<div dir="ltr">Gerhard,<div><br></div><div>Just slightly contrary to what Bill is suggesting, even with the Rev. 24 PA/filter board I'd suggest erring on the high side with respect to the signal level at the bypass connector in order to ensure that any internal crosstalk on the PA/filter board, improved as it may be in Rev. 24, is effectively suppressed. To that end I'd recommend selecting an attenuator on the output of your -43dB coupler such that you achieve somewhere between +7 and +10dBm at the bypass connector. This would require 10 to 13dB of additional attenuation on the output of your coupler.</div><div><br></div><div>The -11dBm ADC overload value and -17dBm Puresignal "green" levels are both referenced to the OUTPUT of the step attenuator, not at the bypass connector. The higher you run the step attenuator the better within reason with regard to crosstalk. Obviously you want to maintain a few dB of headroom where the step attenuator is concerned. Configuring for +10dBm at the bypass connector requires the step attenuator to be set to 27dB leaving 4dB of headroom for minor adjustments between bands. If you are uncomfortable with this and want a little more then shoot for +7dB at the bypass connector giving a nominal step attenuator setting of 24dB and headroom of 7dB.</div><div><br></div><div>73!</div><div><br></div><div>Scott/w-u-2-o</div><div><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, May 19, 2015 at 12:25 PM, Bill Diaz <span dir="ltr"><<a href="mailto:william.diaz@comcast.net" target="_blank">william.diaz@comcast.net</a>></span> wrote:<br><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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Gerhard,<br>
See below:<br>
On 5/19/2015 08:32, Gerhard Burian wrote:<br>
<blockquote type="cite">
<div>
<p class="MsoNormal">Hello,<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><span lang="EN-US">I received my new
ANAN100D last week and made first tests with pure signal,
the main reason why I changed from my FLEX5000A to the
ANAN100D.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Pure signal without
external Linear Amplifier works ok, using the internal
crosstalk.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Using an external
amplifier and feedback coupler shows following problems:<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">My setup:<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">PA with 2 kW (63 dBm).<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Feedback coupler: -43 dB
(as one with 63 dB didn’t work, always in red zone at S-ATT
0 dB). <u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Feedback signal on EXT1
and “ETX1 on TX” checked, S-ATT set to 31 dB, autocalibrate
on.</span></p>
</div>
</blockquote>
The newer PA/Filter boards (REV24) require the
sampler/coupler to be attached to the rear panel "BYPASS"
connector. Since you recently received your ANAN-100D, it is likely
you have a REV24 board. <br>
<br>
The EXT1, EXT2, and XVRT RX ports were disabled for both RX
and TX on the REV24 boards until Doug added the "Disable Bypass"
option to PowerSDR to enable these ports during receive only. This
option was enhanced in PowerSDR 3.2.27. Note that connecting your
sampler to EXT1 would not likely work as intended with the port
disabled during transmit on REV24 boards.<br>
<br>
SNIP<span lang="EN-US"><u></u><u></u></span>
<blockquote type="cite">
<div>
<p class="MsoNormal"><span lang="EN-US">Documents on Wiki say I
must not have more than +13 dBm feedback signal on the RX
preamp (with S-ATT at a high level).<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">If I calculate 63 dBm
minus 43 dB minus 5 dB, I get +15 dBm on the RX preamp. <u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Otherwise Wiki is
requesting -17 dBm after the step attenuator.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Is this correct? Why
does version 27 react this way?</span></p>
</div>
</blockquote>
Since ADC overload occurs at -11dbm, a signal level of +13dbm
would certainly be excessive. A "green" feedback level requires a
signal level of about -17dbm. Therefore, applying +13dbm to the
sample port would require ATT on TX to attenuate a signal applied to
your Bypass port by 30db (+13dbm + -17dbm). Since the ATT on TX
maximum attenuation is 31 db, this would not allow much leeway.<br>
<br>
With your +63dbm signal, the AC2IQ coupler (-43db coupling
loss) and an additional 20-30db of attenuation would lower the
sample applied to the Bypass port to about -10 to 0dbm. The
Linearity form "Auto Attenuate" option would then automatically
adjust ATT on TX to obtain the desired green feedback level (-17dbm)
for a sample provided to your bypass port.<br>
<br>
HTH<br>
Bill KC9XG
<blockquote type="cite">
<div>
<p class="MsoNormal"><span lang="EN-US"><u></u><br>
<u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">73’s<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US">Gerhard OE3GBB</span><br>
</p>
<br>
</div>
</blockquote>
<br>
</div>
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