At the risk of being redundant  I'll add that the marker beacon ground stations Outer/ Middle/BBoundarybeacons are along the ILS final approach corridor, inside the final approach fix. They are typically useful to nominal  3000 ft. AGL.  The antennas are vertically mounted Yagis. The idea is to provide aural and visual que just over each beacon. Hence, receiver sens is designed and adjusted for very low resultant level. 
K3HVG
On 10/14/2025 11:50 AM EDT hvandermarel--- via ARC5 <[email protected]> wrote:
 
 

Thanks for the info that came up.

 

My BC-1023 needs 10 mV ( 10000 uV ) signal to reliable switch.

I might need to fiddle some with components or the relays itself.

 

A BC-357-D I have does switch at 2500 uV

 

My idea of using such a marker beacon switch as watch on the 4 meter band isn’t going to work.

I will never get that kind of signal from remote transmitters on the band.

 

Still, nice playing with this old stuff, my units are WW2 contracts and still work.

 

I also have a BC-357 that is converted to a BC-341 by rewiring the heater circuit to 12 V.

The type plate is manually altered to 341 by scratching.

It does receive but will not switch. The relays is probably open circuit as the unit had some rust and very fine sand on the inside, like it has been in a wreck in a desert.

 

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