I've used similar delay boxes for experimental RX work.
Ordinary toggle switches are used as can be easily seen.
These aren't anything great at RF, but should be fine
at 1.8 MHz. (It is possible that the switches actually
control relays, in which case there is no issue. However,
all the boxes I've seen are passive.)
It is important for the line to be terminated accurately
in its characteristic impedance (in this case 75 ohms)
on at least one end. Otherwise, the amplitude will
vary with delay. It is non trivial to get this termination
because of items such as high-pass BCB reject filters,
and low noise preamps, and even just receivers that might
not be well matched. Also, antennas such as whips are
pure capacitive and will never be matched. It is very
difficult to make a preamp with less than 3 dB NF that
is matched. (If anyone knows how to do this, let me
know).
Summarizing: I'm sure the box will work as advertized,
but there a application hazards that make keep you from
success.
Rick N6RK
On 1/22/2015 9:45 AM, Herbert Schoenbohm wrote:
In my junk box I found two Mathey Video delay line passive control boxes
with BNC connectors which can provide a switchable signal delay of 10 to
350ns. Would these be of any value in phasing two RX antennas and would
they not perform at RF in the same manner that they do at video
frequencies?
http://www.bibbteck.com/Products/857-matthey-vu-360-delay-line-package.aspx
Herb Schoenbohm
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