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rickman · October 29th 14, 05:32 AM posted to rec.radio.amateur.antenna

On 10/29/2014 12:10 AM, wrote:
rickman wrote:
On 10/28/2014 9:27 PM, wrote:
rickman wrote:
On 10/28/2014 8:18 PM, wrote:

snip

Not sure what you are saying. There are tons of examples. But when I
did my search there was very little info on the design of loop antennas.
At least not much in depth enough to let me figure out how much signal
I might get from a given circuit.

I am asking about specific details of loop antenna design. I'm not sure
why people keep suggesting I look at "examples".

WWVB is a US time and frequency standard station and the Internet is
full of articles on DIY antennas and receivers for WWVB.

Many of those articles go into great detail about their design.

As you asked about 60 kHz, it would seem to me to be the place to start
to look for words of wisdom on the subject, no matter what particular
detail you are looking for.

I believe I said I have read much of that info. I did this a couple of

Yes you did, after you made the post I responded to.

years ago and picked an approach. I was not able to convince myself it
would work properly. So now, before I build anything more, I would like
to fill in some of the details.

Of all the design info I found, not one discussed optimizing the antenna
for maximum voltage. When I was discussing this in another group,
specifically about a spice simulation of the circuit, someone pointed
out that I needed to include the effect of the radiation resistance.
Again, I have not found any other discussions of the radiation
resistance of a receiving antenna, specifically a tuned, shielded loop
antenna. Is this a red herring? When designing an antenna with a very
high Q, can the radiation resistance of a shielded loop antenna be ignored?

The radiation resistance is a reciprocal property, i.e. it is the same
for transmitting and receiving.

Yes, but I've never calculated it for either. I have been working with
effective height. That is one thing I'm not clear on, how the two
effects can be separated. I guess the radiation resistance has
different impact depending on the circuit used. It will be more
apparent in a high Q circuit than a low Q one.

I will assume you already know the relationship of resistance to Q.

You say I should "start" with the many words of wisdom on the subject.
I am not "starting" and I have found many words of wisdom on loop
antennas in general, but not much on the specific questions I am asking.

That's all well and good but not evident until way into the postings.

It's a little bit funny, but when the one who shall not be named asked
about short antennas the discussions were full of info on radiation
resistance and details. Now that I am asking about my design, no one
wants to discuss the technical issues and just recommend some site where
they tell you how to build the antenna that suited their purpose.

Again, radiation resistance is a reciprocal property.

To determine such things, you need to use an antenna analysis tool
and plug the resultant numbers into Spice which will tell you whether
or not it can be ignored.

Actually, I was researching to verify my conclusions made the last time
I took a stab at this and found a page that gives a formula for
radiation resistance proportional to (μr N A/λ^2)^2. I hope the Greek
letters show properly. Holding μr and λ constant that makes the
radiation resistance proportional to r^2. I will need to check this to
see if it is significant compared to the resistive losses.

--

Rick