Do you use 50 ohm or 75 ohm coax? I have a ham radio and wanting to
build some antennas to test and play around with. SOmeone said rg6 will
throw off my swr readings. I found a place around here that seels rg8/u
but it is 78 cents a foot. I was hoping to get some cheaper. I was
hoping to play around with building the antennas this weekend.

On 20 Jan 2005 06:26:53 -0800, postulated :
Do you use 50 ohm or 75 ohm coax? I have a ham radio and wanting to
build some antennas to test and play around with. SOmeone said rg6 will
throw off my swr readings. I found a place around here that seels rg8/u
but it is 78 cents a foot. I was hoping to get some cheaper. I was
hoping to play around with building the antennas this weekend.

Check the prices at a large home improvement store such as Lowes or
Home Depot.

There is an interesting question in QST this month from a ham that wants to
put an antenna in the attic and re-use some TV coax already existing. The
answer was that it was probably ok, depending on a few factors like the feed
point impedence of the antenna, the design and band coverage of the antenna,
use of a tuner, and transmitter power (cable TV coax may not be suited to
high power). I'd be more inclined to think that dB loss in coax related to
frequency is more critical than 50 ohm vs. 70 ohm mismatch. That is, I
wouldn't use RG58 for UHF applications, but would use RG 6 for HF. This is a
subject about which I am curious, so I'll be interested in other repsones,
too.

Good DX!

"Fred Zalupski" none listed wrote in message
...

so I'll be interested in other repsones

Well Fred, I was interested also but it doesn't look as if any other
responses are coming.
When the weather gets better I'm planning to go up with one of two scanner
antennas I have sitting in my garage. Unless someone talks me out of it, I'm
planning on using RG-6 for my scanner antenna and RG-58 for my inverted V
shortwave antenna. I'm planning on putting the scanner ant on top of pole
and fastening top of B&W V several feet under the scanner antenna.

I believe there was some discussion on the subject several months ago when I
had other things on my mind and didn't pay a lot of attention at the time.
Guess we'll have to look back through the archives for more info. RM~

When the weather gets better I'm planning to go up with one of two scanner
antennas I have sitting in my garage. Unless someone talks me out of it,
I'm
planning on using RG-6 for my scanner antenna and RG-58 for my inverted V
shortwave antenna. I'm planning on putting the scanner ant on top of pole
and fastening top of B&W V several feet under the scanner antenna.


While the losses below 30 mhz in coax does not mean very much from one type
to another, you might as well use the rg-6 for both antennas . The only
drawback for you is that much of the rg-6 does not use a copper shield and
can be difficult to make a connection to unless using a crimped type of
connector for the shield.

"Fred Zalupski" none listed wrote in message
...
There is an interesting question in QST this month from a ham that wants
to
put an antenna in the attic and re-use some TV coax already existing. The
answer was that it was probably ok, depending on a few factors like the
feed
point impedence of the antenna, the design and band coverage of the
antenna,
use of a tuner, and transmitter power (cable TV coax may not be suited to
high power). I'd be more inclined to think that dB loss in coax related to
frequency is more critical than 50 ohm vs. 70 ohm mismatch. That is, I
wouldn't use RG58 for UHF applications, but would use RG 6 for HF. This is
a
subject about which I am curious, so I'll be interested in other repsones,
too.

Good DX!



Assuming the antenna has a 50 Ohm feedpoint impedance the use of 75 Ohm
cable will cause a 1.5:1 SWR. This is an acceptable match, if you aren't
transmitting you'll not even notice the mismatch. There was an article
several years back about using "End runs" of hardline from the cable
company's.

If you are going to put up an antenna, use 50 ohm cable...
Larry ve3fxq


"Jim" wrote in message
...

"Fred Zalupski" none listed wrote in message
...
There is an interesting question in QST this month from a ham that wants
to
put an antenna in the attic and re-use some TV coax already existing.
The
answer was that it was probably ok, depending on a few factors like the
feed
point impedence of the antenna, the design and band coverage of the
antenna,
use of a tuner, and transmitter power (cable TV coax may not be suited
to
high power). I'd be more inclined to think that dB loss in coax related
to
frequency is more critical than 50 ohm vs. 70 ohm mismatch. That is, I
wouldn't use RG58 for UHF applications, but would use RG 6 for HF. This
is
a
subject about which I am curious, so I'll be interested in other
repsones,
too.

Good DX!



Assuming the antenna has a 50 Ohm feedpoint impedance the use of 75 Ohm
cable will cause a 1.5:1 SWR. This is an acceptable match, if you aren't
transmitting you'll not even notice the mismatch. There was an article
several years back about using "End runs" of hardline from the cable
company's.