Ham Radio - The doublet vs EFHW noise rejection comparison.
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- Опубліковано 22 лип 2024
- The doublet is still my favorite wire antenna.
Here's my video on winding the 4:1 balun:
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Have you tried the efhw with a common mode choke?
I will be doing a follow up video on exactly that. This vid was getting long, so I decided to do a second vid.
@@loughkb i am going to try an attic EFHW, dont except much, but will put a choke a distance away per Steve Ellington. Coax run will be long..
Ed Beckerich I ran an attic antenna for awhile back in the house. Observations: It'll pick up every noise source in your house and they'll be much stronger than the noise from your neighbors. And keep the power low, you'll be right in the field. It will likely interfere with some things like a TV set or stereo system. Cause touch lamps to turn on and off. Stuff like that.
A better option is a loop. Ever thought about using the gutters?
@@tahoma6889 In my case, a loop would mean I'd need to carry two more masts in the RV, I don't have the space.
I have used gutters for antennas back when I was in the house.
Attic antenna, gutters, loop around the perimeter of the roof.
One thing I can say for sure, those three options were great at picking up all the noise sources inside the house. I could choke off hash noise, but chokes don't do a thing for spurious signals and birdies. They were very noisy.
The 80m doublet is the king of antennas. The design has stood the test of time for good reason - it's fantastic. I have used the same one for over a decade and love it. Thanks for sharing !
I only have a small manual tuner (MFJ-902), but this has inspired me to finally learn how to use that tuner so that I can try out a doublet.
You won't be disappointed with a boublet.🐒🐻🤗👍
Thank you, really appreciate your effort to provide realtime A vs B comparison as well as the noise signature of a pure sine wave inverter.
Hi. I decided to build a 80m doublet in Sept after your video and an Elmer swayed me. 63’ each leg with home brew ladder line all 14ga solid copper. Home brew 1:4 balun and 16” of RG-214 to my huge home brew roller tuner. True all band with QRO power levels and no RF in the shack ever. Quiet receive for my SDR interests as well. I’m sold on the 100 year old technology.
I see this a lot.
Install that double exactly the same way as your EFHW and it will be just a noisy.
It's all in the installation.
Put the EFHW up like your doublet, use a common mode choke to make the playing field even.
Put the choke at .05 wavelengths from the transformer. For 40m, measure about 2 meters from the xfmr, wind 8 turns of coax around a FT-240 31 mix core then run it in to the shack.
You can even add chokes in series. Make another one using 43 mix and 4 turns for the higher bands. Just put it down a few inches from the fist one.
Don't bother with commercial chokes. They are inferior to the above and cost several times more.
Both antennas were configured as an Inverted V with similar height. Both had nearly identical coax length back to the tuner. They were very similar in installation.
I'll be doing a follow up vid this week after installing a common mode choke on the EFHW.
Thanks for sharing. I heard a RF engineer explain that doublets are inherently better for low noise. Mainly because they are horizontally polarized. All the RF noise we from the other RVs is vertically polarized (according to the RF engineer all the noise that we have deal with as hams in an urban environment is typically vertical). In the little talk, he went on to say that you can run other antennas like an end fed for example. You can run that horizontally, but it is not horizontal polarization, it's still vertical. And thus you'll have more noise with end feds. Anyhow, I have good luck with a doublet fed with ladder line and I think it's still my favorite antenna. And literally the most simple. Two wires I cut from a spool of wire from Home Depot!
I love my doublet! Multi band, quiet, inexpensive, simple and effective. EFHW probably has noise ground currents on coax shield.
So glad to see you playing radio. There's nothing like building antennas out where room isn't a factor. Be well my friend!
Good video, great comparison of antennas. I’d love to run a doublet here and I’m a big fan of ladder line feeder. It’s hard for me to get the right feeder length though.
Glad you're healthy again. Thanks for another great video.
I built doublet a couple years ago for field day and love it..It is my main antenna on field day..If you have a good tuner and some spare wire around get some window line and good 4:1 and get building you will love it!! :D
Fantastic video. I had heard end fed antennas were more noise prone and looks like you've proven it. I have and end fed in my attic and it's pretty noisy, often S9+. I had a doublet that was bent into rectangle and it was fed with twinlead and it didn't pick up much noise, but did have an odd radiation pattern. I also use the LDG Z11 Pro tuner with a balun, but I use a switchable MFJ balun that can switch between 1:1 and 4:1. I use a barrel connector to connect it directly to the tuner without coax. I'm going to try a doublet gain, but this time in a dipole configuration and hope it will reduce my noise issues.
Great Video!
I have been tempted to put up a doublet as I have all the materials eg wire, 300 twinlead & 450 ladder line.
But the guy's saga of using twisted-pair speaker wire intrigues me.
So I'll start with a simple twisted-pair portable doublet.
Nice comparison Kevin. Great to see another antenna related video. I've done both the 4:1 and the 1:1 current baluns on my doublets, and the 1:1 offers twice the choking impedance given the same quantity of ferrite. Just series the two cores that you paralleled. Most tuners have lower losses at higher impedances so using 4:1 can put the tuner into a lossier configuration. In most cases there is little difference between 4:1 and 1:1, but it makes an interesting experiment to try. Looking forward to the EFHW with common mode choke (and that will require a counterpoise). 73 de w6akb
I hear you on the health issues. Same here for 3 weeks in August. OK now to learn more about HAM radio.
I noticed my doublet was too quiet. Also in the inv V configuration. The efhw seems to perform better. I did find moisture residue in the ladder line. I’ll have to try from scratch. Glad ur feeling better om
I too love my double Zepp (doublet) antenna for all the reasons cited, but there is one thing I noticed when I got a new radio, there is "RF in The Shack" and therefore everything, the radio and the tuner MUST be properly grounded. On many radios (especially tube types), the only problem is getting "bit" or "burned" by the RF, but with my new radio and tuner, the RF gets into the radio and somehow messes up the tuner too. After taking down the antenna and looking for problems at the termination and feed line (and finding none), it finally dawned on me that I had to ground the radio and the tuner per the bolts and nuts provided on them just for that. Proper grounding solved ALL the problems I was having including "RF in the shack."
Bought my firsts Van Gordon All Bander which is this antenna almost 40 years ago. My all-time favorite general-purpose antenna. Used it around the world. Don't believe those are made anymore but of course simple parts anyone can make.
I have a 102 foot doublet with a 4 to 1 balun...... After 20 years of various antennas this is by far my favorite...
Thanks Kevin, I am in process to change up antennas and both are in consideration!
Doublets fascinate me. I just ordered some twisted-pair cable to build another doublet for portable ops. I'm going to measure the impedance at the feedline terminus before deciding whether the twisted pair needs a balun or not.
I think that 4:1 balun is a current balun, which seems to be kin to a common mode choke.
I'll probably have a short coax run, but something less than ten feet for my doublet.
Good video. Thanks!
Hello Kevin, very nice to see are over your illness whatever it was.
I had very similar results. 60 ft EFHW vs 60 ft doublet, 600 ohm ladder line in to the my room, MFJ 986 roller tuner above my radio. With doublet noise level decreased about 1-3 S-units on different bands. And it may work anywhere with that tuner beginning from 3.5 Mhz (from 5 Mhz with good efficiency), and up to 51 Mhz. Of course, above 21 Mhz the diagram might be some strange, funny and unpredictable, but if I hear somebody, I work with somebody. 73!
Interesting, thanks Kevin. My general experience in local QRM rich environments is better signal to noise ratios with balanced antennas like doublets, centre fed dipoles, delta loops, mag-loops. Assume increased noise with unbalaced systems is due to common mode current. I also wonder if many hams often overlook window or ladder line for HF? Even cheap window line will usually be way more efficient than the most expensive co-ax for longer feeder runs. Doublets and balanced feeder remain popular for good reasons.
Seeing is believing. Excellent demo.
Greetings Kevin..good to see you are hanging in there. Your desert dust or winds will carry multitudes of pollen spores ..I get alerts on weather bug app for around Phoenix, and as far south as Florence..for me that's a major allergy trigger, and my field is always a risk of exposure to any and all.
You stated your radio was running on 12 v dc as most of your appliances..during this video, so the noise on the waterfall was strictly noise in the electrical wiring and radio picked all that up? I hear some led lighting drivers can make noise too. I use flex 9913 / lmr 400 in shack with a double flourescent overhead with no noise but handy gets it bad when near either.
Finally getting some spring teasers in the wolverine state, and maybe standing a vertical free standing pole up for new 70cm glass vertical by Celwav, a smaller dual band and possibly a long wire inverted attached below for general coverage for now. HOA in your area disallows anything except a tiny ota tv antenna and cellular yagi out of sight. Since SW roof is covered with solar, NE has the hvac equipment, an attic antenna would be useless. A couple locals mentioned late night operating with a tip up multi but neighborhood is like out of Stepford wives flick .!
Stay busy friend, try some prickly pear jam if you get a chance.
73,
Gary
Nice video Kevin. I've noticed a similar reduction in noise on my fan dipole vs my end fed random wire. I've heard there's something about a balanced, horizontal antenna that's just inherently lower noise, but I don't know enough to be able to explain what.
Very well explained. I learned some things. Thank You Kevin.
2 thoughts: The doublet is less noisy, compared to the EFHW, because your Z-Matching Tuner is acting as a Passband-Filter. Everything around the tuned center frequency is attenuated by the tuner, while the EFHW is broadbanded. EFHW has it´s SWR Minimas at desired Bands, but usually does not go above SWR of 3 between the harmonics. Second thought: Use real parallel Wire, not this wireman excuse of a feeding line. This will increase efficiency of the Antenna considerably. The Way the wireman cable is designed, it interacts with the 2 wires as dielectricum and will cost you some energy loss. Once you´ve tried 2 parallel wires with just some spacers every couple of feet or so, you will never go back ;) At my QRZ com page, there´s a picture of the feeding point of my doublet, showing also 2 spacers..... There is no conecction between my feeder and my Antenna, as it is one continuous wire..... 73 Manuel; DL2MAN
That's a theory. However, consider this. Hash noise from harmonic rich sources is broad banded. Sure, a tuner acts partially as a pass band filter, but we're not bothered by noise that's outside of the receivers tuned frequency and IF bandwidth anyway. If hash is present, it's going to be present across most of the HF spectrum, coming through regardless of where your pass band filter is.
@@loughkb It´s not just theory. Ask for example all the people with a Radio Broadcasting station nearby. Clearly off frequency, yet clearly still affecting our Ham Radio operation exept you Notch it out or use a passband-filter on your side. Another example would be the famous IC7300. Great rig, however: Without anything nearby you (frequency wise) easily overloaded (OVL) by stuff out of Band, when using it at Broadband Antennas. Technically a Doublet and an EFHW are the same thing. Both are Variants of the Dipole. Why should one be more prone to Noise compared to the other if not because of external equipment, needed to tune it ? That would be my point here. A fair way of comparison would be: Classical EFHW, fed by broadband Transformer vs. another EFHW in comparison, fed with a resonant Fuchs Circuit, which makes it also insensitive for Noise out of Band. Which one do you think is less noisy ? 73 Manuel; DL2MAN
@@dl2man Hash noise is not at all the same thing as strong RF signals nearby. Sure the 7300's front end can be overloaded by nearby broadcast transmitters or other nearby transmitters out of band. But that's entirely different.
Kevin, I have the same antenna here and it works great. Only difference is I use a 1:1 current balun vice a 4:1 because the Z on some bands is fairly low at the transmatch at my qth. Since moving to the doublet fed with 450 ohm line my swr/coax problems are gone.. 73s KG5IF
I love doubles. For portable work I have used figure 8 wire used to feed speakers. In theory it isn't ideal as a feeder but availability, cost and no need for any joints where the feed meets the radials compensates for that. Also just look at the length feed you can have giving you height advantage if you find an incredibly tall tree.
Great presentation, Kevin. Thanks.
Doublet is my goto hf wire antenna. I fought with coax, noise, swr and feedline losses for years. i moved to a doublet and those problems are gone. Outstanding antenna.
COVID gave me a cough for 6 months. Good video
An EFHW or any unbalanced antenna will always be prone to commom mode currents. Which leads to all kinds of issues, noise RF in the shack etc..
The doublet is an age old standard, and very hard to beat...
Doublet for the win . Been my go to over all other wire. Especially with a remote tuner...
Hi Kevin. Really liking your drone videos. Very cool. 73 Martin-WD9ABG
Very nice comparison & info video Kevin!! Thanks! 👍⚡📻🎧🎤
Hello Kevin. I really enjoy my Doublet. I run the 135' version and have for severial years. Have you ever heard of ending the 450 Ladder Line with a 1:1 Common Mode Choke wound symmetrically like your 4:1? I can't see how that can work. I wish I could remember where I read about it. I do feed my 450 ohm line to the MFJ-974HB Tuner.
Thank you for displaying the results of the doublet and end fed antennas Kevin! I'm getting ready to set up a 40' tower out at my shop and plan on placing my vertical on top as well as making a doublet and placing the apex at the 35' to 40' height. My parents live in Apache Junction so I'm down there quite often. Do you hang out on 75/80m in the evening? I want to invite you to check in on the northwest country cousins on 3.968 at 7pm every evening. It would be great to meet you!
Nice video. I have a 40m loop with 4:1 balun same as yours. Fed with coax and works well on 40-6m but id like to try this doublet!! Cheers. VK2VRJ Richard
Recently found your very informative channel! Thanks for sharing all this great insight. :)
Would be great to get your thoughts or even a video comparing this doublet to the folded dipole you made with windowline / ladder line in an earlier video.
Well, that would be kind of like comparing apples to oranges. That folded dipole was a mono band antenna. It's performance was terrible on the bands it wasn't cut for, even matched with a tuner. On the flip side, it was a great antenna on it's resonant band, and quiet as far as noise goes.
The doublet performs great on nearly all the HF bands, with a tuner.
I also very much like the doublet but have come to favor a closed loop horizontall sky loop up 40 ft fed with twin lead and tuned with a true balance tuner. A whole S unit quieter than most other antennas!
So during the apocalypse we need a half wave to find all the hidden bunkers eh. Or a way to shield them so that we are less detectable :)
Wow impressive . Definitely going this route. Our home has solar as do others. Is there a way to choke the RF output on the actual inverter?
Swith the wires locations to be sure the doublet results aren't just the results of it's orientation. EFHWs twnd to be in a slope and pick up more man made emi as it's vertically polarized so a dipole/doublet will seem better but a vertical dipole vs a horizontal EFHW will show different results.
As you say a fantastic shortwave antenna.I would never go back to using a coax fed antenna.The noise difference between the two is night and day.🐒🐻🤗👍
I wish you had a video on making the 4:1 balun.
HI, For HF, I am using 2 Type 43 baluns..
Antenna ==> 4:1 ==> 1:1 --> rig
Thank you. 73
Kevin, FB on feeling better! I have a 160 meter loop (skywire, skyloop, ...) which I feed with 450 ohm twin lead into a Balun Designs 4115 dual core current balun they describe as; "Individual cores wound with single wire pair as 1:1 current balun.
Cores are then cross connected to create 4:1 current balun." This sounds the same as yours to me but is it? Want to build a doublet and use it if possible. Thanks!
Have you tried the ZS6BKW version of this? Apparently designed to be resonant on several bands without a tuner.
Excellent experiment... Have you tried a Sky loop yet? I've heard it has the lowest noise and best gain for a wire. Thoughts??
Kevin did you by any chance take photos of those 2 chokes when you were building it and how they wrapped around from one to the other? if so can you share ? I am currently using the Hygain av-680 and love it , but the qrm here in the middle of Los Angeles is nasty , plus it sits 75 feet away from power lines. Really want to make one of those for the qrm reduction. I have built baluns before , but can use help on how you connected them. THANK YOU
Welp I'm off to build a doublet lol I was wondering what those squiggles on my waterfall were. Have a few neighbors running solar. Gives me a new antenna to experiment with. Thanks.
Doublets are superb all rounders for sure.
Very informative, thank you
OK. Do you like the doublet? Love my MFJ 1785 rotatable di-pole which I don't rotate. Great figure "8" pattern, but it needs TLC so I put up a Horse Fence inverted "V" and you're spot on.
80 is great, 40 a little less but still made tons of contacts on 20 this last contest. But it's just a little noisier than the 20/40/80 rotatable.
FYI- the MFJ-1785 works great and it has "whiskers like bicycle spokes for capacitance and after 5- 6 of hot summers and cold winters they have tendency to fall out or get loose which makes tuning next to impossible, thus the wire till it is fixed. Trying a Palomar 9:1 end fed tomorrow
We're fans of Quartzsite too. But I just got into HF about two months ago and was looking forward to our next Quartzsite trip - and bringing my FT-710. However, our trailer runs from 700 watts on the roof, an MPPT controller into two 100 ah Lithium batteries which keep my pure sine wave inverter on that runs our 120v ac fridge (a small RV size but still ac). Hmm. I run a permanent Vibroplex endfedz 135' wire antenna here at home, but I've been wondering what kind of antenna I could take with us on our next south trip. Your simple-looking "doublet" seems to be a good solution. I'll find a good description of how to build this and give it a try. Thanks for your video. Never thought my inverter would be a problem - and it hasn't been until now - ha.
Thanks for watching, here's more information on the doublet in other video I made.
ua-cam.com/video/tA4loiihJwE/v-deo.htmlsi=MOv53WAlcfB6mP_O
I never think of anyone being able to get sick in the desert, glad you're feeling better. Wouldn't the fact you're using a BalUn mean necessarily that common mode is canceled out since the BalUn's output is 180* out of phase and any in-phase signal will be canceled out? In other words, it's not choking, it's phasing?
If you have the supports for it the real best wire antenna is a horizontal loop. Basically as simple as the doublet, does everything the doublet does, and does it better. And you can get it to be resonant on several bands without magic feedline lengths, because a loop is happy on *every* harmonic, not only odd ones.
Dear Kevin happy 2023! My respect for whole great effort you are providing for HAMs education in social media. My question is concerning type of cores you've used for transformer displayed here. 73! SQ5OBV
Type 43.
Not to take away from the subject but you recorded many instances of sounding. The ionosonde or chirpsounding seems strong in the area you are in. I'd be interested in knowing where it originated from. Any ideas?
Looks like the closest sounder I've seen is Vandenberg, which looks to be roughly 730 miles exactly or 1174 km. I wonder if thats the originating station?
The doublet, being balanced and using window line is not getting any CMC on it. Most likely that's why it's quieter. I don't believe the Balun is changing anything other than the impedance. You can test by taking the 4:1 out of line if your tuner can handle the mismatch somewhere. This is one of the reasons that using Ladder and Window line is preferable to coax for multi-band use if you can manage it. Good video, thanks.
Isn’t one side supposed to be shorter than the other?
I'm sold.
Have you ever tried to hook the ladder line directly to the antenna matcher? Just curious Thanks Bob. KC9LRA .
What gauge wire are you using for the 120 foot section? And what gauge ladder line or window line are you using? Thanks great video appreciate the information
The antenna is 14 ga solid core. The window line is 450 ohm from DX engineering. I don't know it's gauge, but it looks like 12, stranded.
What length is the balance feed line? What formula do you use to compute the length?
With a doublet, it doesn't really matter much. It's a non-resonant antenna.
could you disconnect the inverter and only use straight battery power when operating to cut down on the hash that the inverter causes???
Some people do that. As long as your partner isn't watching TV at the moment. ha.
I converted most things to run directly off the battery power so I almost never turn my inverter on.
I'm only a user of scanners for 2 metres and below from my house in England. I'm quite high up and use a home made antenna in my attic which works quite well because there's low noise in this rural area, so I can pick up signals quite well from 50 miles away.
But I also browse around the world, via WebSDRs, and have been meaning to ask what are the diagonal lines that sometimes occur on the waterfall, that can track across all frequencies on band?
Those are probably ionosonde sweeps. Used to measure propagation in real time. They transmit a sweep and have remote receivers tracking it and measuring how much of the signal bounced that far.
@@loughkb Many thanks Kevin for explaining. I've seen these sweeps very occasionally over the years but noticed a few recently whilst listening in to the remaining WebSDR's in Ukraine.
btw the antenna I use in my attic was taken from your video, from 3 or 4 years ago, when you made a quick 2m unit from a split coax, and I attached it to an old broomstick. It works a treat. Cheers!
I have been a 3 year efhw antenna fan but your detailed sharing of your experience here has my eyes wide open as to what I would like to try next. Would you share wire types, open line specs and length so as to approximate what worked well for you at 120' of span. Thanks...
As I recall, the antenna wires are 14 gauge stranded copper wire. The feeder is 450 ohm window line I got from DXengineering. I don't know the feeder length, sorry. If you have trouble getting a tune on some bands, you can either change the antenna length or feeder length a bit.
It's really important to make sure the two legs of the antenna are exactly the same length. Symmetry is what makes a doublet work well.
I also really like doublets but don't have much room on my property. I've tried the 49:1 EFHW and like you, I've noticed it was much noisier a doublet.
The one thing with a doublet that is important to note is that the feed line acts as a matching section of sorts. This is why some folks have trouble finding a feed line length that works on ALL of the bands they want to operate on.
Can you tell us exactly what 450 ohm feed line your using and how long it is?
Would that 4:1 balun work for a OCF Dipole?
I think it would work fine. As long as it's at the point where the resonant impedance is 450 ohms.
Very interesting i have an idea i will build one as i am a shortwave dxer.🐻🤗👍
Is that an artefact or the guy on 7155 is using an echo/reverb effect on his modulation?
Probably multi-path. One path is longer and causes the delay effect since the signal arrives slightly later.
what about a zepp antenna ?
OK, here's a crazy question for you, how well do you think the Doublet would work if you put it up in a "Cage" config?
You did a video back in April 2021 about the properties of the Cage and it seemed to work really well, could the same signal capture properties of the cage be incorporated into the Doublet?
Just figured I'd ask
73, de
WB2ZDB
It would improve. Actually not that uncommon of a configuration, from way back in time.
I have trees that I can put one in they are 160' apart and I can put the antenna 120' feet up. What are your thoughts?
It'll be lack of an antenna and perform great.
Is your EFHW coupled to ground? If you just put the transformer up at the end of a piece of coax, the coax outer shell will pick up noise that appears as common mode noise. My transformer is grounded and I see little noise unless the bands are noisy. 73, JP
It has a counterpoise wire going down to a ground rod below it.
Whats the difference between window line and ladder line?
Ladder line is generally made with two pieces of wire and spacers every few inches to hold them apart. Looks like a ladder. Window line is like a black ribbon with the wires on the edge and windows cut into the ribbon to allow lower wind resistance.
Both are considered parallel balanced feed line.
Hi kev,my garden is only 40ft x30ft so do the doublets work OK if you have to bend them?? Currently using an efhw but the noise on 80m is terrible :( thanks for the video 👍👍
There can be a bend in the elements, but no more than 90 degrees.
@@loughkb thanks kev,was thinking of putting it at top of my 12 meter mast but how far away from the mast does the ladderline have to be and have you any ideas how to achieve this please as racking my brain .the mast is attached to the house so the legs will go away from the house but the ladderline will run straight down and into the house but need a way to keep it away from the metal ???
That's one consideration with parallel feed. You don't want it near metal, and certainly not parallel to nearby metal.
What is the length of your ladder line? I have been wanting to put one up to try out.
I haven't measured it. Since it's a non-resonant antenna and you use a transmatch (tuner) with it, it really doesn't matter too much.
Thank you for putting on this video. Was very informative. I am wondering what dessert were you in? What is your location?
Thanks
George
Alberta, Canada
Southwestern Arizona, U.S.A.
Thanks for the useful follow-up video on the doublet.👍 Question: Can a doublet be run successfully as Off Centre Fed please? I have 150ft one side of my shack and 250ft the other side. Would I be better using a doublet with 150ft on each side? Best 73.
It wouldn't be a doublet since it would no longer be symmetrical. But I'm sure it would work. You would lose some signal on the transmission line due to the asymmetry of the radiator leading to a difference in phase of the signal on the ladder line.
Better to go with coax and a 4:1 balun for an off-center fed dipole.
@@loughkb Thanks for taking the time to reply and I take your points onboard. I may be able to try this as a doublet and also an off centre dipole with coax. Right now, I have the space but not the time! I hope you are staying well.
Very very interesting
Very good video... i must have missed how long your 450 ohm ladder line is. Can you please let me know? Thanks again - great video.
I haven't measured it. In the doublet, it doesn't make too much of a difference the length.
@@loughkb ... Thank you very much. 73 Sir.
Is the EFHW oriented horizontally or vertically?
Both antennas were inverted V.
Hi, Kevin. Liked your video. Maybe I missed it but what is the length of the ladder line on your doublet? I would like to do a doublet with only 25 feet of ladder line. What do you think of this? Alan KZ6B
I don't think I ever measured the length of the ladder line. It shouldn't matter much.
Please do a metal detecting video
Maybe its AGC, you have it set to slow.. AGC if the signal is low on one antenna will crank up the gains. But evern f thats the case it means the HWEF is recieving lessand cranking AGC up
Kevin, great vid.! Q; At what height does the doublet hang ? is that critical ?
Critical? I wouldn't say critical. However, the closer to the ground, the more NVIS it will be. So you want it as high up as you can manage. Unless you're aiming for the smaller and more local footprint of an NVIS antenna.
HF may not be your gig. Noise is a part of much of the HF experience. DX comes in at low angles and that's where your neighbor's inverters are at as well. When you switched to the EFHW, I noticed a major improvement on all of the lower level signals on the sweep. They were above the inverter noise. But QRM is RF. If you don't want RF, I'm not sure what you want here anyway. Have you tried your RF gain control? Try backing that off to improve your noise levels and get your lower angle signals in there. I am assuming you want DX. Maybe not. I don't know for sure.
will 49:1 worked?
A 49:1 is being used on the end fed half wave. The resonant impedance at the end of the wire is around 2450 ohms and must be transformed down to 50 ohms to match the coax impedance.
Is your center support conductive? Does it matter?
No. It's plastic, harvested from a cheap cutting board. It needs to be an insulator so you don't short the transmission line.
@@loughkb OOPS. I meant the support pole.... Is it metal, plastic, wood?
@@tpobrienjr Fiber glass. You could use a metal mast, but you'd need to stand the ladder line at least 6 inches off of it, more would be better. The twin lead feeder needs to be kept away from metal.
Hey.....radio man! 👋
It would be quite interesting for a follow up video to explore what happens when you remove the 4:1 balun from the doublet.
And also, what happens when the 4:1 is installed with the EFHW, instead of the 49:1.
One quick additional observation: a coax fed 80 meter half wave dipole would be a full wave on 40m. That would present an impedance so high even a wide range tuner would be challenged to match.
Thanks for the video.
Thanks Kevin. How high is the doublet?
About 33 feet at the apex and the ends are 6 feet off the ground.
@@loughkb Wow I thought a 40m would need to be a lot higher than that! Like 60ft or so. Everything I’ve read or heard says you would just be burning clouds that low. But results speak the truth. Thanks.
Oh, dipoles do improve if you get them at least a half wavelength above the ground. The closer they are to the ground, the higher the takeoff angle of the majority of the transmitted energy and the shorter the skip distance.
@@loughkb I thought a dipole and doublet were the same thing.
@@bobbyt2788 Yes, doublets are a form of dipole. Two legs, two poles.
Thanks Kevin for the very nice comparison. Is your window line a precise length ?. You got me thinking of changing from HWEF to doublet due to noise in my neighbourhood.
No, it was just what I needed the first time I put it up.
👍