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Re: [Amps] Alpha 87a High SWR between Exciter and Amp vs BadBandswitch

To: "'JOS Earthlink'" <jsternmd@earthlink.net>,"'Mike Schatzberg'" <cherokeehillfarm@earthlink.net>,<Amps@contesting.com>
Subject: Re: [Amps] Alpha 87a High SWR between Exciter and Amp vs BadBandswitch
From: "Dick Green WC1M" <wc1m@msn.com>
Reply-to: wc1m@msn.com
Date: Wed, 3 Jan 2007 00:22:51 -0500
List-post: <mailto:amps@contesting.com>
Jerry,

Did you try just a 6' length of coax between the TS950S and the 87A? I'd be
curious to know how that works, as it's the length originally supplied with
the 87A.

There could be a number of causes for the 80m problem. It could be a dirty
or faulty input bandswitch. Or, it could be that your bandswitch needs
recalibrating -- the contacts may be landing just on the margin in the 80m
position.  If you can hook up a PC to your 87A, you can test whether the
bandswitch needs recalibrating on 80m and can patch a new calibration factor
into the firmware. Contact me directly and I'll walk you through the
procedure.

73, Dick WC1M

> -----Original Message-----
> From: JOS Earthlink [mailto:jsternmd@earthlink.net] 
> Sent: Tuesday, January 02, 2007 10:52 PM
> To: Mike Schatzberg; Amps@contesting.com
> Subject: [Amps] Alpha 87a High SWR between Exciter and Amp vs 
> Bad Bandswitch
> 
> Hi Mike, Hi Group,
> 
> Well I did the experiments and it was interesting.  The best 
> coax length I found was 20 feet and I made the mistake of 
> cutting it further back to 19.5 then 19 only to see things 
> deteriorate but it was worth the $25 in cable hihi.  It 
> didn't solve all the SWR issues but I think it is a fairly 
> good solution.
> 
> Bottom line:
> 
> 10m has improved from SWR of ~2.0 to now 1.5 12m remains the 
> same aroud 2.3 15m improved from 2.2 to 1.7 17m improved the 
> most from 2.3 to 1.5 20m improved from 1.5-1.7 now its a flat 
> 1.1 across the band 30m remains the same about 1.4 40m has 
> improved form 1.3-1.5 now is 1.1 across the band 80m has 
> worsened at the low end.  3500-3600 KHZ was 1.7 - 1.3 and now its
> 2.4 - 1.7.  But I don't plan to use it for CW.  While 
> 3700-4000 Khz was
> 1.3-1.4 it's now 1.2
> 
> 160m worsened from 1.5-2.0 it's now 2.2 across the band.
> 
> The other interesting comment from someone in the group was 
> that the measured SWR may not be an accurate reading if there 
> is significant RF on the shielding.  I don't know why that 
> would be the case in my well RF single point grounded system 
> setup but I tried by inserting a T4 line isolator by Radio 
> Works with a 6' coax on either side to the TS950SD and the 
> 87a and I repeated the experiment.  Lo and behold, my SWR 
> vastly improved and was only
> 1.1 across the bands on 10m, 15m, 17m, 20m, 30m and 40m.  On 
> 80m SWR was 1.5 or less from 3650 - 4000 Khz.  Things 
> improved on 160m with SWR 1.5-1.7.
> 
> However, I have found one remaining problem - a reproducible 
> but intermittent problem when switching to 80m and only to 
> 80m.  Sometimes the SWR read by my Kenwood TS-950SD is > 5 
> and other times it is at < 1.5. When it reads > 5 the power 
> output from the TS-950SD folds back and I cannot get more 
> than 800w output on the 87a. This seems to happen more often 
> when switching from band extremes like from 15m or 17m to 
> 80m.  When it happens that the SWR >5 I can usally get it 
> back to a normal SWR by making smaller band changes, e.g. go 
> from 15m to 20m then to 40m then to 80m.  I am certain it is 
> a problem with the 87a and not the TS-950SD because I can 
> reproduce the intermittent by keeping an 80m frequency on the 
> Kenwood and then selecting a different band on the 87a... on 
> xmit when the 87a autotunes back to the 80m frequency, the 
> SWR sometimes will be > 5.
> 
> I've been told that this can sometimes be fixed by 
> reprogramming the microprocessor that controls the bandswitch 
> position.  Is there any way I can do this at home without 
> shipping the amp back to Alpha?  I'm concerned that with the 
> problem being intermittent and only on 80m that it's more 
> than the bandswitch contact positioning but maybe a bad 
> stepper motor that's beginning to fail.
> 
> 73 Jerry
> K1JOS
> CCA #11906
> 
> 
> -----Original Message-----
> From: Mike Schatzberg [mailto:cherokeehillfarm@earthlink.net]
> Sent: Monday, January 01, 2007 2:44 PM
> To: JOS Earthlink
> Subject: Re: [Amps] Alpha 87a
> 
> 
> ps....you are not matching impedances, they are already 
> matched, each at 50 ohms.  You are shifting the phase.
> 
> 
> ----- Original Message -----
> From: "JOS Earthlink" <jsternmd@earthlink.net>
> To: "Mike Schatzberg" <cherokeehillfarm@earthlink.net>
> Sent: Monday, January 01, 2007 2:33 PM
> Subject: RE: [Amps] Alpha 87a
> 
> 
> > Hi Mike,
> >
> > I found this intereting short dissertation on the use of 
> 1/4, 1/2 wave
> coax
> > and variations to match impedances:
> >
> > http://www.wenzel.com/documents/swr.html
> >
> >
> > I guess the big question for me now is whether this actually makes 
> > things "better' or just becomes an interesting exercise.  Since the 
> > Alpha only require 40-60w for full output, even if my TS950 were 
> > seeing an SWR of 3 into the Alpha 87a, that means the 
> reflected power 
> > my TS950 finals would experience is around 25% or 12.5-15w.  How 
> > harmful are 12-15w of reflected power?  If the TS-950SD 
> were running 
> > barefoot at 150w full output into an antenna with an SWR of 
> 1.8 then 
> > the reflected power (~ 8%)would also be about 12.5w.  So, 
> overall, is 
> > it worth the time and effort to optimize the coax between 
> the TS950SD and 87a??
> >
> > I dunno  but it sure makes me think,read more and ask more questions
> hihi.
> >
> > 73 Jerry
> > K1JOS
> > CCA #11906
> >
> >
> > -----Original Message-----
> > From: Mike Schatzberg [mailto:cherokeehillfarm@earthlink.net]
> > Sent: Monday, January 01, 2007 1:29 PM
> > To: JOS Earthlink
> > Subject: Re: [Amps] Alpha 87a
> >
> >
> > Hello Jerry:
> >
> > I searched my archives, and I see that my memory is a 
> little off.  The 
> > optimal length on average is about 20.5 feet for the jumper 
> solution.  
> > I
> had
> > suggested this experiment to Win W0LZ, and he published his 
> experiment 
> > on the Yaesu reflector.  His starting SWR was about 2:1 on 
> 15 meters 
> > which
> was
> > his worst band.  Please see his data below:
> >
> >  OK, Mike, and anyone else that is interested, I started 
> with 23 feet
> > > of RG8X Premium Low Loss, FV 78% Center # 16, 1.2 db per 
> 100' at 15 
> > > MHz coax from Radio Works. Drive was 30 watts on 15 meters into a 
> > > old SB-220 that is somewhat modified for QSK and 10 meters,among 
> > > other things.
> > >
> > > At 23 feet the SWR was 1.75:1 into the Amp - !,2:1 to the 
> antenna At 
> > > 20.5 feet the SWR was 1.15:1 into the Amp _ 1.2:1 to the antenna
> > >
> > > The readings in between I am leaving out because I was tired and 
> > > don't trust my notes.
> > >
> > > With the 20.5 foot cable SWR on 20 and 10 meters into the amp was
> > > 1.2;1 into the amp and 1.2:1 to the antenna.
> > >
> > > It works for me.  Thank you very much.
> > >
> > > Win
> >
> > The solution is dependent upon the networks involved, and 
> the type of
> cable
> > being used to adjust the phase shift, that is why I asked Win to 
> > publish
> the
> > details about the cable he used to obtain his solution.  Win is a 
> > great
> guy,
> > with a long amateur history since 1960, and will gladly share his
> experience
> > with you.  I have learned over the past 46 years in this hobby that 
> > not
> too
> > many amateurs are familiar with this solution, Win was no exception.
> >
> > 73 and Happy DXing,
> >
> > Mike
> > W2AJI
> >
> > ----- Original Message -----
> > From: "JOS Earthlink" <jsternmd@earthlink.net>
> > To: "Mike Schatzberg" <cherokeehillfarm@earthlink.net>
> > Sent: Monday, January 01, 2007 12:21 PM
> > Subject: RE: [Amps] Alpha 87a
> >
> >
> > > Hi Mike,
> > >
> > > On which band should I be doing this pruning?   I assume 
> I should I do
> the
> > > pruning on 15m as that had the highest mismatch.  How will this 
> > > effect
> my
> > > SWR on the other higher bands which aren't too bad right now?
> > >
> > > 73 Jerry
> > > K1JOS
> > > CCA #11906
> > >
> > >
> > > -----Original Message-----
> > > From: Mike Schatzberg [mailto:cherokeehillfarm@earthlink.net]
> > > Sent: Monday, January 01, 2007 10:41 AM
> > > To: JOS Earthlink
> > > Subject: Re: [Amps] Alpha 87a
> > >
> > >
> > > Hello Jerry:
> > >
> > > The antenna tuner in the radio introduces a phase shift as do all
> antenna
> > > tuners, and this will create and odd multiple of 90 
> degrees, which 
> > > again causes problems for you.
> > >
> > > Do not use the autotuner when you start to prune the coax back to 
> > > the optimal length.  You can coil the coax up after you have 
> > > finished.  It
> > will
> > > not act as a line isolator, you will need a pretty good chuck of 
> > > ferrite around the coax to make one of those.  The line isolator 
> > > does not
> prevent
> > > ground loops, it prevents RF currents on the shield of 
> the coax from 
> > > reaching your transmitter.  This will avoid RF distortion on your 
> > > audio,
> > or
> > > microphone burns from RF on the grounds.
> > >
> > > Solder one connector to the jumper before starting your pruning 
> > > tests,
> the
> > > other end does not need to be soldered, but the cable must make 
> > > contact
> > with
> > > both the center conductor as well as the connector shell. 
>  You can 
> > > do
> this
> > > without a connector with a clothespin attached to the SO 
> 239 input 
> > > connector, or you can just tack the center connector to a 
> PL 259 and 
> > > use
> a
> > > force fit with the braid.  When you are done, solder both 
> > > connections properly, using considerable heat on the shield to 
> > > connector shell.to
> > assure
> > > a good bond.  I am assuming that you have a SO 239 input 
> connector, 
> > > as
> > Alpha
> > > has used a BNC jack on some of its amplifiers.
> > >
> > > The connector does not add anything to the SWR if properly 
> > > connected, it does not change the SWR on or off the cable end.  
> > > There is little or no
> > loss
> > > at HF frequencies.
> > >
> > > Don't let this small task cause you any concern, it is 
> easy to do.  
> > > You
> > can
> > > use low power while driving your amp to achieve the 
> lowest input SWR.
> You
> > > can check later at full drive, but nothing should change.
> > >
> > > You can not harm anything if you use reasonable care 
> connecting the
> cable.
> > > Listen first on your receiver to make sure the connection 
> is proper 
> > > and nothing has shorted from your work.  Then use low power and 
> > > transmit briefly, using a string of high speed dits on 
> CW, not SSB.  
> > > to check SWR with the built in meter in your transceiver.  Do not 
> > > use an outboard
> > meter,
> > > what matters is the apparent SWR seen by the output of 
> your transceiver.
> > >
> > > Whether your input circuits are tuned, as in your case, 
> or broadband 
> > > torroidal input, like the Alpha 76A, this method should lower the 
> > > input
> > SWR
> > > when done carefully.
> > >
> > > 73 and Happy DXing,
> > >
> > > Mike
> > > W2AJI
> > > http://home.earthlink.net/~cherokeehillfarm/id2.html
> > > ----- Original Message -----
> > > From: "JOS Earthlink" <jsternmd@earthlink.net>
> > > To: "Mike Schatzberg" <cherokeehillfarm@earthlink.net>
> > > Sent: Monday, January 01, 2007 10:14 AM
> > > Subject: RE: [Amps] Alpha 87a
> > >
> > >
> > > > Hi Mike,
> > > >
> > > > My inexperience will show in the next few 
> questions...but I will 
> > > > pick
> up
> > > an
> > > > antenna book and start reading.... until then:
> > > >
> > > >
> > > > 1) so I can determine the correct length by only having the coax
> > attached
> > > to
> > > > the 950SD and add a unsoldered connector to the end?  Does the
> connector
> > > > contribute much... I would have thought it's only determined by 
> > > > the
> coax
> > > > characteristics.
> > > >
> > > > 2) Once right length is found can I coil the coax between the 
> > > > exciter
> > and
> > > > amp?  Would that help make it act like a line isolator 
> to prevent
> ground
> > > > loops?
> > > >
> > > > 3) What I find weird is that when I have tried the 
> 950SD antenna 
> > > > tuner
> > to
> > > > bring down the SWR, the efficiency of the RF transfer 
> between the
> 950SD
> > > and
> > > > 87a goes down appreciably.  For example, on 15m at an 
> SWR of 2.5 
> > > > at
> > 21.000
> > > > Mhz I find that 22w output will drive about 1Kw on the 
> 87a.  When 
> > > > I
> set
> > > the
> > > > 950SD autotuner and it gives me an SWR of 1.3 without any 
> > > > reflected
> > power
> > > > then I need 54w to drive 1Kw on the 87a.  Maybe I'm 
> overthinking 
> > > > all
> of
> > > this
> > > > but when something doesn't make sense it drives me nuts 
> hihi.  Any
> > > thoughts?
> > > >
> > > >
> > > > 73 Jerry
> > > > K1JOS
> > > > CCA #11906
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Mike Schatzberg [mailto:cherokeehillfarm@earthlink.net]
> > > > Sent: Sunday, December 31, 2006 6:49 PM
> > > > To: JOS Earthlink
> > > > Subject: Re: [Amps] Alpha 87a
> > > >
> > > >
> > > > Yes Jerry:
> > > >
> > > > That is 21.5 feet.  The coax will act as a transformer, 
> and shift 
> > > > the
> > > phase
> > > > of the input, moving what maybe a node at the input of your amp.
> > > >
> > > > They also claim it will produce the lowest intermod for the
> combination
> > as
> > > > well.
> > > >
> > > > I can't say what the shorter length will do for you, but if you
> haven't
> > > > tried the six feet, you could give it a go.
> > > >
> > > > If you want to see how the length acts as a transformer, start 
> > > > with
> say
> > 25
> > > > feet or so, and prune about 6 inches at a time, 
> watching the SWR 
> > > > as
> you
> > > go.
> > > > You should see the SWR decrease as you cut back the length.
> > > >
> > > > It is not necessary to actually even have a connector 
> at the amp 
> > > > end
> on
> > > the
> > > > coax.  You can carefully trim the end, and place the center 
> > > > conductor
> > into
> > > > the center of the SO 239 connector, and hold the braid in place 
> > > > with a clothespin while you measure.  When you are 
> done, you can 
> > > > solder the
> PL
> > > 259
> > > > onto the end of the coax jumper.
> > > >
> > > > Pruning will allow you to reach the optimal solution for the 
> > > > jumper
> > > length.
> > > >
> > > > 73,
> > > >
> > > > Mike
> > > > W2AJI
> > > > ----- Original Message -----
> > > > From: "JOS Earthlink" <jsternmd@earthlink.net>
> > > > To: "Mike Schatzberg" <cherokeehillfarm@earthlink.net>
> > > > Sent: Sunday, December 31, 2006 4:51 PM
> > > > Subject: RE: [Amps] Alpha 87a
> > > >
> > > >
> > > > > Hi Mike,
> > > > >
> > > > > Is that 21.5 feet or inches ??  I noticed that the 
> Alpha manual 
> > > > > says
> > to
> > > > use
> > > > > a 72" coax between the exciter and the amp but 21.5 feet??
> > > > >
> > > > > 73 Jerry
> > > > > K1JOS
> > > > > CCA #11906
> > > > >
> > > > >
> > > > > -----Original Message-----
> > > > > From: Mike Schatzberg [mailto:cherokeehillfarm@earthlink.net]
> > > > > Sent: Sunday, December 31, 2006 4:49 PM
> > > > > To: JOS Earthlink
> > > > > Subject: Re: [Amps] Alpha 87a
> > > > >
> > > > >
> > > > > Hello Jerry:
> > > > >
> > > > > Before you adjust anything, I would use the old 
> Collins standard 
> > > > > of
> a
> > > > length
> > > > > of high quality RG 8 Type cable, 21.5 feet in length, between 
> > > > > the
> > > exciter
> > > > > and the amp.
> > > > >
> > > > > Measure the input SWR once again with this longer length of 
> > > > > cable in
> > > > place.
> > > > > I'll bet that you will see a lower SWR this time.
> > > > >
> > > > > 73 and Happy DXing,
> > > > >
> > > > > Mike
> > > > > W2AJI
> > > > > ----- Original Message -----
> > > > > From: "JOS Earthlink" <jsternmd@earthlink.net>
> > > > > To: <amps@contesting.com>
> > > > > Cc: "JOS Earthlink" <jsternmd@earthlink.net>
> > > > > Sent: Sunday, December 31, 2006 4:38 PM
> > > > > Subject: Re: [Amps] Alpha 87a
> > > > >
> > > > >
> > > > > > Oops, I forgot to mention that all measurements 
> were made with 
> > > > > > the
> > 87a
> > > > > into
> > > > > > a 50 ohm dummy load and the reflected power LEDs on the 87a 
> > > > > > stayed
> > at
> > > > zero
> > > > > > through the testing I described.
> > > > > >
> > > > > > 73 Jerry
> > > > > > K1JOS
> > > > > > CCA #11906
> > > > > >
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: JOS Earthlink [mailto:jsternmd@earthlink.net]
> > > > > > Sent: Sunday, December 31, 2006 4:35 PM
> > > > > > To: amps@contesting.com
> > > > > > Subject: Alpha 87a
> > > > > >
> > > > > >
> > > > > > Hi All,
> > > > > >
> > > > > > I just got an ETO Alpha 87a with Alphamax and it 
> seems to work
> very
> > > > > nicely.
> > > > > > I only see one problem with the amp - I'm almost 
> certain that 
> > > > > > the
> RF
> > > > input
> > > > > > coils for  many of the bands need to be adjusted.  
> I noticed 
> > > > > > that
> > the
> > > > SWR
> > > > > > out of the TS-950SD was running high into the 87a 
> on a few bands.
> > To
> > > be
> > > > > > absolutely certain I placed my Powermaster 
> powermeter between 
> > > > > > the
> > > > TS-950SD
> > > > > > and the 87a.  I think the 87a RF input circuits are 
> out of whack:
> > > > > >
> > > > > > At 28.0000 - 29.7000 Mhz SWR into the 87a is from 
> 1.5 - 2.0 At 
> > > > > > 21.0000 - 21.4500 Mhz SW goes from 2.3 - 1.8 At 18.068 - 
> > > > > > 18.168 Mhz SWR goes from 1.7 - 1.4 At 3.5000 - 
> 4.000 Mhz SWR 
> > > > > > starts at 1.3 but goes 2.2 above 3.700
> > Mhz.
> > > > > >
> > > > > > I tried this with other tranceivers instead of the TS-950SD 
> > > > > > and
> all
> > > show
> > > > > the
> > > > > > same.  On my Collins 30L-1 it's a piece of cake to 
> adjust the 
> > > > > > RF
> > coil
> > > > for
> > > > > > each band by looking at Reflected power between the exciter 
> > > > > > and
> amp
> > > > tuning
> > > > > > the RF coil for minimal Reflected power but the 87a 
> is a new 
> > > > > > beast
> > for
> > > > me
> > > > > > plus I don't have any schematics.  Any advice appreciated.
> > > > > >
> > > > > > Have a Happy and Healthy New year to All !
> > > > > >
> > > > > > 73 Jerry
> > > > > > K1JOS
> > > > > > CCA #11906
> > > > > >
> > > > > > _______________________________________________
> > > > > > Amps mailing list
> > > > > > Amps@contesting.com
> > > > > > http://lists.contesting.com/mailman/listinfo/amps
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> 
> 
> 
> 

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