The Magic Carpet rides again! This time on 80 meters
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- Опубліковано 1 сер 2024
- This week, Dave, KZ9V, shares with us how he modified his 40 through 10 meter end fed half wave antenna to work as a ¼ wave radiator on 80 meters using the window screen ground.
- - - Links and resources - - -
Extend your end fed half wave antenna into the 80 meter band: • Ask Michael, KB9VBR: H...
Window screen antenna ground network: • Window screen antenna ...
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#Hamradio #AmateurRadio #POTA #ParksOnTheAir #PortableHamRadio #magiccarpet #windowscreen #groundnetwork #80meterband #endfedhalfwave #ehfw - Наука та технологія
Funny, I am the mysterious KF0LTY. Have been licensed since March. I haven’t run 80 much at all. I was at K2529 at Wild River State Park in Minnesota that night and running a Yaesu FT891 with an XTenna at 30 watts. I think that was the first time I had contacts on 80 so that was fun. Thanks so much for the contact! I think I will try that Magic Carpet for 80 soon. I use it with my WRC setup routinely and it works great. 73 de KF0LTY.
Thanks for the contact. It sounds like we were pretty evenly matched. I think Dave was running either 10 or 20 watts that evening.
Fantastic idea
Enjoyed this video. Thanks. 73, M0WHT
Another sweet bonus with this setup is that it's 3rd harmonic has proven to be a good match and a VERY effective performer on the 30-meter ham band.😃
KZ9V
Interesting video. I’ve often done portable operation using a quarter wave sloping wire connected to the feedpoint of my mobile setup in a Toyota Tacoma instead of my usual Hamstick, or more recently a early 1960s vintage Webster Bandspanner 80-10 meter center loaded mobile antenna. The quarter wave wire radiates much better than the mobile whips on 75 and 80 meters, using just the truck body as the counterpoise as in normal mobile operations. I’ll bet you would do really well if you used your RV body as the counterpoise instead of the relatively small (in terms of wavelength on 80 meters)
“Magic Carpet”.
I use a sort of “Magic Carpet” technique to increase the effectiveness of the Tacoma truck body as a counterpoise. The Tacomas and Tundras bed floor and internal lining are a one piece plastic tub instead of the more common steel beds and linings of other trucks. Great concept, one of the reasons I bought a Tacoma, it’s very tough and doesn’t dent or rust. However, for mobile HF operation it leaves
a big open area which would on most other trucks part of the counterpoise of the truck body. I therefore have lined the bed floor with pressed galvanized mesh plaster wall lath material that is bonded to the truck frame, and covered it for cosmetic purposes with diamond plate pattern vinyl mat, also sold at HD. The stamped galvanized mesh is sold in 8 foot by 27 inch panels for about 20 bucks each, and a 4x6 foot indoor/outdoor vinyl mat is about 40 bucks. I imagine the galvanized lath material could also be used as the material for on ground portable Magic Carpets”.
I’d recommend using a much larger “Magic Carpet” than the one I see in your video, I suspect that the reason you have such a wide (400 kHz) 2:1 SWR bandwidth on 80 meters is that such a small counterpoise is very inefficient. A good 80 meter quarter wave vertical radiator against a large and more efficient counterpoise system will have a much narrower low SWR bandwidth. If you want to work across a wide range of frequencies on 80, just add additional length with with quick disconnect jumpers to the end of a quarter wave cut to resonate high in the band.
73 de Chris AJ1G Stonington CT
I love that yall are testing and having a blast and showing us so many geeat ideas...thanks for the time you dedicate and to preserving the info so others can follow along
Good information. I love 80 Meters, we use it a lot here in Texas. I have an end fed 1/2 wave so I will have to see if I can do the same thing.
Genius!…love it Great job again W1FYG
I love using the Magic Carpet with the Shorty Forty and 17.5 ft whip.
Alot of great information that we can use and really enjoyed listening to the stoy of how Dave solved the 80 meter dilemma. Great job, thank you for sharing.
All righty! I have that same setup...I'll give it a try with the magic carpet I'm using with my WRC - looks fun!
Cool! Thanks!
Thank you Dave, I liked this video very much
I like it. I do not have the room for a 1/2 wave wire for 80m nor room for the radials for a 1/4 wave. I could make this work though. Thanks, Dave and Michael! U-rah-rah
Im using a screen with my WRC......it works excellent. I am going to cut 3 bundles of 5 wires that are 2m long for shorter radials though. Hopefully that works too.
I did 12 of those short 2.5m and it worked excellent.. haven't tried adding another 3 because I cut the 12 from the 3-33' wrc sent! Wanted to use what I had
@@k4adz I got some cheap wire on Amazon to not sacrifice the wrc wire. I'm trying to keep them as short as possible....
Hence the 15. Total amount of wire is same though
Great video, Dave and Mike. This shows inguinity! Amazing stuff with the window screen. I noticed you have 2 in a T-shape. Is that because you need more of a radial field for 80m?
Thanks again
For the 80 meter band, and 40 meters to a degree, adding the 2nd screen increased the bandwidth a bit and it helped increase the impedance. With one screen at 80 meters, the impedance (R) was at 29 ohms and adding the 2nd screen increased it to 33 Ohms. The bandwidth increased from 300 KHz to 500 KHz when the 2nd screen was added. SWR at the resonant point was 1.3:1 with a reactance (X) of 0. This information got cut from the video as we did a couple of takes and I used the version where Dave didn't talk about why he was using two screens.
What kind of tape did yall use on the edge of your screen wire?
It's duct tape. Looks like Dave's tape has a camo print.
Could you use faraday cloth instead of aluminum sheeting?
Nice video guys! I’m a big fan of the magic carpet myself for 20M and above (daytime only POTA here) but how high and how “vertical” was the wire? Thanks!
The wire deployed in the video was primarily a sloper configuration. The feedpoint was about 2 feet off the ground, and the far end was aprox. 20 feet in the air. A vertical wire would perform better, but the logistics of deploying a 67-foot vertical wire in the field is impractical.
KZ9V
Kind of what I would have thought so I was just curious. Thanks @@davewhite7679 !
I'm curious if you could use something like this for the 11 meter band, I have a motorhome but it's fiberglass with no good grounding.
It's just for a backup but I'd be interested to know if something like this could work.
This will work for 11 meters. I've used the ground screen successfully on the the 10 meter band, so I see no reason why it wouldn't work on 11 meters.
How do you get the parks numbers
Park information and numbers can be found at www.pota.app
How efficient is this setup vs using the unun and a half wave antenna? I understand the unun absorbs some energy, but the mesh will have a low impedance so won't be as good a match as the unun's 50Ω. Just wondering what's better for making every watt count with qrp.
What we did is disconnect the UNUN from the antenna and attached the wire directly to the center of a piece of coax. The braid of the coax went to the ground screen. This wire then acted like a 1/4 wave radiator on the 80m band. Efficiency should be comparable to a 1/4 radiator. The amount of screening you use will affect the signal strength and adding two or more sheets certainly did improve performance.
Good info but since you are mobile and I assume you move about, why don't you simply run a 130 foot wire and avoid swapping anything? Are there park rules precluding that?
Most campsites have the space for a 65 foot piece of wire for an 40m EFHW, but 130 feet can be challenging to string up without encroaching on your neighbors.
Michael, how many screens are guy using on the ground ? I’m on a small phone. I can’t tell if that’s a 2nd screen or sheet layed out in a T configuration . Thanks Jim, K2WPA
In this deployment, I was using a pair of 36"x80" screens in a "T" configuration. It works okay with just one screen, but on 80-meters I found that adding the 2nd ground screen raises the impedence about 4 ohms, resulting in a better match and presumably lower ground losses.
KZ9V
@@davewhite7679 TYVM Dave , Jim K2WPA
@@davewhite7679 I’m going to have an opportunity to try 80 M later this month at night. I’ll give it a try Thank you sir
More please kc0ysh