hi butch, i didn't want to get in to the stub business, he was using
the rg8x cable and i calculated that 100feet was ok since i
calculated that his cable wasprobably 70 velcity or so. that would
be 90 feet for a quarter wave so he was ok at 100 feet. don't know
his depth of electronics so wanted to stay casual. take care butch,
c u mike w6quv
At 07:36 PM 11/12/2011, you wrote:
>If you were close to a quarter wave, that would be bad, but I don't
>think you are. say for a half wave, 492/2 for a quarter wave, so
>246/1.9 times .66 for velocity factor is comes out to 85.45 feet. The
>only reason a quarter wave per say would be bad is that a quarter wave
>looks like a short if it is open and an open quarter wave looks like an
>open if shorted. That is how tuning stubs work. If you have around a
>hundred feet, forget it. Back in the days when I sold and serviced cb
>radios and people ran 102 inch whips, they had all kinds of problems
>with static electricity taking out the f e t front ends. I's put in a t
>connector at the radio with a shorted quarter wave stub which gave a dc
>ground, but as far as 27 meg was concerned, an open stub.
>73
>Butch
>WA0VJR
>Node 3148
>Wallace, ks.
>
>
>On Sat, 12 Nov
>2011, Mike Cozzolino wrote:
>
> > 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
> >>>>>
> >>>
> >
> >
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