Hello,
Between the following, what do you guys think would work best:
1. A 10 to 11ft whip with UNUN at the base, using a tuner.
2. An 8-9 ft whip with an adjustable coil 2ft from the botton. No tuner.
Both antennas would use a counterpoise.
Opinions? Thanks.
Gil
Hi Gil,
This might not be the choices you provided but it is close. I can honestly say this Antenna is incredible, I have used it to my jeep when stationary. They up the antenna and made contact with a station in Austria from Virginia using a yaesu ft-857. I have also attached the antenna to a picnic table and made contacts on 5watts using the yaesu ft-817. This antenna is very easy to deal with and packs up in seconds. Right now through MFJ the antenna is $99
MFJ-2286
PORTABLE, VERTICAL ,MFJ BIG STICK ANTENNA ,7-55MHZ, 1KW, W/17FT STAINLESS STEEL WHIP
WITH COIL TUNER.
Thanks Terry. I knew about the 17ft whip but not this whole kit with the coil..
Gil
I home-brewed something similar to the MFJ-2286. I made my own coil and put it between 5' of aluminum tent poles and an MFJ 8' telescoping whip. I only use 2 radial wires. It will tune 40-10 with no tuner needed if I adjust the length of the radials along with where I tap the coil with the clip lead. MFJ's manual for the 2289 says just lay down four 12' radials and moving the coil tap will get you SWR < 2:1. I find that hard to swallow.
During last year's QRP Skeeter Hunt I set it up along with my 63' EFHW 40/20 antenna which was up high enough to be a sloper. The EFHW did noticeably better than the vertical, but that makes sense since it is 63' long instead of 14' long and is way up high. The end fed is the orange wire on the left.
Still, the vertical is real handy for when there's no trees. And it collapses down to about 2' long and weighs about 1.5 pounds.
If I had it to do over again, I wouldn't. I probably have 10hrs total into making it. There were more pieces to make than you would think, and I probably have $35 invested in it. For $100 you get one that's longer (17' vs 14') and it's plug and play.
(http://i120.photobucket.com/albums/o170/cockpitbob/IMG_20150809_144149020_HDR_zpspvgvt6r2.jpg)
Here is an update...
I would buy a Chameleon Hybrid Micro and whip for my sumer camping trip, but I doubt I will have the money before I leave. Too bad, I would have liked to review it... Chameleon, pretty please? ;)
So, I need a self standing portable end-fed antenna... Options are the MFJ 17ft. telescopic whip or as Ray suggested, a fiberglass pole. The question is, as always, how to feed it? My tuners are mostly made for longer wires, 9:1 transformers. If I want to use a shorter wire, then a different solution is needed.
Enters the Ruthroff 4:1 UNUN. All credits go to G8JNJ:
http://www.g8jnj.net/cometcha250b.htm (http://www.g8jnj.net/cometcha250b.htm)
See PDF attached as well, end of the article.
I still have a couple FT-140-61 toroids... I am having a hard time finding a 3/8-24 antenna base that won't cost me a fortune in shipping.. I'd need a small one to screw on a Hammond watertight cast aluminum case. The 4:1 Ruthroff UNUN works with wires shorter than 1/4 wavelength and is very easy to make.
Gil.
Martin, G8JNJ suggested that I try 12 bifilar turns on the FT-140-61 for a 4:1 Ruthroff UNUN.
Gil.
Quote from: gil on July 10, 2016, 02:21:51 PM
Martin, G8JNJ suggested that I try 12 bifilar turns on the FT-140-61 for a 4:1 Ruthroff UNUN.
Gil.
For fun I ran the numbers on that. It looks good down to 1.8MHz at 100W. Nice UNUN. It should be good for several hundred watts over a broad frequency range. What frequency range does G8JNJ say it is good for?
QuoteWhat frequency range does G8JNJ say it is good for?
He did not say but I did specify I was going to use it from 40 to 15m. He has a few articles online, check him out... I asked him if I should use the T130-2 or FT-140-61. He said both would work but he would prefer the 61 material.
Unlike the EARCHI 9:1, the Ruthroff 4:1 has to be used with wires shorter than 1/4 wave.
Gil.
New development... I will be reviewing the Chameleon MPAS portable antenna system! It includes the CHA Micro UNUN and the MIL whip. Not sure if the extension will be included. Packet is in the mail, stay tuned...
I will still make the Ruthroff UNUN. I saw a great idea in a video about sticking copper tape inside the elements of a telescopic fiberglass pole. This avoids having to use a wire. It can be used with either a half wave tuner, depending on the length of the pole, like on 20m for a 10m pole, the EARCHI UNUN for multi band use, or the Ruthroff UNUN for shorter poles or 80m.
Gil
After 10 years of testing & reviewing backpacking and hiking gear, I'd love to get a chance to review the Chameleon system. Nice gig Gil. Have fun!
QuoteNice gig Gil. Have fun!
Thanks, I plan a hike in the Pyrenee mountains on the French-Spanish border. It is a section of the GR10 trail starting from Lourdes going East. Those mountains, from what I have seen on videos about the GR10 have few trees, so a self standing antenna is a must. My budget is quite insufficient, but hell, I've done worse than starting a trip with no money ::)
I will be taking my KX2 and Weber MTR as a backup or for when batteries are low. I wish I could review the KX2 with more options like the ATU, microphone and battery/charger. Wayne, pretty please? Those reviews will be great for the Radio Preppers YouTube channel I want to start. I also need a lighter key than my Kent and a solar panel. Leaning towards the CHEOTECH 19W. I will make a video of all the gear I'll take with me.
Gil.
Quote from: gil on June 29, 2016, 07:56:41 AM
Hello,
Between the following, what do you guys think would work best:
1. A 10 to 11ft whip with UNUN at the base, using a tuner.
2. An 8-9 ft whip with an adjustable coil 2ft from the botton. No tuner.
Both antennas would use a counterpoise.
Opinions? Thanks.
Gil
Without a doubt, the one that uses no tuner and adjust to resonance. With the unun/tuner combo there will be much more loss in most cases ! Then there is feedline loss if the swr is high on the coax due to the tuner being inline near the radio end. With the resonant antenna, feedline losses are nil.
Thanks Lamewolf, I thought as much after thinking about it a bit more..
Gil
Lamewolf's comments on losses are true. However, given that one S-unit is a 4:1 power change, even if your losses are crazy and you are loosing 75% of your power in losses, that's only 1 S-unit. To me, operational convenience becomes a big issue. Adjust a coil to resonance or adjust a tuner, or have an auto-tuner and push a button? Those options may be a big deal to you. Personally, I like resonant antennas and having the fewest pieces in my set-up. In other words, I don't like tuners. However, it's really nice to have a tuner that can make that antenna your bitch and force a tune on any band you want to work. Apples and oranges, but it's all good fruit.
Quote from: cockpitbob on July 10, 2016, 07:39:36 PM
Quote from: gil on July 10, 2016, 02:21:51 PM
Martin, G8JNJ suggested that I try 12 bifilar turns on the FT-140-61 for a 4:1 Ruthroff UNUN.
Gil.
For fun I ran the numbers on that. It looks good down to 1.8MHz at 100W. Nice UNUN. It should be good for several hundred watts over a broad frequency range. What frequency range does G8JNJ say it is good for?
Should be good 160 thru 6 meters and possible work on 2 meters also. If you have an analyzer, hang a 200 ohm non inductive resistor on it and sweep it, should be flat on the bands I mentioned.
Quote from: gil on July 29, 2016, 03:17:47 PM
Thanks Lamewolf, I thought as much after thinking about it a bit more..
Gil
No problem Gil ! But I should add that one would have to make A to B comparisons to be sure just how much better it would work and it may not be all that much better. But when using QRP power levels like a lot of us do, its best to get as much power into the air as possible - in other words, eliminate as much loss as possible !
Quote from: gil on July 11, 2016, 04:53:00 AM
QuoteWhat frequency range does G8JNJ say it is good for?
Unlike the EARCHI 9:1, the Ruthroff 4:1 has to be used with wires shorter than 1/4 wave.
Gil.
Why would the Ruthroff be limited to wires shorter than 1/4 wave ? I've never seen that before, but as long as the impedance of the wire is greater than 200 ohms or so that it doesn't drop it too far below 50 ohms on the radio side it would work just fine. If it drops it to far below 50 ohms, it looks like a short to the radio or tuner making it harder to match and increases the losses. A wire that is shorter than a quarter wave is going to be below 50 ohms to begin with and will have a lot of capacitive reactance needing canceled to bring it back up near 50 ohms. Anyway, the Ruthroff 4:1 unun is one of the ones I have experimented with on numerous occasions with various lengths of wire up to and including 125 feet and in fact is what I had on my 88' sloper until I made the 9:1 unun the other day and replaced it. But it worked just fine with various lengths some of which were over 1/2 wave !
QuoteWhy would the Ruthroff be limited to wires shorter than 1/4 wave?
I don't know... That would be a question for G8JNJ who as far as I know is not a member here.. See reference in previous posts..
Gil.
Quote from: gil on August 02, 2016, 01:56:22 PM
QuoteWhy would the Ruthroff be limited to wires shorter than 1/4 wave?
I don't know... That would be a question for G8JNJ who as far as I know is not a member here.. See reference in previous posts..
Gil.
Been looking for info on that but did not find it. But the best situation for a 4:1 Ruthroff would be to connect it to a wire that shows around 200 ohms at resonance and the 4:1 ratio transforms this to 50 ohms. If the wire is 200 ohms at resonance, I guarantee it will be longer than 1/4 wave ! It would probably be more like 3/8 wave. In fact, I have had good luck with a 4:1 Ruthroff feeding a 100' wire which is about 3/8 wave at 3.5Mhz and about 1.5 wave @ 7mhz.
Interesting.. I would like to know more about end fed wires impedance.. I would guess longer equals more impedance...
Gil
Quote from: gil on August 02, 2016, 05:34:25 PM
Interesting.. I would like to know more about end fed wires impedance.. I would guess longer equals more impedance...
Gil
I'm just giving an educated guess here.
The impedance of an end-fed is mainly determined, not by overall length, but by how close to 1/4 or /12 wave long it is, ignoring multiples of 1/2 wave. If it's a multiple of 1/2 wave (0.5 or 1.0 or 1.5, etc) it's impedance will be very high (2.5K - 5K Ohms). At 1/4 wave long, with a ground plane or 1/4 wave counterpoise(a dipole, really) it's around 50 - 70Ohms. In between those lengths the impedance will vary. If you could stretch a wire from 1/4 wave to 5 waves long, its impedance would cycle between low and high every 1/2 wavelength of stretch. Another example is my 63' long EFHW antenna. It's impedance is ~2.5K at 7MHz, 14MHz and 21MHz even though at 7MHz it's 1/2 wave long and 1.5waves long at 21MHz.
For the 9:1 unun antennas, we keep seeing these magic tables of wire length. All of the suggested lengths are NOT some multiple of 1/2 or 1/4 wave at any of the frequencies they say it will operate on. The lengths must be threading the needle between 1/4 and 1/2 wave for all the frequencies they claim it will work with.
Right. I was thinking of the resistive component increasing with wire length also.. An off-center fed dipole is 200 to 400, a dipole about 73. We are talking about end fed wires though.. Maybe a 1/4 wave end fed is about 200 Ohms...
Gil
Quote from: gil on August 02, 2016, 07:00:58 PM
Right. I was thinking of the resistive component increasing with wire length also.. An off-center fed dipole is 200 to 400, a dipole about 73. We are talking about end fed wires though.. Maybe a 1/4 wave end fed is about 200 Ohms...
Gil
No, a quarter wave at resonance is on the order of about 35-75 ohms. To reach 200 ohms, you got to look out to about 3/8 wave which is more than a quarter wave. In a couple of posts back you mentioned that you thought that the longer the wire, the higher the impedance is and that is true to a point. But take the quarter wave for example which will be around 35 - 75 ohms depending on surroundings, ground losses, height above ground etc and then stretch it out to 1/2 wave and the impedance increase to 2.5K to 5K ohms, but add another quarter wave to that which makes it 3/4 wave (odd multiple of a 1/4 wave) and the impedance drops back to around 35-75 ohms. Impedance somewhat repeats at odd multiples of 1/8, 1/4, & 1/2 wave ! So just making it longer doesn't mean the impedance is always higher.
kc8aon
A quarter wave with radials yes, but by itself?
Quote from: gil on August 03, 2016, 07:40:09 AM
A quarter wave with radials yes, but by itself?
Still going to be a low impedance if its a quarter wave. Even if you don't attach a physical counterpoise or ground, you got to take into consideration that a quarter wave is a "current fed" antenna and that current must flow somewhere - be it on the coax shield, equipment cases, or capacitively through you while in contact with the equipment and other nearby structures. But one should never use a quarter wave without some sort of ground return. This can be a physical earth ground, tuned counterpoise wire or tuned length of feedline, or even a random length counterpoise. But in the case of a 1/2 wave, the impedance and voltages are higher since it is a "voltage fed" antenna, the importance of the ground is much less and just a simple static ground is sufficient. The current is still there on a 1/2 wave, its just not at the feed point, its out at the center of the wire just like in a normal center fed half wave dipole.
Definitely. It is easy to picture where voltage and current are just by juxtaposing the wave form on the wire, on paper..
Gil
Quote from: gil on August 03, 2016, 08:29:59 AM
Definitely. It is easy to picture where voltage and current are just by juxtaposing the wave form on the wire, on paper..
Gil
Right ! When using a quarter wave without a ground or counterpoise, you have to picture the other half of the wire as the feed line, equipment, nearby structures, and you and that's where the return current is flowing !
And that is why I never felt pin pricks in my fingers using EFHW antennas, but was bit a few times with random wires..
Gil
Quote from: gil on August 03, 2016, 01:19:39 PM
And that is why I never felt pin pricks in my fingers using EFHW antennas, but was bit a few times with random wires..
Gil
Correct, very little to no current at your end on the EFHW, but lots of current possible with a random wire !
kc8aon