Connector Update February, 2007

In late 2006, Directive Systems was hit with a spate of material price increases that really took our breath away. The increases were all linked to metal price increases that have rippled through the economy. There have been many small increases in past years, but manufacturers have been unwilling to pass them along to customers and, for the most part, absorbed the increases. That changed rapidly in 2006. The price jumps were just too big to absorb! Materials made with copper, brass, aluminum, and stainless steel all experienced huge price increases. Our UT-141 copper coax suffered a 300% increase. Our N connectors went up 67%. The real killer was our high quality Amphenol hoods that provide weatherproofing to our connector assemblies. They experienced a 257% increase in the past year. The bottom line was that our material costs were out of control. Our choice was to either raise our prices, but they had already gone up recently due to high aluminum costs, so we hated to raise them again. OR... we could re design the connector and eliminate the expensive parts entirely.

After much testing and evaluation that really began in 2005, we have come up with a great solution that actually improves our antennas, and holds the costs down to about what we were paying over a year ago before all the increases! The new connector assembly looks like this:

Note that there is a new connector bracket to go along with the new connector. This is now a die punched item, and is cheaper to produce (after we buy the tooling) than our old "in house" brackets. I think they look much better than the old ones did too. The new connector is more expensive, but it is designed for connecting UT-141 semi rigid coax to an N female bulkhead fitting. When you add up the cost of the bracket and the connector, and eliminate the UG-107 hood, we are way ahead of the game!! The above antenna is a 945LY loop yagi made for 3456 MHz, and it sports the new bracket and connector.

I am very excited about the electrical performance of the new connector system. The old hoods required an internal impedance corrector, to maintain a reasonable VSWR at high frequencies. This corrector served to maintain the 50 ohm impedance inside the hood. It worked reasonably well, but the new connector is so much better that it is amazing. Look at the TDR (Time Domain Reflectometer) plot below. We took a 50" piece of UT-141, and attached an old style connector on one end, and the new connector assembly on the other. We then set our TDR system to look through the coax at both connectors. The far end was terminated with a 50 ohm load. The frequency range was 25 to 4000 MHz. Any mismatch shown will be about what one would see at the high end of that frequency range. As can be seen, the old connector/ hood assy was installed right at the analyzer, while the new connector/punched bracket assy was at the far end, a bit over 4 feet away. The old system had a -15 dB return loss bump at the connector interface, while the new bulkhead fitting showed almost no bump at all, with a 50 ohm Narda precision load at the far end. The return loss is over -40 dB down.

Another great feature of the new connector assembly, is that it lacks any air pocket internally, that might allow water to wick inside the antenna from a leaking external coaxial connector. No air inside means that it will be much more difficult for water to migrate inside the fitting as there is no pressure variation due to expanding or contracting air available there. This is an added bonus! The net effect is that our antennas are now better than before, and with no increase in price.

This plot was made with an Anritsu S-331D "Sitemaster" antenna analyzer operating in the Frequency Domain Reflectometer mode. This mode is very handy for evaluating connector and cable performance. Not only will it measure the magnitude of performance, but it will tell you where it is in the cable system. In our case, we have evaluated two connector interfaces at the same time on either end of a short piece of semi rigid coax!