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Anyone have an idea what this is?




 
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Author Topic: Anyone have an idea what this is?  (Read 782 times)
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N4LTA
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« on: June 02, 2022, 04:08:42 PM »

Got this from an old timer, just to get the National Dial.

It has two coax cables.

One  comes in through the coil with the small cap on the dial (a few pF ) with a larger trimmer in series.

The switch selects one of six more trimmers ( I think the ceramic things are dual trimmer caps) in parallel.

The trimmer labelled 3.4 has what looks like a small capacitor to ground.  The two cables tie to the screw type terminal strip and has several old mica caps under it. I can't see how they are connected, but the two cables are isolated, likely by one or both of the mica caps.

Some type of LC filter? I can't see how it could be very sharp




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W7TFO
WTF-OVER in 7 land Dennis
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IN A TRIODE NO ONE CAN HEAR YOUR SCREEN


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« Reply #1 on: June 02, 2022, 08:57:15 PM »

Looks like a passive pre-selector for 80 meter RX.

73DG
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ab1mn
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« Reply #2 on: June 02, 2022, 09:14:47 PM »

How about a tuned circuit to plug into the crystal socket on a transmitter to allow the oscillator to act as a VFO?

Bob,  K7DYB
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W7TFO
WTF-OVER in 7 land Dennis
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« Reply #3 on: June 02, 2022, 10:02:20 PM »

That would be a very wobbley VFO.

The givaway is it has an input and an output.

73DG
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Patrick J. / KD5OEI
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« Reply #4 on: June 03, 2022, 04:32:17 PM »

If it's a preselector, one way to verify that is to try it! If it doesn't seem to do much, try feeding it broadband noise and tuning around the shortwave bands with a receiver. The switch could mean several frequency ranges.
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Radio Candelstein - Flagship Station of the NRK Radio Network.
KC4VWU
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« Reply #5 on: June 07, 2022, 09:31:27 PM »

I'm with Dennis, pre selector. Seems like a waste using the PW dial and gearbox when just a common vernier dial would do, but I guess use what 'ya got in the junk box is the handiest approach.
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KD6VXI
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Making AM GREAT Again!


« Reply #6 on: June 08, 2022, 07:02:20 AM »

As my grandfather used to tell me when I brought him something wierd and wanted to know what it was....

"That's easy, Shane.  It's a
'one of those'".

--Shane
WP2ASS /ex KD6VXI
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AJ1G
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« Reply #7 on: June 09, 2022, 10:13:50 PM »

Or itís a Damnifiknow!

Probably as others have stated, passive preselector.  Still useful today, especially with SDRs to minimize intermod interference from strong local AM broadcast stations.
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Chris, AJ1G
Stonington, CT
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