[hpsdr] Pre-distortion Sampler

[Clyde Washburn]

The compensator for the Bird 4273 (1.8-50MHz) is configured as follows:

Node 1:  input BNC from Bird 4273
Node 2:  two output BNC's, one for the Predistortion Receiver input, the other for Spectrum Analyzer -- terminate unused outputs
with 50 ohms.
Schematic:
51 ohms, node 1 to ground.
680 ohms paralleled with 17uH from node 1 to node 2.

17uH is composed of two Delevan 1537 series chokes in series, with bodies at 90 degrees to each other.  Use only air or
powdered-iron core chokes, no ferrites.

Attenuation at high frequency is 29 dB, decreasing to 18dB at 1.8 MHz -- this provides -15dBm out at 1KW with the 4273 in the middle
of its adjustment range, with about +/-8 dB adjustment from there.

Clyde, K2UE

-----Original Message-----
From: hpsdr-bounces at lists.openhpsdr.org [mailto:hpsdr-bounces at lists.openhpsdr.org] On Behalf Of Helmut, DC6NY
Sent: Wednesday, December 11, 2013 4:38 PM
To: 'Shirley Márquez Dúlcey'; hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Pre-distortion Sampler

***** High Performance Software Defined Radio Discussion List *****

Hi,

RF samplers with capacitive divider have no flat frequency response. A difference of 10-15 dB between 2 and 50 MHz may be sufficient
for monitoring but not for measuring. In the case of the pre-distortion loop new attenuation adjustment would be necessary after
each band change. Not acceptable!

73, Helmut, DC6NY

73 -----Ursprüngliche Nachricht-----
Von: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Shirley Márquez Dúlcey
Gesendet: Mittwoch, 11. Dezember 2013 21:07
An: hpsdr at lists.openhpsdr.org
Betreff: Re: [hpsdr] Pre-distortion Sampler

***** High Performance Software Defined Radio Discussion List *****

The January 2014 issue of QST has a design for a homebrew signal sampler.
The design uses a capacitive divider with 38dB attenuation followed by a 22dB resistive attenuator. This might serve as a starting
point for a sampler for predistortion designs.

On Mon, Dec 9, 2013 at 11:35 AM, Tony Hagen <prosdr at gmail.com> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
> I received my Rigol spectrum analyzer few weeks back The spectrum 
> analyzer with input requirement of max +20dBm.
>
> Is the pre-distortion sampler can be used to couple the output of 
> Munin or any other amplifier of approx. 200 watts with the spectrum 
> analyzer
>
> 73s
> Tony
>
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