This looks like something that was published in QST about 40 years ago. That design was actually a trap as claimed by the manufacturer of this device. The coil is a length of coax which forms both a coil and a capacitor. The capacitance is accomplished by connecting to the shield at one end and the center conductor to the other. I built a couple of these for my club to use at field day, winding rg-58 on PVC tubing. They were okay since we were running in the lower power class. High power would have smoked them. I had a bad experience running high power around PVC when I tried to use PVC as the insulator in a gamma match. The 40M beam worked great for a few minutes. :( Stan K9MFI
Coil shortened DI-poles are usually made for one band, do you suppose they followed a design meant to be a multi-band fan dipole using coils to shortened each leg? Making it into an actual trapped DI-pole is a great idea. I picked up one years ago someone gave up on..
Excellent video, very informative. My QRP trapped DI-pole supposedly covered 40 through 10 meters, with multiple small sealed coils, It came older in design, used and partially disassembled from an E bay seller at a fair price, but it was still well made enough to keep and tinker with. And it had no markings on any part of it to say where it originally came from. Measuring it out with logical 1/4 wave lengths seemed to work, sorting the coils by measurements (compared with what was still assembled in the box).(A few errors were found here). It is close with some slight variation in the individual coils at places. I had often thought of completely redoing it, and adding each of the capacitors required to make it a true trapped DI-pole. They were easy enough to calculate out with an on line calculator, since I had recorded each of the coils inductance value in my calculations. But the original design included no capacitors at all in the coils, so to me, it was not not actually trapped and neither was it shortened.. More likely it was somebodies cheap knock off of a trapped DI-pole from the 60's or 70's. It now works with in the bands I wanted, It is now mounted in my attic. I later dropped the final 40 meter section as there just was no room for it. In HOA's where no visible antennas are allowed, you do what you can. But I still love a good technical jig saw puzzle like it turned out to be putting it together correctly..
Bring back The Fun. Bring back the British Sausage too. I'm not squealing like a pig and my mumma aint coming. A good video, I understood the whole thing and I actually get it. It's good to go over basics again once in a while. Thanks.
The wires inside go through holes at each end of the coil former to terminate the coil. It's not supposed to have capacitors, it's not a "trap dipole" as they claim, it's an inductively loaded short dipole. Something got lost in translation it seems.
Hello I have an equal youkit and like if possible, it indicates to me how I can build a probe to be able to measure my coils, same used in this video, thanks Luis Valadas ct1dte
They label them 7mhz, (40m) but they need to pass at 40 but resonant at 20 Meters, 14 Mhz. A 3.5 Mhz trap, passes 80 Meters but blocks or resonates at 40 meters, 7mhz.
I all ways thought that if you add add a short lenght of wire to it at the far end this acts as capacitor rather like if you had a mobile whip where the coil its self radiates and the whip section is the cap you could do the same job with a capacity hat. ?
Close up it didn't look like anything had been cut out. A bit of research shows it's not a "trap dipole" it's a Diamond W8010, it's actually an inductively loaded short dipole.
ok very good thanks for letting us know my place got smashed by big storm so no hf antennas left ,hope to get them re made soon ill try to say hi on air
My friend wanted to put this antenna into garbage but I save some traps of it. So, it is realy not a trap as could be. Cheap wire coils with some stubs. As amateur I do not undersand such construction, very naroow bandwith and cheap construction. Bad antenna.
This looks like something that was published in QST about 40 years ago. That design was actually a trap as claimed by the manufacturer of this device. The coil is a length of coax which forms both a coil and a capacitor. The capacitance is accomplished by connecting to the shield at one end and the center conductor to the other.
I built a couple of these for my club to use at field day, winding rg-58 on PVC tubing. They were okay since we were running in the lower power class. High power would have smoked them.
I had a bad experience running high power around PVC when I tried to use PVC as the insulator in a gamma match. The 40M beam worked great for a few minutes. :(
Stan K9MFI
Hi, Did you ever check the other traps on the analyser and record the pF capacitors required to have the antenna resonant please?
The coil transmits a nearby frequency and then matches it with the antenna whip again. to shorten the length of the frequency
Coil shortened DI-poles are usually made for one band, do you suppose they followed a design meant to be a multi-band fan dipole using coils to shortened each leg? Making it into an actual trapped DI-pole is a great idea. I picked up one years ago someone gave up on..
Excellent video, very informative. My QRP trapped DI-pole supposedly covered 40 through 10 meters, with multiple small sealed coils, It came older in design, used and partially disassembled from an E bay seller at a fair price, but it was still well made enough to keep and tinker with. And it had no markings on any part of it to say where it originally came from. Measuring it out with logical 1/4 wave lengths seemed to work, sorting the coils by measurements (compared with what was still assembled in the box).(A few errors were found here). It is close with some slight variation in the individual coils at places. I had often thought of completely redoing it, and adding each of the capacitors required to make it a true trapped DI-pole. They were easy enough to calculate out with an on line calculator, since I had recorded each of the coils inductance value in my calculations. But the original design included no capacitors at all in the coils, so to me, it was not not actually trapped and neither was it shortened.. More likely it was somebodies cheap knock off of a trapped DI-pole from the 60's or 70's. It now works with in the bands I wanted, It is now mounted in my attic. I later dropped the final 40 meter section as there just was no room for it. In HOA's where no visible antennas are allowed, you do what you can. But I still love a good technical jig saw puzzle like it turned out to be putting it together correctly..
It is not a trap. Got W-735 from Diamond. And it was not intended to be a trap. It is a inductive loading coil :) 73 de LY3I
Yes it is, thanks. I realized that shortly after playing around with it.
Bring back The Fun.
Bring back the British Sausage too.
I'm not squealing like a pig and my mumma aint coming.
A good video, I understood the whole thing and I actually get it. It's good to go over basics again once in a while. Thanks.
Thanks Ade.
@@vk6cs456 yum yum om
don't worry we are all getting there
hey i have one of these. can we modify them to become more broader? I cannot get 80m below 1.5 and is very narrow
why not
Good question
Hard to believe it came out of the factory like that, I see some wires on the inside, looks like someone have cut all the capacitors out ?
The wires inside go through holes at each end of the coil former to terminate the coil. It's not supposed to have capacitors, it's not a "trap dipole" as they claim, it's an inductively loaded short dipole. Something got lost in translation it seems.
Hello I have an equal youkit and like if possible, it indicates to me how I can build a probe to be able to measure my coils, same used in this video, thanks Luis Valadas ct1dte
They label them 7mhz, (40m) but they need to pass at 40 but resonant at 20 Meters, 14 Mhz.
A 3.5 Mhz trap, passes 80 Meters but blocks or resonates at 40 meters, 7mhz.
Would it be a simple matter to construct the loop attached to the Fg-01? PL259 plus loop of copper wire?
I believe so. I bought this attachment so I don't know for sure.
can you send a link to by one
I bought it from here: www.tetemtron.com.au/product-p/fg-01.htm
I all ways thought that if you add add a short lenght of wire to it at the far end this acts as capacitor rather like if you had a mobile whip where the coil its self radiates and the whip section is the cap you could do the same job with a capacity hat. ?
Lovely
Cheers.
Well that explains it ! Also I'm certain that antenna kit is a Diamond knock off.
Not quite... see edit in box below video.
Agreed; this does not look like a real Diamond product.
It sure did look like some one has cut them out or mabe not quite finished ,vk2pha Nigel.
Close up it didn't look like anything had been cut out. A bit of research shows it's not a "trap dipole" it's a Diamond W8010, it's actually an inductively loaded short dipole.
ok very good thanks for letting us know my place got smashed by big storm so no hf antennas left ,hope to get them re made soon ill try to say hi on air
@@vk6cs456 yep
My friend wanted to put this antenna into garbage but I save some traps of it. So, it is realy not a trap as could be. Cheap wire coils with some stubs. As amateur I do not undersand such construction, very naroow bandwith and cheap construction. Bad antenna.
bellend.