[Boatanchors] Pickup loop

[Sheldon Daitch]

Larry,

by nature, the modulation monitors are not very sensitive devices, in
terms of RF input level required to operate properly.  I'd say that almost
all scopes, waveform monitors and frequency counters are far more
sensitive than modulation monitors.

And with that, there is (almost) always enough drive from the transmitter
to operate the modulation monitor, excess power is probably more
accurate.  Remember, in the broadcast industry, almost all AM operations
measure power at the antenna input or antenna system common point, not
the transmitter power, so power used for the mod monitor is not power
that can be used for the on-air signal.

Also, I'd submit that loop coupling might be more reliable than
capactive coupling, in the event of lightning strikes to antennas,
that is, less chance of a lightning strike taking out the input of the
modulation monitor with loop coupling.

73
Sheldon
WA4MZZ


telegrapher at att.net wrote:

> Some months back i asked about a pickup loop that was installed either
> in broadcast transmitters or somewhere in close proximity so that they
> could provide sufficient power to operate a Gates modulation monitor.
> The Gates unit needs approximately 10W to drive it properly.  I'm
> wondering if a person couldn't use a capacitor arrangement to provide
> the same results.  TMC uses that on their power amps to provide 1/300th
> of the output power to drive a monitor, scope or freq. counter.  Now i
> have a sealed box with the proper connectors on it that takes 1 kW input
> and delivers i forget what (1 mw maybe) to the output in a T
> configuration.  It's not a big box either so i'm suspecting that it's a
> capacitive type unit.
>
> Am i thinking along the correct lines here or has the fire gone out in
> my pipe?  Is this a reasonable line to pursue?
>
> Larry
> W0OGH
>
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