I want to be able to send a UHF TV signal (400-800 MHz) from one end of the
house to the other. I have a UHF digital PLL modulator with an output level
of 7dBmV minimum, and would like to use it to feed a small linear 100 mW
"power" amp to a 1/4 wave whip.

I don't think I'll find such a critter very easily, (if at all) so I would
like some suggestions as to how I might find resources to build one. (Of
course, a pre-designed schematic and PCB layout would be ideal!)

Anyone have any suggestions as to where to start? (Besides Google... BTDT.)

Neil Preston, CET

My suggestion is don't start !

In most countries transmitting at that power level and frequency will
require a radio station licence, which will not be available to you
anyway, since it is within the UHF TV band (unless you own the TV
station you wish to retransmit).

Steve

Within the confines of a house the best and cheapest way to send a TV
signal is via a low cost ready made 2.4 GHz system with a choice of a
number of freqs in the 2.4GHz band .
If you also have a wifi system through a wireless ADSL router you
must ensure that the freqs for both systems are well apart.
I do have these 2 systems in operation without interference problems

Frank ( Highland Ham )

================================ Neil Preston wrote: ================
I want to be able to send a UHF TV signal (400-800 MHz) from one end of the
house to the other. I have a UHF digital PLL modulator with an output level
of 7dBmV minimum, and would like to use it to feed a small linear 100 mW
"power" amp to a 1/4 wave whip.

I don't think I'll find such a critter very easily, (if at all) so I would
like some suggestions as to how I might find resources to build one. (Of
course, a pre-designed schematic and PCB layout would be ideal!)

Anyone have any suggestions as to where to start? (Besides Google... BTDT.)

My suggestion is don't start !

In most countries transmitting at that power level and frequency will
require a radio station licence, which will not be available to you
anyway, since it is within the UHF TV band (unless you own the TV
station you wish to retransmit).

Steve

In article , Neil
Preston wrote:

I want to be able to send a UHF TV signal (400-800 MHz) from one end of the
house to the other. I have a UHF digital PLL modulator with an output level
of 7dBmV minimum, and would like to use it to feed a small linear 100 mW
"power" amp to a 1/4 wave whip.

I don't think I'll find such a critter very easily, (if at all) so I would
like some suggestions as to how I might find resources to build one. (Of
course, a pre-designed schematic and PCB layout would be ideal!)

Anyone have any suggestions as to where to start? (Besides Google... BTDT.)

Neil Preston, CET


I'll take a wild ass guess that you don't want the signal propagating
equally in all directions, but that you have a particular signal path
in mind.

Putting something as simple as a corner reflector (or a parabolic
reflector) behind the transmitting antenna can give you an effective 10
to 12 dB signal increase. Focusing the receive antenna helps as well.
If you build a pair of reflectors, your total investment will be on the
order of 75 cents. Look at freeantennas.com for templates you can
scale for your frequency. Reflectors let you focus the rf energy where
you want it.

If you *really* want to use an amplifier, search ebay for minicircuits.
They make prepackaged rf amplifiers, along with a lot of other rf
goodies. But you're going to have to adapt your gadget and antenna
system to interconnect with 50 ohm lines and SMA connectors. And
somehow I doubt the output of the transmitter is spectrally pure. It's
bound to have *some* filtering in it (one would hope), but when you put
it into a very wideband amplifier (such as the MiniCircuits ZFL-1000GH)
that amp will amplify *ALL* the signal -- fundamental, spurs,
harmonics, you name it. And do you know what the output level of your
transmitter is (into a 50 ohm load)? You need to know that to properly
select the amplifier.

Try the reflector aproach first.

--
Namaste--

On Fri, 02 Dec 2005 06:27:23 GMT, "Neil Preston"
wrote:

I want to be able to send a UHF TV signal (400-800 MHz) from one end of the
house to the other. I have a UHF digital PLL modulator with an output level
of 7dBmV minimum, and would like to use it to feed a small linear 100 mW
"power" amp to a 1/4 wave whip.

I don't think I'll find such a critter very easily, (if at all) so I would
like some suggestions as to how I might find resources to build one. (Of
course, a pre-designed schematic and PCB layout would be ideal!)

Anyone have any suggestions as to where to start? (Besides Google... BTDT.)

Neil Preston, CET

There are legal issues to doing that in most countries. Besides 100mw
is a lot of power for maybe 100ft. You need maybe 10mw and thats a
lot less of an effort. Also if you target isn't moving a corner
reflector at each end will make a big difference.

One last thing most TV system antennas are dipoles and horizonatlly
polarized TX and RX antennas should have the same orientation.
Ignore the gastly bad monopole that comes with TVs for UHF.

Allison

Hi, All;

Thanks for the responses so far.

The intent is to produce a device that will operate within the limits of
Part 15 of FCC rules for unlicensed radiators. Somewhere in the back of my
mind the 100 mW figure floated to the top, probably as a result of the old
100 mW unlicensed CB walkie-talkies we used to play with as kids.

It is probable in this case that a 10 mW output to a corner reflector at the
transmitter site will suffice. The target is a standard residential TV
receiving antenna connected to a household distribution system. The received
signal needs to be large enough to drive a number of splitters and lengths
of coax. This would allow us to view the image on any TV in the house.

The exciter is specified to produce a 7 dBmV output into a 75 ohm load,
which I calculate to be about 2.2 mV or 67 nW. I don't believe this is
enough to drive even a corner reflector to cover the distance we need. (It's
barely enough to give a clean signal on the TV by direct coax connection!)

We have tried using a 2.4 GHz system, but we have several nearby WiFi
systems here that it interferes with. We want to get completely away from
the 2.4GHz range. My initial plan is to use UHF channel 14.

Thanks for the pointer to MiniCircuits. I've seen ads, but hadn't thought of
them. I'll look into them.

Following are excerpts from FCC Part 15 regs
(http://wireless.fcc.gov/rules.html) that I think would apply. Note that the
allowable field strength is the same for both unintentional and intentional
radiators in the frequency range of interest.



Subpart B_Unintentional Radiators

Sec. 15.109 Radiated emission limits.

(a) Except for Class A digital devices, the field strength of
radiated emissions from unintentional radiators at a distance of 3
meters shall not exceed the following values:

[[Page 774]]



------------------------------------------------------------------------
Field
strength
Frequency of emission (MHz) (microvolts/
meter)
------------------------------------------------------------------------
30-88................................................ ..... 100
88-216............................................... ..... 150
216-960............................................... .... 200
Above 960............................................... .. 500
------------------------------------------------------------------------


Subpart C_Intentional Radiators

Sec. 15.209 Radiated emission limits; general requirements.

(a) Except as provided elsewhere in this subpart, the emissions from
an intentional radiator shall not exceed the field strength levels
specified in the following table:

------------------------------------------------------------------------
Measurement
Frequency (MHz) Field strength distance
(microvolts/meter) (meters)
------------------------------------------------------------------------
0.009-0.490...................... 2400/F(kHz) 300
0.490-1.705...................... 24000/F(kHz) 30
1.705-30.0....................... 30 30
30-88............................ 100 ** 3
88-216........................... 150 ** 3
216-960.......................... 200 ** 3
Above 960........................ 500 3
------------------------------------------------------------------------
** Except as provided in paragraph (g), fundamental emissions from
intentional radiators operating under this section shall not be
located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz or
470-806 MHz. However, operation within these frequency bands is
permItted under other sections of this part, e.g., Sec. Sec. 15.231
and 15.241.



Sec. 15.23 Home-built devices.

(a) Equipment authorization is not required for devices that are not
marketed, are not constructed from a kit, and are built in quantities of
five or less for personal use.
(b) It is recognized that the individual builder of home-built
equipment may not possess the means to perform the measurements for
determining compliance with the regulations. In this case, the builder
is expected to employ good engineering practices to meet the specified
technical standards to the greatest extent practicable. The provisions
of Sec. 15.5 apply to this equipment.

http://www.jameco.com/ sells video transmitters for 2.4 GHz. If you
have composite video available, it would be easier and legal to go this
route.

Scott


Neil Preston wrote:

I want to be able to send a UHF TV signal (400-800 MHz) from one end of the
house to the other. I have a UHF digital PLL modulator with an output level
of 7dBmV minimum, and would like to use it to feed a small linear 100 mW
"power" amp to a 1/4 wave whip.

I don't think I'll find such a critter very easily, (if at all) so I would
like some suggestions as to how I might find resources to build one. (Of
course, a pre-designed schematic and PCB layout would be ideal!)

Anyone have any suggestions as to where to start? (Besides Google... BTDT.)

Neil Preston, CET

2.4 GHz is the problem.

That frequency is too congested at this location.

I need to move the signal OUT of the 2.4 GHz band.


"Scott" wrote in message
...
http://www.jameco.com/ sells video transmitters for 2.4 GHz. If you
have composite video available, it would be easier and legal to go this
route.

Scott


Neil Preston wrote:

I want to be able to send a UHF TV signal (400-800 MHz) from one end of
the
house to the other. I have a UHF digital PLL modulator with an output
level
of 7dBmV minimum, and would like to use it to feed a small linear 100 mW
"power" amp to a 1/4 wave whip.

I don't think I'll find such a critter very easily, (if at all) so I
would
like some suggestions as to how I might find resources to build one. (Of
course, a pre-designed schematic and PCB layout would be ideal!)

Anyone have any suggestions as to where to start? (Besides Google...
BTDT.)

Neil Preston, CET

Neil Preston wrote:

** Except as provided in paragraph (g), fundamental emissions from
intentional radiators operating under this section shall not be
located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz or
470-806 MHz. However, operation within these frequency bands is
permItted under other sections of this part, e.g., Sec. Sec. 15.231
and 15.241.

Read carefully ! This specifically forbids operation in the TV bands
except as provided for in paragraph (g) and other sections.

Paragraph (g) does not provide for operation in the UHF band. The only
other sections I spotted that do permit operation in this band are
15.231, which permits only low duty cycle periodic operation, and
15.242, which permits operation only for biomedical devices operating
inside health care facilities.

Steve