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Author Topic: Yaesu FT-920 Antenna tuner capability  (Read 2395 times)
KD1RD
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Posts: 9




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« on: December 13, 2003, 03:32:17 PM »

Hi, It's been a while since I've been active on HF. I renewed my license lately and I decided to buy a new radio. At first glance the FT-920 is awesome. So this leads me to my question: I have limited space for an antenna and an inverted V is my best choice. I was hoping some of you out there have experience in choosing an antenna that the FT-920 auto tuner will be happy with. I am, of course, looking to work as many bands as possible with the same antenna. I'm using a trap dipole now that works quite well on the bands it supports (15, 20, 40) but I am wondering if an 80 meter inverted V will tune up on higher bands. I'm hoping to gain 10 and 80 meter capability. Also, I could use a vertical, but I don't want to spend the money if an inverted V would work just as well.

Thanks for you help.

Paul
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NI0C
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« Reply #1 on: December 14, 2003, 06:07:19 PM »

Feedline losses can be quite high in using an auto-tuner built into your transceiver to match a single band dipole on bands where the antenna isn't resonant.  One way to get around the losses is to use open-wire feedline, but then you would need some sort of matching network or balun to inteface with your auto-tuner.  Based on the information you've furnished here, you would be better off with your trap dipole or a multi-band vertical.

73 de Chuck  NI0C
 
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KD1RD
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« Reply #2 on: December 15, 2003, 12:11:32 PM »

Hi Chuck, thanks for the reply.

I didn't really think that a single-band dipole would do the trick. As I mentioned in my post, the trap dipole I use is limited. I can add traps to gain 10 and 80 meters, but I think I will loose efficency with every trap I add. I guess that's just the way it goes. You mentioned a vertical antenna. I have never used one, but I have read that they can be noisy, and they are quite expensive. I wonder if a vertical has advantages over my trap dipole that justify spending $300-400. There is also the polarization difference between a dipole (horizontal) and a vertical that I have no experience with. If anyone out there can comment on some of these issues it would be greatly appreciate.

Thanks,

Paul
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NI0C
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Posts: 2391




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« Reply #3 on: December 15, 2003, 03:03:12 PM »

With a trap antenna (dipole, beam, or vertical), the lowest band of operation is determined by the physical length of the antenna and higher frequency bands are achieved by resonant traps that effectively shorten the antenna.  I'm not sure how you will get 80m capability with your existing dipole by adding a trap.

You can buy or build multi-band dipoles and verticals that will cover all the HF bands.  It is difficult to get all nine bands in one antenna without severe compromises.  On the HF bands, polarization of signals is of little concern. What are your goals for HF operation?  Is your dipole high enough for what you want to accomplish?  One reason for going to a vertical antenna (quarter-wave or half-wave) would be to achieve a low angle of radiation for DX purposes.  

73 de Chuck
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KD1RD
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« Reply #4 on: December 15, 2003, 04:03:50 PM »

Hello again,

I guess I should have mentioned that, to add 80 to the trap dipole, I would add traps at the end of the 40 meter section that resonate at 80 meters then extend the total length of the antenna to tune 80 to a low SWR. I actually shortened this antenna by performing the reverse of what I just explained, so I have the traps and the extra wire. I only need to add 10 meters then I could use 10, 15, 20, 40, and 80. I would need to raise the apex of the V, which may be a problem, that's why I shortened the antenna in the first place.

As far as my goals for HF, I would like DX to be the first priority and local work to be secondary. I would like the antenna to support 10, 15, 20, 40, and 80 using the tuner in my FT-920. If I understand, I guess the radiation angle of a vertical would be better for DX. My inverted V dipole is at about 30 feet, but I would need to raise this if I extended the antenna to support 80 meters. I don't know what the radiation angle of an inverted V is, but I generally know that it is a function of height above ground and the frequency of operation. If you could explain this point, that would be great.

Let me see if I can ask the right question: If you had a choice between a trap-dipole and a vertical at 35-40 feet, both of which cover multiple bands, which would work better for DX.

Thanks again, Chuck,

Paul


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NI0C
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Posts: 2391




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« Reply #5 on: December 15, 2003, 06:35:03 PM »

Hi, Paul.  Do you have room for both antennas?  That way you would be able to compare performances and take advantage of the directional properties of the dipole, etc.  If I had to choose, I'd go with the vertical.  That's because I prefer the low bands, and 35-40 feet height is pretty low for a dipole for those bands.  If you choose one of the quarter-wave verticals (the Butternut HF-6V or HF-9V are excellent) make sure you have room for the required radials, as the vertical portion is just half the antenna.  

You might also check out the so-called "fan dipoles" that use full size parallel wire elements to avoid traps.

73 & GL

Chuck  NI0C
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NA4IT
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« Reply #6 on: December 15, 2003, 07:01:35 PM »

I use a "fan" dipole arraingement that works very well, and you should be able to get the FT-920's antenna tuner to be happy with it. Check out http"//www.qsl.net/na4it/farm.html .
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KD1RD
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Posts: 9




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« Reply #7 on: December 16, 2003, 10:55:39 AM »

Hi guys,

I want to thank you both for your help in answering my questions. To recap, I have learned that the FT-920 tuner will be happiest with a resonant antenna, and it can extend the antenna's useful bandwidth, but it won't let you use a 80 meter dipole on multiple bands. That is fair enough. I really want to use a resonant antenna anyway, and you guy have given me some options, both multi-band dipoles and verticals. I do have a height restriction and, if I read Chuck's comments correctly, the vertical would work better at 40 feet than an inverted V would.

I will probably end up with both, as Chuck suggests, and I may try adding a 10 meter section to my existing trap dipole using the fan approach. It won't cost much so why not. If it don't work at least I learn something.

As it is winter in NH, and antenna work would be tough at this time, I will do more research and ask around to see what other people think of various verticals designs. The product review section of eham.com is an excellent resource for this.

Once again, thanks guys and happy holidays

73 - Paul - KD1RD  
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WB2WIK
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« Reply #8 on: December 17, 2003, 07:36:20 PM »

Here's a thought:

W9INN (and others) builds shortened trap antennas using coil-only traps (no capacitors) that are quite lightweight and easy to install, but still highly efficient.  (The "resonators" are really like traps with a high L-C ratio, the inductance self-resonates with its own winding capacitance, thus shortening the antenna.)

I've owned a few of these, and they work surprisingly well.  What's even more impressive is that Bill (W9INN) must have a formula for tuning these things without installing them...if you specify your installation height above ground, as well as the heights of the ends above ground (for an inverted vee), he pre-prunes them amazingly closely.  You might still have to tweak a small bit, but not much.

They're made of #14 gauge insulated (dark colored) wire that isn't easy to see against the sky or any background.  His model MPD-5 is only about 80' long and covers 80-40-20-15-10 meters.  I've tried using it on the WARC bands with a tuner, and, impressively, it does work quite well on 30m for some reason, although not great on 17 or 12.  (Actually, it loads on 30m without the tuner -- must be some secondary resonance.)

So, you might consider something like this.

Regarding the verticals and their high prices: If you don't mind installing your own wire radials, the Hustler 6BTV is an impressive performer for only about $189.  It covers 80-40-30-20-15-10 with very low-loss traps and is about 26' tall, but absolutely requires radials to do its job.  I have one installed on a roof tower, about 20' above ground, with 24 radials under it, and it "sings."  Works DX very easily, and is an impressive performer on 40-10 for its size and cost.  On 80, it's got very narrow bandwidth and only covers about 50 kHz without dramatic falloff in performance (you can hear the noise going away, literally), but if you don't mind operating in such a narrow range, it does pretty well there, too.

With our current position in the sunspot cycle, I'd focus mostly on 20 through 80 meters, unless you have a lot of time to operate during daylight hours.

73 & good luck!

WB2WIK/6
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K0TOM
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« Reply #9 on: December 27, 2003, 08:27:48 AM »

   Get yourself a Gap Titan DX,it has a small footprint, and you will not have to bother with the radials. I purchase one to replace my Butternut..
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N4AEP
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« Reply #10 on: December 29, 2003, 08:46:46 AM »

I also recently purchased a FT-920 and really like the ease of operation, simple menu, real controls that one can adjust from the front panel and hey!! Motorola finals!!!! Take that TenTec!!! This rig is a pleasure to use, and with the addition of the Inrad filter kit, it is a top notch receiver.
Oh! I almost forgot,,,,,,,,,,,,Go get a Van Gorden G5RV for a few bucks, that will take care of everything except 6 meters. I don,t see how you can even begin to compare ANY verticle, usually hundreds of dollars, to this antenna. It's inexpensive, more cash for other toys, and will out-perform a verticle on all bands except somtimes on 10 meters where a lower angle of radiation can make a difference.
I bought the FT920 new for $950 from AES with a rebate,,,,,,,,the G5RV for $50 new.
best 73's
N8SKA  
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KD1RD
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Posts: 9




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« Reply #11 on: December 30, 2003, 01:15:44 PM »

Thanks again to everyone who has taken part in this thread; all your input is appreciated.

I can appreciate the savings of a G5RV antenna over a vertical, but I do have a few questions for N8SKA.

First, have you actually been able to compaire a G5RV to a vertical? I guess the real question is cost vs performance. Certainly at six times the cost, a vertical won't perform 6 times better than a G5RV.

Secondly, and more importantly, does the FT-920 tune all bands on the G5RV? The real reason I had for starting this thread was to see what people were using for antennas with their FT-920 and what the tuner could do with those particular antennas. How well does the G5RV tune?

Thanks again and Happy New Year,

Paul
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KC2IVZ
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« Reply #12 on: January 02, 2004, 07:52:46 PM »

I am going to give you the same advise when I bought my FT920 a couple of years ago.  Very few in any long wire antennas are resonat on all bands without an external tuner. That is the plain fact. I run a Caroliner windom 80 along with a Diamond CP6A vericle. Yes, for the price a verticle will set you back $300 and yes they are noisy on the lower bands. I use an MFJ 969 for both antennas. This isn't the recomended tuner if you know about MFJ's quality. I use an Ameritron RCS4 swith which seems to work between both antennas with only one feed line. I also use RG213 coax feed although 450 ohm would probably do better along with a voltage 4 to 1 balun.  The CP6A is very narrow on 80 and 75 so I must switch to the inverted V for lower bands but for the upper bands this CP6A is great. With the FT920 the auto tuner isn't wide enough so I would advise an external one.  I sure hope this advise helps you as it did me..Good luck and 73's.  Lyle KC2IVZ....
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K8AG
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Posts: 351




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« Reply #13 on: March 20, 2004, 01:26:10 AM »

Hi,

I haven't read all of the responses, however I did notice  a lot of commercial name antennas being suggested.  I have an FT-920 and I built a ZS6BKW antenna.  This is basically an SWR optimized version of a G5RV.  Mine is roughly 90 feet tip to tip fed at the center by a matching section (window line) of 40 feet before connecting to 50 ohm coax.  The antenna performs very well, and it seems to like the 920 on every band but 30 and 75.  The rest of the bands, 80 thru 6, including WARC bands and 60M, seem to be fine with the 920 internal tuner.  Turns out it is a simple half wave dipole on 60.  I keep a tuner connected for 75 and 30.

And performance is really great.  I do a lot of QRP and QRPp with anoher radio and the ZS6BKW.  My current record so far is 6000 miles per watt at 500 mw.  I know that number could go up if I could have lowered my output power.  I can hear and be heard with this antenna.

If you do decide to build a ZS6BKW or G5RV, Double Zepp or other dipole like antenna, I would suggest one thing.  Try really hard not to use inverted V.  I would recommend sloping the antenna and even keeping it lower if it meant not making a V.  Some computer analyses have been done and there is a tremendous cancellation of signal with an inverted V.

Another opinion to add to the group.  I am really happy with the ZS6BKW.  It was cheap, I built it myself, and it is very rugged.

73,

John Pawlicki, K8AG
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WB8DGK
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« Reply #14 on: November 12, 2004, 11:30:16 AM »

sir you are very  very wrong about a comprimise ant. working better than a verticle.check your ant books and books that teach you how to wrk dx.i was originally lic.in 1963 as wn8qbc,my ist ant was a verticle later i put up a dipole fed with 72 ohm twin lead .at night my vert out performed my dipole and in the day time on 15 and 10 meters i had a ball working dx that others could not hear .look a little advice about the only thing that can beat a properly installed vert is a beam at the proper hight.i have used a g5rv for about 35 t0 40 years also a 3ele quad and a remotely tuned vert .know insult is intended only helpful advice,a verticle is by far the most popular ant in the world ,get in your car drive 5 min and see how many g5rv or dipoles yousee and how many vert you see. try one you will like it .
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