I am looking for a 6 to 1 balun, 300 ohms balanced to 50 ohms coax. I
don't need one that handles transmitter power as I am only using it for a
receiving antenna.

I have on hand several hundred feet of 50 ohm coax, RG58 modified (IEEE
802.3). I want to use it to connect my 300 ohm TV dipole antenna in my
attic to my HDTV in the basement. And, of course, I would need a 50 ohm
to 75 ohm match at the HDTV.

We only watch over-the-air TV. Why? Because I live within 2 miles of
three 1000 ft TV towers. In fact, the dipole in the basement works quite
well. But I do get dropouts during storms; go figure. I get 17 channels
for free, so why go cable or FIOS. Nothing worthwhile there anyway.

So can someone point me to a good site for balun design. I've done the
Google searches, but all that I find seem to be for high power
applications.

Any help would be appreciated.

Al

alchazz wrote:
I am looking for a 6 to 1 balun, 300 ohms balanced to 50 ohms coax. I
don't need one that handles transmitter power as I am only using it for a
receiving antenna.

I have on hand several hundred feet of 50 ohm coax, RG58 modified (IEEE
802.3). I want to use it to connect my 300 ohm TV dipole antenna in my
attic to my HDTV in the basement. And, of course, I would need a 50 ohm
to 75 ohm match at the HDTV.

We only watch over-the-air TV. Why? Because I live within 2 miles of
three 1000 ft TV towers. In fact, the dipole in the basement works quite
well. But I do get dropouts during storms; go figure. I get 17 channels
for free, so why go cable or FIOS. Nothing worthwhile there anyway.

So can someone point me to a good site for balun design. I've done the
Google searches, but all that I find seem to be for high power
applications.

Any help would be appreciated.

Al


Have you tried the 50 ohm cable directly (with a 4:1 xfmr at the dipole)
to see how it works? The 300 ohms for the dipole, etc only apply at one
single frequency and with signals that strong there really shouldn't be
an issue with additional loss. Reflections will not show up visibly
with digital tv.

Part of the issue here is winding the balun and set transformer at UHF
frequencies. Not impossible to do with inexpensive parts (multicore
ferrites) but I wonder if its really necessary?

GL,
Bill

In message , Bill M
writes
alchazz wrote:
I am looking for a 6 to 1 balun, 300 ohms balanced to 50 ohms coax. I
don't need one that handles transmitter power as I am only using it
for a receiving antenna.
I have on hand several hundred feet of 50 ohm coax, RG58 modified
(IEEE 802.3). I want to use it to connect my 300 ohm TV dipole
antenna in my attic to my HDTV in the basement. And, of course, I
would need a 50 ohm to 75 ohm match at the HDTV.
We only watch over-the-air TV. Why? Because I live within 2 miles of
three 1000 ft TV towers. In fact, the dipole in the basement works
quite well. But I do get dropouts during storms; go figure. I get 17
channels for free, so why go cable or FIOS. Nothing worthwhile there

So can someone point me to a good site for balun design. I've done
the Google searches, but all that I find seem to be for high power
applications.
Any help would be appreciated.
Al


Have you tried the 50 ohm cable directly (with a 4:1 xfmr at the
dipole) to see how it works? The 300 ohms for the dipole, etc only
apply at one single frequency and with signals that strong there really
shouldn't be an issue with additional loss. Reflections will not show
up visibly with digital tv.

Part of the issue here is winding the balun and set transformer at UHF
frequencies. Not impossible to do with inexpensive parts (multicore
ferrites) but I wonder if its really necessary?

GL,

Yes, just go ahead and use a normal 4:1 off-the-shelf TV/FM balun. They
are only a couple of dollars. The effects of the incorrect impedance
transformation will be negligible, and there's little to be gained by
trying for 'perfection'. If it doesn't work, you've lost virtually
nothing. [Note that, if it doesn't work, it won't be because the ratio
is wrong, or that the coax isn't 75 ohms.
--
Ian

On Mon, 18 May 2009 16:01:04 +0100, Ian Jackson wrote:

In message , Bill M
writes
alchazz wrote:
I am looking for a 6 to 1 balun, 300 ohms balanced to 50 ohms coax. I
don't need one that handles transmitter power as I am only using it for
a receiving antenna.
I have on hand several hundred feet of 50 ohm coax, RG58 modified
(IEEE 802.3). I want to use it to connect my 300 ohm TV dipole antenna
in my attic to my HDTV in the basement. And, of course, I would need a
50 ohm to 75 ohm match at the HDTV.
We only watch over-the-air TV. Why? Because I live within 2 miles of
three 1000 ft TV towers. In fact, the dipole in the basement works
quite well. But I do get dropouts during storms; go figure. I get 17
channels for free, so why go cable or FIOS. Nothing worthwhile there

So can someone point me to a good site for balun design. I've done
the Google searches, but all that I find seem to be for high power
applications.
Any help would be appreciated.
Al


Have you tried the 50 ohm cable directly (with a 4:1 xfmr at the dipole)
to see how it works? The 300 ohms for the dipole, etc only apply at one
single frequency and with signals that strong there really shouldn't be
an issue with additional loss. Reflections will not show up visibly with
digital tv.

Part of the issue here is winding the balun and set transformer at UHF
frequencies. Not impossible to do with inexpensive parts (multicore
ferrites) but I wonder if its really necessary?

GL,

Yes, just go ahead and use a normal 4:1 off-the-shelf TV/FM balun. They
are only a couple of dollars. The effects of the incorrect impedance
transformation will be negligible, and there's little to be gained by
trying for 'perfection'. If it doesn't work, you've lost virtually
nothing. [Note that, if it doesn't work, it won't be because the ratio
is wrong, or that the coax isn't 75 ohms.

Yes, I thought I might try that. You guys are right. It should not be an
issue at these signal levels. I have a bunch of the 4:1 baluns that I
have gotten from our town's recycling station.

But it is still odd that I get dropouts when I am so close to the towers.

Al

In message , alchazz
writes
On Mon, 18 May 2009 16:01:04 +0100, Ian Jackson wrote:

In message , Bill M
writes
alchazz wrote:
I am looking for a 6 to 1 balun, 300 ohms balanced to 50 ohms coax. I
don't need one that handles transmitter power as I am only using it for
a receiving antenna.
I have on hand several hundred feet of 50 ohm coax, RG58 modified
(IEEE 802.3). I want to use it to connect my 300 ohm TV dipole antenna
in my attic to my HDTV in the basement. And, of course, I would need a
50 ohm to 75 ohm match at the HDTV.
We only watch over-the-air TV. Why? Because I live within 2 miles of
three 1000 ft TV towers. In fact, the dipole in the basement works
quite well. But I do get dropouts during storms; go figure. I get 17
channels for free, so why go cable or FIOS. Nothing worthwhile there

So can someone point me to a good site for balun design. I've done
the Google searches, but all that I find seem to be for high power
applications.
Any help would be appreciated.
Al


Have you tried the 50 ohm cable directly (with a 4:1 xfmr at the dipole)
to see how it works? The 300 ohms for the dipole, etc only apply at one
single frequency and with signals that strong there really shouldn't be
an issue with additional loss. Reflections will not show up visibly with
digital tv.

Part of the issue here is winding the balun and set transformer at UHF
frequencies. Not impossible to do with inexpensive parts (multicore
ferrites) but I wonder if its really necessary?

GL,

Yes, just go ahead and use a normal 4:1 off-the-shelf TV/FM balun. They
are only a couple of dollars. The effects of the incorrect impedance
transformation will be negligible, and there's little to be gained by
trying for 'perfection'. If it doesn't work, you've lost virtually
nothing. [Note that, if it doesn't work, it won't be because the ratio
is wrong, or that the coax isn't 75 ohms.

Yes, I thought I might try that. You guys are right. It should not be an
issue at these signal levels. I have a bunch of the 4:1 baluns that I
have gotten from our town's recycling station.

But it is still odd that I get dropouts when I am so close to the towers.

That might well be due to multiple off-air reflections. Digital TV isn't
totally immune to the problems these cause (but, of course, you don't
see the reflections like you do on analog TV pictures).

Even if you live in an area of high signal strength, it's often
necessary first to get a clean signal from the antenna, which may need
to be a 'high-gain' design in order to reduce reflections. If you've got
too much signal at the TV set, you can always fit in-line attenuators at
the TV input (fixed barrels or variable 'twiddlers').
--
Ian

"alchazz" wrote in message
news
I am looking for a 6 to 1 balun, 300 ohms balanced to 50 ohms coax. I
don't need one that handles transmitter power as I am only using it for a
receiving antenna.

I have on hand several hundred feet of 50 ohm coax, RG58 modified (IEEE
802.3). I want to use it to connect my 300 ohm TV dipole antenna in my
attic to my HDTV in the basement. And, of course, I would need a 50 ohm
to 75 ohm match at the HDTV.

We only watch over-the-air TV. Why? Because I live within 2 miles of
three 1000 ft TV towers. In fact, the dipole in the basement works quite
well. But I do get dropouts during storms; go figure. I get 17 channels
for free, so why go cable or FIOS. Nothing worthwhile there anyway.

So can someone point me to a good site for balun design. I've done the
Google searches, but all that I find seem to be for high power
applications.

Any help would be appreciated.

Al


I would not worry about the balun for TV reception. Just use the 300 to 70
ohm one. I think you will get a lot of loss with the rg 58 coax. Go to the
rg6 type coax for much lower loss.

I have a 2 meter horizontal M2 antenna up 70 feet and when the cable goes
out I connect it to my converter box. It is fed with about 130 feet of low
loss rg 8 type coax and from there I go to about 25 feet of rg-6 type to get
to the TV. I get about 30 channels with this setup. Probably 30 to 50
miles from most of the transmitters.

It is possible the TV signals are overshooting you. Sometimes almost under
a tower can be worse than being out several more miles. As someone
mentioned you may be getting multible and causing dropouts. I had a 2 meter
antenna in the house hooked on the back of a transceiver and people walking
around the room would sometimes cause a dropout and they were not in a
direct line from the rig to the repeater.

Hey OM:
A 3:1 mismatch you only lose 25% of the power. And that's power not
voltage. So with 50 to 75 ohms you are not going to lose much. And you
need plenty of signal so there won't be any pixelization. And if you
don't use a balun at all: you have the shield of your coax as an
antenna too. I say connect direct and forget about it.

There's only 2 possibles; either you don't get enough signal or you
do. Those are better odds than the lottery.

73 OM
de n8zu

In message
,
raypsi writes
Hey OM:
A 3:1 mismatch you only lose 25% of the power. And that's power not
voltage.

Where does the 3:1 SWR come from? With the off-the-shelf $2 300:75 ohm
balun, connected to a 50 ohm feeder, the mismatch will be only 1.5:1.

So with 50 to 75 ohms you are not going to lose much.

Exactly.

And you
need plenty of signal so there won't be any pixelization.

And if you
don't use a balun at all: you have the shield of your coax as an
antenna too.

Arrrrrhg!!!!. That's NOT a situation you want to have!

I say connect direct and forget about it.

And I say FIT IT and forget about it! It's so easy to do things
'properly'.

There's only 2 possibles; either you don't get enough signal or you
do. Those are better odds than the lottery.

You're correct about this bit!
--
Ian

"Ian Jackson" wrote in message
...
In message
, raypsi
writes
Hey OM:
A 3:1 mismatch you only lose 25% of the power. And that's power not
voltage.

Where does the 3:1 SWR come from? With the off-the-shelf $2 300:75 ohm
balun, connected to a 50 ohm feeder, the mismatch will be only 1.5:1.


A 3:1 swr does not really equate to a 25% power loss. I think it was the
ARRL that published a chart that at first glance may make it look like
that.

On Thu, 21 May 2009 19:08:40 -0500, "Ralph Mowery"
wrote:


A 3:1 swr does not really equate to a 25% power loss. I think it was the
ARRL that published a chart that at first glance may make it look like
that.

In a lossless missmatched feeder, part of power is reflected back at
each end, while a portion is delivered to the antenna and radiated
into space and finally after many reflections most of the power is
finally radiated into space.

The localized voltage and current peaks can be an issue both in the
feeder or transmitter.

However, with a lossy feeder, some power is attenuated i.e. converted
to heat on the initial path to the antenna, also when part of the
power is reflected from the mismatch at the antenna, the reflected
wave will suffer from the attenuation and again after reflecting from
the other end, it will again suffer some attenuation. After several
reflections, quite a lot of the initially reflected power is converted
to heat.

When looking at the ARRL charts, to get a 25 % or -1.25 dB power loss,
the feeder loss when matched would be 0.8 dB and the additional loss
due to the 3:1 SWR would be about 0.4 dB.

Paul OH3LWR