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body { font-family: Tahoma; font-size: 12pt; }--></style></head><body><div>Thanks Scott. </div><div><br /></div><div>The resistive coupler I built is peculiar to the contents of my Junk Box. I used a series parallel arrangement of 9 half watt metal film resistors in three parallel - series groups and a 51 ohm terminator to provide -51 dB coupling and the necessary voltage and power rating for 1 kW. It is flat to a dB or so from 160 - 6m. Actually the Pure Signal 2 implementation is very non critical on sample levels. The software is completely happy with the linear enabled at 800 - 1000W. However turning the linear off and just having 5W from the ANAN 10, although the software flags low level, it still reduces the IMD by ~30 dB. Kudos to 16 bits of dynamic range. A great piece of software ! Thank you HPSDR programmers !!</div><div><br /></div><div>It might be worth including a note on the alternatives here in the Power Signal documentation.</div><div><br /></div><div>73, Dick W0QM, G3FNL</div>
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<div>------ Original Message ------</div>
<div>From: "Scott Traurig" <<a href="mailto:scott.traurig@gmail.com">scott.traurig@gmail.com</a>></div>
<div>To: "Richard Grubb" <<a href="mailto:richard.n.grubb@comcast.net">richard.n.grubb@comcast.net</a>></div>
<div>Cc: "hpsdr" <<a href="mailto:hpsdr@lists.openhpsdr.org">hpsdr@lists.openhpsdr.org</a>></div>
<div>Sent: 9/5/2018 11:40:40 AM</div>
<div>Subject: Re: [hpsdr] Pure Signal RF Sampler</div><div><br /></div>
<div id="xe208c8139532460"><blockquote cite="CAGK9zXpRMDdpf1ejuia7OjvHLTovgpKdFE2wt=tByM3iuxhkAA@mail.gmail.com" type="cite" class="cite2">
<div dir="ltr">You are not missing anything, Dick. You can develop the signal however you wish, as long as you provide a signal whose amplitude is within the dynamic range of the receiver hardware and algorithm.<div><br /></div><div>People have gravitated towards the Xtronic coupler because it provides ruler flat coupling response from 160M to 6M, which takes some of the guesswork out of knowing if you are obtaining the proper feedback signal levels, because the design is bulletproof in terms of power handling, and because the insertion loss is quite small. Oh, and because they don't have to build it and characterize it themselves ;-)</div><div><br /></div><div>There are certainly a few folks who are using their own coupler/sampler designs, LP-100 sensors, and other, similar solutions. The only solution I don't recommend is the Clean RF sampler. Bump that knob the wrong way and it's possible you could fry your receiver, depending on the power levels you are running and how much additional attenuation you have on the sample port. Maximum safe input power level to any port on Apache hardware is +13dBm based on the component data sheets.</div><div><br /></div><div>73,</div><div><br /></div><div>Scott/w-u-2-o</div><div><br /></div><div>On Wed, Sep 5, 2018 at 1:08 PM Richard Grubb <<a href="mailto:richard.n.grubb@comcast.net">richard.n.grubb@comcast.net</a>> wrote:<br /></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">***** High Performance Software Defined Radio Discussion List *****<br />
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<div>I am wondering why the documentation on Pure Signal implies the use of a directional coupler as necessary to obtain the required sample of the transmitted RF. I can understand why that could be desirable when the feedback was not adaptive, or where the sampler is remote from the final amplifier.. However when the predistortion is being generated adaptively I do not understand why a simple resistive non directional coupler would not be perfectly satisfactory and much easier to implement. The antenna system should be quite linear and the voltage sensed adjacent to the final amplifier output should surely always be a valid measurement of the transmitter transfer function. Of course a directional coupler is always useful to measure VSWR and is usually already present in modern amplifiers, although often not readily accessible for use with Pure Signal.<div><br /></div><div>I have implemented Pure Signal on an ANAN 10, Juma 1000 PA combination and used both the published directional coupler design and a simple resistive pick off at the PA output with equally excellent results.</div><div><br /></div><div>What am I missing?</div><div><br /></div><div>Dick, W0QM, G3FNL </div></div></blockquote></div></div>
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