Unboxing the MFJ-2104 Octopus Antenna (

Рет қаралды 23,683

5 жыл бұрын

MFJ sent me their MFJ-2104 Octopus Antenna, a four-band dipole with screw-in elements for 75m (the voice portion of 80m), 40m, 20m, and 10m. This is built on a project in Dec 2007 QST by N1GY. The device uses any pairs of hamsticks on any band from 75 to 2m/440cm to create the four bands. It fits on a 1-inch mast. I'll put it up and test it in a future video.
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Пікірлер: 85

@MrVasile 5 жыл бұрын

Great video Dave. Thanks for giving a shoutout to Geoff Haines N1GY, the inventor of the Octopus Antenna. He is a friend and Elmer of mine here in Florida, and I am very happy to see his great design get the limelight! 73 Tony KB9A

@artdodd815 5 жыл бұрын

Tony Vasile .......Good point Tony. I remember that article. Art. K2ADC

@mrkattm 5 жыл бұрын

I feel oddly connected to this video, I know the inventor Geoff Haines (N1GY) not well but well enough to say hello when I see him, Geoff is The technical Coordinator and an Assistant Section Manager for The West Central Florida Section, he is a very nice guy. Quick story behind this antenna, when MJF first offered the antenna they did not give Geoff any credit as the inventor, he was very hurt as he did not want any money but thought that not being recognized as its inventor was very wrong. Needless to say after a couple of phone calls everything got resolved. Geoff is now very happy and he is still bragging about it during the weekly technical net.

@MoTown44240 5 жыл бұрын

Glad I am no longer restricted to antenna size to lack of real estate. For those that are this is another example of a compromise antenna that might work for the ham lacking enough space to put up several monoband quarter wave antennas. Bandwidth may be small but some bandwidth is better than zero bandwidth.

@roxastherogue 5 жыл бұрын

I really enjoy your videos and the information you give us who are still some what new like me. Keep it up👌

@davemitchell116 5 жыл бұрын

Great video Dave! And here's an alternative to the Octopus: If you have the space for longer antennas, clamp 10 or 12 gauge wire to 3/8" bolts (3" long) and run full-length dipoles instead of the ham sticks. If you cut the wires for 75, 40, 30 and 20, the 40 meter dipole will be odd-harmonic resonant on 15 meters (at 3/2 λ) and 6 meters (at 7/2 λ). The 75 meter dipole will be resonant on 10 meters (at 7/2 λ -- if you don't mind at 2.5:1 SWR). In all, a 7-band antenna. (By the way, MFJ has bumped the price of the hub (MFJ-2100) to $109.95.

@dheller777 5 жыл бұрын

Looks very interesting. Looking forward to your review.

@donsilva4441 5 жыл бұрын

I use single hamstick dipoles for POTA activations and other portable ops, and they work great. Lots of good signal reports using 100 watts ... So the octopus should be just as good. Giving them some height and/or lots of flat ground around them really helps.

@donsilva4441 5 жыл бұрын

Just to perhaps calm some fears...I use hamstick dipoles in a single configuration anyway, and the bandwidth is not narrow like the have pictured. It's hard to believe that it would be very different using the hub. I get 200khz wide under 1.8 on 20 meters, enough for the whole voice portion, and about 100-120 on 40 meters.

@scottmorgan4397 5 жыл бұрын

Great video Dave. I really enjoyed the unboxing. As you stated, this thing looks like a bear to tune. I got to thinking, a good starting point would be to figure out where you want your center frequency, figure the length the dipole needs to be at that frequency, and set the hamsticks to that length. I understand that all the other hamsticks would interfere, but it might be a good place to start. Thanks again for what you are doing for the amateur radio community.

@TheStevenhull 5 жыл бұрын

You can remove the stinger from the 10 meter ones and its perfectly resonant on 6 meters.

@jeromegrzelak8236 5 жыл бұрын

TNX ill try that kg6mn

@yorkshireman6650 5 жыл бұрын

Good video dave like the mfj antenna I have a buddy pole my self they work well but ex’s pensive in the uk looks like mfj are doing well

@BobtheTraveler-WD8NVN 5 жыл бұрын

Great Video ....thanks..

@k2cjbradio 5 жыл бұрын

Looking forward to seeing it up in the air. Thanks Dave! 73 de Chris K2CJB

@bobclarie 5 жыл бұрын

Thanks Dave ! ! ! '73 Bob

@byd3k157 5 жыл бұрын

Glad to see credit going to Jeff N1GY. He contributes a lot to the local ham radio community in the Tampa Bay Area.

@davecasler 5 жыл бұрын

I used to live in Tampa and was a member of the Tampa club back 1977-1980.

@namdogtag 5 жыл бұрын

I have 2 EA of the original Lakeview hamsticks for all bands 6 thru 80....being that I have pre tuned each stick for VSWR individually on my previous one band mount, I guess I'll have to retune them again on the octopus mount....Just a hint: knowing not to push the stinger no more 4" into the stick and not cutting the stinger off too short, I have strong aluminum fence wire to tune the sticks on my analyzer, then after I get a match I, I remove the aluminum wire and cut the stingers to match the length...works perfect!...saves a big problem preventing ruining stingers cut too short.

@davecasler 5 жыл бұрын

Thanks for the tip!

@thevacuumtubejunky9774 5 жыл бұрын

So what I'am understanding is the hub is the central signal distribution to the various lengths of horizontal radials, so whichever frequency the operator chooses, the transmitted frequency will naturally find it's resonate radial into free space???. Thanks for sharing! Kind regards, Eric Dee.

@berkeleygang1834 5 жыл бұрын

Basically, yes. Any dipole is a half wavelength long - 1/4 wavelength each side of the feedpoint. The midpoint has maximum current, and the endpoints have zero current (no where for the electrons to go!). Now double the frequency, say, from 80 meters to 40 meters. The antenna is now a full wavelength long. The ends still have have zero current, but the midpoint of a full sine wave has a null at that feedpoint in the middle. No current can come out of the feedpoint! Thus, the antenna cannot be driven. Double the frequency again, from 40 meters to 20 meters. Now the antenna is two full wavelengths long, and you still have a null at the midpoint, preventing current from entering the antenna. Maybe someone else can describe this better than me, but lets now look at the other way around. Now look at, say, a 20 meter dipole. When you feed it with a 40 meter frequency, the ends can't have zero current anymore, but the current has to go somewhere, so it's reversed back on itself, and cancels out some of the current coming out. It simply doesn't work. I hope this helps. 73!

@thevacuumtubejunky9774 5 жыл бұрын

@@berkeleygang1834 : Yes that makes complete sense. In reference to your last few lines stated in your second paragraph " the current coming back onto itself" would that be where the wavelength to the frequency would incorrect causing a high SWR within the driven element???. Thank you for your reply. Eric Dee

@berkeleygang1834 5 жыл бұрын

@@thevacuumtubejunky9774 I believe so. Energy can't be destroyed. If it isn't dissipated (radiated as RF energy or heat), it's headed back into the shack. I'm an engineer, but not a EE, so take my understanding and response with a grain of salt. Dave (Mr. KE0OG himself) or another EE ought to be able to give a more definitive response, and perhaps a better explanation. :D One thing is for certain - if a 20 Meter dipole would or could work on 40, 80, or 160 meters, there wouldn't be anyone building such antennas.

@thevacuumtubejunky9774 5 жыл бұрын

@@berkeleygang1834 : Thank you for your time. I got this basic understanding down , I appreciate your input. In my thoughts, for myself anyways, antenna theory/ physics and fabrication is 90% of the hobby, so much to learn about the subject it seems infinite, but very fun to learn about, different people with their interpretation is like cash in the bank for me so to speak. Thank you very much and I wish you and your Family a happy Holiday. Kind regards, Eric Dee.

@HamRadioCrashCourse 5 жыл бұрын

It’s like a fan dipole.

@tglenn3121 4 жыл бұрын

In terms of performance, have you ever compared the 2104 to a regular 'wire' dipole? I have a 92' ZS6BKW (centerpoint is at about 30'), so I'm wondering how the 2104 would perform compared to a 'wire' dipole. Any ideas?

@peterlosangelos4108 5 жыл бұрын

For next video: are 80m and 75m general terms, which refer to the same frequency band?

@berkeleygang1834 5 жыл бұрын

The 3.5-4 MHz allocation at 80 meters covers the range from about 85.7 through 75 meters, and 80 meters is the wavelength of the center frequency (3.75 MHz) in the band. Some refer to the top of the band (where voice communication is allowed) as 75 meters, to sort of distinguish it from the CW/data portion of the band (always referred to as 80 meters): 75 Meters : 3.600 MHz-4.000 MHz, phone emissions allowed. 80 Meters: 3.500 MHz- 3.600 MHz CW and RTTY/Data only You can see that the wavelength changes a lot over the band: 10.7 meters. So antenna tuning generally has to reflect the portion of the band you want/need to work. I hope this helps!

@peterlosangelos4108 5 жыл бұрын

@@berkeleygang1834 thanks, clear

@322doug 5 жыл бұрын

Thanks again Mr. Casler, so NO counter poises are needed? im not able to deploy them at my condo. Secondly I also like the looks of the Gap Eagle, any thoughts ANYONE?

@davecasler 5 жыл бұрын

I've never talked with anyone who uses Gap antennas, so can't comment.

@322doug 5 жыл бұрын

my mistake sir, I was asking about the octopus, if it needed counterpoises. I am looking to buy a antenna I can use strapped to the wall of my balcony which is 12 feet off the ground, and I can not run counterpoises on the ground.@@davecasler

@jrreid24 5 жыл бұрын

Any break in the weather yet to tune and test the octo? Blessings! de KM4VHB Jason

@davecasler 5 жыл бұрын

It's going with me to Quartzfest. We leave Saturday.

@tylersutcliffe871 5 жыл бұрын

If you put the sticks at an angle to each other rather than straight across, would you get some gain and a directional antenna similar to a "v-beam"?

@davecasler 5 жыл бұрын

Perhaps, but the true vee beam has legs each more than a wavelength long.

@tylersutcliffe871 5 жыл бұрын

@@davecasler It could be an interesting experiment. I may have to purchase or make one just to try that out. Seems I cannot go wrong with it. Worst case scenario, I end up with a field deployable fan dipole. de KL2SB

@Markinpuff 5 жыл бұрын

What if I wanted to cover say the whole 80 meter band by using all 80 meter sticks tuned on different frequencies?

@davecasler 5 жыл бұрын

Possibly.

@paulshaffer9674 2 жыл бұрын

I have had them for a while. But been unable to get it up in the air. KG7IRJ Ohio Extra.

@jeromegrzelak8236 5 жыл бұрын

You need to use Locktight the antennas will vibe loose kg6mn

@thomashenderson603 4 жыл бұрын

I'm new to ham, I have a FT991A if I got this MFJ-2104 with 2m/440cm, how would I split the signal inside to the radio, with a A/B switch or is there a better way?

@davecasler 4 жыл бұрын

I recommend a separate antenna for 2m/70cm.

@thomashenderson603 4 жыл бұрын

@@davecasler Thank you! I love your videos!

@formeraide529 5 жыл бұрын

Are all the HamSticks the same length? Also what is the length of the dipole?

@joewilson2258 5 жыл бұрын

Not all of the hamsticks are of the same length . As to the dipole the length is determined by the frequency your using it for .

@davidbyrd5065 5 жыл бұрын

Be careful not to push the whip in more than 4 inches as it can damage the loading coil when transmitting. David Byrd KN4BHS

@timg5tm941 5 жыл бұрын

Which he did! lol

@joewilson2258 5 жыл бұрын

I have the book that lists that antenna system by the same name . I am going to try and build one for my field days and POTA when ever I can . 73's from KN4KBH a new tech , Joseph

@davecasler 5 жыл бұрын

Congrats on your new Tech and welcome to ham radio! I recommend upgrading to General before getting HF antennas and equipment.

@uggenstu 5 жыл бұрын

re: MFJ-2104: What mast height do you recommend? Fiberglass or metal mast? Maximum length of feedline?

@davecasler 5 жыл бұрын

Mine is at 20'. You can try various heights, but given its "portable" nature, it's okay to tune it at that height. My mast is metal, and the choice of mast will affect the tuning somewhat. Feedline can be as long as it needs to be, taking into account attenuation.

@uggenstu 5 жыл бұрын

David Casler Thanks David.

@uggenstu 4 жыл бұрын

@@davecasler Thanks (finally) Dave! Got mine up on MFJ 38' HD mast, guyed with 3mm Mastrant line. Works great on 75, 40, 20. 17 has been very dead here. 73!

@johncliff5417 5 жыл бұрын

I have looked through the comments and did not see anyone asking regards will the 40M Sticks also work for 15m band on the 3rd harmonic of that band ?. de G0WXU - John -73

@davecasler 5 жыл бұрын

I doubt it. I'll check the SWR on 15, though, to be sure. We had lots of rain yesterday that's making the snow melt, so I have high hopes of soon being able to do some antenna work.

@VE3IPS 5 жыл бұрын

Dave How does it work? I can unbox a Pizza but it doesn't tell anyone how it tastes

@davecasler 5 жыл бұрын

Testing is set for an upcoming video.

@sgtshultz13 5 жыл бұрын

You might have that thing together by spring

@davecasler 5 жыл бұрын

Certainly when the snow melts!

@firewaterforgeofarizona4304 5 жыл бұрын

Thanks for making this video. 73 de KF7RCM and my wife KF7WWQ.

@jeromegrzelak8236 5 жыл бұрын

U R A lucky couple

@sewren 5 жыл бұрын

Wonder how this compares to their cobweb antenna?

@davecasler 5 жыл бұрын

We'll soon find out.

@davecasler 5 жыл бұрын

@@spadbuoy Not yet, but Cobweb was easy to tune, whereas the Octopus looks like it'll be harder to tune.

@deltahotelxray 5 жыл бұрын

Good video Dave. Just FYI though - Just because someone has subscribed and clicked the bell doesn't mean they will get a notification. I for instance never get a notification about your live stream. It's been going on for a while, youtube likes to do it to gun and conservative channels but I'm not sure there's any rhyme or reason to it. KZfaq just isn't what it used to be.

@davecasler 5 жыл бұрын

Sorry to hear that. Yes, KZfaq is constantly changing and sometimes it's hard for me to keep up.

@jeromegrzelak8236 5 жыл бұрын

We need a 6 band ver kg6mn

@jeromegrzelak8236 5 жыл бұрын

just kidding

@TheRetiredtech 5 жыл бұрын

No innovation involved as there are several diy versions and it had even been in QST

@denelson83 5 жыл бұрын

Did I hear you say "bloody pole"? o_O

@davecasler 5 жыл бұрын

;-)

@jeromegrzelak8236 5 жыл бұрын

Brother do you have a job ahead of you

@jeromegrzelak8236 5 жыл бұрын

Hey put a vhf uhf antenna on top of this thing u now need a mod kit mfj kg6mn hi hi

@Garbanzo884 5 жыл бұрын

When I was looking for a house in 1994, I told the realtor that I had two requirements: 1. NO HOA or covenants and 2. It must be in the country.

@varoujan78 5 жыл бұрын

25 minutes and we still dont know how it performs.

@davecasler 5 жыл бұрын

That's because it's an unboxing video.

@gonebamboo4116 5 жыл бұрын

Desubbing until you return to your subs and turn away from your sponsors. Good luck with that;. Sponsors but fewer subs

@davecasler 5 жыл бұрын

Sorry to have disappointed you. Subscribers, sponsors, reviews, tutorials: all part of a big ecosystem.

@AI4QT 5 жыл бұрын

No offense, I think I'll stay with throwing a wire or two over a tree.

@_iLLuSiv3_ 4 жыл бұрын

The one thing I have learnt in the past about MFJ antennas, is to not buy them. Either make one or put your money into a better product. I bought one many years ago, the quality was poor, the workmanship was disgusting. After weeks of working with it I gave up, it was impossible to tune on certain bands for many reasons. Some of the loading coils they attempted to solder without removing the varnish coating on the wire, good move MFJ, I see you test all of your parts before shipping! The aluminum bridges I will call them, still had the plastic on the back of the aluminum pieces, not where you could see them, but behind the screws to affix them, nice insulators. Since then, I have decided I would never buy another MFJ antenna again.. We all know what MFJ stands for.. More F^%*%^g Junk. Sorry for the rant, just know what you're wasting your money on first, avoid MFJ like a $5 hooker, unless you really want something you was not expecting.

@varoujan78 5 жыл бұрын

To much time wasted in simple fundamental assembly details. that any ham even a beginner understands , lets get to the testing. HOW DOES IT PERFORM? thing

@davecasler 5 жыл бұрын

I've still got a foot of snow on the ground. The testing I hoped to accomplish at Quartzfest didn't happen. The antenna takes quite a bit of setup, which the snow makes impractical. Sorry.