I live about 8 miles from 4 local tv stations, and 25 miles from a much
desired UHF station. Luckily, they are all in the same general direction.
I plan to buy a medium size vhf/uhf antenna. My coax run will be 50 feet.
Although I don't really need "gain" for the vhf stations, I do need it for
the uhf station. "Some" extra gain will be ok for the vhf stations.
Whatever the setup, I want to use the lowest-loss RG6 that I can buy.
Here are my questions:
1. Where (online or else) can I find the very best, lowest loss RG6 coax ?
2. Assuming that I need a pre-amp, if I only have a 50 ft run of low-loss
coax, will my system work well if I mount the preamp at the tv end of the
50 ft coax, as compared to putting it at the antenna? I realize the
advantage of mounting at the antenna, yet I would like the convenience of
having the pre-amp inside. I am considering an adjustable pre-amp, and that
would be more usuable if I had it at the tv instead of at the antenna.
3. Will a brick chimney (with no steel liner or inserts) about 20 feet from
the antenna, but in-line with the desired stations, attenuate the signals
4. Are the Radio Shack pre-amps decent ??
My thoughts: Perhaps I will get a pre-amp that will produce about 20 db
of gain. I will mount it inside. The 50 ft of coax will have a loss of
perhaps 5 db, so I have a net of 15 db gain at the tv. This will be more
than enough for the vhf stations that are pretty close, but I am not sure
about the uhf station 25 miles away. It would seem to be good enough for
that as well.
What do you think ?? Thanks for any advice !!
1_ there is very little differance in the loss of the coax if name brands
are used. Get some that has a braid and foil shield. Forget about all the
stuff that is quad shielded and other things unless you get it at a good
price. Look for Belden if you can find it .
2- with the station only 25 miles away and only 50 feet of coax you should
not need a preamp. With the VHF stations that close you might even get too
much signal and the stations will overlaod the preamp and the reception
goes all to pot. (simple explination)
3- probably not so much that you could tell it.
4= almost nothing from Radio Shack is worth it.
You want quad shielded. They're all pretty much the same. Any electric
supply house would have it. You didn't say where you are. A thousand foot
spool costs $110 at http://www.smarthome.com/8527.html
No real need for a pre-amp if you are 8 to 25 miles away. I would just get
the next size up antenna (or one with just a better UHF element) if you are
worried about a weak signal.
Rapid Realm Technology, Inc.
ditto the quad, rip off. try www.16inch.com for any antenna or satellite
Beldin cable is over rated, get comscope, its what most pro installers use.
avoid anything that is rat-shack, it is going to be cheap, lousy chinese
Use RG-6/U. It definitely has lower loss than the cheap stuff with the
foil shield. And don't use the twist-on connectors. Get good
connectors and a crucher to install them. Most problems are caused by
poorly installed connectors.
Amplifiers introduce noise and decrease signal-to-noise ration. Don't
use an amplifier if you don't need it. If you do need one, avoid the
Radio Shack models. I tried one and it caused lots of problems.
Use two separate antennas, one for the local stations and one (yagi or
corner reflector with gain) cut for the 25 mile distant station. Join
them together with a coupler at the antenna. No preamp should be
Any name brand double-shielded coax (Belden) will be fine.
Don't use a preamp unless you install it at the antenna. Preamps
amplify noise as well as signal. One exception is where you are using a
preamp for distribuiton purposes -- assuming that you have a good signal
at the house end of the coax you can add a preamp to boost the signal
prior to distribution via a multi-set splitter. But if you have a good
antenna you won't need a preamp for a single set installation.
It should not be a problem for stations 8 miles away, but for the 25
mile distant UHF station it could be. If you use the two antenna
configuration will the UHF antenna be pointed far enough away from the
chimney to miss it? If not, consider mounting the entire antenna
assembly on the chimney with a chimney mount.
I'm not a fan of RS products, but their distribution amplifiers work OK.
use a remote line powered preamp near the antenna. Put it in the attic
if you want to be able to serivce it. You can use RG6 or even low
loss RG59 is you use a preamp near the antenna.
since yo uneed it for UHF only, try to find one that has only a little
gain at VHF.
The key to a good signal to noise is to have a minimum loss BEFORE the
fist amplifier. Putting the amplifier after the coax is NOT as good as
putting the amplifer before the coax.
But a few feet won't hurt so mounting it in the attic where you can get
to it easilly is a good compromise.
As a video pro, I recommend the higher quality RG-6/U with braided
Low quality RG-6 with a foil shield will both radiate and absorb
signals on similar channels (say... same channel cable and off-air
signals). If cable tv is not an issue, maybe the cheaper stuff will
work, but you can still have problems if, for example, there is a
channel 3 or 4 in your area and you use a VCR that re-radiates at that
I got tired of the ghosts, threw away all of the cheap RG6 with the
pre-molded connecters and put my own connectors on the best RG-6/U
that I could buy.
No more ghosts... and the best signals I've ever seen... These were
As others have stated, you probably won't need a preamp for signal
gain. However, I use a low gain preamp as lightning protection for the
tv's input circuitry. I figure it's better to replace a $20 preamp than
to replace a $500 tv.
Many people forget their primary school science. They
assume destructive transients enter as if ocean waves.
Crashing and damaging only that one location. Reality: it is
electricity. Electricity first flows through everything in
the circuit. Only then does something (or many things) in
that circuit fail. The poster 'feels' that the pre-amp will
stop or block what 3 miles of sky could not? How silly.
Sacrificial protection is the classic myth. One more
reason why. It would take milliseconds or longer for the
pre-amp to become an open circuit. A destructive transient
does damage in microseconds. Even the fastest 'sacrificial'
protector - a fast blow fuse - takes tens of milliseconds to
blow. Where is protection provided by a pre-amp? Mythical
once we apply numbers.
"Bob S." wrote:
A hotly debatable subject. Based upon a straightwire theory where
voltage produces heat to blow the fuse, you are entirely correct.
However when you add electronic components, everything changes. The
output of transistors in a preamp is limited by the source voltage
(Vcc), thereby limiting any surge until the transistor blows. And bear
in mind I'm talking about a surge from the tv antenna and not a surge
in the ac wiring. Without a preamp, every lightning damaged tv I have
had was damage to the tuner section, which is antenna/cable inputs and
not from ac power surges. So in my experience it is not a myth.
While it will not protect from a direct hit it may help from the spikes
produced by near by flashes. I have a radio repeater on top of a mountain
and the phone line connected to it is my biggset problem . I installed a
couple of very low amp fuses and a couple of coils after them. The fuses
blow often after a thunder storm but they do protect the other equipment.
No doubt that a direct hit would take out everything.
Lightning will find a path to earth ground with or without
that in-line pre-amp. It is nonsense to wish something will
stop, block, absorb, or filter such transients. Anything that
is going to accomplish that protection is already inside the
Either it suffers a direct hit or it suffers nothing. And
that means everything in that path suffers the same current
equally. If nearby strikes were so destructive as implied,
that we routinely see cell phones and car radios damaged by
nearby lightning. Too often the 'so called' nearby strike is
really a direct strike. But that is beyond the scope of this
discussion and is already explained (using a horse as example)
in the newsgroup microsoft.public.windowsxp.basics on 11 Mar
2005 entitled "Power surge safety".
The preamp does nothing to provide transistor safety. For
transistor safety, earth ground defines that. Some inductance
in the coax can assist IF the earthing system exists. But no
earthing system means inline impedance (the pre-amp) provides
Richard Harrison discusses this often in the newsgroup
red.radio.antenna.amateur. He posted this on 12 Dec 2003
entitled "Lightning Arrester":
In this and most every post from experienced industry
professionals, there is nothing stopping lightning damage.
Either it is given a non-destructive path to earth, or it goes
right on through that pre-amp and TV tuner, as necessary, to
find earth ground. For those blessed with basic electrical
knowledge, the transient is a current source. That means
voltage will increase as necessary to overwhelm everything in
that path. That also means everything in that path sees the
same current. Current passes destructively down that wire
EXCEPT if the human provides the transient with a better path
to earth. Earthing is the protection; not some suicidal
pre-amp or fuse.
If fuses blew, well now you know how much protection is
already inside that tuner. The fuses quit long after the
tuner had protected itself and long after the transient had
completely finished. That pre-amp provides no protection.
Ralph Mowery wrote:
I owned a firm which installed antennas and satellite dishes for 15
First, I would install a UHF only yagi antenna pointed directly at the
station you wish to receive. I'm certain you don't have or have
access to a field strength meter, so just use a good grade of RG 6/u
coax and try hooking it up directly to your television. Rotate the
antenna for the best signal.
If the picture is still too snowy, then you need a preamp. The best
preamps these days are Blonder Tongue and they are commercial.
(residential preamps tend to be 300 ohm [flat wire] only and have too
high a signal to noise ratio to be decent). Do NOT install a preamp
at your set - that combination, as others have said, amplifies noise
with signal and won't help much, if at all. If you need to distribute
signal, a line amplifier is cheaper and better.
If you want some lightning protection, you might do this:
1. Run as direct a ground as possible with preferably copper strip to
one or more ground rods spaced 10' apart. Ground rods should be 8
foot 5/8" copper coated steel. If possible, the grounding conductor
should be welded to the rod or rods.
2. Before entering the house, coil the coax into three turns in a 12"
diameter circle. (The purpose is to create a path of greater
resistance to lightning while not affecting the rf signal).
3. Entering the house you should use a gas plug arrestor (Polyphaser
is one brand). This will set you back around $45 but they react in
microseconds and are just about the only effective lightning arrestor.
W_tom knows more about this than I do, but these are uniformly used in
all commercial installations for both cable tv, wireless internet,
cellular telephone, etc. Naturally, the arrestors need to be
connected to the ground system.
If you can't do this, just make certain you ground the antenna with
the heaviest wire you can find.
To expound on your last statement: "Heaviest wire" should not be solid
wire. Because of the surface effect of electricity traveling through a
wire, stranded or braided wire provides much more surface area,i.e.
path of least resistance. Thompsons is a leading manufacturer of
lightning protection equipment and they almost exclusively use braided
wire for down conductors.
Thanks for these additional responses. I am not finding a good source for
low-loss RG-6. I know how and where to find the right antenna and
pre-amp )if needed), but no source for anything other than cheap, high-loss
I did find one source on the net, but only in spools of 1000 feet !!
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