Trap Dipoles

[WB6TMY]

Fellows,

I don't see much about trap dipoles these days, but I have one I'm very happy with and would like to share my opinions on it.

First, let me say I have no way to scientificly measure anything with any degree of accuracy.

My Unadilla Trap Dipole suffered a loss by shorting the capacitor on the 80CW trap at one end when I purchased a new linear and raised power to 1.5KW. Even though it was old, well over a year, when I called Ralph at Unadilla he replaced the trap for free. I think this is over and above what can be expected from a vendor.

The dipole has a number of advantages.

#1 Strength - the traps will withstand about 600lbs of tension. Trap dipoles tend to be heavier than plain wires. Lots of vendors give instructions on supporting the center with ropes. With a Unadilla Trap Dipole, you can put adequate tension on the dipole and not worry about it.

#2 Efficiency - I know guys use PVC all the time. Even QST and good engineers use it. There is nothing wrong with PVC. Saying that, I'm glad my Unadilla Traps have a better dialectric. It's just my opinion, I can't prove it, but that's what I think & I want you to know just exactly how I feel on this subject.

#3 Loading - on 160 meters my dipole is only 160 feet long & I think that's a good length. I can fit it on my city house lot. Furthermore, each trap adds a little bit of loading, so it's not a big lump value of inductance in one place.

I wish more hams would give credit to, and consider using trap dipoles, especially Unadilla Trap Dipoles. I like mine!

I'd be happy to hear from anyone on this subject. Just use my callsign at QSL.net or check my spam filter at http://www.radions.net/spamfltr.htm

Thanks & Very 73,

Tracy WB6TMY

[K6UEY]

Tracy WB6TMY,
Obviously you are new to Ham Radio, so let me give you a couple of pointers, first of all a trap dipole is usually the last choice in antennas as they are very lossy mostly because of the traps.Your statement about the traps adding inductance in step fashion to allow you to tune 160 is some what in error. The purpose of a trap is to offer a HI Z by virtue of a paralell resonant circuit ( see Basic RF circuits ) at the resonant frequency the Z is High in essence cutting the current off to the rest of the antenna, at all other frequencies the Z is low allowing current to flow, with exception of the resistance of the wire in the coil that appears in series, dissapating the signal in the form of heat thus lowering the effeciency, so for each trap it is lowered a little more leaving less signal to be radiated by the antenna.
What you may have been thinking of is inductance loading of a shortened radiater. Traps and loading are 2 separate things, I might suggest reading about AC and RF circuits and Basic Antenna Theory.
No amount of rule changing is going to change the importance of learning the basic fundemantals, they will affect every thing you do the whole time you are in Ham Radio. #Lots of Luck on your experience..... # 73, # ORV
http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[w5alt]

Orv, I think you missed his intent. Of course the inductances, with their inherent Q, do add losses, as you said. However, if you remember the discussion we had a few months ago on here, it seems that much of the "resistance" in coils is due to radiated energy. If the coils are out in the open and part of the antenna, that doesn't strike me as so bad. I can't prove it, but I think that the low Q attributed to loading coils is often unwarranted, if the coils are on the antenna itself and contributing to radiation.

But, if you look at the trap dipole antenna at 160m, you see a series of wires joined by capacitors and inductors in parallel, none of which are resonant. Since the frequency is lower than resonant, XC is higher than XL probably by at least a factor of 2 and probably much more at each trap, so each trap essentially looks like a small inductor. So on 160m, the antenna really does look like a short dipole with some inductors distributed along its length, which is better than putting one larger loading coil at the feed point.

Remember that when designing a trap dipole, you can't just take a 160m dipole (for example), cut it at the 80m resonant points and insert traps. You also have to shorten the ends to bring it back into resonance on 160m, compensating for the effect of the inductance added by the trap on 160m.

73,

[KA8NCR]

Trap dipoles are of course lossy, but I disagree with the assertion that they are the last choice.

An 80/40 trap dipole is actually not all that inefficient for 40 meters because the ends of the dipole on 40 contain little current. There are losses, but not as if it's a random wire and a tuner. Now _that_ is a questionable antenna.

It of course gets more lossy on 80, but certainly not as bad as non-resonant antennas in the bandpass of the trap.

[K6UEY]

Walt W5ALT,
Sorry Walt I don't buy that, the reason they call them TRAPS is because they trap the signal, and do not let the current flow in the rest of the wire (antenna ) from the feed point to the first trap is tuned to the highest frequency and the length of antenna is resonant at that frequency as a series circuit.You insert the first trap,a paralell tuned circuit . As you know a paralell circuit offers maximum Z in series or opposition to current flow at it's resonant frequency. At frequencies above and below resonance the Z falls off allowing current to flow. This is the trap effect, to the signal at the first frequency it sees the HI Z of the trap and that is the end of the 1/2 wave dipole for the first frequency. Now the second frequency trap, the signal will pass the first trap as it is a low Z at this frequency and it will continue to the second trap which it sees as a HI Z or the end of the second dipole. Each signal frequency travels down the antenna to it's respective trap the last frequency travels to the end of the wire since it see's no resonant traps along it's way.The loss comes from the resistance of the wire in each #coil as IsqR loss or heat that can not be radiated as signal.
Problem: You can not take a coil and capacitor and resonate them and insert them into a normal dipole since the loaded Q and the unloaded Q of the tank circuit will be different, as it is loaded it will be pulled off frequency, the same with the basic wire when inserting the trap stray inductance and capacity will detune the wire so both must be tweaked on frequency. Now as to the bandwidth, that will be dependent on the Q of the trap, mainly on the coil it self as the cap can be hi grade with a hi Q.The diameter of the coil and the spacings of the turns and the dielectric of the form #determine the unloaded Q, as do the resistance of the wire, larger wire less resistance but less inductance so depending where it is placed you would need more wire, you see the problem. But the inductance must also be controlled to give you the paralell resonant circuit, not to mention as the coil gets a larger diameter and the Q goes up so does the weight, not to mention the Q determines the voltage that will appear across the capacitor, remember it is a paralell circuit.What I'm getting at there are several factors involved and #a begginer could handle it but it would take a lot of learning about a selected area, not some thing to throw together on the week end. #
Now on the idea that the coils of the traps are radiating on 160 meters. The amount of reactance seen by the coils or inductance will depend on where they are placed and the current at that point. Remember we start with lo Z max current and traverse 90 degrees to max voltage so the current is dwindling as we move along the antenna. For instance the best place to put a loading coil to get the maximum effect is at about 30 degrees from the feed point not at the feed or at the current node.
You mention the trap at 160 meters that may have been a typing error, but I will address it any way, there is no trap at 160 if you take a 160 dipole and add a 80 meter trap, the antenna is already approx resonant at 160 you want to shorten it to look like a 80 meter dipole so you insert a HI Z (a 80M trap) in series with the antenna which cuts off the current due to the HI Reactance at 80 meters of the trap, if that point from the feed is resonant on 80 meters then you now have a 80 meter dipole the 160 part dissapears as far as 80 is concerned.
I hope I have not added more than was required to explain it, I readily admit to getting carried away when explaining some thing . # # # # #73, # ORV
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[w5alt]

Hi, Orv,

I think we're almost saying the same thing, but about different things. I know how the traps work, and I agree and it's well known and has been debated many times, that a trap antenna isn't as efficient as one without traps. Personally, I would prefer parallel dipoles, but that's a different subject. Actually, I'd love to get just about any "real" antenna inside the apartment here!

What TR said was:</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">#3 Loading - on 160 meters my dipole is only 160 feet long &amp; I think that's a good length. #I can fit it on my city house lot. #Furthermore, each trap adds a little bit of loading, so it's not a big lump value of inductance in one place.[/QUOTE]<span id='postcolor'>
Now, looking at the antenna on 160m, it should look like a series of wires with inductance at every trap. The traps aren't acting like traps, of course, but they do provide some inductive loading on 160m which does make the antenna shorter than a full sized 160m dipole. That's all I was talking about. The traps are still there and they do allow you to shorten the antenna some, just like he said.

Sorry for causing a stir on this. It really wasn't my intent.

73,

[WB6TMY]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (K6UEY @ Oct. 12 2003,13:45)</td></tr><tr><td id="QUOTE">Tracy WB6TMY,

Obviously you are new to Ham Radio, so let me give you a couple of pointers,

73, # ORV
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Orv &amp; Fellows,

I am new to Ham Radio, having just recently received my ticket in 1964. #Thanks for the pointers!

My qualifications are at:

http://www.radions.net/rsmewtr.htm

By the way, #if you will re-read my post, I did not ask ANY questions. #What I gave was an unsolicited ringing endorsement of a product with which I am well pleased.

The guy came through for me above and beyond the call of duty and deserves credit.

Very 73,

TR, WB6TMY

[kb9ax]

TMY; I agree with you. There are times that traps are a good way to go. I have used them. They are on my TH7, and seem to perform well.

Shortened radiators are a fact of life for those of us with 1 acre or less, especially when it comes to 80 and 160. I have about .9 acres, and a full size 160 antenna is going to be really tricky. I am planning an inverted L for 160 and 80 meters soon. Hopefully I can get it put up before the snow flies. I am planning on using a vacuum relay at the top of the tower to switch the two different lengths of wire for the 80/160 inverted L horizontal section. I chose not to use a trap because the bandwidth is very limiting on 80 if you wanted to work both 80 and 75. The system will then have two sets of elevated tuned counterpoise wires for 80/160.

My observations have been that if you really believe in an antenna of some type, it doesn’t matter why ( low SWR, size etc. ) they work much better than an antenna you don’t believe in. You can wish your signal out of wire and add 6db of sensitivity for receive just with mind power alone. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

Dan KB9AX

[AG3Y]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">
I am new to Ham Radio, having just recently received my ticket in 1964. #Thanks for the pointers!

My qualifications are at:

http://www.radions.net/rsmewtr.htm

By the way, #if you will re-read my post, I did not ask ANY questions. #What I gave was an unsolicited ringing endorsement of a product with which I am well pleased.

The guy came through for me above and beyond the call of duty and deserves credit.

Very 73,

TR, WB6TMY
[/QUOTE]<span id='postcolor'>

And that, as they say, is &quot;the rest of the story&quot; # # http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif #http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif #http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif #http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

73 from Jim AG3Y

[K6UEY]

KA8NCR/KB9AX,
You are right, that a lot of people use trap dipoles, I should have specified I use trap dipoles as a last choice as the limited bandwith and excessive loss do not fit my parameters for an antenna. As to wire antennas on a city lot for 80 and 160 yes it is a challenge and it as they say, &quot;separates the men from the boys&quot; to meet that challenge with any success in effeciency.Which of course is the total name of the game as any thing will work as an antenna, the question is &quot;How well &quot;. Each antenna has it's good points and bad, the mark of an experienced Ham is to know the difference, and apply the one that meets the required application at your station. As to alternatives for shortened antennas for city lots on the lower bands there are two that I find meet my standards, that is capacity loading (top Hat ) since it does not introduce IsqR or series resistance losses in the antenna to be lost as heat, the other method which I have found to be most successful for my station for the last 10 or 15 years is Linear Loading. The 80 meter antenna design has been in use for at least 15 years and is still under going design changes to improve it's characteristics even more,(obviously not a full time job) allows me to put and effecient 130 feet of wire in a 100 foot space, and it can be shortened even further, but as all abbreviated antennas the effeciency goes down as it gets short for the wavelength, this configuration uses Linear Loading for a wire antenna of my own design. As to bandwidth it is of typical characteristics for a reasonable efficient #80 meter dipole of about 90 khz at the -3 dB points.
As to Trap dipoles, different strokes for different folks, some people still believe VSWR is an important parameter in working with antennas, so what can you do, there are bound to be a few in every crowd.
ENJOY!! The Antenna is the Portal to every good Ham #station ........ # # 73, # ORV
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[ky5u]

I know this line of discussion is about trap antennas, but I'd like to add my plug for multi-band longwires as well. I have a DXCC longwire made by Alpha Delta that works amazingly well. I really like this thing.

Mounted in an inverted &quot;v&quot; configuration, it is 20' off the ground and is 84' long (the &quot;v&quot; uses only about 70' of ground space). It isn't a 3 element beam, but I work alot of DX with this antenna on 70w. Two nights ago, I spoke to &quot;Obi&quot;, a doctor in the Japanese camp in Antartica on CW.

WB6TMY,
Thanks for your post and I agree, but then again like you I have only been licensed since 2/63 so actually don't know anything.

I might note that I use a Unadilla 40 meter trap on my portable antenna out on gas wells in Wyoming. I have owned these traps for over 25 years and am quite pleased with them.

Because of some of the statements made in this post I want to add a few more things.

First from the ARRL Antenna handbook &quot;Since the tuned circuits have some inherent losses, the efficienty of a trap system depends on the Q values of the tuned circuits. .............With tuned circuits that are good in this respect--comparable with the low-loss components used in transmitter tank circuits, for example---the reduction in efficiency compared with the efficiency of a simple dipole IS SMALL&quot; (caps are mine). A trap dipole is not &quot;very lossy&quot; if you make it with air wound coils(say #12 or #14 wire) and use doorknob caps. I doubt that anyone could even begin to hear the difference the losses the traps introduce. Probably in the tenths of a db, but I couldn't find any exact figures.

Now that we have established that traps are not sucking away all the power in those horrible I^2R losses. I want to explain how they work since I know how and this discussion was strange to say the least.

The antenna I'll use is my portable dipole which from the feed point going out has 32 ft of wire, a 40 meter trap, and then 22 ft of wire. So its approx 108 ft long. Putting a 40 meter signal into it the trap shows a high impedence effectively cutting off the outer ends...trap acts like an insulator. Now lets put a 80 meter signal into it. &quot;If the operating frequency is below that of the trap resonance, the trap BEHAVES as an inductor; if above, as a capacitor&quot; (ARRL Antenna handbook). You might want to read the explaination of why this is so, if you don't understand why.(Also in section 7-9 of the ARRL antenna handbook). So the small added inductance shortens the needed wire to 108 feet and it works fine on 80 meters as well as 40 meters.

Now remember we can chose almost any L or C value to make this 40 meter trap, could have big L and small C, or big C and small L. But if we pick the values at 82 microH and 60 pf we can get this trap to let us operate on 80,40, 20, 15 and 10 meters. Because of it acting like a capacitor in the antenna circuit at frequencies above the trap resonance.(you need to pick the proper L&amp;C valueds to make this work) With these values of L &amp; C when we put 20 meter rf into it, it sees the trap as a capacitor effectively electrically shorting the 108 ft lenght to about 99.5 feet. This makes the antenna resonant at about 4.7 mHz...which is 1/3 of 14.1 mHZ. So the antenna on 20 meters looks like a 3/2 wavelenght dipole, and works on 20 meters. The same happens on 15 (5/2 wavelenght) and 10 (7/2 wavelenght).

I use this antenna in the field and the SWR ranges from 1.1:1 to 2.7:1 depending on the frequency and the physical setup. It will work without a tuner but I usually have one in the line just to keep the solid state rig happy everywhere.


WB6TMY, my explanation of how this works was just included because I know how this works and the resident experts had me comfused so I expect the younger lads we really thrown for a loop.(no pun intended)

73 &amp; CUL

Marty WB2RJR
.

[k0jjm]

I do not pretend to have the knowledge that more experienced hams have. Given that: I have a 40 / 80 trapped dipole that has the center point at about 30 feets and the ends are at about 12 feet. I live in Kansas and it is oriented east west. I consistently can use it on 80 meters to check in with a net in Michigan right after using it to check in with the KS SideBand Net. I have reached both coasts on 40 and use it for local on the same band. I am very impressed with this trap dipole. It would NOT be my first choice for higher frequencies but on the lower bands it works quite well. I don't have the room for a 160 meter antenna, but sometime I may just see how this one works on it! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[k0jjm]

I do not pretend to have the knowledge that more experienced hams have. #Given that: #I have a 40 / 80 trapped dipole that has the center point at about 30 feets and the ends are at about 12 feet. #I live in Kansas and it is oriented east west. #I consistently can use it on 80 meters to check in with a net in Michigan right after using it to check in with the KS SideBand Net. #I have reached both coasts on 40 and use it for local on the same band. #I am very impressed with this trap dipole. #It would NOT be my first choice for higher frequencies but on the lower bands it works quite well. #I don't have the room for a 160 meter antenna, but sometime I may just see how this one works on it! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[WB6TMY]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (K6UEY @ Oct. 13 2003,10:12)</td></tr><tr><td id="QUOTE">KA8NCR/KB9AX,
You are right, that a lot of people use trap dipoles, I should have specified I use trap dipoles as a last choice ENJOY!! The Antenna is the Portal to every good Ham #station ........ # # 73, # ORV
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Dear Orv,

I'd just like to express my gratitude for your guidance on this subject, and with almost a thousand postings on QRZ, probably helping out a whole lot of other folks too!

Keep spreading the &quot;good news&quot; and helping others. #If you can post 1,000 times, surely there is no limit.

Good Luck,

Tracy, WB6TMY

P.S.

Hey Orv!

I just had a really great idea! So, I'm editing this post.

Well, her it is. With so many of us old duffers not having a clue and depending on you to give us the right answers,...

Have you ever thought about writing to Kurt N Sturba, Walt Maxwell, and the ARRL? Just think, with all the great info you've been able to share with nearly 1,000 lucky postings on QRZ, just think how you could improve the world by going straight to the top!!

Something to think about,...

Very 73,

Tracy, WB6TMY

[K6UEY]

TRACY WB6TMY,
I thank you for your consideration of the others who read #QRZ and with a 1000 posting count then you are fully aware of all the BS that is posted under the guise that they are helping, even if it is to confuse those with limited knowledge of the subject matter.To acquire all your paper awards over the years you must have had at least some practical knowledge and observed how especially in the area of antennas the majority of Hams are satisfied with believing Ole Wives tales and ficitous theories as what actually takes place.
Thank you also for bringing to my attention that posting on the Internet is considered a bounty to make others cognizant of ones technical proficiency.In all these years of posting I was unaware of the policy. #This may require that my total modus operandi be reviewed as the policy here is not to post on at least 90 % of the postings I read, #unless I can either further explain some point or as in a lot of cases clear up the misinformation that is so generously offered. As a rule when misinformation is offered after my posting I usually simply ignore the thread. #On second thought maybe a simple Caveat #would be sufficient since the norm is misinformation, and let them take their chances.
73, And a good Day to YOU Sir!!
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Post Script:
Tracy,
Having never botherd to look at the number of postings before #I was under the impression you were refering to your postings, maybe as a supplemental to your paper awards, but you are obviously again some thing more than what you appear on the surface, being new to QRZ of course would not justify the attitude, but would indicate you may or may not be familiar with the Internet. Thank you for bringing it to my attention I guess over the years the number of postings do pile up,I will make it a point to watch that in the future..... # http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif
Post Post Script:
You know Tracy with old duffers like you around with your SMART ASS attitude it is a wonder Ham Radio has survived in spite of you. If you are the wizard of all knowledge where have all your postings to help others gone, counting your edit you have only 7 postings,is that the extent of your responsibility as a HaM ?? Or are you waiting for an AWARD to be presented ??.......

[W8JI]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (K6UEY @ Oct. 12 2003,13:45)</td></tr><tr><td id="QUOTE">Tracy WB6TMY,
Obviously you are new to Ham Radio, so let me give you a couple of pointers, first of all a trap dipole is usually the last choice in antennas as they are very lossy mostly because of the traps.Your statement about the traps adding inductance in step fashion to allow you to tune 160 is some what in error. The purpose of a trap is to offer a HI Z by virtue of a paralell resonant circuit ( see Basic RF circuits ) at the resonant frequency the Z is High in essence cutting the current off to the rest of the antenna, at all other frequencies the Z is low allowing current to flow, with exception of the resistance of the wire in the coil that appears in series, dissapating the signal in the form of heat thus lowering the effeciency, so for each trap it is lowered a little more leaving less signal to be radiated by the antenna.
What you may have been thinking of is inductance loading of a shortened radiater. Traps and loading are 2 separate things, I might suggest reading about AC and RF circuits and Basic Antenna Theory.
No amount of rule changing is going to change the importance of learning the basic fundemantals, they will affect every thing you do the whole time you are in Ham Radio. #Lots of Luck on your experience..... # 73, # ORV
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Hi Orv,

&gt;first of all a trap dipole is usually the last choice in &gt;antennas as they are very lossy mostly because of the &gt;traps.

That actually isn't factual at all Orv. It may be true in an antenna advertisement or amateur folklore, but hard data does not support your statement.

See actual measurements with new lab-grade currently calibrated equipment at:

http://www.w8ji.com/traps.htm

&gt;Your statement about the traps adding inductance in &gt;step fashion to allow you to tune 160 is some what in &gt;error.

He actually was correct Orv. Below the resonant frequency of a trap, the trap is inductive.

Each trap, exactly as he said, adds a little &quot;step&quot; of series inductance. Each trap cancels a small portion of capaciative reactance, and by increasing phase lag of current to correct power factor of the &quot;too short&quot; antenna.

&gt;exception of the resistance of the wire in the coil that &gt;appears in series, dissapating the signal in the form of &gt;heat thus lowering the effeciency, so for each trap it is &gt;lowered a little more leaving less signal to be radiated &gt;by the antenna.

The amount of resistance, or ESR (equivalent series resistance) would be more accurate, is insignificant with anything remotely near a reasonable trap design. Loss peaks at trap resonace, where the EPR (equivalent parallel resistance). That is actually the only point of concern.

The WORSE traps I have measured (coaxial traps) would add about a dB of loss (for a pair of traps) to a dipole, and insignificant loss away from that frequency. Better traps add insignificant measured loss.

The traps I have measured have about 1/4 ohm of loss resistance at 50% of the trap frequency. This resistance decreases as the operating frequency is moved away from the trap resonant frequency. Even coaxial traps, the worse types I have measured, have insignificant loss away from the resonant frequency. # #

Keep your antenna Wayne, and you are right-on. I think people have been reading FAR too many antenna advertisements!! #

&gt;What you may have been thinking of is inductance &gt;loading of a shortened radiater. Traps and loading are 2 &gt;separate things, I might suggest reading about AC and &gt;RF circuits and Basic Antenna Theory.

I'd suggest you borrow his copy Orv, since he actually had a more accurate technical description than you.

There really isn't any reason to talk down to people Orv, even if he would have been in error (which he wasn't).

73 Tom

Traps (http://www.w8ji.com/traps.htm)

[K6UEY]

TOM W8JI,
Your right about Marty's description of the commercial version of a Trap dipole. I was not talking about the commercial version as I am not in the habit of buying wire antennas, in true Amateur Radio fashion I build all my antennas and the Ham Version of the trap dipole is exactly as I described complete with the loss from the resistance in the wire of the inductors. If your testing did not show inductors with resistance I would check your calibration procedures. Not sure I totally follow your explanation but will reread it, the fact that the resistance changes when moving away from the resonant frequency of the trap, ordinarly resistance is non frequency dependent and as such radiates heat when having current through it by dissapation this heat is loss that can't be radiated by the antenna. When plotted you will find a separate vector used for resistance than those used for reactance as it is non phase or frequency related.
As mentioned previously I was unaware of the commercial version that uses an out of band resonant trap. Understandably the dimensions are not as forgiving and must be calculated exact due to the out of band traps, so for the average Ham probably would purchase it, but that is the trend with the lack of technical expertise.
As to Marty and Tracy only being licensed since 1962 even though they take a Junior position they have been around long enough to have learned about antennas as Hams from that era took pride in gaining knowledge and experience some even adopted a Smart Ass attitude. #Tom I don't know where you get my talking down to any one, I explained the Ham Version of the Trap dipole for all who cared to read it, and until Tracy followed with his uncalled for attack it was intended for all to read. If he was offended by not having personal attention it was probably because he was new to the forum and had not bothered to see how postings are conducted. If replies were to be intended for personal consumption only they would be conducted by E-mail.
ENJOY!! All the days on the calendar are numbered.....73, # ORV
http://www.qrz.com/iB_html/non-cgi/emoticons/confused.gif

[W8JI]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (K6UEY @ Oct. 19 2003,18:20)</td></tr><tr><td id="QUOTE">TOM W8JI,
Your right about Marty's description of the commercial version of a Trap dipole. I was not talking about the commercial version as I am not in the habit of buying wire antennas, in true Amateur Radio fashion I build all my antennas and the Ham Version of the trap dipole is exactly as I described complete with the loss from the resistance in the wire of the inductors. If your testing did not show inductors with resistance I would check your calibration procedures. Not sure I totally follow your explanation but will reread it, the fact that the resistance changes when moving away from the resonant frequency of the trap, ordinarly resistance is non frequency dependent and as such radiates heat when having current through it by dissapation this heat is loss that can't be radiated by the antenna. When plotted you will find a separate vector used for resistance than those used for reactance as it is non phase or frequency related.
As mentioned previously I was unaware of the commercial version that uses an out of band resonant trap. Understandably the dimensions are not as forgiving and must be calculated exact due to the out of band traps, so for the average Ham probably would purchase it, but that is the trend with the lack of technical expertise.
As to Marty and Tracy only being licensed since 1962 even though they take a Junior position they have been around long enough to have learned about antennas as Hams from that era took pride in gaining knowledge and experience some even adopted a Smart Ass attitude. #Tom I don't know where you get my talking down to any one, I explained the Ham Version of the Trap dipole for all who cared to read it, and until Tracy followed with his uncalled for attack it was intended for all to read. If he was offended by not having personal attention it was probably because he was new to the forum and had not bothered to see how postings are conducted. If replies were to be intended for personal consumption only they would be conducted by E-mail.
ENJOY!! All the days on the calendar are numbered.....73, # ORV
http://www.qrz.com/iB_html/non-cgi/emoticons/confused.gif[/QUOTE]<span id='postcolor'>
Hi Orv,

&quot;Your (SIC) right about Marty's description of the commercial version of a Trap dipole.&quot;

He was correct about ANY trap dipole used on the lowest operating band, and the same applies to any section of the antenna below cutoff.

On the other hand, you were grossly incorrect.

&quot; I was not talking about the commercial version as I am not in the habit of buying wire antennas, in true Amateur Radio fashion I build all my antennas and the Ham Version of the trap dipole is exactly as I described complete with the loss from the resistance in the wire of the inductors.&quot;

It seems like you are trying to say his antenna has no or low loss because it or the traps are commercial and yours has high loss because it is homebrew.

I'd suggest you measure traps to confirnm that, and if your antenna has high loss correct the construction.

&quot;If your testing did not show inductors with resistance I would check your calibration procedures.&quot;

Come on now Orv. I measured .25 ohms loss on the pass frequencies of some traps. There is nothing wrong with my methods or equipment. The problem is in the flawed perception that traps have high loss. I think this perception comes mostly from antenna advertisements in magazines.

Education or opinions based on folklore, rumor, or antenna marketing advertisements isn't always accurate.

My test equipment, on the other hand, has less than 5% error and the data is based on factual measurements of real components, not a &quot;whim&quot; or something from a Force 12 or Radioworks advertisement.

&quot;Not sure I totally follow your explanation but will reread it, the fact that the resistance changes when moving away from the resonant frequency of the trap, ordinarly resistance is non frequency dependent and as such&quot;

Respectfully Orv you seem free to give opinions about other people needing to review textbooks. I'd suggest you follow the advice that you freely give others.

Resistance normally varies considerably with frequency in RF systems. It can especially vary huge amounts with frequency in a resonant circuit.

It might be helpful to review textbooks or handbooks about resonant circuits where the data includes ESR (equivalent series resistance) or parallel equivalent resistances.

When the trap is trapping, you'd use the parallel equivalent to determine current flow. Voltage across that resistance would be dissipation in the trap. When the trap is passing, it would be easiest to use ESR. The dissipation would be I^2 R where R is the value of ESR in the trap.

It really isn't all that difficult.

&quot; radiates heat when having current through it by dissapation this heat is loss that can't be radiated by the antenna. When plotted you will find a separate vector used for resistance than those used for reactance as it is non phase or frequency related.&quot;

I'm sure you are familiar with parallel to series conversions. If not, it would be a good idea to learn how they work when discussing traps. You can't or shouldn't use the vectors separately in a resonant or reactive system in an application like this. You'll get incorrect answers.

&quot;As mentioned previously I was unaware of the commercial version that uses an out of band resonant trap.&quot;

No one said it was. What I said is loss peaks at the resonant frequency. The mechanism is very simple, at resonance circulating currents are highest. The loss is multipled by the operating Q (R unloaded to R loaded) of the trap in the particular application it is used in.

Loss peaks at resoance, and in the WORSE traps I measured (coaxial traps) loss contribution by having two traps at resonance was only about 1dB or less.

My website article, which was part of my talk at the Dayton Antenna forum a few years ago, has enough detail. I'd suggest you read it.

&quot;Understandably the dimensions are not as forgiving and must be calculated exact due to the out of band traps, so for the average Ham probably would purchase it, but that is the trend with the lack of technical expertise.&quot;

Come on now Orv. You can manage. I don't see why you think other people are less competent than you! It isn't that difficult to tune a dipole by cutting the length! Unlike you, I think most hams are smart enough to do that!

It might be something you don't want to believe Orv, but traps are really not that lossy. They actually have LESS loss than many systems people are using to avoid traps!!!!

Most of this is probably because manufacturers have brainwashed people through misleading advertisements.

Show me the data Orv, not wild guesses or rumors.

73 Tom

[K6UEY]

TOM W8JI,
Tom I thank you for your input, although I respectfully do not agree with all your statements. I do not have data on the commercial trap, my lack of education must have limited my ability to express my self. I had never heard of the commercial version of the trap dipole that uses out of band resonances, and the only information I have is what has been written up in the journals. As to the Ham version I discounted them many many years ago when they proved to have more loss than other configurations and for my applications were unacceptable, quite possible at your location they will suffice.
Thank you for the mention of your web site although you did not provide a link, I think I might be smart enough to locate the site.
As to encourageing new people to open the book and learn, yes I do frequently encourage them to at least learn the fundementals by opening the book, and not rely on some one else doing the leg work and hand them the answer,as seems to be the new accepted norm. If you have views to the contrary on that I would also be interested in your view points .
I have no idea of your back ground, but you do strike me as more than the typical uninformed Ham of todays norm. So I would suggest the key word is &quot;EQUIVALENT&quot; series or paralell resistance. In working with RF circuits the actual resistance does not change with frequency or phase,the effects of the resistance places can change due to phase and frequency, thats why they call it Equivalent S/P resistance.
As to the cutting of dipoles yes Tom in the last 50 years I have at least learned to cut a dipole to length ,I haven't given any seminars concerning the subject but I think with a little practice I can get a handle on it.
However I think you should review the construction of the commercial out of band resonance traps, the theory more paralells on loading a dipole than a trap and the sections to resonate on the upper frequencies have to be cut pretty precise,to provide the correct reactance to provide the 180 degrees of the dipole, not the task for a neophyte.
As to being influenced by the ad's and BS the antenna manufacture's put out, I don't really think that could apply to me, I have been designing and building my own antennas for several decades now and am not readily influenced by modern marketing techniques, those are directed more at the crowd who won't open the books. I will locate your web site and may post a further comment..... # #73, # ORV
Post Script:
Tom your web site is not listed in the data base,it will have to wait until I have more time to search through all the web sites. # # 73, # ORV
http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
PS 2:
Tom located your site finally,looks like a lot to cover ,will get back to you....73, ORV

[K9STH]

OK, children, enough of this. Things are starting to get personal and that is not allowed on QRZ.com.

Glen, K9STH
One of the QRZ.com moderators

[KC7ATO]

Does anyone know when &quot;Dipole Trapping&quot; season opens? http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

[wb6bcn]

Tracy, WB6TMY:
No hatchets or knife throwing here. Just observations and comments of one item we have in common.

Looked at some of of the material on two of your info sites:

Prior to a unit with about 36 TO-3 transistors in the final deck, and some unusual problems related to strong counter emf, I spent about 5 years keeping a RCA BTM-1A alive. The FM side had a Gates FM3H.

Of course there were Gates 24 cart carousels, Gates single cart machines, and a half dozen Scully ½ inch &quot;hernia makers&quot; and an assortment of ¼ inch reel to reels.

The jargon used by the jocks was &quot;Spec Tape&quot; rather than &quot;Audition Tapes&quot;.

I never cut a spec tape, because I was content to stay here and raise my family. The only on air I did other than random, but properly logged transmitter checks during the time the station was off the air, was weekend sign on from 5 AM to 8 AM.

Got my Novice in 1968, and my second phone in 1971 and the first phone in 1972.

It was really interesting when the station got 24 hour status. I had to make four 833's happy with only 10 watts output.

I think if/when I retire I may want to get back into weekend announcing and/or engineering. It has been a long time since the last proof of performance (over 20 years), But I am sure I can do it again once I become familiar with the new equipment.

[WB6TMY]

http://www.qrz.com/iB_html/non-cgi/emoticons/wow.gif4--></span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (wb6bcn @ Oct. 20 2003,19http://www.qrz.com/iB_html/non-cgi/emoticons/wow.gif4)</td></tr><tr><td id="QUOTE">The jargon used by the jocks was &quot;Spec Tape&quot; #rather than &quot;Audition Tapes&quot;. #

I never cut a spec tape, #because I was content to stay here and raise my family.

I think if/when I retire I may want to get back into weekend announcing and/or engineering.[/QUOTE]<span id='postcolor'>
Dear Doug,

Thanks for the nice posting, it's always fun to meet someone with whom you have someting in common. #As with you, I'm just working to earn a living, &amp; trying to save enough to retire.

I would like to announce again someday, nothing grand, just a little station somewhere via voice track. #My kind of presentation is pretty dated these days and I'm not getting any younger. #I'm hoping I can make it happen before I retire, just an hour a day or something like that in my spare time, then &quot;zip&quot; down the internet to wherever it's going. #I'd also be glad to cut commercials or &quot;whatever,&quot; I'm not fussy. #But definitely, I can't afford to give up my day job for a hobby.

May God Bless You,

[W8JI]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (K9STH @ Oct. 20 2003,16:09)</td></tr><tr><td id="QUOTE">OK, children, enough of this. #Things are starting to get personal and that is not allowed on QRZ.com.

Glen, K9STH
One of the QRZ.com moderators[/QUOTE]<span id='postcolor'>
Being called a child by a moderator who says name calling is forbidden really confuses me!

Is he really a moderator, or was that just a troll?

73 Tom

[K9STH]

JI:

Calling someone a child when they are acting like it is not &quot;name calling&quot; in the sense where the &quot;names&quot; that people call each other on these Internet sites that gets pretty profane or obscene.

If you are acting like a child then I will call you a child! If the shoe fits, wear it!

However, I was attempting a bit of humor in the warning! If you want me to get more specific I can certainly accomodate you! The &quot;regular&quot; users of this site know when I am getting a &quot;bit&quot; upset with the posts. If you have been acting like a &quot;child&quot; then take heed to the warning. If you haven't been acting like a &quot;child&quot;, then the warning was not intended for you. If you are offended, then I must believe that you were at least contemplating adding to the furror!

Glen, K9STH
One of the QRZ.com moderators

hmmmmm Imagine that............

http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif I use a two band dipole that is 82 feet long and works 40/80 meters. Its made by Alpha Delta and has an inductor in each leg, no traps.It covers the entire 40m band (less than #2:1 swr)and a nice slice of the 80m band. Its a strong heavy wire dipole that should last a long time. This is an old design dating back to the 20's but it works quite well.I had a trapped dipole some years back but the sun ate up the traps and it fell down.
W5wlb

[W6JWB]

Gentlemen:

For those who may still be a bit confused about how traps behave above and below their resonant frequencies, I would suggest looking up the 5-band trap dipole design, with one trap on each side, that has been shown in the ARRL Handbook and the ARRL Antenna Handbook for at least the past 50 years. The text explains how the traps behave as capacitors below their resonant frequency and as inductors above, allowing the antenna to work on 80, 40, 20, 15 &amp; 10 with only one trap on each side. In 1977, I bought the traps for one of these, and cut the wire to size, and it has worked very well. Perhaps it is not as good as a single-band dipole, but it is very convenient, and the loss is not bad. Don't forget that height above terrain, coax losses, and ground conductivity also affect the radiated signal strength. The way to a good signal is to improve the weakest link in your antenna system, and then improve the next weakest link, until you have a great system. Experiment with your antennas, and you will learn a lot about them! That is what ham radio is for!

de John, W6JWB

[WB6TMY]

Well, it has been awhile...

I really owe it to all of you to give the final chapter.

The Unadilla, of which I was so enamored has turned out to dissapoint me. #Since my last posting I have lost the 80, 40, and 30 meter traps. #Not only that my HyGain 77DX lost its 40 meter trap. #I've never had so much bad luck with traps.

My new vertical is a Butternut HF2V which has no traps and uses thick heavy inductors with doorknob capacitors. #I have built new 80 meter traps with doorknob capacitors and am still fooling around building a pair of 40 meter traps. #You can see what I've built at http://www.radions.net/traps/ #They certainly aren't cheap, but I'm hoping they will last.

Very 73,

Tracy WB6TMY

[WB2RJR]

Tracy,
Thanks for the update. I wonder how much power were you running when the traps blew?

My Unadilla 40 meter traps still are working fine but last winter when I was moving to a new wellsite, and it was 28 below, my antenna wire got caught in some sage and I really pulled hard and one of my traps came apart. I did RTV it back together, and rewound the wire for the coil and it still works OK. Not bad since I bought these back in the 70's I think. This is my portable antenna for 80-10 (a single trap as described in the ARRL handbook for years) and I usually only run 100 watts into it, although sometimes I do use my SB200. I am really curious if your traps failed running 100 watts or higher power.

Merry Christmas.......and I don't think you'll see your new traps with doorknobs and separate coils blow.

73, Marty WB2RJR

[k5jyd]

As Lew McCoy said I try to avoid traps if I can so I use a 88 foot wire loaded with a coil in each leg, works two bands (40 &80) no capacitor to worry about and no tuner needed .The bandwidth on 80 is of course limited. With a tuner I get all bands. w5wlb

[WB6TMY]

Well Fellows,

It's May 6th, 2005 and I have another update. Now my 10 - 15 - 20 meter traps are all dead too. That makes it 100%!! Just shows what a fool I was.

I will say it gets plenty hot in the summer in Santa Rosa and everything wears out in the sun. I lost my roof after 20 years, and I need a new roof on my Miata after only 10 years, so perhaps I'm being harsh.

The pretty blue plastic shrinks in the sun and at some point it becomes too short to complete the circumfrence around the coaxial capacitor. A deep crack appears, it looks like a "V" and it goes right down to the cap. On all my traps the V faces directly upward and of course the rain goes right in and finishes it off.

The biggest traps go first, the 10 meter ones were the last. Being a lazy guy and also knowing it was useless, I just stuck an allegator clip lead around the 80's and then tacked a few feet on the ends. When the 40's went I did the same and tacked a few more feet on the ends. So it has gone. As to how much power, only 100 watts is all I have, but the interesting thing is I can be running on 40 meters and lose the 20 meter traps. That's because there is water sitting in the coaxial capacitors.

I just finished making a pair of W3DZZ 40 meter traps today and I'm hoping to get a new dipole up and running this weekend if I have time and it doesn't rain.

God Bless you all!

TR WB6TMY

[wa9cwx]

Interesting thread.
I have nowhere NEAR the knowlege or experience #displayed here. But I have read, re-read and re-re read the ARRL books, and many #others over the years. Even called and talked to authors with questions, read Sterbas stuff, Bill Orr, etc. and it is STILL voodoo to me!
For years I just tried to get a resonant wire in the air for the band(s) I was on. Then one day I was re-reading Lew McCoys Antenna book ('McCoy on Antennas', I think) and he said something about open wire line ( I had NEVER even considered it) and as much wire up as high as you can go. So I put up a 400' piece of wire (put up a Rohn 25 at 92' just for it!) fed it with 450 ohm ladder line and WALLA!!! It works SLIGHTLY better on a few bands than my 40/80 single coax fed dipole at 55' on the side of my regular tower. It does do about as well, maybe a LITTLE better, than my long wire (120' at 30' off the ground) on 160.
I have a feeling that on the LOWER frequencies, most of us are just dribbling in goo.
What I mean is that MOST of our antennas just are not that great below 10 megs. A counterpois is needed for unbalance antennas, resonance is needed with LOOONG runs of coax, but overall, once the BASICS are taken care of...MOST of us just do not have the resources, realestate, money or neighborhood approval to put up antennas that make a HUGE difference.
It is good to make the best, and for those that get it, to understand the science, but to fight over traps vs loading vs top hats...seems like a joke compared to curtains, phased 5/8th wave verticals, and loops the size of a small farm on multiple towers!
Meanwhile, I LIKE my dipoles, AND.. over the years I have learned to use BIG wire and tough insulators, spings, #and something I call a wire 'fuse' to prevent serious damage to supports, etc. And I agree, you should LIKE your antenna, WHATEVER it is!
All our stuff works, some works a little better, but nothing MOST of us will ever do will shake the ether like the commercial or the old military antennas on these lower HF freqs.

Just a thought...
Frank

[kb2vxa]

Hi Dan and readers,

Unless you live south of the equator you have plenty of time before the snow flies. (;->)

"I am planning on using a vacuum relay at the top of the tower to switch the two different lengths of wire for the 80/160 inverted L horizontal section."

WHY? It would be much easier to use one wire and an ATU at the feedpoint. A 1/4 wave for 160 is a half wave on 80 so the only difference is current feed vs. voltage feed respectively. Series L and paralell C on the antenna side works wonders, short out the coil and open the variable cap all the way for 160 and then by changing the tap on the inductor you can tune everything up to 10M.