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antenna tunners
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by KB3QVX on October 31, 2009
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am new to ham radio.have a ic-718 with the ah-4 antenna tunner which is outside, plus a mfj949e which iam not satisfied with. i can use either an dipole or a long wire. so the antenna tunner should accomdate both. any help in recommending a good antenna tunner would be greatly appreciated.thank you harold k3rnk
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RE: antenna tunners
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by K3AN on October 31, 2009
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Can you describe the antenna that's connected to the AH-4? Also, what kind of ground/counterpoise are you using with that tuner?
Are you using both the AH-4 and the MFJ tuner at the same time (to tune the same antenna)? If so, why?
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RE: antenna tunners
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by VA7CPC on October 31, 2009
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The AH-4 is sold as a "long-wire" tuner, and lots of marine operators use it. Its tuning range is quite wide.
I suspect that an AH-4, placed at the feedpoint of a dipole, could tune it just fine. You'll find some examples of that kind of setup in SGC's user manual for the SG-230 (which is similar to an AH-4). You can find the user manual here:
http://www.sgcworld.com/PubInfoPage.html
I'd put a balun (unun? common-mode choke?) at the tuner's RF input (the coax from the rig, at the tuner).
You should be able to match most antennas, on most bands, with low losses in the tuner and low losses in the coax feedline (which will be working at SWR 1:1).
Charles
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RE: antenna tunners
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by 5R8GQ on October 31, 2009
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KB3QVX said
i can use either an dipole or a long wire.
Use the dipole, cut it to resonance, and take the tuner out of line.
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RE: antenna tunners
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by W8JI on November 1, 2009
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You would have to tell us why you are unhappy or dissatisfied with what you have. Any accurate answer could only be based on what makes you unhappy and what your setup is. Otherwise no one can really help unless we all just start guessing, and that would confuse you.
on a second note:
Where does SGC say to put a balun on the tuner input?
If you did do that two things would happen:
1.) A current balun on the input would work no better than a balun on the output would.
2.) You would still have to decouple all the power supply leads or control leads with suitable RF chokes.
Tom
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RE: antenna tunners
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by VA7CPC on November 1, 2009
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Tom --
SGC doesn't suggest a balun at the tuner input.
I found that a common-mode choke helped reduce "RF in the shack" in my marine installation. And yes, I put chokes on the SG-230 DC supply leads as well.
Blame me, not SGC.
But I have a question (since you raised the issue):
The SG-230 is (I think) a pi-network tuner, so its circuitry is unbalanced.
If you put it at the feedpoint of a balanced dipole, the antenna _is_ balanced.
Question: Would that situation lead to common-mode currents on the coax feedline?
Thanks --
Charles
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RE: antenna tunners
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by N5LRZ on November 1, 2009
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RE Original Poster...
The little MFJ you have right now is OK for what you have right now. However as you move up the food chain of licenses you will be looking toward a situation where it will become obsolete.
SO here is my personal recommendations, and keep in mind that I do not think cheap. I think GOOD but never cheap.
Most importantly brand is of no importance as long as the tuner is good and covers a very very wide range of antenna input loads
The most important features will be the varable caps being able to handle max power and a rotor inductor also capable of max power. Max power being defined as 1500 watts PLUS. You may NEVER have to use these high power abilities BUT BUT BUT SHOULD YOU ever get a max power amp you will be able to put your tuner to use immediately and not have to spend more money on buying a max power tuner.
The tuner should have the ability of several antenna inputs and of different styles. The tuner should be able to input as is ladder line and or open line and coax. It should have at least 2 or 3 antenna input options to eliminate antenna switching boxes.
The tuner should have a built in SWR/POWER meter. External meters are OK but a built in meter system eliminates the need for an external meter system (UNLESS you want an external meter). I strongly urge you to get a cross needle built in system . This way you can see your forward power, reverse power AND SWR all at the same time. MOST IMPORTANTLy no adjusting required.
Still on the SWR Meter topic, get if at all possible in your model of choice a meter that has BOTH Peak and Average reading settings.
And this may seem trivial but if your tuner has a built in SWR system try to get one with a built in back light so you can read the meter in the dark. IF your tuner does NOT have a backlight you can simply install a home made to suite your tuner internal design LED behind the meter to light up the menter. You have a wide varitey of LED colors these days to consider. JUST BE SURE that the color you use does not wash out the markings on the meter.
Note...I installed a battery powered LED on my tuner using a blue medium intensity LED. The blue did not wash out the meter colors and using a medium bright rather than a high bright LED did not blind me. Bottom line EXPERIMENT with brightness and colors.
Lastly and this would be nice to have, a built in Dummy load for low power tuneup and radio testing.
SHOULD YOU GET a tuner that has a digital display rather than an analog meter display for power, SWR, etc. WELLLL I will leave that up to you. I, myself prefer a meter with a nice soft blue glow. YOU may prefere an amber background with little dots forming letters and numbers. At either rate its just a matter of personal preference. Digitals I find currently are more expensive but perhaps they will come down in price.
OHHH lastly you want a counter on your tuner connected to your roller inductor. The counter will click off a number value as your rotor inductor connector moves so as to allow you to take note as to the cap and rotor settings for each band or frequency. This way you just jot down the counter number and cap settings numbers. Next time you want to go there just move the setting to those numbers--and just touch up.
While on this topic I also add that you might want to get a tuner that does not use a belt to link the inductor and counter but rather some kind of clock work gearing system. I found that my belt linking my rotor kept slipping off and I had to undo all those damn screws to on the enclosure remove the enclosure to put it back on. I would have killed to have gearing rather than a belt link system. So IF POSSIBLE get the one with the use of metal gears and not belts.
NOW the bad part...THE COST...
Looking thru the current listings of commercial tuners available the closest thing that I could find to this 'Ideal' tuner cost just OVER 500 bucks (before shipping and tax of course). In other words the BAD PART will be when you whip out the Credit Card. BE PREPARED for Sticker Shock.
On the GOOD SIDE....
A good well built tuner having all the functions and features that in the end game will not only meet your needs now but ALSO in the end game (years into the future) is a lifetime investment that you pay only ONCE.
So buy GOOD NEW STUFF FACTORY FRESH, buy once. IF you make the right decision that 500 plus spread out over 50 years of radio enjoyment and versatility will be the best bargan you ever found.
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RE: antenna tuners
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by W8JI on November 1, 2009
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Charles,
My website explains a balun on the input vs output.
http://www.w8ji.com/tuner_baluns.htm
As for direct feeding a balanced load with an unbalanced network, the common mode depends entirely on the effective length of the feedline for common mode currents and the type and size of antenna.
There are cases where a balun would not make a difference at all, and other cases where it could make a big difference. For example a ground terminated 1/4 wave long feedline hanging vertically from a dipole in open air would never need a balun at all, and the antenna would be almost perfectly balanced. If the feedline was 1/2 wave long to ground, unbalance would be severe.
So it all depends.
Tom
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RE: antenna tunners
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by NR4C on November 6, 2009
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First, the AH-4 is an antenna tuner. And, yes they mention that it is great for long wire antennas such as sailboat "Backstays". But, that is not it's only use. It can be used just like any other tuner.
I have an ICOM 706 eith an AH-4 in my car for mobile/portable use. I grounded my AH-4 to the chassis of the car. Then connected a length of RG-8X to the output of the AH-4 (with the shield connected to the AH-4 ground terminal) and ran it thru the fender of the car to the base of the "hershey Kiss" antenna mount for my vertical mobile antenna. When I want to work portable, with a wire antenna in the trees, or whatever, I remove the coax from the car antenna, and hook the coax to a balun connected to the wire antenna. Works great. AH-4 has geat range and works very well with the ICOM radio.
You should be able to ground your AH-4, and connect the coax from your radio to the AH-4. Now connect the your antenna/balun/feedline to the AH-4 Output and grund.
...bc Nr4c
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