How Antenna Traps Work (

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Күн бұрын

Here's the correct video! Antenna traps and how they work.
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Пікірлер: 74

@ibannymous 3 жыл бұрын

I love how Dave explains complicated matters so that it may be digested. Thank you for your efforts!

@rsluggy6485 3 жыл бұрын

Dave's explanation of the way a J-Pole antenna works is the first that I've actually comprehended.

@AnthonyBecerra 3 жыл бұрын

Dave! You are looking great! Glad you are on the mend. Take care and 73

@davidincalifornia3711 Жыл бұрын

Dave, I sure do appreciate your channel. Your help has been invaluable now that I’m getting back into ham radio after 20 years away.

@jrfoleyjr 2 жыл бұрын

I was trying to describe the trap to my new ham nephew and then I found this video you made. THANK YOU and 73

@K2CTC 2 жыл бұрын

Thanks! That helped make sense of a great deal of info on the General test and it is practical and helpful as I put together my HF shack. I hope I can shake your hand one day and say thanks in person!

@theophaniaepiphany3953 3 жыл бұрын

you sir are a rare gem. effecitive teaching. visuals , clear words. to the pointe. I have to tip my hat to that foundation which you stand and the expertise , you generously share. i learn much when I watch your videos....tippin my hat now.

@davecasler 3 жыл бұрын

Wow, thank you!

@stridermt2k 3 жыл бұрын

Outstanding and appreciate the explanation!

@mbarreto64 3 жыл бұрын

I am using a trapped dipole Diamond W-8010 and it is impressive the extremely low bandwidth in the 80m band (about 25KHz for a good vswr). There 2 traps each side of the dipole in the 80m wires that reduce the bandwidth, but I think the balun is also not so good below 7Mhz. Anyway the antenna is compact for what it is and is good in 15m and 10m and reasonably good in 40m and 20m. Strange thing when it rains the vswr goes crazy high and it works only for 15m and 18m ))). For curiousity we were colleagues (worked in the same company) but I only knew it when you retired :) 73

@sm3ttz 3 жыл бұрын

LOVE your sweater! I want one too!!! :D Great vid Dave, you explain things so we understand.

@bradcfi2 3 жыл бұрын

Awesome Subject. I knew traps provided linear loading but never understood the trap function. Thanks!

@larryprice9970 3 жыл бұрын

Thank you Dave for another great video

@macuser1232 3 жыл бұрын

Very informative. Thank you!

@K3KTB 3 жыл бұрын

Great video Dave. I have an 80 meter trapped dipole and never thought to check if it was resonant at another frequency. Sure enough it's resonant just above 30 meters.

@1HayesEng 2 жыл бұрын

Good show!

@donalfinn4205 Жыл бұрын

Well done!👍☘️

@banihex 3 жыл бұрын

Great video!

@tedclapham4833 3 жыл бұрын

You might want to describr the coaxial trap as well! I have a vertical design that will cove all of 80 meters anone that will cover all of 160 with simple remote tuning!

@arkorobotics 3 жыл бұрын

Hi Dave, the slide at 2:53 says the trap “presents a high impedance to 7 Mhz”, but your explanation implies that it should say “14 MHz” as it’s the resonant frequency of the trap.

@KE8MWQ 3 жыл бұрын

Thank you for the video very informative 73

@thomasmanson1119 7 ай бұрын

Great video and explanation Dave. It also seems to explain the Diamond SRH 320A Tri-band antenna designed for the the VX-6 tri-band HT. So I’m assuming that what I like to call the “load” in the middle of the antenna is in fact a trap that segregates some of the three band resonances that make it a tri-band. But if that is correct, why aren’t there two “loads” (traps) for separation/segregation of all three resonant sections? I’ve loved antenna theory ever since my bachelor’s of EE, and have enjoyed researching and learning more and more of all the theory of antennas and how they work. Thanks Dave and 73 Tom KC3QAC.

@EvgeniX. 4 ай бұрын

well explained 👍

@che59v 3 жыл бұрын

Thanks, Dave, One good option is the multi-band doublet antenna fed with an open wire ( balanced feeder). you avoid most traps with this one. lol

@BartVanAllen 3 жыл бұрын

and with the tuner at the end point, then choke on coax to the radio. They will work very well even if they are not resonant on any band natively, usually much better than any trapped antenna.

@ky4tgtodd203 3 жыл бұрын

I love that shirt! 👍🏻

@jada2068 3 жыл бұрын

Outstanding Dave! Thankyou....de AF8E (John)

@KirkMonteux 3 жыл бұрын

Thanks so much

@jonnewman9904 3 жыл бұрын

Have a look at aerial 51 dipoles, quite impressive bandwidth on most hf bands

@BersekViking 3 жыл бұрын

Just found this channel. Great videos! 73 de LA8SB

@siddharth4662 9 ай бұрын

Great video... thanks for the same... Somehow I thought you were sitting with a backpack because of those blue straps on your T-shirt... 😅

@epedja 3 жыл бұрын

One question seems to be subject of different opinions: what should be resonant frequency of the trap. So far I found these claims: - spot on bottom of the band - just below bottom of the band (this one prevails) - anywhere below bottom of the band - at the middle of the band / middle of the part of the band you want to use antenna I believe in one occasion I even saw claim that trap should be slightly above the band. What is correct?

@kg5pte 3 жыл бұрын

Hi do you have a video on the effects of ice build up on antennas ? With this blizzard that hit Texas, My MFJ1982 end feed antenna SWR are all out of whack. Along with my vertices. Thanks

@dannonight 3 жыл бұрын

Hi Dave. Sorry to hear about your ankle. Get well soon. 73 VK6FANG

@scott798075 3 жыл бұрын

good info for anyone studying for their extra exam

@RichardHopkinsLobosSolos 3 жыл бұрын

K6ARK has a video where he was making tiny traps for some of his antennas. He does a lot of SOTA where he's packing everything up/down the summit so his antennas tend to be very lightweight.

@shanerorko8076 2 жыл бұрын

What if you used ladder line to feed a off centre dipole at 22% feed point but had coax feeding along the ladder line at different points. Then had a inductor at the matchbox/tuner, but the inductor was more like a variable transformer which could tap in at different points along the ladder line.

@Harvestersz 3 жыл бұрын

Do traps have an effect on receive as well as transmit? I'm an SWL rather than a Ham, and I'm wondering if the traps have any negative effect on an antenna's receive capability.

@slickspade 3 жыл бұрын

Can you do a beginners playlist? To radio and licensing?

@oz457 3 жыл бұрын

Hi David, can you make a video about a very interesting question: How come a dipole's bandwidth gets smaller when going lower in frequency and gets a larger bandwidth when the frequency gets higher. Also, how can you enlarge the bandwidth on lower band dipoles. My home made dipole on 80m has a crappy bandwidth of less than 100khz. Will higher height increase the bandwidth? Thanks for the perfect explanation!

@davecasler 3 жыл бұрын

The bandwidth is pretty much a percentage (about 5% max) of the center of the operating band. All dipoles are like this. Your home-made dipole is perfectly normal. You can increase bandwidth by increasing the conductor thickness. Unfortunately this effect is minor, and to cover the 80m band you would need a width of several feet. The ARRL’s headquarters station has a “cage” dipole of four wires about 4 feet apart in a square configuration

@markbunce4560 3 жыл бұрын

Hi Dave, thanks for an interesting video on how traps work, If I wanted to make a trap vertical for say 10 meters, 20 meters and 40 meters, I understand that the first part of the aerial will be for 10 meters then the trap, what would be the length of wire from the 10 meter trap to the 20 meter trap be? Is there a formula for this? Also what would be the length be between the 20 meter trap and the 40 meter trap?. I noted with interest that the one you described was a dipole with 16 foot each side and from the 40 meter trap it was only 5 feet, what formula did they use ?.. I have only ever used half wave dipoles, but now thinking about a wire multiband vertical with traps. Your help will be helpful with this project. Many thanks mark..

@epedja 3 жыл бұрын

You alrady have length of wire used for lower band so you just add extension to get proper length for lower band. Calculation is the same as for ordinary dipole, just decrease dipole length for wire already used for higher band.

@bill-2018 2 жыл бұрын

I guess a trap dipole on it's lower frequency will be less efficient because it's shorter than a dipole cut for that band.

@kevingary7018 3 жыл бұрын

I watched a video where a 8010 end fed half wave wire antenna was split in half, with a 500 pF capacitor installed in the middle with an insulator, linking the two pieces of wire together. The capacitor (by electrically shortening the length of wire) supposedly allowed the antenna more of the 80 meter bandwidth, while not affecting the other bands. Would this modification be considered a trap? What are the disadvantages to this modification? The video did not show how to protect the capacitor. I wonder how the ceramic capacitor holds up to the storms and wind it incurs?

@davecasler 3 жыл бұрын

No, it’s actually a capacitor that allows the antenna to be used on 75 meters instead of the low end of the 80 meter band. It doesn’t affect the other bands (too much).

@AG8000 2 жыл бұрын

👍👍👍

@k9yk 3 жыл бұрын

Why mess with any of this? Put up an 80m doublet with a remote tuner and work all parts of all of the bands. Yes, including all of 80m & 75m

@firewaterforgeofarizona4304 3 жыл бұрын

Can you recommend a good high Q 20/40 dipole antenna? Offset is ok.

@davecasler 3 жыл бұрын

Try the reference antenna, the MFJ-2010, an off-center-fed dipole that covers all of 20 and 40, and, as a bonus, 10 and 6.

@kevinkc3onohelijeepworld953 3 жыл бұрын

Glad you got the right vid in its spot. I thought the other version was very similar to yesterday’s vid 😜 thought it was a dream 🤣KC3ONO

@Justin-bd2dg 3 жыл бұрын

How about a video on WHY lower frequencies translate to larger antennas. I've never found a good way to explain this to the layman.

@che59v 3 жыл бұрын

How "low" will you go? lol

@Justin-bd2dg 3 жыл бұрын

@@che59v lol

@bill-2018 2 жыл бұрын

It's the wavelength which gets longer and so the resonant frequency needs a longer aerial. Compare a 2m quarter wave aerial against say 40m.

@greglawrencemusic 3 жыл бұрын

"My Elmer, My Elmer!"

@K6TJO 3 жыл бұрын

Now could you explain capacitor hats. 73 de K6TjO

@johnaweiss 2 жыл бұрын

If a trap is very high Q, will you get extra gain at the resonant frequency? Meaning, if you're only receiving a single frequency, then it seems like a trap has no downside, only upsides: shorter antenna, no heat, no losses. Correct? thx!

@davecasler 2 жыл бұрын

Traps cannot create power. In this case, higher Q translates into narrower bandwidth. Traps are RLC circuits and can have high circulating currents, which causes some loss in the R component.

@johnaweiss 2 жыл бұрын

@@davecasler So they don't create gain, but concentrate energy on a particular frequency, correct? Doesn't that help compensate for losses? Isn't the whole point that the trap provides less loss at a given frequency than you could achieve otherwise (with a broadband antenna)?

@davecasler 2 жыл бұрын

@@johnaweiss The short answer is no. A trap is a passive filter that either allows energy to pass or blocks (traps) it, depending on the frequency. Prudent choice of traps allows you to create a multi-band antenna, and only the correct part of the antenna will radiate. The choice of frequency is made by the radio's internal oscillator. Think of it this way: depending on frequency, a trap either allows use of a certain part of the antenna or blocks it, so for different bands the antenna has different effective lengths. Note that traps largely went out of style about 30 years ago, and few new antennas use them (although you can still buy them). Nowadays it's end-fed-half-wave dipoles that cover many bands, or off-center-fed dipoles that can cover several bands. Hope that helps.

@kg5pte 3 жыл бұрын

I am using a 132 foot MFJ 1982MP wire antenna and can't get ten meters and eighty meters to tune , forty through twelve is fine. I am using a nano VNA to do frequency sweeps.

@davecasler 3 жыл бұрын

MFJ told me that the coax from the radio to the balun should be quite short. I finally figured out it's primarily for portable use. By contrast, the MyAntennas EFHW 80-10 works really well even with a long feed line.

@kg5pte 3 жыл бұрын

@@davecasler Thank you sir.

@va3hie Жыл бұрын

Dave, your comment that no antenna will cover the entire 80m band is inaccurate. I use a 160m through 6 meter windom. 3.5Mhz to 4Mhz on a yaesu ft950 using ONLY the inboard tuner.

@USXPOP 3 жыл бұрын

Electrons have to move to make a signal. Don't trap those electrons, set them free. Joking here, not serious. Nice explanation.

@garrysekelli6776 3 жыл бұрын

Hello garries Worldwide.

@paulalmquist5683 3 жыл бұрын

I'm no electronics expert but I noticed what appears to me to be an inconsistency in your presentation. At 3:50 you declare in the diagram and audio that the trap is a tuned circuit. At 5:28 in the audio you say: "This right now (pointing to the trap in the diagram) is no longer a tuned circuit because it is below the frequency that it is tuned for." The frequency of the RF going into the antenna does not change the fact that the trap is still a tuned circuit. You need to rephrase your comments.