Posted: 9/15/2008 6:31:55 PM EDT
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Ok first my setup. I have 2 HF rigs. Primary Icom IC-730 powered by IC-PS15 Secondary Icom IC-703 Powered by a Samlex 1223 Feedline ~50ft of RG58 terminated with Male PL-259's Antenna 40M dipole w/ 1:1 balun(purchased premade) No tuner(other than the builtin in the 703) Antenna feedpoint is on the apex center of my raised ranch with the elements going to opposite corners and the last 4ft snaking back into sort of a Z shape. The givens, since I'm having problems lets assume everything I talk about hereafter is using the ic-730, 100w in the general phone portion 40M band. I know my antenna setup is going to be a problem with QRP so lets leave the IC-703 out of this for now. Also I am operating from Blue Springs,MO. Now to the problem.... I have to date only made 3 contacts. 1 in TN report was a 59 due to the contact using software that was hard coded. He was 58 on my end. 1 was in NM report was 55, he was 58 on my end. 1 was in WA report was 58, he was 59+10 on my end. Apart from these 3 contacts nobody hears me. And I can hear very few really good. Most stuff I hear is S5-9 range, mixed in with noise. The noise floor averages between S7 and S9 for me(on 40m only other bands I can hear decently fine). I have only heard part of a QSO on 7.213 once. Other than that I have seen others post about QSOs or calling CQ at specific times and heard nothing. Questions: Is the band really that bad, or is my setup flawed, or am I just having operator error? The RX noise is bad on both radios so I know its not the radios. |
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First regarding the noise floor, that might be about right. Are you running your preamp on or off? Suggest you leave it off and some nights you will probably need to run attenuation. As far as your antenna set up goes nothing grabs me; but maybe there is something wrong with the balun? (grabbing straws) try taking that out of the system for a while and see how it plays. Add a choke balun, several coils of coax, instead. Try straightening the ends out and see how that plays. How high do you estimate the center is? and the ends? Could you move it away from your roof? I speculate that asphalt shingles (is that what you have?) are horrible RF absorbers. -Just ideas Bill |
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Ah yes, should have mentioned in the givens, preamp is off, with preamp on noise usually increases by .5-1 units. Center of the roof is probably 20ft, ends probably 15ft on one side 20ft on the other. House is essentially 1 story in the rear, 2story in the front. Unfortunately I really can't get it off the roof much. I do have asphalt shingles. There is a tree, within reach of the feedline, maybe I can get the feedpoint up in it, and run the elements down towards the roof. Would that make a difference perhaps? I also have a aluminium back porch roof, could it be that parasitic? I can make a crude drawing of my house and antenna layout if that helps.  Yellow is the aluminium pourch roof. Purple is the feedline, runs along back of the roof, down the wall, back along the wall, then in the basement. Red is the dipole with the X being the feedpoint. Big green circle is the big ash tree, green bush is a crab apple tree. Orange is the contour line depicting which part of the ground is lower. I also have a shed, but running a element to it or the crab apple tree would be an absolute last resort. Unless I can use maybe 24awg or less. |
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My setup isn't that much different. However, the antenna is set up as an inverted Vee. Feedpoint is at the peak at the end of the roof. The lines run diagonally down the roof, from the rear peak to the lower front sides. wire is shielded 12Ga from menards. IT's stapled to the roof at the ends, and by the coax balun.  have made many contacts with that setup, and an FT-857. Made belgium this weekend on psk. |
I forgot to mention in my drawing up is north. NAM, Do you get any directionalness out of it that way or is it pretty omnidirectional? If I did this like you show, the open end of my V would be facing due West. Should I be concerned about any directionality? |
Mine is facing north also (up is north). Seems most of my contacts are EDIT: come to think of it, the somewhat directionality of my antenna could be because of that power line acting as a resonator of some sort... |
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Have you tested the swr of the antenna? Turning the ends of the dipole back like that will change the resonant frequency, as will mounting the antenna close to the roof. You may have detuned the antenna enough that you're losing most of your transmitter power to the mismatch and/or transmitter SWR protection. You may also be picking up RF noise from within the house with the antenna that close. Try listening above and below the 40m band at night for foreign broadcast stations, or just in general to see what you can hear. |
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I agree that you need to check the SWR first. The Radio Shack one should work fine but you might find something better on the Web. I haven't looked at them in years. Also, what are the details of your station ground? Lastly, I would suggest ditching the RG-58 and upgrade to RG-8 Mini Foam or even RG-8 Foam or something similar if you can swing it. |
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You can download a copy of the IC-730 manual here. There is SWR meter functionality available on the IC-730, but you have to move switches under the top access plate. You'll see that in the manual, you can switch between SWR and Power indicated on the front panel meter. I get good signal reports from Colorado and into Ohio. I've also had a good QSO with R-32 north of Seattle even though he's off the end of the dipole. In this configuration I lose a good 20db from the ground absorption but still get good NVIS operation. To get better use from this I'll get the center up about 15'. I'm sure you are suffering loss from the antenna laying on your roof, but at least it's up in the air. I use an old IC-730 with just a very low 40M dipole as shown below, not to scale: [eta] The patio is just pavers and is not enclosed, I'm operating off the table out there and the 300 ohm twin lead is about 1' above the planter box along the east edge of the patio. 
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SnakeEye: Thanks I apparently missed that part of the manual. I'm getting over 3 on the swr meter.  pcsutton: It's grounded like the manual recommends, direct to the power supply, which I assume is getting its ground from the house wiring. This is probably bad I assume. I mentioned to my helper monkey that I need to move my antenna. That can probably happen next week. I will also get a tuner soon, was on my list anyways. That should take care of my TX problems right? Now the ground, you think bad ground/noise is causes my bad reception on 40m? I'd say from reading my ground is very far from optimal, but why is my RX on other bands, particularly 80m so much better than 40m? I'm willing to improve my ground, just need some ideas. I'm below ground, about 6-7ft from a window, ground can not use the same path as the feedline, because the feed line is in the wall. Any ideas? I can take pics of my operating area if needed. And I'm not asking how to do it, I'm just asking for ideas on improving/fixing my setup. |
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You can improve your station ground when operating from a basement relatively easily. Are there any metal floor drain pipes, drain pipe, water supply lines etc,? Bond them all together electrically and ground your station to that. If you don't have anything like that drive a ground rod outside as near as possible (think short runs, short as possible, they get near fractions of wavelengths and can cause problems at the upper ends of HF) and tie into that. -Bill |
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Got a spot cleaned off on the drain pipe to ground to. I didn't notice a difference in noise on 40M(will talk about this in the next para). I did notice a slight decrease in SWR from 3+ish to 2.5ish. Noise on 40M is still making most things uncopyable, but there was a significant decrease in noise tonight as opposed to when I first posted this thread. Ground or not makes little to no difference. Tonight noise floor(am I using the correct terminology?) is ~S2, lastnight it was ~S3-4, where as when I originally posted it was in the between S5 and S9 range usually on the higher side. I hope getting my antenna off the roof will improve things, in addition to buying an autotuner, I'm gonna stop by AssociatedRadio tomorrow if I get time and look at some and talk to the folks there. I'm leaning towards the LDG Z100, Something I can use that will suit me for the house and portable for now. Speaking of portable, I'm gonna be out in the wilderness this weekend teaching a class on tactical comms. I plan on operating with my ic-703 in my downtime. Antenna situation will be unknown till I get there and know where we will be bivouced. It'll either be a dipole in NVIS config or a end feed long wire. If all plays well hopefully I can make a couple contacts. |
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Update, If anyone still cares... I bought a LDG Z100 today. Hooked it up to test only so far, knocked my SWR way down, really close to 1 on the ic-730's meter. Havn't given it a TX test yet other than sending my call in code to test the SWR. My Z100 came with a power/interface cable that mates up to my 703, Do I need to do anything to make the 703's tune button tune the Z100 or does it know its there and automagically uses it? |
Congratulations!! That will help you get more from your rig/antenna combo. Getting the antenna clear of the roof will be the next big improvement you'll really notice. |
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With regards to the grounding issue, you need to tie all your station components to a grounding bus block, then tie that to ground. As was previously advised, keep the ground run as short as possible. Having a ground ring all the way around the footer of your house is the ideal setup. Ground rods at each corner and every 8 feet in between. You can also run a second ground off of your service/main breaker box to a second ground rod. That really helped in my case. The best grounds are a series of ground rods tied together with 4-guage solid copper wire or flat copper strip. As to the noise floor, try this: hook your radio to a battery. Now tune to the hghest level of noise you can find. When you have done this, go to your breaker box and turn off the master circuit whch wll kill all power to your house. Did the noise level drop? If it did, turn the main back on and trip each breaker, one at a tme, untll the noise agan subsides. When you find the one that eases the noise, unplug or turn off everything on that cicuit one at a time until the noise again stops. When you have found the culprit/s, try putting some chokes on their power cords, or ground the circuit. If you believe your antenna is resonant and the radiating elements aren't somehow being shunted to ground, look for your noise source in your home wiring/appliences before you pull your antenna down. Let us know how it goes!! 73' |
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Honestly I haven't had much time to do any experimenting. Probably won't have any time till after the first week in October. I've got a bunch of quarter end tasks for work due by the first, and then I'll be in Europe for a week. I had wondered about the noise coming from my house. Maybe I can atleast do the first part of testing for that this week. The noise level has been better than it was tho. And I do still plan on atleast moving my antenna. I think I'm gonna try to get it into an inverted vee by suspending the feedpoint from the tree. That too will have to wait till I'm back from Europe however. I'd like to thank everyone for their wisdom and advise in getting my problems fixed, or atleast made better. Now I just need time to implement them. |
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I would suggest that you remove the tuner from the antenna system. Then get the antenna in air as high as you can, or just get it off the roof. Then CUT the dipole for resonance on the frequency of the band you like to operate the most, or the "middle" frequency, Check it with the SWR meter. Then place the tuner back into the antenna system. This will give you the most options including going DIRECT to the dipole when you are near the middle of the band (near the Frequency the dipole was cut for) Tuners simply make the radio happy. If the antenna is not resonant the power is lost in the tuner and in the coax from the tuner to the dipole. Did I mention you should CUT the dipole? |
As an after-thought, Do you have a plasma TV? My plasma TV puts out a humoungous amount of noise. I have to shut it off if I want to hear anything on HF. Europe, eh? I'm jealous. 
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Nope we have good ole fashioned tube tv's here. We haven't had a real vacation in a long time, we are going to 4 countries(Netherlands, Belgium, France, Great Britain) over the course of 9 days. |
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UPDATE: So last weekend Mel's brother and I got on the roof and moved the antenna feed point to the tree, elevating the elements off the roof. Well it stormed all week and I was busy the rest of the time. I got to trying it lastnight, considerably greater results, made more contacts with ease on 40m. I hopped on quick earlier and made a 20m contact in between chores. Then comes the gale force winds, and while I was taking some goodwill items out to the shed for storage until the next pickup, I noticed the feedpoint and balun laying on the roof. It's going to be a busy week, and I'll be in the field all the weekend. So it looks like I'll be out of commission just as the 40m is opening up. |
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Update again.
Every single time I get the dipole off the roof. We get a wind storm. My actions generate regional severe weather. We had replaced the poly/nylon cord I used to tie down the ends of the dipole with 550 cord. But in our wind the other day, one of them failed, not sure what happened as the whole apparatus is covered in snow. I'm just going to have to do something else... |
| Try to get some dacron cord, your local ham retailer should have it. It is black, UV resistant and VERY strong. Also, what are you using for end insulators on your dipole? If you're just tying the wire to the rope, you might be breaking knots. I use the ceramic dogbone insulators and they're working just well for me. |
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Quoted:
Try to get some dacron cord, your local ham retailer should have it. It is black, UV resistant and VERY strong. Also, what are you using for end insulators on your dipole? If you're just tying the wire to the rope, you might be breaking knots. I use the ceramic dogbone insulators and they're working just well for me. Ideally you want some relief built into the dipole as well. Like the dipole ends going through a ring or pulley with a weight so that things can move/flex. If you're tying directly to tree limbs or the like, when those limbs thrash around in the wind something will break. |
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How we have/had it ran, was lose enough for the normal movement of the tree.
The ends of the dipole are a doubled over loop with a crimped on piece of metal. As for the knot tied, I'm not sure what knot Jason tired, I was supervising from the ground. I'm about to just start over and start brain storming on the design again. And Gamma, thanks for the offer of assistance even tho it didn't work out. |
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You mentioned 00:00-05:00. For me 40 m is good during the day, and the band is bad after sundown. I understand this will change in the coming years.
From your drawing, I know you have changed the antenna now, but I was concerned at the v'ing back of the ends and the proximity of one end to the aluminum patio cover (or whatever that is). How long are you dipole elements? For 40 metes each side should be on the order of 32-33'. I know you can bend the ends about 90 degrees, but just how far back toward the feedpoint you can go before it becomes a problem I don't know. I do know if folded back on itself it is electrically removed, as if the wire were cut at that point. |
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First, you can go here and it will start a download of antenna.exe. Go on and chose Save.
http://www.w2blc.us/antenna.exe This program lets you chose dipole reduction, lengths from 100% down to 30%, and lets you make some choices of coil diameter, how many turns per inch, etc. Here's a shortened 80 meter antenna: http://www.qsl.net/vk3jeg/loadpole.html And here are some sketches. First, from my friend Rick K1WYH. This is a, get this, 31' overall length 80 meter dipole: 
And here are two more similar antennas. 
This antenna is the same length as an 80 meter halfwave dipole, but works on 160 and 40 meters. The inner section is for 40 meters, and the coils choke off extra length at 7 mhz. But at 160 meters frequencies the antenna is effectively lengthened acting as a coil loaded dipole for that band. 
Between the little program antenna.exe and the above diagrams, perhaps you can work something out. So, you could put Rick's 31' 80 meter dipole up, and in addition, make a 50% reduction 40 meter dipole and also a 100% 20 meter dipole, all in approximately the same space, without having to bend the ends of your dipoles. Rick indicates his 31' 80 meter dipole, in his attic, only loses less than 1 S-unit as compared to a full length dipole. The alternative is no antenna at all, so that is pretty good, I think. ––––- And I just found this... intestesting! http://www.parc.care4free.net/cardpole.htm |