[Elecraft] K3 sensitivity below 40 meters

[Richard Fjeld]

Okay, digest this;  my budget allows an 80 meter delta loop fed with open 
wire and I tune it with a manual tuner. As far as my radio is concerned, it 
looks at a resonant antenna system allowing a  maximum transfer of power on 
both transmit and receive.  Any fault with that statement?

We are way off the original post which was asking why he had to "to engage 
the 20 dB preamp on the K3 to get it to hear an S9 signal at  the 
appropriate level of other receivers?"

Now I know why people reply off line.

Rich, n0ce

----- Original Message ----- 
From: "David Gilbert" <xdavid at cis-broadband.com>
To: <elecraft at mailman.qth.net>
Sent: Tuesday, November 13, 2012 6:12 PM
Subject: Re: [Elecraft] K3 sensitivity below 40 meters


>
> Even that misses the point, I'm afraid.  Remember that the original
> comment referred to the receive capability of an antenna.
>
> The only thing that matching or "tuning to resonance" does is improve
> the amplitude of the combined signal and noise feeding the rig ... it
> does not improve the signal to noise ratio.  A good receiving antenna,
> however, has some pattern to it that captures the desired signal while
> discriminating against unwanted noise, whether the noise is man made or
> atmospheric.  A Beverage antenna, for example, has quite a strong
> pattern in one direction so it has a good signal to noise ratio feeding
> the rig.  A Beverage is pretty inefficient, though, and the desired
> signal is pretty weak, so typically a matching transformer (9:1 or so)
> is used to optimize the signal transfer and a low noise preamp (either
> in the rig or external) is also used ... but the signal to noise ratio
> is determined by the antenna independent of whether it is matched or
> not.  I guarantee that an unmatched Beverage with enough low noise gain
> after it will outperform any practical resonant or matched ("tuned to
> resonance") antenna available to hams.
>
> 73,
> Dave   AB7E
>
>
>
>
> On 11/13/2012 4:29 PM, Don Wilhelm wrote:
>> Yes, I agree.
>>
>> Given a bit of "benefit of doubt", I would think the poster would have
>> better said, an antenna "tuned to resonance" rather than a resonant 
>> antenna.
>> Many very good antennas are not inherently resonant, but resonance (and
>> therefore good power transfer) is achieved by means of some kind of
>> tuning mechanism.
>>
>> 73,
>> Don W3FPR
>>
>> On 11/13/2012 6:21 PM, David Gilbert wrote:
>>> Particularly as far as receiving goes, that's a totally erroneous
>>> statement that has been dispelled many, many times.  There is nothing
>>> magical or beneficial about a resonant antenna short of the fact that it
>>> sometimes makes it easier to match.  Check out how (and how well) a
>>> Beverage antenna or one of the flag/pennant antennas work for receiving
>>> to see the fallacy of your comment.
>>>
>>> The key to a good receive antenna is having a pattern that discriminates
>>> against QRM or QRN as the case may be.  As long as there is enough low
>>> noise gain after the antenna all else is misconception.
>>>
>>> Dave   AB7E
>>>
>>>
>>>
>>> On 11/13/2012 12:13 PM, Richard Fjeld wrote:
>>>> In summary, even a good radio needs a resonant antenna.
>>>>
>>>> Rich, n0ce
>>>>
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