On Sun, 27 Jun 2004 19:55:58 -0700, "CW" no adddress@spam free.com
wrote:

When I made my prior comments about the lack of
consideration given to receive antenna, I was referring to the antenna
group. I didn't realize that the message was cross posted. It just amazes me
that they will debate a transmitting antenna to minute detail but receiving
antennas deserve no consideration other than a random piece of wire thrown
into a tree.

Hi OM,

As generalizations go, this one falls short with them all.

We here at rec.radio.amateur.antenna often recite the credo that
"reciprocity rules." This means that all considerations given to a
transmitting antenna are equally applied to receiving antennas.

However, I am sure you are responding to the disparity in coverage
between receiving and transmitting antennas - and this is for good
reason. Reception and Transmission are NOT reciprocal operations. A
receiver has far more latitude to accomplish its goal than does a
transmitter. Unless you have an abysmal receiver poorly connected to
an inadequate whip, the stock receiver with a simple length of wire is
often very close to doing a good job. If the receiver suffers from
any of a multitude of issues, there is generally a solution that
answers the problem specifically. About the only thing you can do for
the transmitter is to turn up the power, or lower the transmission
loss. It stands to reason that our focus is on optimizing the loss
side of the balance ledger.

Returning to the credo of "reciprocity rules," any gain to the
advantage of a transmitter is enjoyed by the receiver and the SWLer
stands the same advantage. But if that advantage is measured at 3dB,
this has the significance of 50W in 100W compared to the SWL S-Meter
change from S5 to S6 (BFD). Even though it is the same 3dB, there is
the illusion of perspective (my 50W compared to your 5µV). If the SW
station is buried in S9 noise, then this is not an antenna problem
(unless you can null the noise out through careful lobe positioning).
Filtering and/or DSP stand to answer the problem, but these are
obviously not remedies to transmission issues.

There is another thread discussing the goal of constructing a small
loop for 80M reception (and how well 5 turns might achieve some
benefit). The same issues of loss prevail for the comparison of
Radiation Resistance to Ohmic Resistance for a 1 Meter loop. The loop
Rr is in the thousandths of an Ohm and about on par for a small wire's
Ohmic loss. There's that 3dB again and what concerns the transmission
efficiency is far easier to tolerate with the receiver and its surplus
of gain. If the SWLer pays attention to this issue as it concerns the
transmission problems, then that SWLer stands to gain in the
efficiency returned. However, this is not to suggest that there is an
actual need to obtain this efficiency; but if the SWLer mismanages the
construction, the topic is discussed to the necessary depth to correct
it.

A simple basis of comparison will illustrate. Many SW radios have a
ferrite stick antenna that will work with at least some stations (VOA,
WWV, BBC and a host of others). Try transmitting through that same
ferrite stick and it will be like trying to shout through a straw.
Our only alternative is to add an amp, but the big KW is only going to
render smoke.

73's
Richard Clark, KB7QHC