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<div class="moz-cite-prefix">I had a problem on the HiQSDR
Preselector that prevented it going into TX and now it's fixed I
decided to test with the integral 10W PA that uses the BPF's for
both RX and TX.<br>
<br>
Hermes was set up with 2 RX, one on 20m and one on 40m and
connected to the Lightning Bolt Quad.<br>
<br>
HiQSDR was connected to the 40m 1/4 wave sloper fed against the
tower.<br>
<br>
When I activated PTT on the HiQSDR I got ADC overload flashing on
Hermes using cuSDR64 and 20dB attenuation.<br>
<br>
Any thoughts or suggestions?<br>
73 ... Sid.<br>
<br>
On 04/03/13 02:51, Joe Martin K5SO wrote:<br>
</div>
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cite="mid:776ABF44-E034-402A-9733-2C4C3A1E48A3@valornet.com"
type="cite">
<pre wrap="">***** High Performance Software Defined Radio Discussion List *****
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Hi Byron,
<div><br>
</div>
<div>Yes, when using OpenHPSDR receivers with high power
transmitters you do need to use a T/R switch to remove the
receiver from its antenna when the local transmitter(s) are
operating, or at least you should provide some type of
antennuator switching when the local transmitters are
transmitting to ensure that the input level to the Hermes
receiver is not excessive. Such T/R switching relays are
provided on the Alex Tx filter board and on the ANAN-series PA
boards, as examples of OpenHPSDR hardware. Alternatively, you
may certainly use your own external T/R relay but whatever
arrangement you use, the T/R relay should be activated by the
PTT lines of the local transmitters in order to achieve the
necessary protection. </div>
<div><br>
</div>
<div>The ADC overload warning on Hermes (and Mercury and Angelia)
comes on when a signal is greater than about -10 dBm at the
input of the receiver. The warning indicates that the input
signal has exceeded the amplitude conversion range of the ADC.
Levels greater than that maximum level result in distortion in
the output of the ADC, of course. </div>
<div><br>
</div>
<div>Personally, I don’t apply rf levels to my OpenHPSDR receivers
greater than the “alert” warning level even though the receiver
inputs can likely take ten times that amount or perhaps more
before actually destroying devices. </div>
<div><br>
</div>
<div>For reference, typical test equipment inputs (e.g., on high
end spectrum analyzers, etc) have max rf input limits around +7
dBm; that fact might give you an idea of what is generally
considered to be a dangerous rf input level. </div>
<div><br>
</div>
<div>73, Joe K5SO</div>
<div><br>
</div>
<div>
<div>
<div>On Mar 3, 2013, at 6:05 PM, Byron Engler wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">***** High Performance Software
Defined Radio Discussion List *****<br>
<br>
<p dir="ltr">Hi all,<br>
I am looking at using my Hermes in a contest station.
There will be 2 1kw transmitters that can be transmitting
at any moment. I plan on using Hermes to monitor which
bands are opened and not for the actual QSO's and plan to
use some form of random long wire antenna. Should I be
concerned about 'burning out' the ADC? <br>
Any precautions I should take to protect the Hermes board.
<br>
What is the maximum safe magnitude of Rf at the RX
connector?<br>
</p>
<p dir="ltr">73<br>
Byron, ZL3DXT</p>
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<pre class="moz-signature" cols="72">--
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Senior Staff Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks
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