In my case I did find water in the sections of LDF5-50 that were unprotected but with an ohm meter and a hacksaw was able to remove the affected portions resulting in a >10M ohm reading after removing just a couple of feet. The nature of the foam inside LDF5-50 doesn't permit water to travel quickly very far.
I'm successfully running my KPA500 on all bands. No idea about carbon tracking. YMMV jim ab3cv On Mon, Jul 29, 2013 at 3:11 AM, Dr. William J. Schmidt, II < b...@wjschmidt.com> wrote: > I have a different opinion on buying used heliax. Unless you scan it (TDR > minimum) you will never know if what you are purchasing is a piece of good > used heliax... or something hit by lightning now has carbon track shorts > and/or dielectric that is saturated with water. While some lucky people > have purchased used heliax with success, I would use the same common sense > as when purchasing any used coax. > > > Dr. William J. Schmidt - K9HZ / J68HZ/ 8P6HK/ ZF2HZ > > Owner - Operator > Big Signal Ranch > Staunton, Illinois > > email: b...@wjschmidt.com > > -----Original Message----- > From: elecraft-boun...@mailman.qth.net > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Miller > Sent: Sunday, July 28, 2013 7:51 PM > Cc: elecraft@mailman.qth.net; John Fritze > Subject: Re: [Elecraft] KAT-500 and 30' Flag Pole Antenna Users? > > John > > When working through your setup consider getting some 7/8" hardline to use > as feed which depending on your run length to the antenna may allow you to > keep the KAT500 in the shack with acceptable loss. You'll still need some > coax jumpers to get from the hardline to the rig inside the house so you'll > need to calculate and add that loss along with the little bit at the > antenna. > > Any of the online loss calculators will give you the answers. Use 10:1 as > the max SWR estimate at the antenna to calculate the feedline loss since > the KAT500 can't tune more than that anyway. > > Here's some examples: @10:1, LDF5-50, 3.5Mhz, 100ft yields a total loss of > 0.32db. Same for 28Mhz yields 0.86db. > > http://www.arrg.us/pages/Loss-Calc.htm > > Such hardline is readily available at much less than new prices if you buy > used. I paid a bit over $1/ft for mine if you're luck you might even find > it free. Connectors are pricey but since you only need two, no big deal. > > The tradeoff is having the tuner in the shack where is it visible and > usable without concerns for weather vs temperature and humidity issues > outside. > > 73 > > jim ab3cv > > > > On Sun, Jul 28, 2013 at 8:24 PM, Javier Campos > <nm6e_...@sbcglobal.net>wrote: > > > Thanks to all for the replies. Excellent points and real life experiences > > have provided some valuable insight. > > > > The antenna should be her in about a week or so. > > > > I will use my MFJ antenna analyzer (I hope it still works) after I get it > > standing up and eventually (need to let the "look" set in of just the > > aluminum) for the neighbors before I attach the UNUN and the radials. > > > > After all, it's a "Flag Pole" to my HOA so I just need to let it sit > there > > and let the novelty wear off before I attach UNUN, lay the radials and > dig > > the trench for the coax. > > > > It will also give me time to freshen on on plotting the R+jx on the smith > > charts, again after 24+ years from doing in it in college. > > > > Thanks again and you will all here from me once this is all installed and > > put together and on the air. > > > > Javier NM6E/5 > > > > > > ________________________________ > > From: John Fritze <fritzej...@gmail.com> > > To: elecraft@mailman.qth.net > > Sent: Sunday, July 28, 2013 2:35 PM > > Subject: Re: [Elecraft] KAT-500 and 30' Flag Pole Antenna Users? > > > > > > Javier, > > > > Here's some additional info for you to my first post. > > > > A lot of great info can be found here regarding the antenna design you > are > > considering: > > > > http://www.sgcworld.com/technicalInfoPage.html > > > > If the tuner is at the radio and the output from the tuner is coax (such > as > > a built in tuner in the K3) the tuner is tuning the coax and not the > > antenna. It will make the rig happy and isn't that what we mostly are > > looking for anyway? But the main problem is how do we get the most > > transfer of power between the coax and the antenna? > > > > A schematic circuit of any antenna is a resister, inductor and capacitor > in > > series. By adjusting the capacitance or the inductance we can try to > > arrive at 50 Ohms to match to coax. That's what a remote tuner is trying > > to do by adding capacitors and coils into the circuit. Once the match is > > found, then the rig output, coax, and antenna are all 50 ohms giving us > the > > maximum transfer of power so it is not burnt up as heat in the coax. > > > > A remote tuner tunes the antenna and the coax is effectively flat SWR > from > > the rig to the tuner. One problem I have found is that coax should NEVER > > be used at the output of a remote tuner (BUT we all do it don't we, even > I > > do on occasion)! From the remote tuner to the antenna it is all antenna > > and it is all radiating. West Marine sells a product called high voltage > > wire, it is 10 or 12 gauge, stranded and tinned, covered with a white > PVC. > > It is not cheap but it is a really good product. Sometimes a remote > tuner > > will tune with a short coax at the output, but it won't be happy and you > > will find that the tuner will hunt for a solution. > > > > One other issue folks sometimes have is trying to tune the vertical when > it > > is too short for the tuner. Ideally you need to be 42-43 feet to work > > 80-10 meters. If you want to sometimes get on 160, then you need to be > > closer to 55 feet at a minimum, but then you are compromised at 10-6 > > meters. Not because the antenna won't tune the longer vertical but > because > > angle of take off is too high. If you try to tune an antenna which is too > > short, the voltages at the relays can be very high, causing arching and > > burning of relay contacts. One way around this is to tune at a very low > > output, then raise power once the relays have set where they need to be. > > Be careful to not vary too far in frequency however! Another solution is > > to add in inductance by jumpering in a coil when you want to work the > lower > > bands. There are numerous articles in QST about getting a 42 foot > vertical > > onto 160 meters. > > > > Remember: a properly grounded vertical antenna is only about 25-30 ohms. > > So right off the bat you have a 2:1 mismatch. I also do not use an UNUN > or > > balun of any type and have not had any issues. Again, you need a VERY > GOOD > > GROUND. > > > > I know for the real antenna gurus out there everything I have stated is > > kind of simplistic and there are tons of variables and best solutions per > > application. I am just giving you 30 years of real world experience. > > > > > > -- > > John Fritze Jr > > K2QY > > AARA president 2013 > > ACACES secretary 2013 > > Albany County RACES Radio Officer > > ARES ENY DEC Northern District > > Hudson Div. Asst. Director > > Twitter: @k2qy > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:Elecraft@mailman.qth.net > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:Elecraft@mailman.qth.net > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
