>RE: LMR-400 For Repeater Reply
by KI6DYR on December 1, 2009 Mail this to a friend!
I'll look into that. But first we need to change the antenna that up until recently has worked great. It is a Hustler G7-144. It has a SO-239 at a 45 degree angle with specific instructions not to weather seal the connection. I have always been troubled by this.<
::Your G7 has an SO-239? Wow. Mine has a type N female on it, I *thought* that was "standard" with the G-7. Maybe it isn't. Might be a different P/N to order or something. I haven't bought one in about ten years, maybe they made a change. About the WX sealing, it's a double-edged sword. Great WX sealing seems like a good idea, but unless everything is pressurized, condensation will form inside the connector when the temperature drops, anyway (unless the humidity outside is always zero), and when you perfectly seal a connection, that condensation will remain in there pretty much forever. Letting the connection "breathe" will potentially let more stuff in, but also let it back out and condensation will be able to evaporate.
One "problem" with the G7 and many other antennas is the connector's on the bottom and running a coaxial line straight down a mast from that point is not a good idea. You should *always* use a "drip loop," a 360 degree circle formed of the coax itself, immediately below the antenna connector and bound to the mast to hold its form. This can serve two useful purposes: A way to prevent water from ever migrating down the transmission line any farther than the bottom of that loop; and a strain relief if you use "heavy" cable below the loop and it starts to pull a lot.
When using hardline/heliax, you normally don't make the loop out of that, but out of double-shielded flexible line like RG-214/U (or LMR-400), and then connect to the hardline at the end of the loop.
>Candidly, what started out as a group effort turned into a one man bank account insufficiently funded by a 7 year old with cancer. I have had to wait or compromise but now neither is acceptable. What I won't do is give up the coordination over a minor technical snag solved by turning the power down. A Kreco Coaxial might be affordable more so than a Station Master.<
::Sorry about your daughter's cancer, our best wishes are with you and your family.
Note that desense/noise/junk in duplex repeater systems can have a lot of sources. Could the antenna itself; the connection to it; the transmission line; the duplexer and all the obvious things. Could also be from intermod mixing in the repeater's transmitter (mixing the repeater's TX signal with some other signal source out of your control, such as another transmitter located LOS to you and quite strong, not necessarily on your property but close by), or another TX on your property, or sometimes even an AM BC station operating near 600 kHz -- lots of stuff. Turning down the TX power would often relieve the problem almost no matter what its cause.
>It dawned on me the daytime to nightime changes up here year round. Daytime may be 80ish and nightime in the 40's. Right now we have snow on the ground, daytime temps of ~60 and currently 27. These wild swings sure can cause condensation but I did not associate this with desense. Live and learn. With help from fellow hams it won't be as painful.<
::Temp changes make repeater operation more challenging, but obviously not impossible. I had repeaters in northern NJ (beginning in 1973!) at locations where the temp could be 100F in the summer and -20F in winter, and sometimes the day-to-day or day-to-night changes were 40F or more, so we were presented with lots of challenges! One by one, you learn to overcome all of them and make the damned stuff work LOL.