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Message |
    
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 655
Registered: 10-2002
| | Posted on Thursday, December 27, 2018 - 2:48 pm: | 
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I am in the process of getting my General ham license. I already have the Tech. I have seen a lot of Dipole antenna design's and some of them same as other's but with different figure's specs. So reason I am asking here is I want to rely on any one experience to save time and wasting money. Now here is my question Now, I would like to make a dipole that will cover 160 to 10 meter's. I found a FAN dipole. has anyone tried it and what have you had to do to make it work with low SWR?? If you all can would you share the specs that made it work correctly?? Also what is your favorite HF dipole |
N8fgb
Intermediate Member
Username: N8fgb
Post Number: 136
Registered: 5-2002
| | Posted on Thursday, December 27, 2018 - 7:50 pm: |
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Doublet. 160 meter dipole fed with twinlead. Tuner like MFJ 949, 969, 989 will give you 160-6. |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 656
Registered: 10-2002
| | Posted on Friday, December 28, 2018 - 10:27 am: |
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N8FGB Thank you for the quick reply I will look that up. For my hf I have ALINCO dx-sr8t I have a MFJ 986 tuner. For now I am only doing 10 meter on it. I plan on getting my General license in Feb. Of course the weather is not nice enough to do any dipole for now but perhaps I can soon. Anyone else out there have any helpful suggestion's?? |
Tech237
Moderator
Username: Tech237
Post Number: 1936
Registered: 4-2004
| | Posted on Friday, December 28, 2018 - 5:29 pm: |
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Depends on your areas of land. I have sued everything from Longwires (nice long fence line) to Hex Beams and Verticals. I had a flat-top the same 102ft length as a G5RV, but feed with parallel 50 ohms coax runs (inner conductors to antenna, shields joined and connect at ATU only). Ran nicely for 80-6 as was with low noise. Join the inner together, run that to the antenna and add a counterpoise and it worked 160.
Heck. Even used an A-99 on 6-15m, because that as all I had room for.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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N8fgb
Intermediate Member
Username: N8fgb
Post Number: 137
Registered: 5-2002
| | Posted on Saturday, December 29, 2018 - 9:40 pm: |
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I have the same tuner, u will like. will not give u 6 meter though. Just make dipole for the lowest band that will fit on property, and feed with twinlead. |
Tech833
Moderator
Username: Tech833
Post Number: 2419
Registered: 8-2002
| | Posted on Monday, December 31, 2018 - 5:42 am: |
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Like Simon says, depends on your land and setup. No antenna is the perfect antenna for everything.
You mentioned (like every newbie does) that you want an antenna to cover from 160 to 10 meters. Such an antenna is either going to be a compromise at the low end or the high end.
Personally, I suggest two or more HF antennas. One antenna that excels on the longer bands, and another that works best for the shorter bands.
If one antenna is all you have room to install, I suggest an inverted L with a bunch of radials just below the surface and fed with a 9:1 balun. You can find this type of antenna in pre-built configuration all over ebay, and just about any good ham radio store. The inverted L that I use is about 30 feet to the bend, and about 100 feet long horizontally. Works FABULOUS (with tuner) on 80m. Doesn't need the tuner for 40-10m, and works very well on 40 and 20m. It's a bit long and becomes directional on 20-10m but is still almost as good as the A99 on 15 and 10m.
Yes, you would need to use the tuner for some bands. That would give you great 80-10m performance with a severe (but workable) compromise on 160m.
The more time you spend on the ham bands, the more you will realize that 160m is pretty dead and almost completely worthless.
At night, 80 and 40 are great. During the day, 20 and 15 are decent. When sunspots are in, 20-10 kicks butt during the day.
Your radio 'Mythbuster' since 1998
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Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 657
Registered: 10-2002
| | Posted on Monday, December 31, 2018 - 11:19 am: |
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There are a lot of tall mountain's where I am and the valley are narrow. I would not care to try to use a mono antenna but that would require a lot of antenna's and or wire dipole's. I know when it comedown to multiband antenna's they are not as efficient but I was trying not to have so many cable's and wire's to deal with not to mention cost. I have 3 acres of land most of which is hill side. Everything on prices has gone through the roof. Thank you Tech 237 and 833 I will look up the information you have helped me with. |
Ke0koy
New member
Username: Ke0koy
Post Number: 2
Registered: 12-2018
| | Posted on Monday, December 31, 2018 - 11:47 am: |
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My favorite is the Coupled Resonator Dipole. Its like the fan dipole but only the lowest band element is physically connected to the feed line. They are very easy to tune without affecting the impedances of the other elements much. Think of hanging successively shorter dipoles 4 inches under the last. Every element of shorter wavelength under the driven one is a solid half wavelength wire, no feed connection in the middle at all. When I made mine, I used PEX tubing (PVC works well too) with holes drilled in them as spacers. As I ran the wires through the tubes, I would feed it in one side and out the end, tie a knot in the marked location, and feed it back in the tube and out the other hole so the wires all stayed put (wire knots inside tube). The top wire must support the weight of the entire antenna, but it is very durable and very forgiving dimensionally. |
Tech833
Moderator
Username: Tech833
Post Number: 2420
Registered: 8-2002
| | Posted on Tuesday, January 01, 2019 - 2:39 pm: |
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KE0KOY,
Nice to have you here, than you for joining.
The antenna you describe has dome drawbacks, like very narrow bandwidth, low gain, etc. however, you are correct that it is very simple to build and fairly robust. Compared to a traditional fan dipole, it is pretty lossy since the goal is to resonate the parasitic lengths of wire.
Charlie is in a valley, so his best bet is NVIS (look it up if not familiar). Since he doesn't have a shot to the horizon, his best bet is to send signal straight up and get the short bounce. The best antenna for that is a loop.
To wrap your mind around this, picture a 2-element quad antenna for the CB band. Now, instead of putting it up on a tower or mast pointed at the horizon, lay it flat on the ground with the reflector now being the ground itself and the driven element pointing straight up. That's basically how a loop NVIS antenna works. Spacing above ground is not critical, and you can always use a tuner and balanced feedline if you wish. There is almost no "wrong way" to use a horizontal loop on HF.
Your radio 'Mythbuster' since 1998
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Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 658
Registered: 10-2002
| | Posted on Tuesday, January 01, 2019 - 7:00 pm: |
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Thank you Tech 833 and KeOKoy, I am enjoying looking up every bit of information that is given. I already have some old 3/4 inch tv line ran to the top of the hill at the end of my property. I believe on the HF frequencies 160 80 40 and such being low that this cable would have low signal loss at 750 foot. Of course I would have to deal with it being 75 ohm. I am considering all my option's and the information given here. Some of the operator's here are using the G5RV PRO on top of the mountain with a tuner and the same line that I had mentioned. It would seem from the advice here that unless I run multiple dipole's and line's to it that I will have to use the tuner anyway. No big deal. So my friend's it is getting late and I have to get off for now. Thank all for the help but, please keep sending me information so I can see what is best for me to install. So far I am leaning toward 833 advice on using two antenna's that can cover as much range as possible. I have plenty of the 3/4 tv cable I had mentioned. Till the next post I will catch ya later. |
Ke0koy
New member
Username: Ke0koy
Post Number: 3
Registered: 12-2018
| | Posted on Tuesday, January 01, 2019 - 11:46 pm: |
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Tech833,
Thanks for the welcoming!
I am familiar with NVIS although I seemed to have overlooked the mountain valley post, perhaps blinded by the original posts intent of 160m-10m. Apologies for not fully reviewing the thread. As for NVIS, i would guess the ground conductivity will be his limiting factor as rock tends to be more of an insulator than the assumed conditions in most NVIS literature. A ground system may be needed. And with an interest in 20m and 10m (per post #1), I would think that D layer absorption during the day and lack of sufficient refraction at night at such high take-off angles would make an NVIS strategy almost useless for those bands. Perhaps giving 10m and 20m their own antenna focusing on Sporatic E and Auroral??? It might also be worth noting the possibility of VHF knife-edge diffraction using a beam pointed at the peaks of the mountains. Troposcatter, temperature inversions and other modes might prove useful if aimed properly. |
Tech833
Moderator
Username: Tech833
Post Number: 2422
Registered: 8-2002
| | Posted on Wednesday, January 02, 2019 - 11:29 am: |
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Charlie: Based upon that new information, I would absolutely suggest a tuner no matter what. Keep in mind that with the tuner at the radio end, any standing waves will create hot spots in the feedline, so your power must be kept well below what your cable can handle. I mean like 5% of what it can handle or less.
KE0KOY: Good points. He would certainly benefit from some radials under a loop, or just about any antenna. And, you are correct about the higher bands and NVIS. That is why I suggested 2 antennas. A large loop for the lower bands and an Imax 2000 or similar on one of the supports for the higher bands.
Your radio 'Mythbuster' since 1998
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Ke0koy
New member
Username: Ke0koy
Post Number: 4
Registered: 12-2018
| | Posted on Wednesday, January 02, 2019 - 2:42 pm: |
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If he is running 3/4 inch twin lead TV cable, his primary concern with arcing is in the tuner. Allow me to explain.
Vrms = Sqrt(watts*ohms) so if he runs full legal limit of 1500w into 75ohm cable, there is 950v in the forward direction. Assuming total signal reflection (infinite SWR), adding the reflected wave to the forward wave, there will be approx. 1900v across the "hot spots". RG-58 would surely fail, but TV twin lead is rated for around 9kv rms, thats more than plenty.
Being air has a dielectric breakdown of approx 3kv/mm, the tuner's capacitor plates would be the focus of my power handling calculations in that situation. If it suddenly arcs, the amplifier is likely toast. If your tuner is rated for that wattage and you are running 3/4" twin lead, wtth respect to the cable, go for it! |
Ke0koy
New member
Username: Ke0koy
Post Number: 5
Registered: 12-2018
| | Posted on Wednesday, January 02, 2019 - 2:51 pm: |
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I must say though, I am confused. what do you mean by 3/4" TV cable? 3/4" twin lead, as in the flat stuff? If so, thats not 75ohm, more like 300ohm. I do not know of any coaxial type 3/4" line at 75ohm used for TV... |
Ke0koy
New member
Username: Ke0koy
Post Number: 6
Registered: 12-2018
| | Posted on Wednesday, January 02, 2019 - 3:28 pm: |
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If you are indeed running a coaxial type TV cable at 75ohm rather than a 3/4" wide ladder line like I assumed (and I should have caught the 300ohm/75ohm thing then...), I very much agree with Tech833!
Taking a look at the maximum RMS voltage of RG-6 75ohm coax (the worst listed in the ARRL Handbook) it appears to be rated at 300Vrms. Assuming an infinite SWR, that leaves you with 150Vrms forward if you want to push your luck. 150V^2/75ohm=DO NOT EXCEED 300W!!! In fact, Id run no more than 200 to be safe!
If it is 300ohm 3/4 inch twin lead (flat stuff), at legal limit, your tuner might see upwards of 5400 volts peak to peak.... |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 659
Registered: 10-2002
| | Posted on Wednesday, January 02, 2019 - 10:31 pm: |
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I am talking about what the TV company use for pole to pole main Tv line 3/4 inch round. It is 75 ohm and has one center wire that is copper coated and the shield is aluminum really stiff. This is what the TV company gave away when they changed to fiber optic cable. I forgot the rating of power it will take but I believe it is like 10k if I remember right. I do not intend to run an amp anyway, just the 100 watt the radio will put out. My tuner is rated at 3k pep |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 660
Registered: 10-2002
| | Posted on Wednesday, January 02, 2019 - 10:31 pm: |
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I am talking about what the TV company use for pole to pole main Tv line 3/4 inch round. It is 75 ohm and has one center wire that is copper coated and the shield is aluminum really stiff. This is what the TV company gave away when they changed to fiber optic cable. I forgot the rating of power it will take but I believe it is like 10k if I remember right. I do not intend to run an amp anyway, just the 100 watt the radio will put out. My tuner is rated at 3k pep |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 661
Registered: 10-2002
| | Posted on Wednesday, January 02, 2019 - 10:31 pm: |
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I am talking about what the TV company use for pole to pole main Tv line 3/4 inch round. It is 75 ohm and has one center wire that is copper coated and the shield is aluminum really stiff. This is what the TV company gave away when they changed to fiber optic cable. I forgot the rating of power it will take but I believe it is like 10k if I remember right. I do not intend to run an amp anyway, just the 100 watt the radio will put out. My tuner is rated at 3k pep |
Ke0koy
New member
Username: Ke0koy
Post Number: 7
Registered: 12-2018
| | Posted on Thursday, January 03, 2019 - 12:08 pm: |
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You will have no issue whatsoever. Half inch 75ohm CATV hardline (my only reference, which would handle less) is rated for 2500Vrms. Sqrt(100w*75ohm)=87 Vrms. Assuming total reflection, 174 Vrms on coax at "hot spot". You are totally fine to run 100w thru that cable. The coax and tuner can handle that at infinite swr, just dont cook the radio and tune up with minimum power first.
At 750 feet, expect about 2.6dB to 3dB loss. 100w in will give you about 50 to 60w at the antenna. Getting that much hard line for free is a total goldmine!! Although this amount of loss very impressive for 750 feet, you could achieve 1/4 the loss using a homemade open-wire line, but then you need to deal with 600ohm. |
Ke0koy
New member
Username: Ke0koy
Post Number: 8
Registered: 12-2018
| | Posted on Thursday, January 03, 2019 - 10:02 pm: |
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Another thing worth noting is that 3 dB loss to the antenna means 6dB loss for the reflection when it arrives back at the transmitter. That means at an infinite SWR, only 25 out of the 100 watts will return, the coax absorbs the rest and makes heat of it. In other words, you may be tricked into thinking your swr is good when in fact the measurement is skewed by the loss of the coax. You will likely never see an swr over 4:1 when in fact its infinite. So if your radio says things are OK but no one hears you, beware! That's a long run of coax!!! |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 662
Registered: 10-2002
| | Posted on Friday, January 04, 2019 - 12:45 pm: |
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Thank You for your help and information. People in my area ( non Ham's ) use this on 11 meter. They run amp's that output is over a 1k . Of course I know it is illegal but that is them. I am not there boss. LOL. They use tube type amp's that are really old. They use about 100 foot rg 213 lead off each end of the CATV hardline to fool the radio into a match. Believe it or not they run as much as 2,000 foot to get to the top of the mountain and they do get out well. I met an fellow ham that been a radio person in the 60's in the military. He design's ham antenna's and dipole's. He is helping me with the design. Thank you all very ,very much for your help. I will be using your information to continue my education into the hobby. EVERYONE HAVE A BLESSED DAY AND GOD BLESS |
Tech833
Moderator
Username: Tech833
Post Number: 2423
Registered: 8-2002
| | Posted on Friday, January 04, 2019 - 4:45 pm: |
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You don't have hardline. You have semi-rigid cable like Heliax. If you had hardline, it would come in 10 or 20 foot sections with flanges on each end that bolt together.
Hams make that mistake all the time. But it helps to know which one you have because the power handling is different between heliax and hardline.
FYI, one of my broadcast stations uses 3-1/8" hardline (20 foot sections) and runs 35 KW out of the transmitter 24/7, and even with almost no reflected power, the hardline is still a few degrees warmer than ambient.
Your radio 'Mythbuster' since 1998
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Ke0koy
New member
Username: Ke0koy
Post Number: 9
Registered: 12-2018
| | Posted on Monday, January 07, 2019 - 3:55 pm: |
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Although heliax is common for CATV use, there ARE a vast number of HARDLINES for CATV. Ive used it before. An example would be Commscope 5333503 if you wish to google it.
heres a half mile of catv hardline for $1,550. It has a SOLID aluminum outer conductor, not that corrugated looking stuff....
https://www.ebay.com/i/132806836142?chn=ps
or try...
https://picclick.com/seller/aerialunderground |
Ke0koy
Junior Member
Username: Ke0koy
Post Number: 10
Registered: 12-2018
| | Posted on Tuesday, January 08, 2019 - 9:53 am: |
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I scoured the net for over an hour and found that multi-million dollar companies call their semi-rigid products "hardline".
I said hardline with respect to wide spread common usage. Perhaps I, like millions, are wrong. What troubles me is the relative nature of the term "hard". Compared to the flexible coax that most hams are familiar with, semi-rigid is very much hard. Compared to rigid transmission lines made of heavy gauge pipe, not so much. Hard vs rigid from a dictionary standpoint would suggest that hard is a good definition for both. That said, the term "hardline" should not be used in either case and one should say semi-rigid or rigid to eliminate the ambiguity. Convincing several million casual radio operators who have never seen or heard of rigid transmission line to use the term semi-rigid rather than hardline to appease a few would be a challenge. It is therefore very pointless to even consider going back and forth about it.
Ambiguity of terms aside, there is absolutely no way anyone will google half-inch CATV "hardline" and be misled into thinking it can handle tens of kW. I have trouble even finding rigid transmission line for sale let alone the specs for it. There are only a few companies that sell it and nobody will stumble upon it by accident.
73! |
Tech833
Moderator
Username: Tech833
Post Number: 2424
Registered: 8-2002
| | Posted on Monday, January 21, 2019 - 12:23 pm: |
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You can boil it down to this: If it comes on a spool, then it is NOT hardline. Hardline sections come in crates. Hardline is not bendable, Heliax is bendable and spool-able.
I don't care if a million hams are wrong, that does not make it right, it just means a million are wrong.
I believe it is worth discussing. If a whole group of school children was taught that 2+2=5, then do you not correct them because there are so many?
Your radio 'Mythbuster' since 1998
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Raya
New member
Username: Raya
Post Number: 4
Registered: 6-2017
| | Posted on Thursday, May 16, 2019 - 1:15 pm: |
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Try this if you have the room. Make a dipole or inverted V antenna whose leg lengths are at lease long enough to qualify for an 80 meter antenna/the longer the better. Using 450 ohm ladder line as transmission line fed into an antenna tuner capable of tuning said ladder line. Jumper from the tuner to the transmitter of course. Use the tuner to match the antenna/ladder line to the radio.
Said antenna system should be good for 10 thru 160.
Keep in mind that the antenna tuner has to be able to handle both the 160 meter band, the power being applied and ladder line. Special methods running the ladder line will be required--it is not exactly like coax. |
