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Re: Stupid Questions from a newbie



KF4FDJ (Mike in Ft. Myers, FL) wrote:
> 
> Tim,
> 
> In my opinion, the only "stupid" question is the one which remains
> unasked.  You're doing fine.
> 
> "Timothy S. Zibrat" wrote:
> > I have a Drake 2880 downconverter that I finally got around to modifying and
> > getting ready to install.  I have a R. Myers SB-32DX dish antenna.  What
> > kind of feedline can I run from the downconverter to my station?
> You do have a lot of questions, but I'll attempt to wade in.  As usual,
> use the lowest loss feed line you can beg, or buy.  However, since you
> are running the 144 IF frequency down to the shack, the losses will be
> much less than if you had the converter in the shack. 9913, LMR, and
> others have good loss figures.
> 
> Judd, W1PEA, talked me into covering my Myers disk with brass mesh.  He
> asserted the gaps in the "charcoal grill" don't capture all the signal.
> I THINK I noticed a 3 dB gain.  My measurements were made using the sun
> as a source, and 3 hours difference in time.  The path may have changed
> in that time.
> 
> > Can I, or should I run something like RG8X, or the RG6 cable
> > TV cable?  What's the impedance mismatch going to do to me if I use the RG6?
> Why?  Hard line can sometimes be "begged" from your local cable
> installers as spool ends.  If you aren't concerned with cutting the line
> to a specific length, the line will show an SWR of 1.5:1.  If you use 75
> ohm line, (such as hard line), AND you cut the line to an exact multiple
> of 1/2 wavelength, the impedance will be repeated.  That is, the radio
> end of the coax will show the same impedance as the load end.  If your
> load is 50 ohm, you will see a flat SWR.
> 
> > Will RG8X fit in an F connector?  What if I got one of those California
> > Preamps?  Do I need one?  I'd like to be ready for P3D and maybe try to
> > receive the UO-11 Mode S beacon.  Feedline length: about 50'.
> I would probably use a good gold plated F to N adapter, and put N
> connectors on your coax.  The new 1 piece solder on types are
> wonderful!  A preamplifier at 2.4G will most certainly help.  If you
> have the funds, by all means get one.
> 
> > I've heard different opinions on feedline for 435 and 144MHz.  I plan on
> > picking up some 9913Flex, but I heard that 8214?? is much more flexible and
> > has negligible losses (maybe for HF but for V-UHF as well?), and is cheaper.
> > I've also heard that 9913 is prone to water infiltration over time.  Is this
> > true as well?  If so, how do I prevent it?  Feedline length: about 50'.
> 50' of 9913 will serve you well.
> 
> > Where can I get a good deal on feedline/rotor cable?
> Just look for some good Belden wire.  Search the Internet or your Yellow
> Pages.
> 
> > Should I run my cables through some kind of conduit to protect them from UV?
> More trouble than it's worth.  Most good cable is UV resistant.
> 
> > My 435/144 antennas are currently configured for RHC polarization.  Is this
> > the preferred polarization for all current satellites?
> Switchable polarization sense is desirable on MOST of the birds.  If you
> are receiving a LHCP signal with a RHCP antenna, your loss could be
> somewhere around 20 dB.
> 
> > What's a good weatherproof method to use on the connectors?
> Good 3M electrical tape, followed by black coax seal, is what I use.  I
> like to slip a piece of heat shrink tubing over the coax before
> attaching the connector.  After soldering, I slip it over the junction
> between coax and connector and shrink.
> 
> Feel free to ask more questions.  The collective knowledge and
> willingness to help on this reflector is awesome!
> 
> 73, Mike in Fort Myers, FL
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Hi the only thing I can think of to add is the addition of a 2meter IF
Postamp immediately after the 2880 would help negate the Coaxial line
loss to the shack... it would set the Noise Figure at the point of
insertion... also a 2.4Ghz pre-amp is a GREAT addition... DEM makes
excellent kits for this... Also "Meshing In" the reflector will help to
reduce the distortion caused by the diffraction of the signals  caused
by the elemental type of reflector... be sure to follow the curve VERY
closely, or you may do more harm than good , as it can change the f/D
ratio and hence the focal point of the reflector...Good Luck and 73 de
Jordan...
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