[OKDXA] The weak spot in my dipole

Fri Jul 1 17:30:00 EDT 2016

One additional point about my recommendation for the Alpha-Delta 
TT3G50 arrestor is that the active component is replaceable and 
is available in 200 Watt and 2 kW versions and is rated at > 600 
firings.  They are available in "UHF" and "N" versions. 

* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* Oklahoma City, OK * 
* USAF, Ret'd 61-81 * 
** FAA, Ret'd 94-10 * 
* * * * * * * * * * * 

> From: af5cc2 at gmail.com
> Date: Fri, 1 Jul 2016 10:06:35 -0500
> To: okdxa at mailman.qth.net
> Subject: Re: [OKDXA] The weak spot in my dipole
> 
> Thanks for the suggestions-PROBLEM SOLVED!
> 
> I borrowed another manual tuner and a dummy load from a friend.  The
> antenna was doing the same thing with the other tuner, so that eliminated
> the tuner, which would have been the most expensive part of the system to
> replace.  My next plan was to unhook the coax from the balun and hook it to
> the dummy load, so see if the coax was ok.  While getting ready to do that,
> I noticed one part of the system I forgot to mention-the lightning
> arrestor.  It is one of those cheap ones that has a PL239 on 1 end and a
> SO239 on the other, with a screw you attach the ground wire to, and it is
> supposed to bleed static off of the antenna.
> 
> Obviously the lightning arrestor wasn't sealed very well, because when I
> removed it, the SO239 part of it was rusty.  I found some sandpaper, sanded
> the corrosion off of the PL259 on the end of the coax, threw away the
> lightning arrestor, hooked the coax up to the balun, and everything is
> working fine now!  Made a few 40m QSOs in the Canada Day contest with no
> problems.
> 
> When telling this to the XYL, she agreed that maybe next time I get a
> lightning arrestor, I shouldn't get one for $5 off of ebay.
> 
> John AF5CC
> 
> On Thu, Jun 30, 2016 at 9:32 PM, Perry Jenkins via OKDXA <
> okdxa at mailman.qth.net> wrote:
> 
> > Check your coax with a megaphmmeter. Disconnect from the antenna and test.
> > This tests  for breakdown in the dialectic of coax at high voltage. This
> > can find defects that don't show up with continuity checks with a standard
> > VOM.
> >
> > Perry N5PJ
> >
> > Sent from my iPhone
> >
> > > On Jun 30, 2016, at 14:22, John Geiger <af5cc2 at gmail.com> wrote:
> > >
> > > spot" in my dipole
> > > <
> > http://www.eham.net/ehamforum/smf/index.php/topic,110022.msg935431.html#msg935431
> > >
> > > « *on:* *Today* at 11:45:32 AM »
> > > [image: Reply with quote]*Quote*
> > > <
> > http://www.eham.net/ehamforum/smf/index.php?action=post;quote=935431;topic=110022.0;num_replies=0;sesc=5c1acd5339f71a99ad263040698a5c0e
> > >
> > > [image: Modify message]*Modify*
> > > <
> > http://www.eham.net/ehamforum/smf/index.php?action=post;msg=935431;topic=110022.0;sesc=5c1acd5339f71a99ad263040698a5c0e
> > >
> > > [image: Remove message]*Remove*
> > > <
> > http://www.eham.net/ehamforum/smf/index.php?action=deletemsg;topic=110022.0;msg=935431;sesc=5c1acd5339f71a99ad263040698a5c0e
> > >
> > > ------------------------------
> > > I have a homebrew G5RV type dipole that I made around 18 years ago.
> > > Overall it has been a very good antenna for me and I have worked lots of
> > DX
> > > with it.  It is around 100 feet of copper wire, joined to a run of 300ohm
> > > Radio Shack twin lead, maybe 25 feet or so.  At the twin lead to coax
> > > junction I have a Unidilla 4:1 Voltage Balun, and then 20 feet of RG11
> > > 75ohm coax.
> > >
> > > A couple of years ago I was using a MFJ 918 1:1 current balun, and on
> > some
> > > of the lower bands, I couldn't keep the antenna "tuned".  I am using a
> > MFJ
> > > 941D tuner, and I would tune the antenna tuner on 40 or 80 for the lowest
> > > SWR, and once I started transmitting the SWR would jump up to infinity,
> > so
> > > I would transmit a carrier, retune it, and once I transmitted again, same
> > > problem, the SWR would jump up.  A few months ago I replace the MFJ balun
> > > with the Unidilla 4:1 Voltage Balun because when I originally built the
> > > antenna, I had a Van Gordon 4:1 voltage balun, and it worked fine.
> > >
> > > Changing baluns seemed to fix it for a while, but now I am having the
> > > tuning problem again, but it happening on all bands, not just 40 and 80.
> > > Luckily I have a miniquad for the higher bands, but I tried the dipole on
> > > 20 and 17 today with the same losing tune problem.
> > >
> > > Before I go climbing around on the roof changing stuff out, does anyone
> > > have an idea of where to start-what might be causing this tuning problem.
> > > Same thing as before, I would load up the dipole to a 1:1 SWR, using a
> > less
> > > than 100 watt carrier, but once I go and start transmitting at full power
> > > the SWR quickly jumps way up.  I go retune it,which just requires a
> > slight
> > > adjustment, and the SWR jumps up again, and it just keeps doing this.  I
> > > don't think it is the MFJ tuner because it doesn't have this problem with
> > > the miniquad, which also goes through the tuner.
> > >
> > > Also, the dipole shows a low SWR (2:1 or less) on 12 and 15 meters, and
> > > when I put the tuner in bypass mode I can transmit on the dipole with no
> > > problems with losing its tuning.  On 80m the SWR is also low, and
> > > transmitting on bypass mode to the dipole usually works but once in a
> > while
> > > it will its tuning.  On 30m it will show a low SWR initially but once I
> > > start transmitting (in bypass again) the SWR quickly goes to infinity.
> > On
> > > 40m when I tune the antenna and then transmit at 10 watts it seems to
> > stay
> > > tuned.  Going up to 25 watts detuned it again.
> > >
> > > So, any ideas or guesses as to where the problem in my system is?
> > >
> > > 73 John AF5CC
> > > Report to moderator
> > > <
> > http://www.eham.net/ehamforum/smf/index.php?action=reporttm;topic=110022.0;msg=935431
> > >
> > >    199.96.203.51
> > > <
> > http://www.eham.net/ehamforum/smf/index.php?action=helpadmin;help=see_member_ip
> > >
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