Message-ID: <506B61B0.7080501@iup.uni-heidelberg.de>
Date: Tue, 02 Oct 2012 23:50:40 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
References: <BLU153-W24D0C2EF3574121D01B5B6CF860@phx.gbl>,<506A399A.2070800@iup.uni-heidelberg.de> <BLU153-W35E503797E74CECCC22B4ECF860@phx.gbl>
In-Reply-To: <BLU153-W35E503797E74CECCC22B4ECF860@phx.gbl>
Subject: Re: Strefans LF: LF/MF modification of TS850 for LF
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Hi Laurence,

Am 02.10.2012 23:20, schrieb Laurence KL7UK:
> http://kl7uk.com/850.png
>
> Stefan - heres the part of the circuit concerned - its the coupling 
> after the 3rd mixer - so its at TX base band frequency, so I can 
> see perhaps why this C219 could be increased to reduce LF losses, but 
> not a lot me thinks as the reactance to "Earth" is pretty low at 137 - 
> the aim is to improve LF without mucking up the HF side so you can 
> only go so far.
Maybe you can make a series resonance for LF by adding a L in series. 
This L must have a C in parallel or a low self resonance frequency. My 
first guess...
At least a to high C across C219 will make a almost short cut for HF to 
ground...


>
> Still very poor LF and MF - nearly no signals from Siberia/Mongolia on 
> LF - still at least the snow has stayed away. Loran was around 15dB 
> down from "average" last nite. Getting very dark in the mornings and a 
> Huge Male Moose ran into a car on the road into work this morning - 
> both car/driver and Moose didnt make it.
R. Tell me when the band opens. BTW i'm 3...5 dB stronger since the last 
success in december so we may play a lot more this year.


Just played arround with a NE612 for the first time in my life ;-) Quite 
useful IC! It became a 475 kHz transmit mixer (460 kHz LO) and is used 
in combination with my mechanical filter which i use for MF RX as well. 
Then applying white noise from the SpecLab SG i can see the resonance 
curve again, now confirming > 50 dB att. in 2 kHz outside the passband!

73, Stefan/DK7FC

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Hi Laurence, <br>
<br>
Am 02.10.2012 23:20, schrieb Laurence KL7UK:
<blockquote cite="mid:BLU153-W35E503797E74CECCC22B4ECF860@phx.gbl"
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  <div dir="ltr"><a moz-do-not-send="true"
 href="http://kl7uk.com/850.png">http://kl7uk.com/850.png</a><br>
&nbsp;<br>
Stefan - heres the part of the circuit concerned&nbsp;- its the coupling
after the 3rd mixer - so its at TX base band frequency, so I can
see&nbsp;perhaps why this C219 could be increased to reduce LF losses, but
not a lot me thinks as the reactance to "Earth"&nbsp;is pretty low at 137 -
the aim is to improve LF without mucking up the HF side so you can only
go so far.<br>
  </div>
</blockquote>
Maybe you can make a series resonance for LF by adding a L in series.
This L must have a C in parallel or a low self resonance frequency. My
first guess...<br>
At least a to high C across C219 will make a almost short cut for HF to
ground...<br>
<br>
<br>
<blockquote cite="mid:BLU153-W35E503797E74CECCC22B4ECF860@phx.gbl"
 type="cite">
  <div dir="ltr">&nbsp;<br>
Still very poor LF and MF - nearly no signals from Siberia/Mongolia on
LF - still&nbsp;at least the snow has stayed away. Loran was around 15dB
down from "average" last nite. Getting very dark in the mornings and a
Huge Male Moose ran into a car on the road into work this morning -
both car/driver and Moose didnt make it.<br>
  </div>
</blockquote>
R. Tell me when the band opens. BTW i'm 3...5 dB stronger since the
last success in december so we may play a lot more this year.<br>
<br>
<font face="TimesNewRomanPSMT"><br>
Just played arround with a NE612 for the first time in my life ;-)
Quite useful IC! It became a 475 kHz transmit mixer (460 kHz LO) and is
used in combination with my mechanical filter</font> which i use for MF
RX as well. Then applying white noise from the SpecLab SG i can see the
resonance curve again, now confirming &gt; 50 dB att. in 2 kHz outside
the passband! <br>
<br>
73, Stefan/DK7FC<br>
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