Re: LF: LF EbNaut test from JN80 on 137370

[Andy Talbot <andy.g4jnt@gmail.com>]

Looked at like that it makes good sense.   On a vector scope plot, with I along the positive X axis and Y vertically upwards, a positive frequency rotates anti-clockwise, from I to Q, ie from right hand side x axis to vertical up.   So Q comes after I and is "lagging"

On a different matter, the zero frequency spike (1kHz leakage) is now sorted.    I added an RF gain stage with about 20dB gain, and another 500kHz low pass filter on its input. The amp is a design borrowed from audio, a two transistor design with simple resistive feedback to set the gain.  

The LPF should remove the damaging 13V narrow  spikes and reduce the total energy in the resulting square wave  should I leave it connected to the Procomm active antenna whilst transmitting.  As the amp runs from 12V, is biased mid way and has various bias resistors in series with the transistor terminals, so high levels of input should not damage it.  And even if devices do pop, they are only BC846 (NPN) and BC859 (PNP) taking no more than a couple of minutes to replace.

Andy  G4JNT

On 13 December 2015 at 13:34, Wolfgang Büscher <dl4yhf@freenet.de> wrote:

Am 13.12.2015 um 13:59 schrieb Andy Talbot:

The terms "leading" and "lagging" are the most confusing terms I've ever come across in AC.  A waveform on a scope, to the right of another one looks as if its leading it.   But it is later in time - so its lagging.

See my point ?

Yes... bare with me, old habits die hard .. but the 'vor- oder nacheilende Phase' (as we called it in german at school) came back to mind.
Indeed what I meant was when treating "I" as the reference, the waveform at "Q" appeared to (!) be "90° late", when viewed on a (kind-of) oscilloscope. Of course the signal at "I" doesn't appear at "Q" later - it only looks like that.


Cheers,
  Wolf .