[Tech-Assist] STL problem now critical

[Chip]

From: Tom Taggart <tpt at literock93r.com>

>See if you can find a preamp for the receiver.  We've used
>the ones made by Hamtronics (have one on a 25 mile path
>now), but I see they no longer make one for anything up that
>high. (You might call them anyway, maybe they still have the
>circuit boards & can make one for you).

No no no, not Hamtronics.  Their stuff is very badly designed.  I once  
served in a very large repeater club, several thousand members, and we  
had one of their repeaters.  It was a serious problem, and took about  
two visits a week to keep the spurious emissions down.

You'd be much better off buying a wide TV pre-amp and put a band-pass  
or high-pass filter in front of it!  See Microwave Filter Company.

GLB used to make very nice pre-selector pre-amplifiers but, sadly,  
Gilbert Boelke has passed away.

On the other hand, it appears many people stole his design, especially  
for receivers, so you might be able to find a similar unit.

http://www.repeater-builder.com/glb/glb-index.html

Just stay away from Hamtronics.  It is junk.

One other thing -- the pre-amp needs to be at the antenna or the noise  
figure won't be improved at all, and will most likely get worse.

For such a short path, there has to be something drastically wrong.  I  
would look for bad lines, a bad receiver, bad jumpers, bad antennas.   
Take the STL transmitter to the receive site and check the line for  
loss, and VSWR.  If you have access to a TDR, check the lines.  Check  
out the entire system with a network analyzer.

--chip