On 15 Nov 2003 18:48:21 GMT, (WP20032) wrote:

This is just a mental exercise, as I have already run coax directly to the rig
from the outside antenna on my trailer.

Hi Wayne,

Speaking of the loss of passive repeating, compare that to the loss of
the shielded inclosure you are trying to transceive through. No doubt
the latter will overwhelm the former giving you a new appreciation to
the chestnut "can you hear me now?"

The losses of passive repeating are typically compared to the coupling
from your set to the inside antenna (this is the loss to be computed
as it is by far the greatest). Losses within the coupling between
antennas (if matched) are trivial in comparison. Further, when the
topic arises, the simple observation that you are sitting next to a
window that is extremely large (in terms of wavelength) dilute the
argument that the passive re-radiator is needed at all (and serves
only as placebo).

73's
Richard Clark, KB7QHC

This is just a mental exercise, as I have already run coax directly to the
rig
from the outside antenna on my trailer.

Hi Wayne,

Speaking of the loss of passive repeating, compare that to the loss of
the shielded inclosure you are trying to transceive through. No doubt
the latter will overwhelm the former giving you a new appreciation to
the chestnut "can you hear me now?"

The losses of passive repeating are typically compared to the coupling
from your set to the inside antenna (this is the loss to be computed
as it is by far the greatest). Losses within the coupling between
antennas (if matched) are trivial in comparison. Further, when the
topic arises, the simple observation that you are sitting next to a
window that is extremely large (in terms of wavelength) dilute the
argument that the passive re-radiator is needed at all (and serves
only as placebo).

73's
Richard Clark, KB7QHC

Richard--
The question came up in my mind because I was not able to hit a relatively
close repeater from inside the trailer. The windows are screened, but there
are some minor leak areas around the refridgerator vent, etc.

My question was directed at a theoretically RF tight container. In such a
case, how effective would the reradiator be....20 dB down....40 dB, etc. I am
not sure how this would be calculated in the relatively near field, with
reflections.

TIA
Wayne

On 16 Nov 2003 23:42:38 GMT, (WP20032) wrote:

My question was directed at a theoretically RF tight container. In such a
case, how effective would the reradiator be....20 dB down....40 dB, etc. I am
not sure how this would be calculated in the relatively near field, with
reflections.

TIA
Wayne

Hi Wayne,

Resonant cavities are RF tight containers, and they exhibit less than
1dB to several many. The lower values are a function of low loss
(very large resonators), the higher values are a function of either
high loss or poor coupling. No doubt when you have folks residing
within the "cavity" loss becomes an issue - and then add coupling loss
to boot. This says nothing as to the state if the cavity is resonant
or not.

If the radiating antenna is within less than a wavelength of the
pickup, you don't stand much chance of coming out with less than 3dB
loss. You may as well count on at least 20dB loss.

A low power, half duplex, cross band repeater would probably remove
all the presumptions and actually work. One half residing within a
shield would also cut down on annoying hits on a shared frequency.

73's
Richard Clark, KB7QHC