[hpsdr] Pure Signal RF Sampler

[Scott Traurig]

Klaus,

It is most unfortunate that Hilberling chose to use a 60dB coupling factor.
This does, of course, result in a coupled output level of 0dBm at 1KW
(60dBm). With that configuration, the PureSignal linearization function
becomes unusable on the ANAN-7000 and -8000 below approx. 100W, which is
the point at which the step attenuator on the receive path reaches the
bottom limit its dynamic range, i.e. 0dB attenuation.

PureSignal also becomes problematic at that level on the older ANAN series
radios, although the cause is somewhat different. The older radios have 6dB
more gain in the receive path, but when the step attenuator drops below
approx. 6dB crosstalk inside the radio starts to dominate.

If the coupling factor had been set to 50dB, with a resulting maximum
coupler output of +10dBm, then PureSignal linearization would have remained
usable down to 10W, a level below which it really doesn't matter. But for
non-QRO operations between 10 and 100W, an operator may be forced to switch
to a separate coupler to obtain optimum PureSignal linearization operation.

+13dBm is the maximum safe input level to Apache Labs hardware, leaving a
3dB safety factor, and this is a very conservative number as the input to
the step attenuator is actually rated at +20dBm max. Those who don't want
or need a +10dBm output can use an external attenuator, thereby giving
those who do need +10dBm the ability to obtain it.

The ubiquitous Xtronic coupler provides a 44dB coupling factor thereby
allowing it to be fine tuned by an external attenuator.

Palstar wisely chose a 50dB coupling factor on their LA-1K amplifier.

The RF-KIT amplifier also supplies a 50dB coupling factor.

Early Elecraft KPA-1500 amplifiers used a 60dB coupling factor, but I had
heard a rumor they were changing this to 50dB--can anyone confirm this?

Linear Amps UK chose a 60dB coupling factor and that configuration will
suffer from the same limitations as the Hilberling.

73,

Scott/w-u-2-o
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20180907/50f121fd/attachment.html>