Hi Jeff,
Same story here and that is one reason why I am so disappointed my Rig Experts
AA-170 failed me. It's really a nice instrument to use in so many ways. Now I
thought the explanation of doing stubs was not nearly as good as using the
MFJ-259b. The MFJ had just been sitting out in my shop unused until this little
problem caused me to use it. Antenna analyzers are a serious cash commitment
and being tight I looked long and hard before deciding on the RE. Now I suppose
it's either junk or maybe they will take it back and plug in a new circuit
board and send it back. Doubt they would really trouble shoot it down to
component level like we used to do at Tek. But that's the world now days.
Terry
KI7M
> On June 10, 2018 at 7:28 AM Jeff Blaine <KeepWalking188@ac0c.com> wrote:
>
>
> The MFJ259 is a fine box but when you get to 80m with anything near a BC
> it's going to be problems. In fact I discovered the hard way that even
> up on 20m the box can read funky if your antenna is big enough or high
> enough. I have a Rig Expert now as well and really love that thing -
> plus it's apparently immune to the local BC stations. Not quite as
> capable as a VNA but has OSL cal, runs forever on battery and does stuff
> like stub tuning as you are trying here. Don't think I have used the
> '259 since i bought the RE last fall.
>
> 73/jeff/ac0c
> alpha-charlie-zero-charlie
> www.ac0c.com
>
> On 10-Jun-18 8:59 PM, k8gg@voyager.net wrote:
> > Hi All,
> >
> > I was discussing this thread with a microwave engineer on 75 meters this
> > morning and he reminded me that I had AM RF in my RX antennas at my
> > previous QTH. So much that I used Hi-Pass filters on my beverages and
> > pennants.
> >
> > Terry, Do you have an AM radio station near by that could be messing with
> > your instruments?
> >
> > Just a thought. GL,
> >
> > de George, K8GG
> >
> >
> >
> >> Hi guys and gals,
> >>
> >>
> >> Well, to make a long story short my Rig Experts AA-170 has quite working.
> >> Looks normal but a 56 ohm resistor at the end of the 75 ohm coax reads
> >> infinite. On the MFJ-259b it reads 56 ohms. Check SWR and the MFJ reads
> >> 7.499.2 Mhz 1.1:1 SWR R=56/57 ohms X=0. Coax is 55' 4 3/8" long when I got
> >> very near 7500 KHz. With the shorted coax the MFJ-259b read 7.484.2 to
> >> 7.523 Mhz, 20.2 SWR, R=2 ohms, X=0. Seems like the velocity factor is
> >> considerably higher than what was stated to me by DX Eng.. The velocity
> >> factor is some where around 0.84401... as best I can figure it. So I guess
> >> that makes it 0.84 VF FWIW.
> >>
> >>
> >> Anyway, I have it figured that 55' 4 3/8" will do the trick for my 80
> >> meter 4-Square at 3.750 Mhz.
> >>
> >> But why my RE analyzer went out today I don't have any idea. Back to the
> >> MFJ!
> >>
> >>
> >> Terry
> >>
> >> KI7M
> >>
> >>
> >>> On June 9, 2018 at 6:59 PM terry burge wrote:
> >>>
> >>>
> >>> Good point Wes. I will see if I can find a decent value of resistor.
> >>> My Rig Experts AA-170 was purchased because I did not trust the
> >>> readings my MFJ-259b was giving me while working on my hytower.
> >>> Pretty penny for these antenna analyzers. But I will bet if it won't
> >>> do the stub frequency checks it won't do the velocity factor and
> >>> more. Did work pretty good for checking SWR and feedpoint impedance
> >>> on antennas like the hytower. Really liked it until this.
> >>>
> >>>
> >>> Terry
> >>>
> >>> KI7M
> >>>
> >>> > > On June 9, 2018 at 5:11 PM Wes Stewart wrote:
> >>>>
> >>>> Since he said the coax was 75-ohm, a 75-ohm termination would
> >>> be better.
> >>>>
> >>>> On 6/9/2018 5:07 PM, Richard (Rick) Karlquist wrote:
> >>>> > > As a sanity check, terminate the coax with a 50 ohm
> >>> resistor and verify
> >>>> > > > that you have good coax. Flat line at 1:1 SWR, etc.
> >>>>> Rick N6RK
> >>>>>
> >>>>> On 6/9/2018 4:57 PM, terry burge wrote:
> >>>>> > > > I don't know what is wrong here but I keep getting
> >>> in this situation where my
> >>>>> > > > > typing starts running back over my writing.
> >>> I will try again to reply.
> >>>>>>
> >>>>>> Joel,
> >>>>>>
> >>>>>> I have tried all that the manual says without
> >>> success. All I see is the
> >>>>>> horizontal solid and dashed lines of R and X. No
> >>> indication of a resonance
> >>>>>> point anywhere from 1880 KHz up to 10,500 KHz. Go
> >>> figure? At least my
> >>>>>> mfj-259b is working old as it may be. Rig Experts
> >>> is going to get a nasty
> >>>>>> note I think. Disappointing, huh?
> >>>>>>
> >>>>>>
> >>>>>> Terry
> >>>>>>
> >>>>>> KI7M
> >>>>>> > > > > On June 9, 2018 at 2:54 PM Joel Harrison
> >>> wrote:
> >>>>>> > > > > > Hi Terry,
> >>>>>>> I replaced the 1/4 lines on my 80 meter 4
> >>> square this past fall and used
> >>>>>>> my AA-170 to set the length with no problem.
> >>>>>>>
> >>>>>>> Just select "all" for the mode and set the
> >>> freq you're aiming for and then
> >>>>>>> trim the line until X equals zero with the
> >>> far end open. Should work fine.
> >>>>>>> I always calculate the length x VF then add
> >>> a few feet to start.
> >>>>>>> 73 Joel W5ZN > > Hi guys and gals,
> >>>>>>> >
> >>>>>>> >
> >>>>>>> > > > > > I have got DX Engineering 75 ohm
> >>> foam coax to make the
> >>>>>>> > > > > > > stubs/feeders for
> >>>>>>>> my Comtek 80 meter 4-Square and am
> >>> finding some difficulty.
> >>>>>>>> Neither my
> >>>>>>>> MFJ-259B nor my Rig Experts AA-170
> >>> seem to indicate a 1/2 WL at
> >>>>>>>> 7500 KHz
> >>>>>>>> or a 1/4 WL at 3750 KHz? Or any
> >>> frequency up or down from there.
> >>>>>>>> Seems to
> >>>>>>>> me the last time I did this a few
> >>> years ago I didn't have a problem
> >>>>>>>> getting a 1/2 WL dip indicating a
> >>> resonance location. But now I
> >>>>>>>> just don't
> >>>>>>>> get any indication of a resonance.
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> DX Engineering said they had got some
> >>> 75 ohm foam coax that
> >>>>>>>> instead of
> >>>>>>>> 0.84 VF was more like 0.80 down to
> >>> 0.76 VF. But checking all the
> >>>>>>>> way down
> >>>>>>>> to 6000 KHz on 40 meters or 2500 KHz
> >>> on 80 meters fails.
> >>>>>>>>
> >>>>>>>> My test is to use either antenna
> >>> analyzer with a PL-259 installed
> >>>>>>>> at one
> >>>>>>>> end and an open or a short at the
> >>> other. I started with 57'7" of
> >>>>>>>> coax.
> >>>>>>>> Tried both with the coax in a roll and
> >>> strung out. What am I doing
> >>>>>>>> wrong?
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> Terry
> >>>>>>>>
> >>>>>>>> KI7M
> >>>>>>>>
> >>>>>>>> 😞
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