The Author's place is on a plateau, with a 360° view and a 10-acre field for antenna R&D. In the background of the right picture is one of the structures for testing antennas; the other R-25 tower is not in view. For general "tests" the Author mounts the antenna to a fence post while using the vehicle for a power and RF transmitter source and a general "table" to spread equipment for this procedure. The metal fence can actually help make a ground plan with signal tests later. The watt meter can be nicely hung on the fence as well. Some of the following pictures are small to help dial-up folks, however are enlargeable by clicking on the center if you wish to examine one. This page/document was quickly "thrown" together in one evening; it may be changed, later.

The HUB repeater that connects the out of town 80/20 coverage may have a bad antenna. It's an old Andrews out of commercial service and its been in SRG's operation for anther 15 years or so. Time to replace it. The Author did some research on his old supplier of Sinclair, however learned their prices increase out of hand, therefore, checked into other brands. Telewave came to mind, so they were contacted. They provided excellent email and telephone response and support. When come time to decided on which model the Sales person connected a conference with the factory engineer to verify this would be a good choice for the type of service needed. The two main criteria was the length needed to be about 20 foot (for mounting top and bottom) and good gain, because one of the link paths was 156 miles. Doug, N7BFS offered to pay for the antenna, so with shipping he spent about $1K on the package. Since we planned on the major/annual trip in two weeks the company said they could make that deadline. They exceeded it by a week so the new antenna arrived in good condition. Shipped inside the usual cardboard "tube", it was carefully unpacked and temporarily mounted on the Author's testing area on the fence post out front.

The antenna was supplied with a "pigtail" N-N jumper, therefore, was installed as part of the test. Normally the upper part of the tail (inside the base of the antenna) is taped ahead so to avoid this task on the 100 foot tower. In the permanent installation an outer mastic pad is layered over the base coat of the Scotch "88" tape layer for superior sealing. Just as a side note, improper sealing against water is the best way to "kill" a good installation over a short time in the winter. You can see the label specified the frequency coverage of "430-475" MHz.

The tests

Our tower crew set up a work station with the Anritsu antenna analyzer, AKA as "SiteMaster" unit. Someone scowled up one's face after seeing the plot! Yikes !

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The first test show some interesting plots. Here's some snap shots on what we observed. Although the antenna was advertise as broad band (430-475 area) as you can see it really is only real good at the commercial band 462 and above. We did a final plot and saved it inside the SiteMaster. Later the "file" was converted to a more friendly form, which you can view HERE in jpg form.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The second test with a handy spare repeater operating at 444 MHz duplexed well, however as the previous test indicated the return loss was not too good. For you "watts" readers, here's the Bird thru-line version of operating on 444 MHz with a 25D slug. Keep in mind this is 3 MHz higher than the frequency we ordered the antenna. The left picture is forward power of 18 watts forward, and right picture of 1.4 watts reverse. Rough calculations come out to a VSWR of 1.77 and a RL (return loss) of 11.09 db. Not too good.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Second test was to verify the antenna would duplex properly with no "noise". After this, the crew drove into town for the coverage test. These two tests seemed to be successful.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Conclusions: This antenna had excellent specifications for the commercial 450-470 MHz band and the Author would recommend it for that use. For Amateur it will work , however you would have to put up with excessive RL making your transmitter or isolator work harder. The best way is communicate and ask to see the plot from the manufacturer on your frequency before buying. It will save both parties some grief.

 

STAY TUNED: As of 2009 another brand of antenna is being purchased and going to be evaluated !

 

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