On Mon, 4 Oct 2004 19:30:19 -0500, "John Smith"
wrote:

The Narda coupler has no calibration plate. It says model 30611, serial no.
4235. It also appears to have been made for Motorola, as their part number
appears on it.

Hi John,

This is not a NARDA model number according to their own catalogue,
although I see it described as NARDA in more than one ebay auction. I
would say this is a special run for Motorola (which is probably their
contract number with NARDA).

However, all ebay auctions list this as an 960 MHz device.

Typically, directional couplers are within their nominal ratings only
over a octave range and some of those octaves from within their
catalogue are 500 MHz to 1 GHz. Others are 450 MHz to 900 MHz. Some
are listed as 0.05 GHz to 1 GHz, but the coupling is VERY MUCH
different than nominal outside the octave range (by as much as 10 - 15
dB). Generally, you don't suffer this much variation near the octave
band edges, but they do track off from their otherwise flat response.

It looks like you need to measure the coupling directly (at both
ports) across your frequencies of interest. The coupling factor is
not so important as is the ports tracking. I will discuss the raw and
finished data separately.

73's
Richard Clark, KB7QHC