[Heath] Fw: Heathkit SB-610

[ronkp2n at earthlink.net]

Dick .... You want a coax cable that has very low capacity
per foot.  That's why the RG-62.
Maybe your exciter (HW-100 etc) falls on the low
edge for signal output.  Try a higher valur of
pick off capacitor.  I remember back when that I ended
up with a 10 pf.

73  Ron  KP2N



-----Original Message-----
>From: Dick KF4NS <kf4nsradio at verizon.net>
>Sent: Mar 7, 2012 2:43 PM
>To: ma.locksmith at juno.com
>Cc: Heath puck list <heath at puck.nether.net>, heathkit at mailman.qth.net
>Subject: [Heath] Fw:  Heathkit SB-610
>
>Ok guys, most responses have been related to the coax. Since there is no loss in the 610 and the vert amp 
>is doing its job the loss is obviously in the originating equipment. Also, Heath does not say you should 
>use RG-62, it only mentions the best coax for the xmit input/output. There they say to use 50 or 75 ohm 
>coax.
>
>I was doing some thinking (bad for someone my age) and remembering electronics school, as I recall 
>capacitors in series are equal to a value lower than the lowest capacitance. (smaller than the smallest 
>as I remember) so my 5uuf cap in series with the 93ohm coax should result in total capacitance less than 
>the 5uuf cap in series.
>
>Hmmmm! Is my age showing or am I thinking correctly. Some have said they use all different types of coax 
>with no trouble. What if I used just a piece of insulated wire from the 2nd IF to the jack on the xcvr 
>back and use coax from there to the 610 ?
>
>73, Dick KF4NS
>St Petersburg, FL 33714 USA
>Keep The Glow!
>
>
>----- Original Message ----- 
>From: <ma.locksmith at juno.com>
>To: <kf4nsradio at verizon.net>
>Sent: Tuesday, March 06, 2012 6:52 PM
>Subject: Re: [Heath] Heathkit SB-610
>
>
>| Yes, the coax IS faulty....  but, not because it's broken
>|
>| You have selected wiring with very high capacitance.  This makes a
>| capacitive divider for the signal.  If you only have 5 pF capacitance in
>| the cable, you have a 2:1 reduction in signal strength.
>|
>| RG174 and RG58 have high values.  I think the 58 is 32 pF per foot.  Not
>| sure about the 174 unless I look it up.
>|
>| I expect the "right" cable between the set and the 610 will be RG 62.
>| And, more than likely, unshielded wire inside.
>|
>| Ed
>| K1ZOK
>|
>| On Tue, 06 Mar 2012 15:58:50 -0500 "Dick KF4NS" <kf4nsradio at verizon.net>
>| writes:
>| > Looking for your input and recollection of what you did. I have now
>| > completed a full restoration of my
>| > SB-610 and have concluded that the one remaining fault, low vertical
>| > gain, may  be due to how I have
>| > connected it to my HW100.
>| >
>| > It did work pretty good at one time so now there is a bit of head
>| > scratching. I  have no losses in the
>| > 610 and the vertical amp, when driven with a sig gen at 3395khz
>| > modulated at 50%, I see .4v (spec.
>| > recommends .5v input) at the grid and get 23v at the plate. That
>| > sounds like the 610 is doing the job.
>| > The vertical gain pot is fine. So now I suspect it has to be the
>| > connection to the rig.
>| >
>| > I used RG-174 in the HW100 from the second IF plate and have a 5uuf
>| > cap in between. Outside the rig I
>| > have a short run of RG-58 to the 610. I can only see .1v from the
>| > rig. The coax is not faulty nor is the
>| > capacitor.
>| >
>| > What did you use in your Heathkit rig for coax and coupling cap. and
>| > what did you feed the 610 with? Did
>| > you connect to the first or second IF and at the control grid or the
>| > plate? I did do a mod to the 100
>| > which lowers the IF gain to improve gain distribution. This came
>| > from my friend Mark's (WB8JKR now SK)
>| > presentation for optimizing the HW/SB transceivers. When the scope
>| > was working fairly good this mod was
>| > already there. I did realign the rig though at some point since
>| > then. The 100 is working great.
>| >
>| > Thanks and 73, Dick KF4NS
>| > St Petersburg, FL 33714 USA
>| > Keep The Glow!
>| >
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>| >
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