I have a TV antenna as a back up to my dish.
I believe the head end unit of the antenna amplifier is defective. It is on
the antenna.The twin lead from the antenna connection goes in one end and
the coax goes on the other. The coax then goes to a plug in unit in the
house which is connected to the TV.
Is this unit on the antenna a special device or is it nothing more than a
standard converter from 250 ohm twin lead to 75 ohm coax?
If so, that will save me buying a whole new amplifier.
Thanks
DS


=^..^=

"R.Smyth" wrote in message
...
I have a TV antenna as a back up to my dish.
I believe the head end unit of the antenna amplifier is defective. It is
on
the antenna.The twin lead from the antenna connection goes in one end and
the coax goes on the other. The coax then goes to a plug in unit in the
house which is connected to the TV.
Is this unit on the antenna a special device or is it nothing more than a
standard converter from 250 ohm twin lead to 75 ohm coax?
If so, that will save me buying a whole new amplifier.
Thanks
DS


=^..^=

What makes you think it is defective? What is the " plug in unit in the
house"? It has to have some sort of identification.

It could be an amplifier up there with a power supply down below or the unit
below might be the amp and the part on the antenna is just a 300 ohm twin
lead to 75 ohm cable transformer. But if your signal has deteriorated and
you have an amplifier you really have to find out where it is. The
transformers themselves rarely go bad, but the connections out in the
weather may have corroded. Tell us what you have.

Charlie

On Wed, 8 Sep 2004 19:18:15 -0400, "R.Smyth" wrote:

I have a TV antenna as a back up to my dish.
I believe the head end unit of the antenna amplifier is defective. It is on
the antenna.The twin lead from the antenna connection goes in one end and
the coax goes on the other. The coax then goes to a plug in unit in the
house which is connected to the TV.
Is this unit on the antenna a special device or is it nothing more than a
standard converter from 250 ohm twin lead to 75 ohm coax?
If so, that will save me buying a whole new amplifier.
Thanks
DS


=^..^=

Does the plug in unit at the TV also plug into a wall socket? If not
you do not have an amplifier. You have a impedance, balance to
unbalanced transformer.

.The twin lead from the antenna connection goes in one end and
the coax goes on the other. The coax then goes to a plug in unit in the
house which is connected to the TV.

I would buy an inexpensive 300 ohm to 75 ohn transformer and a piece of 75 ohm
coax cable. Unhook the twin lead at the antenna and hook it into the new
transformer. Hook the new coax into the other end of the new transformer and
run it right to your TV. You have to bypass BOTH the amplifier (at the antenna)
AND the power supply (plugged in at the back of your set).

If that fixes your problem, you could either replace the amplifier, or, it may
in fact be a "good enough" signal, especially since you say it is only a
back-up.

John

"Charlie Bress" wrote in message
...
"R.Smyth" wrote in message
...
I have a TV antenna as a back up to my dish.
I believe the head end unit of the antenna amplifier is defective. It is
on
the antenna.The twin lead from the antenna connection goes in one end
and
the coax goes on the other. The coax then goes to a plug in unit in the
house which is connected to the TV.
Is this unit on the antenna a special device or is it nothing more than
a
standard converter from 250 ohm twin lead to 75 ohm coax?
If so, that will save me buying a whole new amplifier.
Thanks
DS


=^..^=

What makes you think it is defective? What is the " plug in unit in the
house"? It has to have some sort of identification.

It could be an amplifier up there with a power supply down below or the
unit
below might be the amp and the part on the antenna is just a 300 ohm twin
lead to 75 ohm cable transformer. But if your signal has deteriorated and
you have an amplifier you really have to find out where it is. The
transformers themselves rarely go bad, but the connections out in the
weather may have corroded. Tell us what you have.

Charlie

The unit on the antenna is just a small box, about the size of a small
candy bar. There is no power going to it. The only wires are the twin lead
at one end and the coax at the other. (If it's an amplifier, it would need a
power lead, no?) The other unit is a box , maybe a little bigger than a
cigarette box, which plugs into the wall in the house. The coax from the
antenna goes on one connection and a coax cord to the TV set goes on the
other. There is a gain control on it and an FM signal trap. This would seem
to be the actual amplifier. It's a Radio Shack product.
I believe the top unit is defective because I may have broken something in
getting the old coax connector loose. I'm just wondering what will happen if
I merely replace the top unit with a 250 to 75 ohm transformer.
Thanks.
ds

R.Smyth wrote:

The unit on the antenna is just a small box, about the size of
a small candy bar. There is no power going to it. The only
wires are the twin lead at one end and the coax at the other.
(If it's an amplifier, it would need a power lead, no?)

Not necessarily. From what you say below, it sounds like the
plug-in unit would likely be feeding a DC voltage up the coax
to power the amplifier up at the antenna. Same principal the
cable company uses, actually. There is 60 VDC on the big
feeder cables to power the amps and line extenders. It gets
trapped out at the tap units where your house connects.

The other unit is a
box , maybe a little bigger than a cigarette box, which plugs
into the wall in the house. The coax from the antenna goes on
one connection and a coax cord to the TV set goes on the other.
There is a gain control on it and an FM signal trap. This would
seem to be the actual amplifier. It's a Radio Shack product.
I believe the top unit is defective because I may have broken
something in getting the old coax connector loose. I'm just
wondering what will happen if I merely replace the top unit with
a 250 to 75 ohm transformer. Thanks.

Maybe nothing, but likely improved if you broke the center
conductor loose in the coax connector. Yes, you can replace
it with a 75-300 Matching Transformer. Your downfeed cable
should already have an F connector on it, and the other end
you can srip the twin lead on both the antenna wire and the
"lugs" end of the 75-300 MT, twist wires and electrical tape
to secure. Soldering wouldn't hurt but isn't necessary.

Get rid of the plug in wall box down below, a female-female
F connector "Barrel" will tie those two cable ends together.

HTH.

--
The real Tom Pendergast [ So if you meet me, have some courtesy,
aka I-zheet M'drurz [ have some sympathy, and some taste.
Accept no substitutes! [ Use all your well-learned politesse,
$1 to Mick for the .sig ---[ or I'll lay your soul to waste.

"R.Smyth" wrote in message
...

"Charlie Bress" wrote in message
...
"R.Smyth" wrote in message
...
I have a TV antenna as a back up to my dish.
I believe the head end unit of the antenna amplifier is defective. It
is
on
the antenna.The twin lead from the antenna connection goes in one end
and
the coax goes on the other. The coax then goes to a plug in unit in
the
house which is connected to the TV.
Is this unit on the antenna a special device or is it nothing more
than
a
standard converter from 250 ohm twin lead to 75 ohm coax?
If so, that will save me buying a whole new amplifier.
Thanks
DS


=^..^=

What makes you think it is defective? What is the " plug in unit in the
house"? It has to have some sort of identification.

It could be an amplifier up there with a power supply down below or the
unit
below might be the amp and the part on the antenna is just a 300 ohm
twin
lead to 75 ohm cable transformer. But if your signal has deteriorated
and
you have an amplifier you really have to find out where it is. The
transformers themselves rarely go bad, but the connections out in the
weather may have corroded. Tell us what you have.

Charlie

The unit on the antenna is just a small box, about the size of a small
candy bar. There is no power going to it. The only wires are the twin
lead
at one end and the coax at the other. (If it's an amplifier, it would need
a
power lead, no?) The other unit is a box , maybe a little bigger than a
cigarette box, which plugs into the wall in the house. The coax from the
antenna goes on one connection and a coax cord to the TV set goes on the
other. There is a gain control on it and an FM signal trap. This would
seem
to be the actual amplifier. It's a Radio Shack product.
I believe the top unit is defective because I may have broken something
in
getting the old coax connector loose. I'm just wondering what will happen
if
I merely replace the top unit with a 250 to 75 ohm transformer.
Thanks.
ds

First, it does seem that the unit on the antenna is only a twin lead to coax
transformer and the amplifier is down near the tv. If you think you broke
something at the transformer while getting the coax connector loose then it
is very likely that what broke is the short piece of the inner conductor of
the cable. If this is true, you would be well advised to replace the cable
with a preassembled cable that has the connectors already in place. It is
possible to just cut the cable and attach a new connector. But given your
inexperience with this sort of stuff it is unlikely that you can accomplish
this so that you have a weatherproof connection. It is one thing to hack
together a fitting to use inside the house, but making a weather resistant
connection is not as forgiving. If the cable that you have is a commercially
assembled one you could just reverse it and put the end that had been in the
house in the air and then put a new connector on the end that is now
indoors. Or as someone else has suggested replace both the transformer and
the cable. It won't hurt anything and will likely help.

Charlie

On Wed, 8 Sep 2004 22:10:00 -0400, "R.Smyth" wrote:

The unit on the antenna is just a small box, about the size of a small
candy bar. There is no power going to it. The only wires are the twin lead
at one end and the coax at the other. (If it's an amplifier, it would need a
power lead, no?) The other unit is a box , maybe a little bigger than a
cigarette box, which plugs into the wall in the house. The coax from the
antenna goes on one connection and a coax cord to the TV set goes on the
other. There is a gain control on it and an FM signal trap. This would seem
to be the actual amplifier. It's a Radio Shack product.

The Radio Shack device IS an amplifier. These things are generally
poorly made, and tend to fail, I've gone through a few of them in the
past 10 years.. Fix the other problem first, then see if you really
need the amplifier.

The device at the top is most likely just a 75-300 ohm balun. You can
replace that, but probably need to replace the F connector on the
coax.

J Kelly wrote:

The device at the top is most likely just a 75-300 ohm balun.
You can replace that, but probably need to replace the F
connector on the coax.

Sorry, I disagree with that part. If he was fighting to get
the end off, it's much more likely that he would've broken the
"panel mount" female F connetor loose. It's pretty hard to
break the male connector on a piece of cable, short of running
it over or otherwise mutilating it.

--
The real Tom Pendergast [ So if you meet me, have some courtesy,
aka I-zheet M'drurz [ have some sympathy, and some taste.
Accept no substitutes! [ Use all your well-learned politesse,
$1 to Mick for the .sig ---[ or I'll lay your soul to waste.

On 10 Sep 2004 01:40:29 GMT, "I-zheet M'drurz"
wrote:

J Kelly wrote:

The device at the top is most likely just a 75-300 ohm balun.
You can replace that, but probably need to replace the F
connector on the coax.

Sorry, I disagree with that part. If he was fighting to get
the end off, it's much more likely that he would've broken the
"panel mount" female F connetor loose. It's pretty hard to
break the male connector on a piece of cable, short of running
it over or otherwise mutilating it.

Not if it wasn't installed correctly to begin with. I meant that the
balun needs replaced, and probably the coax connector also. I didn't
word that well...