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 _________________ Topband Reflector Archives - http://www.contesting.com/_topband
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