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Author Topic: Need 160 meter transmitting antenna advice  (Read 1481 times)
W0BTU
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« on: February 11, 2010, 08:21:42 PM »

I almost feel a little foolish asking this question, but I wonder if anyone can offer some suggestions as to why my transmitted signal on 160 might be so weak.

I can hear very, VERY well on 160. I'm in a very quiet rural location, and I have two 580' 2-wire bi-direction Beverages which hear VERY well. I've been playing with receiving antennas on 160 for a long time, and I decided it was finally time to see what I could accomplish on 160. But after finally erecting a transmitting antenna, my transmitted signal on 160 is very weak to every person I've ever tried to work. DX and stateside, CW and SSB. I put up the best xmit antenna that was possible at this time of year, just before the CQ 160 contest.

I can only run 100 watts at this time.

I tried the inverted-U antenna as described in the links below. It is very similar to the one that K3LR used in the first link. The antenna is over the top of a 60' oak tree, and the two elevated radials are about 10' high.

http://lists.contesting.com/_topband/2006-12/msg00161.html
http://users.erols.com/k3mt/inv_u/u_160.htm

I'd put down a lot of radials and a top-loaded T antenna, but that's just not possible with the weather this time of year.

Am I expecting too much with just 100 watts? I don't think so; I've heard of many hams working DXCC without an amplifier. It was my intention to get a transmitting antenna working well at the 100 watt level, and then building a legal limit amplifer.

I've operated 80-2 meters since 1976, but this is the worst experience I have ever had since I've been licensed. I know this is almost a stupid question, but I have to ask it before I go crazy.

Thanks in advance for your patience.

73, Mike
W0BTU
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W5GNB
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« Reply #1 on: February 11, 2010, 08:41:02 PM »

I found the "Inverted U" antenna to actually work quite well.  It is really an Inverted ELL but I won't go into that!

It seems to work best for short distances since the angle of radiation is quite high. I have been able to work some DX on 160 with this antenna but it isn't easy. I use mine for receiving as well.  It is a bit noisy but what the heck, If you can hear them, you will probably work them as well.

I run mostly 100 watts or so but I have found that higher power on 160 is a definite advantage, probably since other operators are fighting poor antennas and noise, the extra punch seems to be valuable on this band.

I have the arrangement that is in the article for the "Inverted U" and I have added about six radials around the base.  I also use a high grade tuning capacitor, a broadcast type Mica along with a wide spaced variable on a syncro motor that allows me to tune the system remotely from the shack.

From your explaination, it sounds as if you have the better than average receiving antenna so that may be why the noted poor performance on your transmitting antenna.  You are able to hear much farther than you can transmit.

Try some higher power and you will be amazed at the difference on the 160 meter band.

73's
Gary - W5GNB
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W0BTU
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« Reply #2 on: February 11, 2010, 08:46:10 PM »

<< From your explaination, it sounds as if you have the better than average receiving antenna so that may be why the noted poor performance on your transmitting antenna. You are able to hear much farther than you can transmit.

Try some higher power and you will be amazed at the difference on the 160 meter band.

73's
Gary - W5GNB >>

Thanks, Gary.

73 Mike
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K0ZN
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« Reply #3 on: February 11, 2010, 09:03:56 PM »

Sorry, but the reality on 160 Meters is that power DOES make a difference. Often, more than theory would seem to indicate. This is probably because of the relatively high noise floor on the band. Keep in mind that the stations you are working may not have a sophisticated receive antenna, so the only way you are going to improve the signal to noise ratio on their end is more power (assuming you can't improve your antenna).

Another factor is that the average ham antenna, even a fairly good one, is NOT terribly efficient because if it is horizontal it is electrically low or if it is a vertical of some type, often the radial system is pretty marginal; these factors reduce ERP, so higher power over comes some of this too.

CW will do significanly better on 160 with low power than SSB will. On SSB, power becomes even more important due to the wider receiver band pass.

You *can* work a fair amount of stuff on 160 with 100 watts, particularly "local/regional", but from what I have seen in many years of hamming, if you want good results 160 you need QRO. This is especially true if you are chasing DX on 160. Again, this is NOT a "quiet" band.

Bottomline:  Unless you have a really "killer" antenna on 160, you need QRO.

73,  K0ZN
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W0BTU
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« Reply #4 on: February 11, 2010, 09:19:36 PM »

<< Bottomline: Unless you have a really "killer" antenna on 160, you need QRO.

73, K0ZN >>

Thanks. Maybe that's the problem, after all.

I've had my eye on a Russian GS-35B. If only I can find a HV transformer to power it.

73 Mike
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WX7G
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« Reply #5 on: February 11, 2010, 09:21:38 PM »

How well do you receive on the TX antenna? That is how you sound to another 100 watt station who has the same noise level.

Your 100 watts produces the same power at his receiver as his 100 watts produces at your receiver. If you hear him S-7 he hears you S-7. Give it a try and see how the signal strength part of the signal reports match (given the same TX power). If the other guy is running 1500 W expect a 2 S-unit difference.
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N3OX
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« Reply #6 on: February 11, 2010, 09:28:28 PM »

Am I expecting too much with just 100 watts? I don't think so; I've heard of many hams working DXCC without an amplifier.

I worked 116 with 100W and a not super efficient antenna.  I estimate about 25W ERP, maybe 30, by comparison with model.  Now I run 400W out, maybe 100W ERP and just worked #124, TX4T on French Polynesia.  

Of course, I'm a lot closer to a lot of the DX than you, since EU is so active, and that could make a huge difference if you can hear really well.  But it shouldn't for everything.  Carribean and Pacific should be straightforward.  Pacific was tough for me with 100W but I still worked some: couple KH6, VP6DX... the extra 6dB makes it a little bit easier, and I've added VK, FO, FO/A, KH4... and I don't currently do mornings, so that axes a lot of the opportunities for Pac stations.

I don't work a lot of domestic stations, so I don't know what my real reports would be there.   I do pretty well at getting heard when I'm in a contest with 100W.. I can work pretty easily this side of the Mississippi and a little bit beyond when I run 5W.  

Given that you can't change it up much, I guess, just don't worry about it much and keep trying.  I would consider keeping some doubt that a couple of radials 0.02 wavelength from the ground are enough.  A lot of people swear by elevated radials, but performance could be quite variable.  Do you have a choke at the feedpoint?  That could make a difference in terms of efficiency with a sparse ground system.

Even if everything's working well, though, you may have to be prepared to really outhear yourself.  I missed a good number of DX stations, temporarily or permanently,  just because I wasn't loud enough on any given night, and all I have is a flag in a pretty noisy suburb.  

I worked a lot too, but sometimes I just couldn't get through even if I was just the only one calling.   If I waited a few nights, maybe I did, but I just had to wait for that extra 6dB or 10dB from propagation instead of from an amplifier.   Your version of that is possibly going to be considerably more painful since you can probably hear so much more for a given incoming signal level.  

I guess you can just stick with it, gather more info, try the better antenna when you can.

73
Dan

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W8JI
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« Reply #7 on: February 11, 2010, 10:30:31 PM »

Mike,

It is not POWER you need, it is as much ERP as possible. No matter how much "fluff" and "exaggerated exuberance" you might read about a wire folded back on itself thrown over a tree with two or three radials, it WILL really stink for efficiency.

Working 7 DXCC is meaningless, because the USA, Canada, and Mexico would make up three! Add a few 1000 mile Caribbean stations, or work a few Europeans across 2500 miles of saltwater on a good night from the NE USA, and you have a great story that really does not tell you a thing about how the antenna really works.

I have worked Sweden and other countries on 160 SSB, and even 10,000 miles into Australia on 160, from my MOBILE! My mobile antenna has about 1% efficiency!

Three major things can kill the efficiency of that "U" antenna system:

1.) High voltage areas can be in a tree or back near earth where dielectric losses are high.

2.) It has a VERY poor ground system with the sparse radials, likely 20 or more ohms of effective loss resistance.

3.) It is folded back on itself.

We should consider ourselves lucky if an antenna like that is within 5-10 dB of a good Inverted L antenna. I'd expect efficiency to be 10-20% at best, making your 100 watts the equal of 10-20 watts at best.

You also are north and are inland, aren't you?

With 100 watts, low antenna efficiency, and a less than ideal geographic location it's no wonder you have a problem getting answers. One of the Europeans you called gives me about the same reports I give him, and hears me about as well as I hear him. I run 1500 watts to a 7 dB gain antenna with hundreds of radials using many ten's of thousands of feet of wire, and he and I hear each other about equally. I have about 6 kW or more ERP compared to a good full size vertical, and he hears me like I hear him.

You are trying to do the same with a -10 dB gain antenna and 100 watts, so you are calling with the equivalent of 10 watts ERP. I'm sure Europeans that are closer with better receiving antennas might hear you on good nights, but it won't be common.

I'm sure you could pick up 5-10 dB with some antenna work, especially by installing a good inverted L over a reasonable ground system of 20-30 radials. Adding an amp would also help a great deal, but you can't squeeze most of the applied RF out of a big resistor in the back yard. 

Unless you can get up to 500 watts ERP, which would take 2500-5000 watts into your present antenna or 500-1000 watts into a good Inverted L, you will run into nights like this.

Don't believe all the exaggerated hyperbole about working the world on 160 with a wire laying in the tree and three radials. It's one step above a mobile antenna. I'd do the antenna first, plus get at least 500 watts.

73 Tom
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G3TXQ
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« Reply #8 on: February 12, 2010, 03:33:35 AM »

Mike,

I replied on another forum that Rrad models as about 7 ohms. K3LR observed close to unity VSWR when fed directly with 50 ohm coax. That implies an efficiency of 14%, or -8.5dB. You need an antenna with higher Rrad and a better ground.

Steve G3TXQ
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KB9CRY
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« Reply #9 on: February 12, 2010, 07:55:59 AM »

Am I expecting too much with just 100 watts?


Yes
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KB9CRY
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« Reply #10 on: February 12, 2010, 07:57:16 AM »

Let me add, those with 100 watts that seem to have no problem getting through, take a survey.  

Are the stations that receive these 100 watt signals no problem using a special receiving antenna?

Most likely the answer is yes.
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W4VR
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« Reply #11 on: February 12, 2010, 08:24:02 AM »

I use an inverted U on 160, but I have fifty 100-foot radials laying on the ground.  That antenna works like a champ.  I work European SSB DX in late afternoon with good reports.  You need to add a good radial system to yours to make it work.  As for power, I rarely run into anyone on top band that runs less than 500 watts.  As for me, I've been using a minimum of 1 kilowatt on 160 since the 60's.
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N4OGW
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« Reply #12 on: February 12, 2010, 10:28:07 AM »

"I use an inverted U on 160, but I have fifty 100-foot radials laying on the ground. That antenna works like a champ. I work European SSB DX in late afternoon with good reports."

Working EU SSB on 160...not surprising given you are located in MAINE Smiley

Tor
N4OGW/5
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NO2A
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« Reply #13 on: February 12, 2010, 03:08:01 PM »

We used an inverted vee cut for 160M (half wave)up at 100 feet from our club station. We usually ran the legal limit on ssb and about 800 watts on c.w. I`ve worked coast to coast and some dx too. This is one band where you cannot cut corners with an antenna. I`ve heard noise levels as high as s9+20,and on average s7 (less at times but very rarely). It`s the gentleman`s band,I always enjoyed it.
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KQ7W
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« Reply #14 on: February 13, 2010, 03:56:57 PM »

I am using a lazy U on 160m with 100w (no amp) I understand it is a marginal system, but it is all I can do until I can move into some acreage.

I have worked SM, GM, FO, FK, JA, RW0, caribbean, etc.. the EU's I worked were on some very good nights though, I do not know if it works any better than the inv U though, I hear a lot better than I am heard so I hope an amp will solve that , maybe someday ill get one.

matt -
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