Message-ID: <4C9BC35A.9090406@ecsykes.com>
Date: Thu, 23 Sep 2010 17:15:06 -0400
From: Steve Sykes <steve@ecsykes.com>
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References: <000c01cb5a7a$44cfcc50$0401a8c0@xphd97xgq27nyf> <4C1A271605FB0B62@smtp208.alice.it> <1285185012.2042.23.camel@gerhard-desktop> <4C1A26CF0601C347@smtp207.alice.it> (added by postmaster@alice.it)
In-Reply-To: <4C1A26CF0601C347@smtp207.alice.it> (added by postmaster@alice.it)
Subject: Re: LF: PA0RDT miniwhip in TX?
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  There is also a possibility that diodes used like this will cause IMD 
when used near a strong RF Field.  I agree with Roelof, don't try to fix 
a problem that isn't there.  I have used the antenna less than 5 feet 
away from a 150 watt HF data transmitter without issue.  The U310 is a 
very good device.

Steve KD2OM/NNN0HSB
On 9/22/2010 4:34 PM, Marco IK1ODO wrote:
> Hello Gerhard,
>
> the 100n capacitor will do nothing, it is in series with the input pad 
> capacitance (a few pF).
> The diodes will clamp at 0.6 V, that is too low (every static "crack" 
> will send the diodes in conduction) and limits the dynamic range.
> More, they will add capacity (2 pF each?) at the very critical point 
> of the amplifier input, decreasing the gain.
> I think I will leave the gate alone, as in the original design.
>
> Possibly the idea of a small reed relay to be closed in TX may be 
> better; those have very low C. But I will do that only after the ninth 
> burnt J310 - they are so cheap from Roelof :-) (just jocking, of 
> course, I could not resist)
>
> 73 - Marco IK1ODO
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.851 / Virus Database: 271.1.1/3152 - Release Date: 09/22/10 02:34:00
>


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    There is also a possibility that diodes used like this will cause
    IMD when used near a strong RF Field.&nbsp; I agree with Roelof, don't
    try to fix a problem that isn't there.&nbsp; I have used the antenna less
    than 5 feet away from a 150 watt HF data transmitter without issue.&nbsp;
    The U310 is a very good device.<br>
    <br>
    Steve KD2OM/NNN0HSB<br>
    On 9/22/2010 4:34 PM, Marco IK1ODO wrote:
    <blockquote  cite="mid:4C1A26CF0601C347@smtp207.alice.it%3E%20(added%20by%20postmaster@alice.it)"        type="cite">Hello Gerhard,
      <br>
      <br>
      the 100n capacitor will do nothing, it is in series with the input
      pad capacitance (a few pF).
      <br>
      The diodes will clamp at 0.6 V, that is too low (every static
      "crack" will send the diodes in conduction) and limits the dynamic
      range.
      <br>
      More, they will add capacity (2 pF each?) at the very critical
      point of the amplifier input, decreasing the gain.
      <br>
      I think I will leave the gate alone, as in the original design.
      <br>
      <br>
      Possibly the idea of a small reed relay to be closed in TX may be
      better; those have very low C. But I will do that only after the
      ninth burnt J310 - they are so cheap from Roelof :-) (just
      jocking, of course, I could not resist)
      <br>
      <br>
      73 - Marco IK1ODO
      <br>
      <br>
      <pre wrap="">
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No virus found in this incoming message.
Checked by AVG - <a class="moz-txt-link-abbreviated" href="http://www.avg.com">www.avg.com</a> 
Version: 9.0.851 / Virus Database: 271.1.1/3152 - Release Date: 09/22/10 02:34:00

</pre>
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