Ron, I suggest you hook the monitor scope to the grid of the 1st. IF
tube. The reasoning behind this is non-linearity is reduced to some
extent. I had a hookup to my receiver one time and when people found
out they wanted reports on their envelope. Well there are many things
that will affect that pattern. The SB 614 I owned had some 60 cycle hum
in it and it is very difficult to get out. If you notice in the manual
of the 614 Heath said to put an RCA plug with a very short piece of wire
attached from the center pin to ground into the Vertical Input jack.
The purpose is to eliminate any 60 cycle pickup and introducing
additional distortion on the displayed pattern.
So after a couple of times of people wanting reports, I disconnected it
to keep from trying to explain what I was seeing. Most people wanted
quality reports and I wasn't comfortable explaining that what I saw
might not be what they were transmitting. To be accurate you need to
check the linearity of all the stages preceding the attach point. If
you seen much, be hesitant about giving reports. This hook up is kind
of all right for baseline reports but the linearity of the received wave
will be affected by the distortion you have in your receiver. If the
distortion is low, you are good to go, if it is high then you won't be
telling the guy the entire picture.
Get a distortion analyzer and check your receiver to get an estimate of
how much distortion is present before you get to technical. Don/K4KYV
found some problems with his HO 10 and had to modify it to correct the
problems. He might explain which would help you.
Jim/W5JO
Thanks Jim
You make excellent and insight points as always. I have encountered
the
issues you speak about in interfacing my 610's with various vintage
receivers like my NC-300 and 75A4.
Thank goodness that I stumbled across small 455Khz and other
frequencies
"IF" cans at Antique Electronics Supply in Phoenix. With some minor
surgery
both 610's are monitoring received signals on my receivers. On the
NC-300 I
went directly to the plate of the 2nd IF and coupled it through a 5PF
mica.
On the 75A4 I went to the grid of the 2nd detector tube and used 4.3
PF
mica. Both have full deflection and ad a bit of "fun" to monitoring
by
being able to see the everyone's signal.
But then, it has been mentioned from time to time that I am "a tad"
obsessive about these beautiful old boat anchors.
Cheers my friend
Ron Weaver W6OM
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