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

[jeremy-ca]

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
>> >
>>
>>
>
>