[FARC] Antenna Tuner

Wed May 30 21:19:28 EDT 2007

Bob,

Yes, it's a cheap tuner.

Yes I have the vertical antenna outside grounded (8 ft. ground rod) and the 
ground wire connected to an MFJ window unit, but no the radio equipment 
isn't ground connected to the window unit. Kind of a waste of time, huh.  I 
had every intention of running a ground strap to the window unit, but the 
window unit is at one end of the room and the radio equipment at the 
opposite end.  Computer desks, chairs, sewing machines, and bookshelves 
necessitated that antenna leads and ground wires meander around or behind 
furniture, meaning there would have been a very long ground strap (over 25 
ft) from the equipment to the window unit.  From the ham books long ground 
wires are a no no, so I didn't know quite what to do there.  Which is worse, 
no ground or too long of a ground?  You get "burned" either way.

Connectors are fully seated, tight, and brand new, though the antenna leads 
are over 25 ft. long as described above.  I realize I'll have to rearrange 
the room but I haven't gotten around to it yet.  It was only two months ago 
that I had a 2 meter mobile unit for a radio and an 18" mag-mount antenna 
sitting inside the room on top of a stainless-steel mixing bowl.  Compared 
to now, those were the good ole' days, happy in blessed ignorance.

I figured out the SWR meter on the radio, with the help of W3ICF, so that is 
actually ok now.

Yes, the antenna is marginal, sort of.  It actually was an experiment from 
W3ICF as he had this old antenna in his garage and never used it and he just 
wanted to see how it would work.  The antenna is ground mounted on a 1 ft. 
pipe, but there are no RF ground radials; supposedly it didn't need any. 
W3ICF put his antenna analyzer on it and got acceptable (barely) SWR on 40, 
20, 15, and 10 meters.  Using it with my Kenwood TS-2000 and its automatic 
antenna tuner, it works fine on these bands.  "Works fine" is my term for 
1:1 or 1.5:1 SWR and making contacts in the North East, South East, Mid 
West, and far western USA. I can hear plenty of DX international stations on 
20 meters, but due to traffic pileups and propagation haven't been able to 
contact any.  So, does a radio and antenna work with no ground, long antenna 
leads, and a marginal antenna? Sort of.  Would it work better if everything 
in the shack was set up by the book? Absolutely.

So, if the antenna and a radio with an automatic antenna tuner sort of 
works, why did I purchase an antenna tuner?  Well, it all stemmed from 
buying the wrong radio in the first place.  The Kenwood TS-2000 is too much 
radio for a rookie ham operator like me.  Sure I can use it fine on 2 meters 
and 440, and on some HF bands, but I'll never, repeat never, be able to 
realize the capabilities built into the Kenwood TS-2000.  There is so much 
to learn and the manual so intimidating, it just isn't fun.  So, with this 
in mind I bought a bare-bones Icom 718, which is a basic HF rig designed for 
beginners. Since I wanted to experiment with dipole antennas I thought I 
needed a manual antenna tuner, and there you have it.  I guess this 
situation is analogous to a newly licensed driver getting a Ferrari for the 
first car.  It just won't work.  I'll keep the Kenwood and learn bits and 
pieces as I go and maybe if I live long enough the Kenwood TS-2000 will 
actually appreciate in value, like a Ferrari.

Thanks for the info and the help.

KB3ONM
Kirk

----- Original Message ----- 
From: "Bob Moroney" <windbrkr at erols.com>
To: "Frederick, Maryland ARC" <farc at mailman.qth.net>
Sent: Wednesday, May 30, 2007 7:02 PM
Subject: Re: [FARC] Antenna Tuner

> Kirk,
>  From the sound of it, you could have a screwed-up tuner, you could have
> a screwed-up antenna, you could have some station grounding problems,
> you could simply not be using the tuner quite as it's meant to be used,
> or you could have some combination of the above.
>
> Does that make you feel any better?  Probably not.
>
> Basically, you need to deal with one problem at a time, starting with
> the antenna and feedline.  If that system isn't behaving as it should,
> you might as well be beating your head against the wall.  Have you or
> anyone else put an antenna analyzer on the end of the coax that goes
> into your transceiver?   That alone will tell you a lot about your
> antenna and feedline; e.g., what its impedance is at various frequencies
> and where it's naturally resonant.
>
> Is your station's grounding system solidly bonded to a real earth
> ground, and is all your station equipment solidly tied into that
> system?  An ohmmeter will help answer that question.
>
> Are all your coax connectors "good" and fully seated into one another?
> Another job for the ohmmeter, at least as a start.
>
> I didn't know it until today, but I too have one of these tuners; I just
> never fully assimilated the make or model number.  To me it was simply
> the somewhat cheap manual tuner I bought maybe ten years ago from some
> mail order place (Radio Works?).  It's an OK tuner as far as it goes,
> but it's definitely nothing special.  I can't say that I've ever looked
> at the manual.  Although I bought this tuner ten or more years ago, I
> would doubt that the manual I have is any different or better than
> yours, so loaning you my manual probably won't help.
>
> On the tuner, one thing I would say right off the bat is that the knobs
> on the front panel (other than the "Output Select" knob) have no stops.
> As you suggest, they will turn forever.  So just picture what they do.
> Matter of fact, it wouldn't hurt to unscrew the cover from the tuner and
> view what lies beneath to help you visualize.
>
> You'll see two variable capacitors and a coil.  The two variable caps,
> one "transmitter" and one "antenna" are just plates that twirl around,
> interleaving (or not) to various degrees, depending on how much they've
> been twirled, then start it all over again.  The "inductor" (coil) has
> taps off of it that are connected to the "inductor" switch.  You can
> turn this switch forever as well, but in reality you are just cycling
> through the same tap points over and over, adjusting the impedance of a
> capacitance/inductance bridge in various combinations until the antenna
> is "tuned".  Unfortunately, though, an antenna can't really be "tuned"
> without increasing or reducing the length of its radiating elements to
> match the frequency desired.
>
> So the idea of an "antenna tuner" is to achieve a reasonable impedance
> between whatever radiating contraption you hooked up to the "tuner" and
> the transmitter, so you don't wind up releasing the smoke from your
> transmitter's output transistors.  The transmitter finals are happiest
> when they sense a 50-ohm impedance on their output; thus you need to
> fiddle with the tuner controls until the radiating contraption
> (antenna)  "matches" what the finals want to see.  So you could view a
> tuner as a "pacifier" for your transmitter finals, more than anything
> else.   It may or may not really increase the power that winds up going
> to the antenna, but it will help to keep the transmitter output stage
> happy and smoke-free.
>
> Put the inductor switch into the position recommended by the "manual"
> for a given band, then tweak the transmitter and antenna variable
> capacitors within their range, until SWR is minimized.  Make sure you've
> got the "Output Select" switch set to the "Tuned" segment so you're
> getting the correct meter readings, and make sure you've got the
> "Peak/Avg" push button "out", so that you're getting average readings
> instead of peaks that depend on your voice modulation.  Also, if you can
> get your transmitter to key in CW mode, do that instead of using SSB,
> which as you note, various according to the volume of your voice.  I
> don't know your rig, so I don't have any suggestions there, other than
> plugging in a key.
>
> Well, I'm tired of typing, and I've got to make some cole slaw for
> supper, so hopefully all these words may help you a little.  Feel free
> to write or call if they don't, or whatever.
>
> 73, Bob K9CMR
> ======================
> Kirk Talbott wrote:
> > I recently bought a Vectronics VC300DLP antenna tuner and I am using it 
> > with
> > an ICOM 718 transceiver. My antenna is a hy-gain model 18 AVT/WB-S 
> > vertical.
> > I bought an antenna tuner based on a consensus of other experienced hams
> > that if I used the ICOM 718 I would probably need an antenna tuner
> > regardless of what antenna used.
> >
> > I am new to ham radio, HF, and antenna tuners in general and that is 
> > mostly
> > the problem,   however I am having specific problems with the tuner and 
> > am
> > ready to pitch it into the street!
> >
> > The instruction manual for the tuner is essentially useless due to many
> > typos and obvious errors in English translation.  I was able to divine 
> > how
> > to hook it up to the transceiver and to set the defaults for the
> > transmitter, antenna, and inductance controls on the tuner for a 
> > particular
> > band.  Since the labels on the tuner's controls didn't match the labels 
> > in
> > the manual, it's a toss-up as to whether I had things set right from the
> > get-go.
> >
> > Now to transmitting.  Do I have it tuned?  Probably not.  Both the 
> > forward
> > and reflected power needles dance back and forth wildly to the lows and
> > highs of my voice during SSB transmission, making it nearly impossible 
> > to
> > read the SWR at the intersection of both needles. The tuner has a dummy 
> > load
> > built-in which is convenient, but remember, there is no carrier in SSB
> > transmission, so you can't just hold the PTT switch down while you
> > simultaneously fiddle with the three tuner controls.
> >
> > Put the transceiver in FM or AM mode so you have a continuous carrier 
> > you
> > say?  Nope, I tried that.  The transceiver has no FM, and using AM pegs 
> > both
> > needles to their stops on the tuner with some erroneous indication.
> >
> > After much fumbling I was able to finally coordinate mike, talking, and
> > twiddling the controls but to no avail, adjusting the controls did 
> > nothing
> > to change tuner meter needle indications.  As a matter of fact, the 
> > controls
> > on this tuner will turn past their stops  infinitely, giving you what 
> > tuner
> > setting as a result?  One ham said, "After you tune, write down the
> > settings."  So I would write down, 20 turns to the right past "6" on the
> > antenna knob?  Or 5 turns to the left past "1" on the transmitter knob?
> > This can't possibly be the way it works.
> >
> > Now, fortunately the transceiver has an SWR meter so I could use that 
> > maybe
> > as an indicator of getting close to doing something right, and not burn 
> > up a
> > transmitter in the process.  Nope again. The transceiver's SWR meter 
> > varied
> > between 1:1 to 9:1 depending on the highs and lows of my voice during
> > transmission.  If I spoke softly, it would read 1:1 all the time.  Raise
> > your voice, and it would peak out at 9:1 then drop back to 1:1.
> >
> > Anyone up for some antenna tuner 101?  Or better yet, would someone like 
> > to
> > purchase an antenna tuner, cheap, that is before I reduce it to its
> > elemental parts with a sledgehammer? You don't have much time.
> >
> > Plodding along blind
> > KB3ONM
> > Kirk
> >
> > _______________________________________________
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> >
> >
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