hello tom, 100 feet of coax is not even a quarter wave of feed line
on 160m. if you take in to account the velocity factor of your coax,
you are very close to an electrical quarter wave on 160m. so do not
cut your feed line. and as far as coiling up the excess, think of
the rf chokes that are made by coiling up coax. make the coils about
a foot in diameter, and you will be ok. you need to shorten the
antenna and don't cut off the extra wire, just wrap it back on the
antenna so you can have plenty of adjustment. you may not ever get a
1 to 1 swr, but you should get an swr close enough to make the radio
happy. ok on the counter poise, that sounds ok. i don't know how
high the antenna is off the ground both at the fed end and the lower
end, but remember you are way under a quarter wave. un less you have
a tower that is 130 feet tall smile. your antenna is seeing lots of
capacity from the ground. so for that reason you will find the
antenna is going to be some what shorter to resonate at the desired
freq. take care, c u 73 mike
At 04:50 AM 11/12/2011, you wrote:
> Mike:
>
>The shield of the coax is connected to a counterpoise, and the sloper is
>grounded to my galvanized steel mast via a ground wire and a ground rod.
>
>Based on what you say, then, I will not worry about the extra coax, at least
>for now.
>
>This is all a major learning experience for me, and I appreciate everyone's
>patience.
>
>I am replying to a number of posts privately here, but I will post replies
>to the list if I think they might help others, and also because I want folks
>to know that I am listening.
>
>Thanks again, Mike, and all.
>
>73 from Tom Behler: KB8TYJ
>
>----- Original Message -----
>From: "Mike Cozzolino" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Friday, November 11, 2011 10:53 PM
>Subject: Re: Need helping making sense out of contradictory SWR readings
>
>
> > hi again tom, yes the broadcast station is messing up the
> > analyzer. i can not use my mfj 269 here because of the a.m.
> > broadcast and have talked to others that have found the same to be
> > true. so forget the analyzer, and go by the swr bridge. leave the
> > coax to your 160m antenna alone, 100 feet is nothing to even to
> > consider. adjust the length of the 160m antenna and by the way what
> > do you have the shield of the coax connected to? the shield at the
> > feed point. you need to work against a tall tower or a counter
> > poise. but like i was saying earlier tom the only to get a accurate
> > swr reading is right at the feed point or through an electrical half
> > wave or multiples of that. since you really can't do the latter then
> > adjust for the best swr that makes the radio happy. the tw1 is a
> > very poor device, it is not very accurate, and remember swr bridges
> > have diodes and again the voltage that is coming down the feed line
> > from the local broadcast will also effect the swr bridge. so put
> > your radio at about 10 watts to override the broadcast effects. good
> > luck, c u 73 mike
> >
> >
> >
> > At 07:00 PM 11/11/2011, you wrote:
> >> Mike:
> >>
> >>You have a very interesting point here about local broadcast signals.
> >>
> >>I happen to live about a half mile from the tower for the only commercial
> >>A
> >>M radio station in our little Michigan town. ... It broadcasts on 1460 AM,
> >>with a night-time power of, I believe, 1000 watts.
> >>
> >>Are you saying that this is what's messing the analyzer up?
> >>
> >>Again, just to be sure I'm understanding you, are you saying ignore the
> >>analyzer, and just go with what my TW1 and TS590 meters are saying?
> >>
> >>Obviously, my 160 meter antenna is still too long electrically, so that
> >>will
> >>need to be shortened.
> >>
> >>But, here's another question: When we put up the 160 meter sloper, I only
> >>had a 100-foot piece of RG8X coax to connect between the antenna and the
> >>rig, which gives me about 40 feet of excess coax. ... Should I cut that
> >>coax
> >>to only what I need? Would that change anything?
> >>
> >>Again, you are giving me some very interesting observations here.
> >>
> >>73 from Tom Behler: KB8TYJ, Big Rapids, MI
> >>
> >>
> >>----- Original Message -----
> >>From: "Mike Cozzolino" <[log in to unmask]>
> >>To: <[log in to unmask]>
> >>Sent: Friday, November 11, 2011 9:30 PM
> >>Subject: Re: Need helping making sense out of contradictory SWR readings
> >>
> >>
> >> > hello tom, the analyzer is almost useless on 160 and 80m
> >> > antennas. the reason is because you have so much broadcast signals
> >> > coming down the feed line that the analyzer is all messed up. in
> >> > areas where folks don't have the broadcast crap the analyzer does the
> >> > fine job. so go by the swr bridge and ignore the analyzer. even a
> >> > swr bridge is influenced by the length of the feed line, you could
> >> > have a 1:1 some where along the coax where the swr is really much
> >> > higher. the only way to use an swr bridge is through a electrical
> >> > half wave to the antenna or with the swr bridge at the feed
> >> > point. you can also use multiple electridal half waves between the
> >> > swr bridge and the ant. take care, c u 73 mike
> >> >
> >> >
> >> >
> >> > At 05:28 PM 11/11/2011, you wrote:
> >> >>Hi, folks.
> >> >>
> >> >>Well, I have managed to get hold of an MFJ 259B antenna analyzer to
> >> >>help
> >> >>try
> >> >>to figure out what is going on with my 80 meter and 160 meter sloper
> >> >>antennas that we put up a few weeks ago.
> >> >>
> >> >>However, when taking some preliminary readings with the analyzer
> >> >>tonight,
> >> >>and comparing them against what my TW1 watt meter and the SWR meter on
> >> >>the
> >> >>TS590 say, I am getting very confusing results.
> >> >>
> >> >>Let me give a few examples:
> >> >>
> >> >>On 80 meters, my sloper has an SWR of about 5 to 1 on the top and
> >> >>bottom
> >> >>of
> >> >>80 meters, with a dip of 1.0 to 1 around 3.887 mhz. But, when we put
> >> >>the
> >> >>analyzer on the antenna, it shows the lowest SWR to be about 1.3 to 1
> >> >>at
> >> >>3.887 MHZ, but the SWR's skyrockets quickly on either side of that null
> >> >>to
> >> >>infinity on the lowest part of the band, and to over 8.1 to 1 on the
> >> >>top
> >> >>of
> >> >>the band.
> >> >>
> >> >>With my 160 meter sloper, my lowest SWR is about 5 to 1 at the very
> >> >>bottom
> >> >>of the band, according both to my TW1 and the TS590 SWR meter, but the
> >> >>needle on the analyzer doesn't even budge when tuning through the
> >> >>entire
> >> >>band, and stays up at some ungodly figure of an SWR of about 20 to 1.
> >> >>
> >> >>I just checked for a short on my coax feed lines, and there does not
> >> >>appear
> >> >>to be any problem there.
> >> >>
> >> >>We are using fresh batteries in the analyzer which were just bought
> >> >>tonight.
> >> >>
> >> >>Are we perhaps not adjusting the analyzer correctly?
> >> >>
> >> >>I am sure that, to some, all of this seems very elementary, so please
> >> >>bare
> >> >>with me while I do some learning here.
> >> >>
> >> >>73 from Tom Behler: KB8TYJ
> >> >
> >
|
