Print

[K4RKX]

please correct my mis-understanding but if i am in need of an external antenna tuner b/c the internal one inside the ic7300 will not tune shouldnt i should purchase an antenna specific to the band that is having high swr instead of masking the problem?

Please correct my thought process! thank you so much !

[W1VT]

There are four places where power is commonly lost.  Typically the feedline, antenna tuner, nearby ground, and the antenna.
If the feedline is very low loss, it may be quite practical to use an antenna tuner, even if the SWR is high.  A common example is open wire feeding an HF dipole.  Or if there is no feedline, like a tuner mounted at the base of a flagpole vertical.

Tuner losses can be high if the frequency and impedance being matched are low.  This is a common tradeoff because hams want a tuner to cover 80 through 10 meters.  A simple solution is to scale the capacitors and inductors by a factor of four, and use it on just the low bands. 

Verticals often have high ground losses unless a good radial system is installed.

Inexpensive mobile whips often have high losses.  Not entirely bad as they make tuning more practical on the low bands as this increases the SWR bandwidth.

While low loss is a desirable goal, it isn't always practical.  Many hams use inefficient 160M antennas because they have no practical alternative.
I run 600W to a 36 ft high Inverted L with four short elevated radials.  I know it is inefficient, but if I'm patient I can work DX when the band peaks on FT8 and CW.

[KE6SLS]

Hello Chris,

Great question.  An antenna tuner is a person with a pair of dykes and a soldering iron,  who is able to understand some simple math. 

Following the wonderful wisdom of MY elmer, a matchbox is a device to match an impedance mismatch to that of the connected equipment -- usually 50ohm.

The built in matchboxes are 'very limited' in the breadth of mismatch they can handle.  Typically around 3:1.

An external matchbox is able able to match a much wider mismatch.

Some antennas are NEVER resonant.  Like my big doublet antenna (210 feet.)  My matchbox does the matching work for my radio and the antenna performs exceptionally well.

Other antennas have lobes that are close, like an End fed half wave type of antenna.  Some bands will be good, others need a little matching for the sake of the radio.  Typically, the built in matchbox is just fine with that.

The simplest antenna is the random wire (shorter than ~2 wavelengths) or long wire (longer than ~2 wavelengths) which WILL require that external matchbox.

I understand people love jargon/slang, but I always mentor my new hams with old school clarity.  You are the tuner and a matchbox will handle the mismatches

73 om,  Hope to hear you ON OVER THE AIR soon!

Jaye

[K1KIM]

please correct my mis-understanding but if i am in need of an external antenna tuner b/c the internal one inside the ic7300 will not tune shouldnt i should purchase an antenna specific to the band that is having high swr instead of masking the problem?

Please correct my thought process! thank you so much !

I have a IC-7300 as well. My trapped vertical is a Hustler 5-BTV (10M-80M) with 40 ground radials 32' long. The radio will "tune" whatever band I choose on that antenna and a very narrow portion of 80M. For that band I switch to a dedicated 80 horizontal wire.

My local 10M net is all horizontal, so I built a dedicated horizontal dipole for that purpose. For 6M I built a Squalo, and for 17M a horizontal dipole since the 5-BTV does not do 17M.

Bear in mind, the vertical is adjusted properly for each appropriate band.

To accomplish this I have an antenna switch at the base of the vertical to choose the various antennas.

The 7300 internal tuner should tune your antenna unless something is not proper in your feedline, antenna or both.

[WB6BYU]

There are many types of antennas that, by design,
don’t have a low SWR when used with a 50 ohm
feedline.  That doesn’t mean they are bad antennas,
just that they are optimized for other criteria (gain,
front-back ratio, multiband operation, simplicity,
efficiency, or any of a number of other factors).

Often these are multiband antennas, where attempting
to get a low SWR on every band where it can work is
simply impractical, at least within the design criteria.
A wide-range antenna tuner with a low-loss balanced
feedline can make a very simple and effective multi-
band antenna.

Now, if the antenna is designed for a 50 ohm feed,
and you still need a tuner, then either something
is wrong with the antenna, or the bandwidth is too
narrow.

When you are using coax, the losses will generally
increase with higher SWR.  (There are certain
exceptions, but don’t count on them.)  When the
SWR is less than 5 : 1 or so (at the antenna), losses
generally aren’t a major issue, with a reasonable
choice of coax for the frequency and length.

One problem, however, is that the SWR in the shack
generally is lower than at the antenna, and that can
mask potential losses. 


So when using a tuner, especially with coax, it is
worthwhile to do some analysis to make sure that
the losses in the coax (and the tuner) are acceptable.
If they are, there is no problem with using a tuner.
In other cases, over half your power - and occasionally
even 90% - of your power may be lost in the feedline
rather than radiated from the antenna.


So a tuner can be a useful device, but some due
diligence is in order.

[K0UA]

I once had a QSO on 15 meter SSB with a station in Venezuela with the antenna being a metal ink pen hooked to my home made "ultimate transmatch" That I got the plans for out of the ARRL handbook.  Was my 6 inch ink-pen a good antenna? No, of course not. The YV station barely heard me, but he did hear me. Also band conditions at the time were exceptionally good. I am sure the 120 watts of RF right there in the shack on the back of the "tuner" might have had some interesting voltages on it. I will assure you I didn't get any closer to it than I had to.  But you will have to admit the coax losses were low, because there wasn't any coax.  yep, the ink-pen was clamped right on the single ended feeder ceramic post. I still count this as my best DX with almost no antenna. 

[RFRY]

There are four places where power is commonly lost.  Typically the feedline, antenna tuner, nearby ground, and the antenna. ... Verticals often have high ground losses unless a good radial system is installed. ...

Below for consideration is an example of a 10-meter tall, multiband HF, vertical, OCF antenna system elevated 8" AGL, capable of good gain/radiation efficiency, low SWR(50) across a given band, and low loss on the feedline.

The elevation of the feedpoint is about 1.8 meters AGL, and the feedline shield OD is grounded about 1 meter from the vertical plane of the dipole.  No common mode chokes are needed or used.

[WA3SKN]

What problem?
Antennas are simply not 50 ohms.
A free space 1/2 wave dipole with thin wire measures near 72.3 ohms.  That's not 50 ohms.
A 1/4 wave over a metal ground plane measures about 36 ohms.  That's not 50 ohms.
A 5/8 wave is both reactive and resistive, but not 50 ohms.
We simply take the antenna impedance and convert it to 50 ohms so the power transfer on transmit is maximum!  You want a low loss radiator with a low angle of radiation for most HF communications.  Pick an antenna that does that, THEN worry about matching it!
After all, a dummy load IS 50 ohms, it just doesn't RADIATE too well!

-Mike.

[AK4YA]

please correct my mis-understanding but if i am in need of an external antenna tuner b/c the internal one inside the ic7300 will not tune shouldnt i should purchase an antenna specific to the band that is having high swr instead of masking the problem?

Please correct my thought process! thank you so much !

I have a IC-7300 as well. My trapped vertical is a Hustler 5-BTV (10M-80M) with 40 ground radials 32' long. The radio will "tune" whatever band I choose on that antenna and a very narrow portion of 80M. For that band I switch to a dedicated 80 horizontal wire.

My local 10M net is all horizontal, so I built a dedicated horizontal dipole for that purpose. For 6M I built a Squalo, and for 17M a horizontal dipole since the 5-BTV does not do 17M.

Bear in mind, the vertical is adjusted properly for each appropriate band.

To accomplish this I have an antenna switch at the base of the vertical to choose the various antennas.

The 7300 internal tuner should tune your antenna unless something is not proper in your feedline, antenna or both.

im interested in your 210ft doublet.  Ive read a lot about 102/111/134 ft ones but never a 210.  why did you pick that?

[WB6BYU]

im interested in your 210ft doublet.  Ive read a lot about 102/111/134 ft ones but never a 210.  why did you pick that?

I think that was KE6SLS with that antenna.

I can’t speak for him, but I can see several possible
reasons.  There will be some added gain and directivity
on 80m, and better coverage of 160m with the longer
doublet.

The patterns will be different on the higher bands,
particularly 40m, which might or might not be
better for one’s individual operating preferences.

Making the doublet non-resonant is often recommended
to avoid particularly high impedances, although that
depends on the feedline length.

Or that might have been a particularly convenient
distance between two supports, possibly with the
idea of getting as much wire in the air as possible.

[KE6SLS]

I think that was KE6SLS with that antenna.

I can’t speak for him, but I can see several possible
reasons.  There will be some added gain and directivity
on 80m, and better coverage of 160m with the longer
doublet.

Thank you Dale,

Yes, I have a 210' doublet in  a small lot in town here.  After conceiving of 3 different antenna designs that might help me maximize my signals, especially on low bands (160, 80, 75 & 40,) this doublet idea fared the best in practicality and looked good on the graphs.

The simple idea was the most antenna that could possibly fit in a small area.  Very much like putting a square peg in a round whole.  More wire will help me on 160/80/75 where I really enjoy operating.  The antenna didn't graph well on 40 however.

Imagine an inverted "V" antenna.  But where an inverted "V" would normally terminate, the wire folds back around to form an inverted  "M" .. Fed on my tower with 450Ohm window lead at about 45' to the two 30' masts at far end of back yard and ending at two 24' masts along the sides of property .. The masts are self supporting (fencing top rail) one foot inside the property line (and fence.)

Antenna works very well.  Matchbox and window lead does the heavy hitting and my barefoot signals are heard far far better than my original and much shorter inverted "V" antenna.

I could only wish I had a place where I could put up a flat top. which would work much better, but at least this antenna radiates a commanding signal on the air despite the small lot.

As an elmer, I feel obligated to spotlight the slang used (tuner,) correct it, and help the poster with some "uncommon" knowledge.   This is a complicated journey where first we think SWR is BAD and degrades our radio stations.  I hope the poster has read the thread thus far since many posters have posted some VERY GOOD information.

Now the HEX beam is a whole different story! 

Tnx & 73
Jaye