Station Master Measurements Revisted

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rescue161

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A while back, I posted here: https://communications.support/threads/17390-VHF-Station-Master-Internal-Dimensions about the element lengths of a Station Master antenna to see if I could recreate the math involved and roll my own elements out of copper tubing/pipe. Well, our maintenance guys just took down our old pager antenna that was on ~143 MHz, so I asked to take it home for measurements. Right off the bat, I realized something was weird as the newer 143 antenna was much shorter. 19 inches shorter to be exact. I have not taken it apart, but I swept it and it does work from 140 to 150. I am very curious to see how this much shorter antenna is constructed compared to the older one. The older had slotted screws and a soldered tip. This one has allen/hex screws and a set screw holding the tip on. I just measured the outside dimensions and got the following:

Older 153 MHz:
Base Length - 27"
Overall Length (Including Base) - 21' 5"

Newer 143 MHz:
Base Length - 28"
Overall Length (Including Base) - 19' 11.125"

I suppose I would be able to make a ham antenna out of the older one since it is shorter. I guess I'll see when I dig into the newer one.
 

CARC383

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Very interesting. The last Stationmaster I had apart was a 5dB UHF and it was made of some roughly 1/2 dia rigid coax with what looked like a solid polyethylene dielectric. The elements seemed quite short so the dielectric constant must have been low like .66. The higher the dielectric constant the longer the element will be to the point of 100% being full length like a ground plane vertical element. Since the company that makes Stationmasters has changed hands several times it could be the current mfr has changed the innards using a solid dielectric with lower VF over the older units with a mostly air dielectric that you showed in another post.
 
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rescue161

rescue161

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While I am referring to the antenna as new, it has been on the tower for years. We took the paging system offline in 2012 and it had been on the tower for many years prior to that. We tried to remove it about 4 years ago, but one of the climbers had a medical emergency at the 160 foot mark, so the work was postponed indefinitely. Fast forward to last week and they were able to incorporate the removal of that antenna as part of the tower climbing and rescue training.

It kept wanting to rain today and the humidity is very high, so I'll wait until it cools off a bit to dig into this one.
 
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