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

[jeremy-ca]

10:1 of almost nothing is still almost nothing. The issue is how LITTLE of a 
signal is required to drive the scope and not the amount shunted to ground.

Carl
KM1H




----- Original Message ----- 
From: "Bob Macklin" <macklinbob at msn.com>
To: "jeremy-ca" <km1h at jeremy.mv.com>; "Dan Pividal" 
<dpividal at tampabay.rr.com>; "heathkit at mailman.qth.nt" 
<heathkit at mailman.qth.net>
Sent: Tuesday, December 11, 2007 7:37 PM
Subject: Re: [Heathkit] SB-610 scope to SB-303 receiver


>A 2pf cap connected in series with a 22pf cap produces a 10:1 voltage 
>divide
> at any frequency!
>
> Bob Macklin
> K5MYJ
> Seattle, Wa,
> "Real Radios Glow in the Dark"
> ----- Original Message ----- 
> From: "jeremy-ca" <km1h at jeremy.mv.com>
> To: "Bob Macklin" <macklinbob at msn.com>; "Dan Pividal"
> <dpividal at tampabay.rr.com>; "heathkit at mailman.qth.nt"
> <heathkit at mailman.qth.net>
> Sent: Tuesday, December 11, 2007 4:29 PM
> Subject: Re: [Heathkit] SB-610 scope to SB-303 receiver
>
>
>> Luckily, 22pf has minimal effect at the frequency of interest.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message ----- 
>> From: "Bob Macklin" <macklinbob at msn.com>
>> To: "jeremy-ca" <km1h at jeremy.mv.com>; "Dan Pividal"
>> <dpividal at tampabay.rr.com>; "heathkit at mailman.qth.nt"
>> <heathkit at mailman.qth.net>
>> Sent: Tuesday, December 11, 2007 5:37 PM
>> Subject: Re: [Heathkit] SB-610 scope to SB-303 receiver
>>
>>
>> > 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
>> >> >
>> >>
>> >>
>> >
>> >
>>
>>
>
>