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Old 2nd Mar 2020, 12:02 am   #1
gezza123
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Default Having fun with my old Equipment.

Having fun with my old equipment.

Using old X-Y (Telonic 121 scope) and a (Heathkit Ig-18) audio generator.
with a (Tenma 27-5015) sweep Function generator to set up an AR88D I.F.
I set the audio generator to 10hz and fed it to X on the scope to give me a line.
Then I set the main sweep of the Tenma to start at 400 KHz
and set the width to stop at 600 KHz, then fed it into the grid of the mixer pin8 of the 6sa7.
The output of the AR88D pin 5 diversity to scope input set at 100mV/DIV, I then trimmed up the I.F to 455KHz
The results look good.
Here are some pics.Hope you like
gezza123
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Old 2nd Mar 2020, 12:04 am   #2
gezza123
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Default Re: Having fun with my old Equipment.

crystal no 5 pos.
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Old 4th Mar 2020, 11:15 am   #3
Kevin Hoyland
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Default Re: Having fun with my old Equipment.

Morning gezza.
Thanks for taking the time to up load the photos of the trace on your scope. I have 5 AR88 2 ds and 3LFs


Kevin.
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Old 4th Mar 2020, 11:29 am   #4
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Default Re: Having fun with my old Equipment.

You're probably sweeping too fast for the crystal plot. It's a matter of Hertz per second, so going to a narrower sweep will help. Narrower filters simply take longer to settle, so if a tone sweeps past too quickly you get partial response and a lazy-looking decay. Ideally you want to reduce the sweeping rate until changes in it make no difference.

There's also the AGC response rate. You can avoid this smoothing out the plot by setting the AR88 to manual gain control and looking at the 455kHz IF signal directly. That 1740 scope in the background has plenty of bandwidth

David

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