch of combined modules. The Nautel 50 has 8
RF and 4 modulator power modules. There is no final stage.

Ok, Don't call the modules "finals" then but what is the output voltage
to the antenna? I would like to know what the RF current is as the
output is supposed to be 50KW.

31 Amperes

KFI transmitter off the air
 

Billy Burpelson wrote:
Telamon wrote:

So what is the voltage out the finals on a solid state transmitter?

Do you mean the DC voltage on the collectors of the output transistors
or the RF voltage into the feed line?

Telamon wrote:

Ok, Don't call the modules "finals" then but what is the output
voltage to the antenna? I would like to know what the RF current is as
the output is supposed to be 50KW.

I'm surprised a smart person like you isn't familiar with Ohm's law...

To find the RF voltage for a 50 kW transmitter, assuming a 50 ohm
transmission line:

Simple Ohm's Law:

V= the square root of (RxW) (V=volts, W=watts, R=feed line impedance in
ohms...assume 50 ohms)

To find the current:

I= the square root of (W/R)

Sometimes you're just to, too, two clueless. :-)


This is even simpler:

http://www.sengpielaudio.com/calculator-ohm.htm

KFI transmitter off the air
 

Telamon wrote:
In article ,
"David Eduardo" wrote:

"Telamon" wrote in message
...

I'll assume that there are 10 modules so each would put out about 3
amps. The outputs could be protected by limiting that source current and
there would also have to be a another protection against VSWR. Maybe a
temperature sensor on the output FET but that might be too slow.

So how do the separate modules work together? Do they all put out the
same voltage and current in phase through some kind of card backplane?

The principle manufacturers of solid state transmitters are Harris, BE, and
Nautel in the US/NA. Each as a website, and I believe there are both
functional diagrams and some white papers about design. I have never worked
inside a big ss transmitter so am of limited use in describing how they
work.

Thanks for answering my questions Eduardo. I'll check those sites out.

Can you tell me who makes the hardline between transmitter and antenna?

I'm just the curious sort. I have never really worked with RF power and
I just haven't though of the obvious answers to some of the questions I
have asked in the thread. In my work experience the RF power is 0 dBm
and less coming out of equipment like network analyzers and synthesizers.

I can tell you that there is a lot more to actually fabricating
electronics than the schematics can explain.

www.eriinc.com/pubs/Catalog07_168-171.pdf

Scroll down for specs at 0.64 MHz

KFI transmitter off the air
 

Telamon wrote:
In article ,
"David Eduardo" wrote:

"Telamon" wrote in message
...
. :-)
You are such a retard. I was wondering what the line loss would be and I
am not familiar with the FCC rules. The 50Kw could be the max the
transmitter puts out or the input to the antenna or it could be based on
antenna field strength measurements.
There are several isssues here.

1. It's usually the licensed power into the antenna for non-directional
stations. So most new solid state transmitters deliver 10% to 20% more, so
that if the line loss is a couple of percent, the line is fed with the
licensed power plus line loss.

2. Directional systems feed the licensed power plus phasor loss to the
common point (input) of the directional phasor. So if phasor loss for a 50
kw station is 5 kw, then they feed the common point with 55 kw.

3. Some classes of AM service have a maximum field strength at a determined
distance. If the radiator is too efficient (a 5/8 wave or a Franklin) the
station may actually feed less than licensed power to the tower to
compensate for the radiation efficiency.

SNIP

The 5/8 wavelength antenna is a good one to use for local mobile
communications. I think that is because it has a good low to the horizon
lobe creating a better ground wave than a 1/4 wavelength antenna would
generate. That sound right to you or is there another reason?


That is correct. Most flamethrowers are electrically near 1/2 5/8
wave. Half wave antennas are harder to feed.

KFI transmitter off the air
 

In article ,
Dave wrote:

Telamon wrote:
In article ,
"David Eduardo" wrote:

"Telamon" wrote in message
.
..

I'll assume that there are 10 modules so each would put out about 3
amps. The outputs could be protected by limiting that source current and
there would also have to be a another protection against VSWR. Maybe a
temperature sensor on the output FET but that might be too slow.

So how do the separate modules work together? Do they all put out the
same voltage and current in phase through some kind of card backplane?

The principle manufacturers of solid state transmitters are Harris, BE,
and
Nautel in the US/NA. Each as a website, and I believe there are both
functional diagrams and some white papers about design. I have never
worked
inside a big ss transmitter so am of limited use in describing how they
work.

Thanks for answering my questions Eduardo. I'll check those sites out.

Can you tell me who makes the hardline between transmitter and antenna?

I'm just the curious sort. I have never really worked with RF power and
I just haven't though of the obvious answers to some of the questions I
have asked in the thread. In my work experience the RF power is 0 dBm
and less coming out of equipment like network analyzers and synthesizers.

I can tell you that there is a lot more to actually fabricating
electronics than the schematics can explain.

www.eriinc.com/pubs/Catalog07_168-171.pdf

Scroll down for specs at 0.64 MHz

6 1/8 inch is what most radio stations use?

--
Telamon
Ventura, California

KFI transmitter off the air
 

"Telamon" wrote in message
...

6 1/8 inch is what most radio stations use?


Pretty common for FM and TV stations.. not so much for AM. IIRC, 1520 in
Portland used 3" Heliax for 50KW.

KFI transmitter off the air
 

In article ,
"Brenda Ann" wrote:

"Telamon" wrote in message
...

6 1/8 inch is what most radio stations use?


Pretty common for FM and TV stations.. not so much for AM. IIRC, 1520 in
Portland used 3" Heliax for 50KW.

Someone wrote that 50 ohm was standard. Why am I seeing 75 ohm
components then?

And while I'm back on the impedance subject I expect that tower
impedance can be much lower than 50 ohms so that why a matching network
is needed at the antenna?

--
Telamon
Ventura, California

KFI transmitter off the air
 

Telamon wrote:
In article ,
"David Eduardo" wrote:

"Telamon" wrote in message
...

SNIP

Some time I need to find a time where our engineers can take you to Mt
Wilson. One of our sites is shared with multiple users, including several
TVs. You would have a lot of questions for the follks at that manned site.

SNIP

Now that would be an interesting field trip.

As long as you don't plan on having children...

KFI transmitter off the air
 

In article ,
Dave wrote:

Telamon wrote:
In article ,
"David Eduardo" wrote:

"Telamon" wrote in message
.
..

SNIP

Some time I need to find a time where our engineers can take you to Mt
Wilson. One of our sites is shared with multiple users, including several
TVs. You would have a lot of questions for the follks at that manned site.

SNIP

Now that would be an interesting field trip.

As long as you don't plan on having children...

I could wear lead lined depends.

It's just an hour or two of RF not as bad as holding a cell phone to
your head.

--
Telamon
Ventura, California