On 6/26/2015 9:46 PM, rickman wrote:
On 6/26/2015 12:38 PM, amdx wrote:
On 6/26/2015 7:24 AM, rickman wrote:
I read this post in an antenna group and I don't get how this guy is
coming up with a negative noise figure. Looks to me like he is
calculating the noise figure of a resistor, not the amplifier. Anyone
care to explain this to me?

The part that seems bogus is this...

The negative NF is defined as the amplifier noise being less than the
increase in noise due to the amplifier gain.

I thought noise figure was NF = SNRin / SNRout

Rick

I once ask Ratzlaff about the FSL antenna, in his comments he said,
"high Q or low Q has little relation to how the FSL will actually
perform for receiving weak signals.", but then went on to say, "Of
course using Litz is the only type of wire to use."
When I ask him about why Litz is important if Q isn't, he got ****ed
off and wrote back, "When you make sarcastic replies to the info I
passed along, and question what I say, then I write you off as just a
tire-kicker, not interested in possibly learning something, and I have
no interest in saying anything more."
Seems to me he said something incorrect and didn't like having someone
ask him to clarify it. I'll leave it to you to figure out which part was
incorrect.
I thought Q would be important, an FSL is a ferrite loaded tuned loop.
With magic mixed in! ;-)
If Q is not important, why use Litz?
I suspect you might have already tried to ask him, and now he's mad at
you too!
Mikek

I suspect he said he didn't like your sarcastic replies because you made
sarcastic replies much more than he didn't want to discuss anything he
said.

I was not being sarcastic in my response when I ask about the Litz.
My understanding is Litz reduces R losses thus Q increases, if Q is not
important, why is Litz the only type of wire to use?
He probably realized that what he wrote made no sense and being ask
about it offended his ego and I'm that's why got angry.
On the other hand, if both of his statements are correct, it would be
interesting to learn why. I would learn something, because as it stands,
I can't reconcile the two statements.
In the end, the ferrite loaded antenna I was working on had a low Q,
I was using some surplus ferrite material I had, and it was lossy,
especially in the upper AMBCB. It had Q's under 100 down to 40. To
support Ratzlaff's theory, it did bring in stations that the radio
didn't hear if not near the Ferrite loaded antenna. But that's
subjective and I don't know what it would be like if it had a Q of 800.
Mikek