[hpsdr] Pure Signal RF Sampler (Update from Linear Amps UK)

[Scott Traurig]

Update: Roger Banks from Linear Amps contacted me directly to inform me
that their Gemini HF-1K does indeed provide a 50dB coupling factor, rather
than the 60dB noted below using information from the Linear Amps website.
This is good news for those who are looking to use PureSignal with the amp
in standby. 73--Scott.

On Fri, Sep 7, 2018 at 9:39 AM Scott Traurig <scott.traurig at gmail.com>
wrote:

> 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/20180907/52964f50/attachment.html>