Beginner Antenna Questions, yet again

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ke0ncp

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I am sure this has been covered and I have found some useful information by digging through the forums and browsing the web but figured I would ask here for some more tips and pointers.

I am in a temporary living situation for the next 6 months to a year and in a HOA regulated development that has a no antenna policy. So I have an OCF Dipole 133' total length with 88' on one leg and 45' on the other that is fed with 75' of rg8x into a 4:1 balun at the split. The feed comes off my tuner for about 10' before it makes a 90° andgle up and into the roof. I have the balun just laying on the apex of the roof which is 36' off the ground with the short leg going Tina tree in the front yard and the long to a tree in the back yard and then kind of zig zaged in the same general direction without ever crossing over itself or really with in 10' of itself. The legs are at a horizontal angle of 130° and both legs go out at about a 70° to the trees. I have used a few pieces of neoprene to keep the actual wire from being on the roof itself, not sure it really makes a difference or not. The roof is a standard shingle roof with no abnormal metal structures around.

My question is what should my expectations be with this current set up and a standard 100w transceiver be? This is the very first set up I have ever used, seen or set up. So just able to go off of what I can decipher from the web.

I know there are lots of variables such building material, height and angle of the antenna but I feel this might be about as good as I can get it given my current restrictions.

But maybe I am missing something obvious, or not so obvious?

I currently only have a receive capable radio and have a rx/tx on order so want to be ready to go when it arrives. So far listening has not been super successful as we have been plagued with storm here in the Minneapolis area. But I am concerned that my set up is also a major contributing factor into this.

Any suggestions or tips would be great!

73 - ke0ncp - Matt


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popnokick

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First- the HF bands have been kinda soft / dead the past few months. Not the usual openings anyway and quite high noise / low signals. You have to be on the right band at the right time. And even then you may not hear what you think you would. But assuming all your connections are made properly (no opens or shorts) you have a very usable setup. KEY QUESTION: Do you have an antenna analyzer? How about a tuner? One / both of those will tell you if you got the basics right. And if the fundamental construction is correct, the tuner will help. Not an absolute requirement with an OCFD but will help with the WARC bands.
 

ke0ncp

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First- the HF bands have been kinda soft / dead the past few months. Not the usual openings anyway and quite high noise / low signals. You have to be on the right band at the right time. And even then you may not hear what you think you would. But assuming all your connections are made properly (no opens or shorts) you have a very usable setup. KEY QUESTION: Do you have an antenna analyzer? How about a tuner? One / both of those will tell you if you got the basics right. And if the fundamental construction is correct, the tuner will help. Not an absolute requirement with an OCFD but will help with the WARC bands.



Yeah from what I've been hearing across the bands is that it's been loud. Don't get me wrong I have had several strong signals come through, no DX whatsoever. Which only a couple of months ago I ran a speaker wire off of a mag mount into a tree about 5' up and was catching lots of DX, this was also during one of the big contests too so that probably had lots to do with it.

As for the analyzer, I do not have one. A tuner I have BUT I am not sure it works correctly as the Yaesu FT-100 I have died and will not transmit so I do not know if it works, ldg 200 pro is what it is.

I have reached out to several of the local hams for a little assistance but have not had a ton of luck in this area.

I think getting an analyzer on it is probably the best bet, well that and someone who knows how to use it as well :)

Thanks for the insight on and conditions. I'm new and really do not know if what I am hearing is normal band conditions now or I'm reflecting at the wrong angle or something else is going on.

Can't wait until we buy our house and I can set a tower up on the roof.


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wyShack

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seeing as room doesn't seem to be a problem, I would suggest going with a simple dipole for 20 meters and another one for 40. In my experience, anything longer than a 1/2 wave (1/4 wave each side) starts getting directional to the "ends" (away from the feedpoint). With the limitations you have, the broader pattern of a dipole will work in your favor. Extend the dipole with rope to get to supports. Remember that 20 is a daytime band (40 is shorter range days but good day or night). You may also want to either make dipoles for 80 (mostly nighttime or local say a couple hundred miles) and 30 (another around the clock band) or try to use your OCF. If you have a tuner (I assume you do), you can use the 40 meter on 15 if and when it 'opens' and get on 17 with the 20- meter dipole.

The antenna is the biggest factor for a station, although electrical noise limiting receive is also an issue. Once you get antennas up, tune around and see what you can find. Get a shortwave broadcast schedule (or use the web) and scan the bands near the amateur bands to look for openings.Aviation VOLMETS(HF weather stations) are another way to 'check' your receive capabilities(if you can't hear 'em you can't work 'em).The website dxmaps.com is another good source of propagation information as it shows contacts in real time. Keep in mind that many stations on the website are using higher power and/or better antennas.

Other than that, the bands have been poor lately, so you may have to just wait it out.

73 and good luck
 
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SCPD

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How your antenna will perform is a good question, KEZero.... it is, at most, a randomly assembled wire arrangement. Since it has no real orientation, and is at a low elevation, my best assessment would be "Questionable."
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That is not saying "Poorly"... just "Unknown." A lot will be dependent on the frequency(s) you plan to use it on. My guess is it will work as a Near Vertical radiator (NVIS is another term for it.) For HF communications, it will likely prove satisfactory as a 2-700 miles omni directional on frequencies 3-7 Mhz--- the higher bands?... if there is skip it might surprise you-- when 'skip' is present you can talk to the world on a wet noodle.... :)
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I wish I had a better assessment for you- but I will leave you with a "Pearl" I have lived with as both a ham and professionally: This "Pearl" is for HF, on frequencies below 10Mhz, using random antennas such as yours (usually in my case these are terminated long wires--,) Power levels in the 100watt output range
.....If the station I which to communicate with can move the "S" meter, I can talk to them. Below that theshold-- ??? Try it anyway. Remember too, that a lot will be dependent on the skill of the other station's operator. Some people don't listen, know how to listen, have a noisy location, QRM you can't hear- or plain don't know how to use their radio. Its not always your fault they don't answer.
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Of course, it goes without saying your SWR should be less than 2:1.
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The neat thing about Ham radio is the experimenting that is possible with antennas. Your's should provide quite a few insights into the art and mystery of their construction.
Personally I'd steer you towards a vertical, but that's another topic. Good Luck ! ....... :)
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........................................CF
 

paulears

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It's odd that all of a sudden you can't be a radio enthusiast without an analyser. I managed 35 years without one! Now I have one, it tends to simply tell me what I already know - an antenna is not resonant, but it does help by telling me where it IS resonant. What it fails miserably to do is tell you how good it is an an antenna! I have one (probably faulty) marine band vertical here for VHF. Even local stations are weak and distance is out of the question - however, the analyser tells me it is 1.15:1 at 156.9MHz. So is my dummy load!

You seem to have a decent enough antenna, so now you naturally want to know if it's good or not. The chances are that it's a random bit of wire in the sky at the moment, so an ATU would seem a sensible thing to buy/make. I guess you need to wait till you can transmit to stick a meter on it, but even a random length should receive something. Why not rig up a comparison in the meantime. Make a simple half wave dipole with any old cable and cut it accurately for a specific frequency that you can hear on your proper antenna. Then swap the cables to the new purpose cut one, stretch it out temporarily and see if this is better or worse. Maybe if you can find the time - start with a long one, cut and compare, then gradually move up in frequency and keep trimming. If you plot all this on graph paper you will build up a decent picture of how well your longer antenna performs. It will take time and effort, but without the comparison, how will you really know.
 

popnokick

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Interesting to note that a couple of replies in this thread are apparently not familiar with Off-Center Fed Dipoles (OCFD) on HF.... and instead steer you to a different type of antenna, suggesting your OCFD is
- "...a randomly assembled wire arrangement"
- "...random antennas such as yours"
- "...random bit of wire in the sky at the moment"
A properly constructed and installed OCFD is not random at all and a very effective multi-band HF antenna, offering
- multi-band coverage in a single antenna
- ability to be fed by standard 50 ohm coax all the way to the radiating elements (and balun)
- gain over a dipole
HOWEVER, note that I wrote "properly constructed and installed". And that drives a couple of questions and review of your installation:
- OCFDs need properly constructed baluns. Did you make your own balun, or was the entire antenna purchased as a manufactured product? There are many OCFDs made and sold commercially, and our club and members have had great results with the OCFDs sold by Buxcomm, Buckmaster, MyAntennas, and others.
- Angles are critical with OCFDs. Ideal installation is at least 25 feet above ground and run in a straight line.... but if you have to bend it then it should not be sharper than a 110 degree angle. I can't tell exactly from your descriptions, but I think the 90 degree angle is in your coax feedline (not a problem at all... but if in one of the radiators a big problem). It's OK to install as a sloper or inverted vee, but better as a "flat top" like a dipole. You can droop the ends (as described in the link below).
- It is a good idea to keep the radiating elements out of trees and away from metal objects. Either of those will change the tuning of the antenna, likely making it resonant someplace other than the ham bands.... and impeding the pattern and gain. This is "The Book" on off-center dipoles, also known as the Windom antenna. Theory, history, design, dos and donts, and usage -
Windom Antenna Home Page, and Handbook
Finally, my suggestion on a tuner or analyzer was merely to confirm that you are seeing resonance in one or more ham bands, and not experiencing a coax or connector open (or short), bad balun, or other common installation problem that can occur with any antenna. The nice thing about an analyzer (vs. a tuner) is that an analyzer DOES NOT need a transmitter to check your antenna.

If you've followed the "rules" above, you have a very capable antenna.... and just need to spend time looking for band openings. The suggestion to listen for SW broadcasters and the time signal stations is a good one as it can give you a sense of what might be open. I've found that in my location 20M has not been open most of the day... but 17M has been for the last several days.
 

prcguy

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The OPs antenna setup is actually as good or better than what most hams can put up. I currently use a 133ft OFC dipole from MyAntennas and love it, its a great 80 through 10m antenna and all bands except 80 phone have a great match without a tuner. These antennas will have a bunch of gain lobes and nulls on the higher bands but they are published and easy to figure out.

At the reported height it will be great for regional comms on 40 and 80m via NVIS and should also do ok on 20m and higher DX. When antennas get too close to the roof you can be dealing with nearby metal and wiring in the building which will degrade performance and alter the radiation pattern.

An OFC dipole by nature is unbalanced and some mfrs use current baluns which help with RF on the feed line while others use voltage baluns and the coax will radiate quite a bit with those. Its best to place a good ferrite choke balun near the feed point to keep RF off the coax and you may also benefit from a lower noise floor by keeping some RFI induced onto your coax from computers, etc near you radio. I placed a very effective common mode choke near the antenna and radio and my noise floor was reduced by a surprising amount.

Even though you have a communist HOA, enjoy what you have and use it!
prcguy
 

ke0ncp

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- OCFDs need properly constructed baluns. Did you make your own balun, or was the entire antenna purchased as a manufactured product?
The antenna is a Maxcon and was built with a 4:1 balun at the feed


Angles are critical with OCFDs. Ideal installation is at least 25 feet above ground and run in a straight line.... but if you have to bend it then it should not be sharper than a 110 degree angle. I can't tell exactly from your descriptions, but I think the 90 degree angle is in your coax feedline (not a problem at all... but if in one of the radiators a big problem). It's OK to install as a sloper or inverted vee, but better as a "flat top" like a dipole. You can droop the ends (as described in the link below).

The angle of the legs is at 130° and is as wide open as I can get them. They are oriented in a general north to south position. I realize this is not optimal and I am searching a way to get them at 180° or a straight horizontal line.


It is a good idea to keep the radiating elements out of trees and away from metal objects. Either of those will change the tuning of the antenna, likely making it resonant someplace other than the ham bands.... and impeding the pattern and gain.

Well the ends of both legs are in trees, no way around that for me. And I have the split/balun as far away from vents on the roof as I can.

Thanks to all for the input and it seems as all though I might not be able to get DX across all bands. But I should be able to use this current set up for nvis on 80m, 40m I should be able to get a little more distance on and might be able to catch some DX on 20m and 17m if band conditions are in favor.


I will continue to listen and look for ways to get get the angle closer to 180° as it seems this part from height might be the best way for me to improve my current set up. If I was able to get it up on a mast in my current location I would then be able to get it at 180°. There are is a serious about of tree branches down low that gets in the way of me getting to 180°. So need to figure that out.

Unfortunately I just can not run multiple dipoles cut for each frequency as I am already pushing the boundaries with my current set up.


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paulears

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Popnokick's message I missed - not sure how, but I think he is actually thinking the same as me - the caveat after the "however" - An antenna design the relies on specific geometry, and decent baluns can indeed be a load of wire in the sky. I guess we have to wait and see.
 

SCPD

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There has been some good comments follow'd by advice- but one thing remains clear to me; KEZero, by his own admission, is a "Newbie." He has posited a question about an antenna for frequencies not specified. An Off Centre Feed design, while perfectly satisfactory for those experienced with antennas, is not a good place for a beginner to start-- especially erected as our original writer describes. I dare say what he has is, for all practical purposes (ham radio)- a non resonate on any band.
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I am hardly picking on you, Matt. It is how we learn about such stuff- by playing with it-- but I hate seeing someone start their hobby with such handicaps thrown up before their first days. Yes, that random wire will radiate something, but far better antennas can be constructed with equal, or less, effort.
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For example- a simple antenna tuner, a good ground, an SWR meter- all feeding a well insulated random length wire extending out a window to a tree--- simplicity in itself- made easily resonate on a lot of frequencies. Also, as mentioned, this can becomes an antenna to use as a form of 'standard' to compare others against. When you move to a better location, then try the more exotic's like the OCF's- but for now stick to the simple antennas... resonate dipoles and the like.
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Along that same line, I too find it amusing that today everyone needs an antenna analy'zr. Don't get me wrong, I use them (plural) all the time, in all their many configurations, in my work.... some of the HP's models will knock your socks off with what they tell us-- But they are not Sages, nor are they magic wands. It takes experience to intrepret what they are telling you----- for, as pointed out- a dummy load can look like the perfect radiator. A beginner can do just fine with an good SWR meter, reliable Texts, and a cheerful disposition :)
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I hate to throw out this tired saying: "KISS it," You all have heard it time and again- to keep it simple.... but as one who works in this field - this is something I face everyday from designers with their pie-in-the-sky ideas. Forgive me; I am free associating as I look over one of our latest "wonders'- pondering what to do with this microwave 'thing' before we have to answer for it............
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Along those same lines---------------
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A few years ago we were asked to revisit an antenna design that dated to the Vietnam era. It was re-invigorated by the return of military interests in the long neglected field of tropical warefare; in this case-- The Tree Antenna.
We're not talking about a tree for supporting an antenna, but using the tree itself AS the antenna. I will spare the details of how you match a transmitter to a tree, but it is sufficient to say they work-- sort of. But so does a 50 foot piece of wire thrown UP into the tree. You get one guess as to what I wrote up as the summation of those tests.
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.......................................CF
 
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majoco

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From the original post...
The feed comes off my tuner for about 10' before it makes a 90° andgle up and into the roof

There is no need for a tuner - it won't do anything other than act like a bandpass filter. The balun (it's not really a balun, it's an "un-un") has matched the antenna to the coax so just plug the coax into your rig. That's the whole idea of the OCFD and the un-un - it tunes all/most of the ham bands without a tuner - Google for "OCFD" and you'll see plenty of VSWR plots.

...and I go back to my usual expression..."One test is worth a thousand opinions" :)
 

ke0ncp

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I appreciate all of the feedback and wi try and make some small adjustments to maximize my current situation. I will also probably cut a length of good insulated wire for mid 20m and compare it to my dipole.

Again thanks for all of the insight.




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prcguy

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On the contrary, the OCFD the OP is using is resonant on most HF amateur bands without a tuner and is a no brainer for a newbe. Its 133ft long or 1/2 wavelength on 80m, a full wavelength on 40, two wavelengths on 20, etc. You are exciting a resonant antenna on many bands and its simply got the feed point moved over to the left where its around 200 ohms on most bands and fed with a 50 to 200 ohm broad band transformer.

By cleverly feeding it this way it will load and perform well on even resonant bands, unlike driving an 80m dipole on 40m where its very high impedance at the feed point and just doesn't work. You also get some odd bands like 17 and others by choosing a few magic off center points. I've gone through countless wire antennas over the years and currently use a similar antenna by choice because it works very well on many bands.

Check out the VSWR plots for this one if you are curious: OCF-8010E-3K - MyAntennas.com
prcguy


There has been some good comments follow'd by advice- but one thing remains clear to me; KEZero, by his own admission, is a "Newbie." He has posited a question about an antenna for frequencies not specified. An Off Centre Feed design, while perfectly satisfactory for those experienced with antennas, is not a good place for a beginner to start-- especially erected as our original writer describes. I dare say what he has is, for all practical purposes (ham radio)- a non resonate on any band.

.......................................CF
 

SCPD

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I will concede that an OCF antenna does not take a Rocket Scientist to assemble and operate- but in Matt's case he has not assembled it properly. As he describes it, its a jumble of wire, running every-which-way; out into the trees, doubling back on itself- the apex lying on the roof ridge, wire running down close to the earth...........if it works, it will be by luck, not design.
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If he had placed it according to its design-- that would be one thing- but I really do not think he understands the basic elements of antenna design- and therefore their proper installations and tuning. For that reason this is not the antenna he should be devoting energy on.
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As I read this, he wants to get on the air and enjoy his new hobby- as painless as possible-- am I correct Matt? If so, I would seriously explore the simpler alternatives and save your OCF antenna for the time (and place) where you have room to assemble it properly.... and believe me, I'm on your side.... get on the air, have some sucess's, and then advance your antenna explorations.
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:)
....................................CF
 

paulears

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I think that newcomers often enter the hobby thinking it is incredibly complicated and needs a level of knowledge and skill that make buying things safer, when in fact the hobby is ALL about experimenting, and getting it wrong. Then learning from it and gradually improving. Sometimes, especially with antenna topics, much of the blame is in the sources of information. Knowledgeable people who forget how to structure their info in a manner suitable for beginners. Dipoles vs Off centre Dipoles is an excellent one. An ordinary, symmetrical dipole made from block connectors and bits of wire always work more than they don't. Complex designs often are biased to fail. I spent many hours making and re-making stacked UHF coaxial antennas from many sources on the net, and they were ALL horrible. If just one article had pointed out that mm accuracy was very important, and suggested the dimensions for the solder joints, I'd have wasted far less time.

Lots of people post questions before they even get their post - and try them out. I am very much of the 'try it out, ask only if you get problems' brigade. I note many newcomers tend to be 'tell me exactly what I need to do when it comes, in case I blow up my radio' camp. Nothing wrong with that in many hobbies, but ours has thousands of variations, so fiddling is essential.
 

ke0ncp

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I will concede that an OCF antenna does not take a Rocket Scientist to assemble and operate- but in Matt's case he has not assembled it properly. As he describes it, its a jumble of wire, running every-which-way; out into the trees, doubling back on itself- the apex lying on the roof ridge, wire running down close to the earth...........if it works, it will be by luck, not design.



You are correct goal is to get out there and on the air. However it is not a jumble of wires by any means. The short leg is fully extended and the long leg only has a couple slight bends in it in the last 10' - 15' that sort of zig zag it out into the trees. It doesn't even come close to doubling back on itself.

I do understand that my main limitation here is height of the apex, but it's something I have to deal with for now.

I'm going to get out there today and open it up so it's in a straight line on the x axis and fully extended the long leg with no bends in it. Hopefully this will help a tad.


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popnokick

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KE0NCP - We're still not clear on what you ARE receiving on the OCFD. You mentioned "I ran a speaker wire off of a mag mount into a tree about 5' up and was catching lots of DX".... but nothing regarding the receive performance of the OCFD. Are you using the same radio (FT-100?) that you used with the random length speaker wire? You should be able to hear one or more of the time signal stations... despite not hearing the 5mHz or 15mHz WWV signal earlier this morning, I heard both WWV (Ft Collins) and WWVH (Hawaii) on 10 mHz this morning with my OCFD. Let us know if you can receive any of the following time stations - this will give us some idea that there is not anything grossly wrong with your OCFD (these are AM signals, although you will hear them with SSB as well) -
5.000 mHz - WWV
10.000 mHz - WWV / WWVH
15.000 mHz - WWV / WWVH
7.850 or 14.670 mHz - CHU (Canada)
 

ke0ncp

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KE0NCP - We're still not clear on what you ARE receiving on the OCFD. You mentioned "I ran a speaker wire off of a mag mount into a tree about 5' up and was catching lots of DX".... but nothing regarding the receive performance of the OCFD. Are you using the same radio (FT-100?) that you used with the random length speaker wire? You should be able to hear one or more of the time signal stations... despite not hearing the 5mHz or 15mHz WWV signal earlier this morning, I heard both WWV (Ft Collins) and WWVH (Hawaii) on 10 mHz this morning with my OCFD. Let us know if you can receive any of the following time stations - this will give us some idea that there is not anything grossly wrong with your OCFD (these are AM signals, although you will hear them with SSB as well) -
5.000 mHz - WWV
10.000 mHz - WWV / WWVH
15.000 mHz - WWV / WWVH
7.850 or 14.670 mHz - CHU (Canada)



Sorry I was not clear on that. I was able to catch the 10.000 mHz - WWV / WWVH although it is very noisy right now using my OCFD.

I also have made some big improvements to my OCFD. First of it is now at about 175° or very near straight the entire length. I also fed the shorter leg at the same height as the apex and moved the longer leg so it's fully extended with only the last 2' pointing at the ground at about 30' up. So there is about an 5' - 10' difference in elevation between the apex and the end of the longest leg.

This FT-100 that I have has some serious issues to say the least however I was able to get out and on air on 20m across the band with no tuner. Made a quick contact and moved on. Tuner worked on all bands I tested and then the radio decided it was done working again and that was it.

So it's back to listening. But mid day I heard multiple stations on each band from 80m - 17m so I would say that I am about as optimized as I'm going to get under my current restrictions.

Thanks again for the input from everyone and I will keep reporting if anyone is interested.


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popnokick

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If you heard WWVH on 10 mHz your antenna is doing fine.... propagation today has been the pits for the most part on the higher bands. I think after all the weeping and gnashing of teeth in this thread.... and when you get your radio fixed... your OCFD is going to serve you well. Easy to blame the antenna... it's a much cheaper fix than the radio.
 
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