[Heathkit] SB-610 scope to SB-303 receiver

[Bob Macklin]

Remember that coax like RG-174 is about 22pf/ft. The coupling cap and the
capacitance of the coax will be a voltage divider.

You want to use the smallest possible coupling cap to reduce the loading on
the IF stage. I would recommend using a GIMMICK.

Bob Macklin
K5MYJ
Seattle, Wa,
"Real Radios Glow in the Dark"
----- Original Message ----- 
From: "jeremy-ca" <km1h at jeremy.mv.com>
To: "Dan Pividal" <dpividal at tampabay.rr.com>; "heathkit at mailman.qth.nt"
<heathkit at mailman.qth.net>
Sent: Tuesday, December 11, 2007 1:35 PM
Subject: Re: [Heathkit] SB-610 scope to SB-303 receiver


> Well at first you said bypass and now you say coupling; there is a huge
> difference.
>
>  Mmf is now pf;  mf is still mf.
>
> Either the manual has a typo or you need glasses or maybe both <G>
>
> A very low value of 1-12pf is more like it and you select a value that
> doesnt overdrive the scope. Use a trimmer if you have one and then measure
> the value that gives the best results and replace with a fixed value.
>
> For such a short run any miniature coax is OK, RG-174, 178 and 179 are
> common ones.
>
> Carl
> KM1H
>
> ----- Original Message ----- 
> From: "Dan Pividal" <dpividal at tampabay.rr.com>
> To: "heathkit at mailman.qth.nt" <heathkit at mailman.qth.net>
> Sent: Tuesday, December 11, 2007 3:46 PM
> Subject: [Heathkit] SB-610 scope to SB-303 receiver
>
>
> >I am trying real hard to hook up an SB-610 to an
> > SB-303.
> > If anyone has done the mod to monitor the receive envelope please let me
> > know what value of coupling capacitor you used with success.
> > Seems the Heathkit SB-610 assembly manual says to use a 1.0mmf
> > Also says, they supplied the 1.0mmf as well as a 2.2mmf and a 12mmf
> > capacitor in the original kit.
> > I believe that long ago mmf meant Picofared.
> > That would make a big difference.
> > Tech notes I have from Heathkit says to use a 1.0mf coupling cap to the
> > 3rd IF via a RG174 coax to a spare RCA plug in the back of the receiver.
> > To which document do I pay heed.
> > Thanks in advance for any help in clearing this up.
> > Dan/N4VET
> >
>
>