Richard,
Thanks for your detailed answer.
I am not really set upon combining. I am glad to run another wire. I gather
from your response I am better off with the coax and two transformer setup
than with using 300 ohm twin wire for the strictly AM radio purpose.
Thanks,
Eric

"Richard Clark" wrote in message
...
On Mon, 23 Jan 2006 15:29:13 GMT, "Eric"
wrote:

1. Can one antenna feed both tuners by being hooked up in parallell? Is
there a signal loss?

Hi Eric,

Yes/Yes. Does the loss matter at a distance of 18 miles? Probably
not. However, this question is rather hazy given the ones that follow
seem to ask the same thing again.

2. Am I better off using 300 ohm flat TV type cable or should I use two
300/75 transformers (one at the reciever and one at the loop antenna)
with
RG-6 quad shield? I am wondering if the transformer loss is worth the
possible noise reduction from the coax.

Again, the presumption of loss is exaggerated. Your problem, as you
describe it, is noise. However, the transformers are probably more
suited for FM than AM. On further consideration, that may not matter
either as it is the shielding action of the coax that may in fact
offer more payback in noise reduction for the AM operation than any
issue over the expected transformer loss.

To take this one step further, at the AM antenna end of the coax,
simply coil the coax around an empty liter coke bottle with a dozen or
so turns. This is more to help isolate from noise than anything else.

3. Should I be able to use 1 loop for the two tuners and the coax, is it
best to split the 75 ohm coax and use independent 300 ohm transformers or
to
split the 300 ohm feed from one tuner to the other?

Another hazy question. Run separate lines for AM and FM. You can
combine them, and split them out at each end so that there is only one
long run of coax (which is commendable). However, as you are
approaching this with a known problem, it is in your best interest to
keep the bands/antennas/lines separate.

4. Is it possible to use the FM antenna for the AM and how would it be
best
to split that up? (I would have to feed two FM and two AM tuners but only
two could be used at once).

Another hazy question. Through all this haze, it seems you are quite
set upon combining things. With such a wide separation in frequency,
you would tend to end up with a single solution that poorly serves two
purposes. It raises the complexity factor, and any problem compounds
that further.

This simply means that, yes, you can; but it would not seem likely you
are actually doing yourself a favor.

73's
Richard Clark, KB7QHC

On Mon, 23 Jan 2006 19:37:34 GMT, "Eric"
wrote:

Richard,
Thanks for your detailed answer.
I am not really set upon combining. I am glad to run another wire. I gather
from your response I am better off with the coax and two transformer setup
than with using 300 ohm twin wire for the strictly AM radio purpose.
Thanks,

Hi Eric,

Why you would use 300 Ohm twin wire for AM antennas is odd, but not
prohibited. However, it does demand all the attention to keeping the
line balanced (like I said, move away from coax, and problems become
compounded). If there are 300 Ohm issues both at the antenna and at
the radio, you must preserve them through transformers if you do
migrate to coax.

Balanced goes by many requirements, none of which can be ignored. An
unbalanced condition is a tacit allowance for the intrusion of noise.
As you describe a problem with noise - well, you see where this leads,
an absolute exercise in driving out the imbalance.

Where does it occur? How do you find it? The problems are stacking
up already. It happens at the antenna itself when it is mounted near
conductive materials. This observation only leads to more questions,
what might be conductive that is nearby, and how near is nearby? The
same problem exists with coax feeds, but you can solve those easier
with the coiled lead at the end (you probably could do the same with
twin lead - and winding either lead 4 or 5 times through a ferrite
core could be equivalent fixes). However, this is only at the antenna
end, and that may not be the source of the imbalance. For twin leads,
it could be as easily that the lead traces up against metal ducting,
or along house wiring.

If you are scrupulous about these kind of details, twin lead may
indeed work fine.

Another method of tackling the problem is to carry a small transistor
radio around the house, and try to locate the noise itself. Killing
the source is a one pound cure for a ten pound problem. If the noise
comes from outside the house, then you have antenna issues, and all
the wishing in the world in trying to avoid a different antenna will
come to naught.

73's
Richard Clark, KB7QHC