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Author Topic: ant tun vs more power  (Read 537 times)
AI4WX
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« on: June 15, 2009, 01:42:42 AM »

hello there, i am planning on getting my first HF rig soon and am looking at 2 radios. the Icom 703 plus vs the yaesu 897D. my question is.. 1 has a built in ant tun, the other has alot more power. which is more important on HF?? T.I.A.
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G8UBJ
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« Reply #1 on: June 15, 2009, 02:55:24 AM »

Its a little more complex.. if you are planning to use mostly digital modes the IC-703 may be more appropriate. But the real comparison should be the IC-706 and FT-897 or maybe the FT-857..

I would go for the FT-897 but thats because I find it easier to drive than the Icom. Also being able to run a bit more power is useful and you can always build a cheap HF ATU or pick up a cheap 2nd hand one or just run a resonant antenna while you save for an auto-atu or something nicer.

You have to try them both and see which is best for you.

73 Rex  - G8UBJ
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WA3SKN
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« Reply #2 on: June 15, 2009, 04:04:18 AM »

FIRST HF rig?
Are you planning desktop, mobile, or portable operations?

-Mike.
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HB9PJT
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« Reply #3 on: June 15, 2009, 04:23:16 AM »

I would go with 100 watt as a starters rig. It is easier to make contacts and that is what a newcommer needs. An antenna tuner is in most cases necessary. If there is no budget for an automatic tuner when the 100 watt rig is choosen then there may be a second hand conventional tuner available anywhere.

I would suggest the Kenwood TS-480SAT with an integrated antenna tuner. That rig is significat better than the Yaesu 857/897 and the Icom 706.

73, Peter - HB9PJT
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KZ1X
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« Reply #4 on: June 15, 2009, 04:28:58 AM »

1)  Your HF station performance is about 90% based on your antenna performance and 10% on the radio.

2)  An "antenna tuner" is there to protect the radio from damage, not to "tune" the antenna, which is isn't doing at all.  The name of the device is a misnomer and confusing to new hams and often encourages people to use grossly ineffective antennas; the technically-correct term is "autocoupler."

3)  I agree with the advice from the G above, with the possible exception of Yaesu vs. Icom.  In the US at least, Icom support is heads-and-shoulders above Yaesu, as is, in general, product reliability.  Yaesu has decided to compete on price and features.  So be it.

4)  Did I mention how important your antenna is?
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HB9PJT
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« Reply #5 on: June 15, 2009, 04:54:19 AM »

"An "antenna tuner" is there to protect the radio from damage, not to "tune" the antenna, which is isn't doing at all."

This is not the case. For protecting the radio there is a protection circuit. When the rig is not tuned then the protection circuit of the radio does decrease output power. It produces the full output power and a cleaner signal when tuned to the antenna.

The difference between internal tuners and most of the external tuner is, the external tuner have a larger tuning range. When the tuner is directly at the antenna then the loss in the antenna cable is lower (sometimes much lower).

There is no difference between the terms "tuner" and "coupler". Just two different words. Nowhere you can read of a different meaning of this two words.

73, Peter - HB9PJT
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W5FYI
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« Reply #6 on: June 15, 2009, 05:15:28 AM »

And you can add "matcher" to the list of terms. If used properly, they all insure that the maximum amount of power is transferred from the transmitter to the antenna system.
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K1BXI
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« Reply #7 on: June 15, 2009, 06:18:58 AM »

A bit off the posters topic, but a tuning network does indeed "tune" the antenna. Those that believe it only fools the transmitter need to read up on a conjugate match and how it applies to our antenna systems.

http://p1k.arrl.org/~ehare/temp/conjugate_match/conjugate_match_theorum.pdf

John
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N5LRZ
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« Reply #8 on: June 15, 2009, 07:56:14 AM »

Easy answer....

Antennas are the ears of your radio.  Better antennas mean better ears.  If you cannot hear them then you cannot talk to them.

The less you need to tweak them (tuners) the better the antenna.

As to tuners...QST recently did a comparision of built antenna tuners.  With the exception of a Ten Tec model radio plus one other model radio every built in antenna tuner was almost useless above 3 to 1 error correction.  

IF you want a true antenna tuner you will have to in general get a 'GOOD' external antenna tuner.  Good being in general defined by those models costing at the very least 300 or so bucks to start and then go up in cost due to additional features.
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KZ1X
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« Reply #9 on: June 15, 2009, 08:15:55 AM »

Sorry, guys ... but a built-in-to-the-rig's "antenna tuner" works that way only if the antenna is connected at the radio.

If the antenna is not connected at the radio, and is instead at the end of a transmission line (the piece of coax that everybody uses) then what you have is an interesting mix of transmission line and antenna, the complex impedance of which is "matched" to what the radio wants.  If the antenna looks like some impedance that is near the transmission line, goody.  I can stand the little bit of loss in the cable and the tuner.

It's more often than not the case, however, that new hams use some kind of who-knows-what for a skyhook at the end of the hose.  The resulting arrangement frequently provides less performance, watt for watt, than an arrangement where the "antenna tuner" is located ***at the antenna.***

But the rig sees a great SWR.

Commercial examples of similar situations abound. AM broadcast stations often have a electrically short radiator and need to match the feedpoint impedance.  Why don't these guys locate their antenna matching circuits in the transmitter building instead of out at the tower base?  It's probably because they use 50 ohm unbalanced transmission line (usually Heliax) and they want the kilowatt they are paying for to not heat up said coax but to get to the antenna.

True Confession Time: I routinely use the built-in tuner in my radio to force a match at the radio end of the coax, knowing full well my system efficiency is probably going to hell.  Not all of my antennas look like 50 ohms everywhere I want them to (and even the ones that do might not radiate worth a darn).  I can still communicate, usually.  But I harbor no illusions about my ERP.

I wish I had a nickel for each new ham that comes to me at club meetings looking for a way to get some useful signal out.  Many of them bought some pre-made G5RV or a variant, installed it in some makeshift fashion, hit the 'tune' button on the rig, see the 1:1 match and the 100W reading on the meter, then get discouraged that nobody can hear them.  I am not blaming the autotuner, but new hams need to understand what it is capable of ... and what it cannot do.
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WB5JEO
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« Reply #10 on: June 15, 2009, 11:48:52 AM »

And they need to understand that, although there are some attractive things about some of the popular wire antennas, some are quite sensitive to nearby metal objects. In other words, they're neat when they can be mounted just right, but they're not so tolerant of compromise installations. So new hams need to read carefully beyond the manufacturer's glowing description AND pay attention when the maker talks about how it should be mounted. Figure the makers to give their products every advantage in the way they are mounted. They usually give you a hint about what will cause problems, but it's usually in the form of a "recommended" installation, without going much into what bad things will happen when you don't get close to that setup.

I'm very much for new hams to get on with the most easily understood antenna that is tolerant and can be mounted in their particular compromised way (they are all compromise) without getting too upset. It's pretty much a given that any distinct advantage of any kind has one or more liabilities on the other side.

Read enough, and that old flat-top fed with ladder line and a matcher starts looking good, if you have the space and know to avoid the "bad" lengths of feeder. The old guys didn't know SWR from a brass transistor and didn't know from coax, and their wires worked just fine.
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W7ETA
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« Reply #11 on: June 15, 2009, 03:39:54 PM »

You will have more FUN with the "lot more power" rig.

As pointed out, you can add external tuners if you need one,

My first ham station was a 100 watt rig, and SWR meter, and trapped dipole for 40 and 80 that loaded fine on 15 meters.  With the SWR meter, I was able to adjust the antenna so that my rig could use the antenna in the parts on those bands where I was allowed to operate.

Later, i bought more coax and an antenna switch box and made a wire ground plane antenna for 20 and 15 meters--still didn't need a tuner.

the next addition was HF amplifier--still no tuner.

73
Bob
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