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Tram 1480--poor SWR

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#1
So I just put up a Tram 1480 and it quite honestly sucks. 2m SWR is OK with a 1.5 at 147mhz but totally unusable with a 3 at 445mhz. How should I adjust this stupid thing? I bought it months ago on Amazon so I can't return it. It is being fed with 35ft of brand new LMR-400.
 

jwt873

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#2
Did you connect the upper and lower elements with the coupler (the element joint) and set screws before you screwed the two halves together?

You probably did, but I've read about people who didn't :)

What is the SWR at 440 and 450?
 
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#3
Yeah I connected the coupler in the middle.

The SWR on 440mhz is 3. It goes down from there and is about a 1.2 on GMRS. It's almost like it's resonant on 2m and GMRS somehow rather than 70cm.

I don't know how these antennas are constructed but my multimeter shows continuity between the center element and the radials on the bottom of the antenna but no continuity between the center conductor of the so239 and the center element.
 

vagrant

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#4
I have a Tram 1480 and it performs a little better than a Diamond X50 I had on the same coax in the same spot. My SWR is less than 1:1 for both bands, but on 70cm it is a tiny bit higher than 2m. I put it together and wrapped coax tape around the center joint. Nothing was adjusted.

That lack of continuity between the connector and the center element does not sound good.
 
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#5
I'd try to get as much whip length as possible, just leaving enough inside the base neck to hold it securely.
Sounds like it's too short overall if it's resonating up in the 460-470MHz band.
 
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#6
Check the capacitors connected to the coil in the base. I have seen them unsoldered and/or shorted to the coil (missing capacitor leg insulator). The center connector pin is connected to the coil with a 10 pf capacitor so you won't see continuity. The antenna rod is connected to to the connector shield (and radials).
BB
 

mancow

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#7
I have the 17' Tram. It stopped working, similar results as you encountered. I found the capacitors at the bottom had blown out (well one had) and one had its leg melted. Take the allen nut out and try to pull the guts out from the bottom and check it. I bet it got water in it and fried. I ordered new caps from Digikey and fixed mine then coated everything in liquid electrical tape.
 
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