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<DIV><FONT size=2 face="Times New Roman">OK, now the brain is beginning to
compute correctly. I do see what you all are saying. I was way off track.
It does make sense. Actually Heath recommends a 1uuf cap for the 3395khz
IF. Sound like if I lower it to 1uuf and replace the RG-174 with some RG-62
and also use RG-62 from my xcvr to the vert input of the 610, I will gain some
gain. I will also remove the mod that lowered the IF gain at the 2nd IF
with a drop in screen voltage and realign the HW-100. The combination of that
should give me the higher gain that the 610 calls for at the vert input (min.
.5v). </FONT></DIV>
<DIV><FONT size=2 face="Times New Roman"></FONT> </DIV>
<DIV><FONT size=2 face="Times New Roman">Thanks for all the great responses and
I appreciate the theory lesson. I just don't have the processing power I used to
have.</FONT></DIV>
<DIV><FONT size=2 face="Times New Roman"></FONT> </DIV>
<DIV><FONT size=2 face="Times New Roman">73, Dick KF4NS<BR>St Petersburg, FL
33714 USA<BR>Keep The Glow!</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=rgroh@swbell.net href="mailto:rgroh@swbell.net">Robert Groh</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=mdilli@nnwifi.com
href="mailto:mdilli@nnwifi.com">mdilli@nnwifi.com</A> ; <A
title=kf4nsradio@verizon.net href="mailto:kf4nsradio@verizon.net">Dick
KF4NS</A> ; <A title=ma.locksmith@juno.com
href="mailto:ma.locksmith@juno.com">ma.locksmith@juno.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=heath@puck.nether.net
href="mailto:heath@puck.nether.net">Heath puck list</A> ; <A
title=heathkit@mailman.qth.net
href="mailto:heathkit@mailman.qth.net">heathkit@mailman.qth.net</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, March 08, 2012 9:36
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Heath] Fw: Heathkit
SB-610</DIV>
<DIV><BR></DIV>
<DIV
style="FONT-FAMILY: times new roman,new york,times,serif; FONT-SIZE: 12pt">
<DIV>Morris has it dead on. If you think about it this
way:<BR><BR>You have a cap (5 pf in your example) connected from the source
(the IF Amp plate) to a load (the coax which drives the SB-610 and then the
input circuit of the 610 which has some (assumed) input impedance - lets say
the 610 input looks like 20K ohms in parallel with 10 pf. <BR><BR>For all
practical purposes, we can say the coax just looks like a shunt capacitor (x
ft at y pf/ft). This coax capacity is in parallel with the 610's
input.<BR><BR>So we wind up with our source driving through a 5 pf cap to a
parallel RC network - and the easiest way to think of this is that the
combination is a voltage divider (yeah, I am simplifying it!). As
an example, assume we have 5 pf in the series capacitor, 15 pf of coax
capacity, 10 pf of input C at the 610 and we ignore the R component. We would
have a voltage divider of 5 pf working against 25 pf or a 5/30 voltage
divider. <BR><BR>You can readily see that the longer the cable or the
higher the coax capacity per ft, the higher the voltage division ratio. You
can of course increase the series cap to offset this (e.g. 10 pf --> 10/35
ratio) but the trade off is that you are now affecting the tuning of the IF
stage more. <BR><BR>A picture is worth a thousand words but hopefully this
will help.<BR><BR>73<BR>Bob Groh, WA2CKY<BR></DIV>
<DIV
style="FONT-FAMILY: times new roman, new york, times, serif; FONT-SIZE: 12pt"><BR>
<DIV style="FONT-FAMILY: arial, helvetica, sans-serif; FONT-SIZE: 10pt"><FONT
size=2 face=Tahoma>
<HR SIZE=1>
<B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B> Morris
<mdilli@nnwifi.com><BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B>
Dick KF4NS <kf4nsradio@verizon.net>; ma.locksmith@juno.com<BR><B><SPAN
style="FONT-WEIGHT: bold">Cc:</SPAN></B> Heath puck list
<heath@puck.nether.net>; heathkit@mailman.qth.net<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Wed, March 7, 2012 6:25:29
PM<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: [Heath] Fw:
Heathkit SB-610<BR></FONT><BR>I may be wrong but I've always expected the
capacitance of coax to be<BR>expressed from shield to center conductor, not
serially. In this case you<BR>would not have a simple series connection
of two capacitors and the<BR>equipment in question.<BR><BR>Morris
<BR><BR><BR><BR>> -----Original Message-----<BR>> From: <A
href="mailto:heath-bounces@puck.nether.net"
ymailto="mailto:heath-bounces@puck.nether.net">heath-bounces@puck.nether.net</A>
<BR>> [mailto:<A href="mailto:heath-bounces@puck.nether.net"
ymailto="mailto:heath-bounces@puck.nether.net">heath-bounces@puck.nether.net</A>]
On Behalf Of Dick KF4NS<BR>> Sent: Wednesday, March 07, 2012 2:43
PM<BR>> To: <A href="mailto:ma.locksmith@juno.com"
ymailto="mailto:ma.locksmith@juno.com">ma.locksmith@juno.com</A><BR>> Cc:
Heath puck list; <A href="mailto:heathkit@mailman.qth.net"
ymailto="mailto:heathkit@mailman.qth.net">heathkit@mailman.qth.net</A><BR>>
Subject: [Heath] Fw: Heathkit SB-610<BR>> <BR>> <BR>> Ok guys, most
responses have been related to the coax. Since <BR>> there is no loss in
the 610 and the vert amp <BR>> is doing its job the loss is obviously in
the originating <BR>> equipment. Also, Heath does not say you should
<BR>> use RG-62, it only mentions the best coax for the xmit <BR>>
input/output. There they say to use 50 or 75 ohm <BR>> coax.<BR>>
<BR>> I was doing some thinking (bad for someone my age) and <BR>>
remembering electronics school, as I recall <BR>> capacitors in series are
equal to a value lower than the <BR>> lowest capacitance. (smaller than the
smallest <BR>> as I remember) so my 5uuf cap in series with the 93ohm coax
<BR>> should result in total capacitance less than <BR>> the 5uuf cap in
series.<BR>> <BR>> Hmmmm! Is my age showing or am I thinking correctly.
Some <BR>> have said they use all different types of coax <BR>> with no
trouble. What if I used just a piece of insulated <BR>> wire from the 2nd
IF to the jack on the xcvr <BR>> back and use coax from there to the 610
?<BR>> <BR>> 73, Dick KF4NS<BR>> St Petersburg, FL 33714 USA<BR>>
Keep The Glow!<BR>> <BR>> <BR>> ----- Original Message ----- <BR>>
From: <<A href="mailto:ma.locksmith@juno.com"
ymailto="mailto:ma.locksmith@juno.com">ma.locksmith@juno.com</A>><BR>>
To: <<A href="mailto:kf4nsradio@verizon.net"
ymailto="mailto:kf4nsradio@verizon.net">kf4nsradio@verizon.net</A>><BR>>
Sent: Tuesday, March 06, 2012 6:52 PM<BR>> Subject: Re: [Heath] Heathkit
SB-610<BR>> <BR>> <BR>> | Yes, the coax IS faulty.... but, not
because it's broken<BR>> |<BR>> | You have selected wiring with very
high capacitance. This makes a <BR>> | capacitive divider for the
signal. If you only have 5 pF <BR>> capacitance <BR>> | in the
cable, you have a 2:1 reduction in signal strength.<BR>> |<BR>> | RG174
and RG58 have high values. I think the 58 is 32 pF <BR>> per
foot. <BR>> | Not sure about the 174 unless I look it up.<BR>>
|<BR>> | I expect the "right" cable between the set and the 610 will
<BR>> be RG 62. <BR>> | And, more than likely, unshielded wire
inside.<BR>> |<BR>> | Ed<BR>> | K1ZOK<BR>> |<BR>> | On Tue, 06
Mar 2012 15:58:50 -0500 "Dick KF4NS" <BR>> | <<A
href="mailto:kf4nsradio@verizon.net"
ymailto="mailto:kf4nsradio@verizon.net">kf4nsradio@verizon.net</A>><BR>>
| writes:<BR>> | > Looking for your input and recollection of what you
did. <BR>> I have now <BR>> | > completed a full restoration of my
SB-610 and have concluded that <BR>> | > the one remaining fault, low
vertical gain, may be due to how I <BR>> | > have connected it to
my HW100.<BR>> | ><BR>> | > It did work pretty good at one time so
now there is a bit of head <BR>> | > scratching. I have no losses
in the 610 and the vertical <BR>> amp, when <BR>> | > driven with a
sig gen at 3395khz modulated at 50%, I see <BR>> .4v (spec.<BR>> | >
recommends .5v input) at the grid and get 23v at the plate. That<BR>> |
> sounds like the 610 is doing the job.<BR>> | > The vertical gain
pot is fine. So now I suspect it has to be the<BR>> | > connection to
the rig.<BR>> | ><BR>> | > I used RG-174 in the HW100 from the
second IF plate and <BR>> have a 5uuf <BR>> | > cap in between.
Outside the rig I have a short run of <BR>> RG-58 to the <BR>> | >
610. I can only see .1v from the rig. The coax is not <BR>> faulty nor is
<BR>> | > the capacitor.<BR>> | ><BR>> | > What did you use
in your Heathkit rig for coax and <BR>> coupling cap. and <BR>> | >
what did you feed the 610 with? Did you connect to the first or <BR>> |
> second IF and at the control grid or the plate? I did do a mod to
<BR>> | > the 100 which lowers the IF gain to improve gain <BR>>
distribution. This <BR>> | > came from my friend Mark's (WB8JKR now
SK)<BR>> | > presentation for optimizing the HW/SB transceivers. When
the scope<BR>> | > was working fairly good this mod was<BR>> | >
already there. I did realign the rig though at some point since<BR>> | >
then. The 100 is working great.<BR>> | ><BR>> | > Thanks and 73,
Dick KF4NS<BR>> | > St Petersburg, FL 33714 USA<BR>> | > Keep The
Glow!<BR>> | ><BR>> | >
_______________________________________________<BR>> | > Heath mailing
list<BR>> | > <A href="mailto:Heath@puck.nether.net"
ymailto="mailto:Heath@puck.nether.net">Heath@puck.nether.net</A> <BR>> <A
href="https://puck.nether.net/mailman/listinfo/heath"
target=_blank>https://puck.nether.net/mailman/listinfo/heath</A><BR>> |
><BR>> |<BR>> |
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target=_blank>http://thirdpartyoffers.juno.com/TGL3141/4f56a369cf49522b580cst01duc</A><BR>>
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<BR>> <BR>> -----<BR>> No virus found in this message.<BR><SPAN>>
Checked by AVG - <A href="http://www.avg.com"
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Database: 2114/4856 - Release <BR>> Date: 03/07/12<BR>>
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