| W1DB |
Rating:  |
2008-08-23 | |
| Gem Quad, rev 2.0 |
Time Owned: more than 12 months. |
I finally retired my 20 year old Gem. The spreaders were weather beaten and sun bleached and the fiber was rough and exposed since the surface resin had been worn away. It can be re-coated, no doubt. In it's place, I installed a brand new quad, purchased just prior to the demise of the company. I wired it for 5 bands and used the dimensions as listed on EI7BA's web site. The original quad used tywraps to hold the stress relief spaghetti tubing and I secured the tubing with copper wire, twisted around half a dozen times.
For the feed, I experimented with a 5 relay switch box with individual loop excitation, but after a short in the CAT-5 switch wire, I pulled the entire mess and did a simple center feed with balanced ladder line. I could not detect any difference in performance. It works just as well!
Hope it lasts another 20 years!
Dave
One of the best features of a quad that is seldom mentioned is the low angle of radiation achieved with just modest height. Mine is now at 50 ft.
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Earlier 5-star review posted by W1DB on 2003-11-30
My Gem quad has been up and in service for 14 years now. It has survived NH ice storms, hurricanes, heavy snow and wind, and is still up at 65 ft. Originally I fed it with the normal RG-8 and used the toroid balun supplied. However, I like balanced transmission line, own several Johnson Matchboxes, and about 10 years ago switched over to balanced line fed directly to the center tie-point.
I scored about half a dozen rolls of RDW (rural distribution wire) used by Verizon as the telephone drop from the pole to the house. They were in our local recycle center (it is not PC to call it a “dump”) and this wire is amazingly strong. The conductors are copper coated steel, with a smooth polyethylene outer jacket. I applied a micrometer to get exact conductor diameter and center line separation and ran the formula for characteristic impedance….it worked out to about 65 ohms. So this is my transmission line, fed with a Matchbox.
In order to tune the F/B, I got my buddy who lives about 15 miles away to give me a low wattage carrier on each of the 3 bands. We conversed via the local repeater, and I lugged my old Kenwood R-1000 SW receiver up the tower, pulling a 100 ft extension cord along. This rx has a nicely visible S-meter. With the quad pointing away from the source, I used a jumper wire with a couple of alligator clips to slide up and down the Gem tune loop while watching the S-meter. I was tuning for a minimum signal level. I got a subtle dip but nothing too exciting. In all cases, it was close to the top of the loop, which leads me to think I could have left them out.
The tie-wraps degraded after about 5 years of sunshine, and had to be replaced with copper wire holding the plastic sleeveing in place.
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| G4DYO |
Rating: |
2007-09-27 | |
| Phenomenal |
Time Owned: more than 12 months. |
I had a Gem Quad on my 60ft tower for many years and it was respeonsible for me being the first G4+3 to reach #1 slot HR. (Sadly, I was QRT for some years so now well down the list).
From square one I was not keen on the feed method so I devised my own, feeding each band with a simple co-ax gamma match to a remote switch box on the tower. I later added 10 and 17m and experimented with loops for various VHF bands, all switched by the remote switch and so easy to instal on the Gem Quad. The antenna was amazing and I could hold my own against any yagi.
After the antenna had been up many years the gamma matches deteriorated and, as they were a pain to renew, I gave them up. I then fed each loop with a quarter-wave matching section of 75ohm coax to the remote switch, then 50ohm (as always) back to the shack. It made not a scrap of difference to the performance - still busted pile-ups with ease. I've never used an ATU or matchbox - my religion forbids their use!! All my antennas are tuned at the antenna.
The recent 3B7C DXpedition brought home to me how good the Quad was. Nowadays I have nested inverted Vee wires hanging from the tower. Whereas with the Quad I'd be in there after a couple of calls, I now have to take my turn, sometimes for days!!
If I ever get my life over, I'll definitely put up another Gem Quad, the best antenna there is. |
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| SP1EK |
Rating: |
2003-06-25 | |
| 5 |
Time Owned: more than 12 months. |
| Hi all, I suppose that I have GEM Quad because I bought it in Poland from SP3GEM who is mading this Quad.Looks the same.I used it in IOTA Contest 2002 and I have to tell that is great aerial.Great Gain and F/B.I know a lot of HAM`s from Poland who use it and I`ve never heard any wrong word about it.This aerial is very popular in SP.If you need more information please write to me sp1ek@wp.pl and I try to tell you more about this aerial. |
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| W7UIV |
Rating: |
2002-07-02 | |
| Success! |
Time Owned: 0 to 3 months. |
My search has ended for an antenna that will work well at relatively low level and fit into the surrounding trees of my backyard in a (formerly) antenna restricted area. Even though the restriction is gone I still don't want to upset anyone. The spreaders are painted with military spec green camouflage, which is a "real" green, not the regular store spray paint green that looks like some kind of weird blue next to natural foliage.
For a little contrast about how I am making my evaluation; The antennas tested at low level (more or less 30 feet) over the past three years were; GAP Challenger, 20 meter double bazooka, 20 meter halfsquare, WindomHSQ and TMG miniquad. Having normally three of them up to do A-B-C testing, I arrived at the halfsquare and TMG as most effective of the lot on 20 meters. The TMG miniquad is significantly the most quiet of all so far as local noise pickup, but receive signal level between it and the halfsquare seems largely a matter of conditions. Directivity on signals of the TMG at only 31 feet is marginal, even though tests with a field strength meter show significant directivity. If it's anything like my big old tribanders were, it needs to be up at least 35 feet or more to start working right on propagated signals. But due to it's low noise pickup I could sit back and easily copy signals that were difficult to copy in the local noise pickup of the halfsquare, so at that point in testing I had come to the conclusion of receiving on the TMG and transmitting on the halfsquare, because I could hear better on the TMG miniquad but the halfsquare got the better signal reports.
My initial testing of the GEM two element quad at 18 feet shows this antenna to be a whole different animal. There is no "borderline" difference between it and the halfsquare, as there was between the halfsquare and others. Yes, it is true! I've found some signals (of S 1-2) I can copy on the quad that I can't even hear on the halfsquare. I know my halfsquare is working as well, and generally better on Europe than the other antennas. (the differences between them can sometimes be borderline, even though there will be a big difference on a particular signal or signals at a given time. Under various conditions one may work better than another, and this will change from night to night or even hour to hour, but over time the halfsquare became my standard of measure.)
Unlike these results between the halfsquare and other antennas, the GEM is always better than the halfsquare on any signal. Of course it should be, since it's a full sized antenna. However it is also only 18 feet off the ground! Yagi tribanders I've had simply ceased to function very well when cranked down below about 30 feet. Directivity goes to heck along with FB and FS ratios. But the quad is strong in all these areas even down where it's currently setting. (Sure I can crank it up to 48 feet with the AB577 mast, but an effective low antenna is what I was after.)
Assembly and mounting of the GEM quad wasn't as tough as I'd visualized it was going to be. In fact I mulled this thing over in my mind for a year, as can be seen if one goes to the beginning of this thread. Although one very helpful thing is the fact I can crank the AB577 down (to as low as eight feet) to reach the rotor on a step ladder for mounting. At this point the spreaders are touching the ground, and the feed point and the stub adjustments are convenient while standing at ground level. The 22 pound antenna was easy to handle, even for this 60 + year old overweight and out of shape office chair guy. The difficulty of handling a three dimensional quad is one of the things that scares off some people. Surely other hams can come up with a way to overcome any difficulties, if one is convinced the attributes of a quad are worth investigating. (see "Cubical Quads" by Bill Orr) Anyway it's been my observation that amateur radio operators generally seem to have more Ingenuity than mere civilians (hi) so I wouldn't let the extra effort to deal with mounting a quad get in the way of trying one.
From a personal view there's a lot of satisfaction when, after trying various ways and means with marginal results you finally come down to that "one" that stands out from all the others. This is that one I was looking for, and I am please with it's engineering too. It's light, it's tough, it's integrated to one small center boom, and its reasonably effective at low level too. In summary I'd say any of the quads on the market that have survived the test of time are probably fine. I only know that considering my particular installation, this is the one for me.
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Earlier 5-star review posted by W7UIV on 2001-03-11
In my quest for an antenna I could "sell" to the homeowners association as "portable" to use in my CC&R area I arrived at the GAP Challenger, which is working well with no challenges coming from the association. I needed an antenna that would work as well ground mounted as on a roof, and not require the support of a cement base. The covenants plainly state no roof mounted antennas, and none attached to any permanent part of the property. A cement base, I am told, is considered permanent. But driving a base into the ground, or digging a posthole to set in a piece of PVC pipe that the antenna slides down into, is not permanent.
With a desire for some portable kind of beam, and through an ad on this site, my attention was drawn to the HEXBEAM, which I am still considering, but which is still somewhat a "compromise" type of design. A two element quad is no compromise, and from many articles and experiences you will find that a two element quad is about equal to a three element yagi. Not only that, but they are quieter and more broadbanded in each band then a yagi. I had heard of these spider design quads but never paid too much attention until my current need of something lightweight as this came up. Don't know the price or where to order yet, but have sent off an email for prices and distributers as of today. Will report back as I go.
Jim, W7UIV |
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| K3KEI |
Rating: |
2002-06-17 | |
| Great ant for the price |
Time Owned: more than 12 months. |
I purchased my Gem quad in 1978. It was my first HF directional ant for 20,15 & 10 mtrs.
No problem assembling it but attempting to get it to tune with a single feed line was a bear. After trying many different systems, I altimatly ended up with a gama match on each band and connected them all together using #12 electrical wire. I covered each variable cap with a pill box and sealed it with RTV. The swr is 1.3:1 or less on each band. I only have it up about 30 ft on a
TT-45 fold over tower. This is the most convienent method of servicing this type of ant. I have had to take it down for minor maintance about 5 times over the last 24 yrs.
It was a good investment. |
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| VE3IOS |
Rating: |
2002-02-16 | |
| Work Everybody |
Time Owned: more than 12 months. |
I am surprised how long this antenna has with stood the elements. I have had it up since August 1997. High winds, hail, ice storms, you name it nothing seems to break it. I have it up 50" fed with a quarter wave 75 ohm stub. I only need the tuner when I run the amp which is a real pleasure without all that tuning during band switches. I would recomend this antenna to anyone that is a serious dx'er. Very quiet and you can work anyone you hear. And... you can hear everyone well after the stations have given up. They are a pain to work on for tuning but once done they are real performers.
http://www.escape.ca/~gemquad/
Jeff
ve3ios |
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| M0CTQ |
Rating: |
2001-12-30 | |
| very pleased |
Time Owned: more than 12 months. |
| bought mine secondhand for £50 minus wire,instructions,baluns ect.I first installed 10,15,20 mtr bands fed individually with a 1/4 wave length of 75 ohm coax,it seemed to work very well.then i installed a relay switching box i had made and added 2mtr 12mtr and 17mtrs.i decided to try feeding it with 50 ohm coax direct from my switchbox,the match was better with the 50 ohms coax dont know why but it is.The performance is at least as good as friends 3/4 el tribanders with f/b at abt 20db.I think a big advantage with a quad is the flexibillity,go outside and throw another band on it for the price of a piece of wire,monoband performance,lots of bands on 1 antenna.worked 284 dxcc in 2001 on it thats good enough for me.thanks |
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| VE7EPQ_MIKE |
Rating: |
2001-10-17 | |
| 3 Element triband Quad |
Time Owned: 0 to 3 months. |
Although it is difficult to get the company to respond (don't bother emailing--He wont answer), once you do it is a pleasure dealing with them. The antenna arrived very well packaged. The instructions were pretty good, although I would have liked more configuration information on wire length for different feed styles. The two things I noticed about the Gem Quad, that deserve serious consideration.
1. If you decide to go to this type of quad, a tilt-over tower (for tuning) is just about a must. It will not work with the hazer-style mount. I rented a 46' power lift so I could install and tune on my 40 ft. tower. Also...putting up the antenna with a gin pole is really a task. Everything is in the way, due to the close spacing at the mount.
2. I am going to split the feed so that every band has a separate feed point (next summer). Consider getting a remote antenna switch at the same time as the antenna.
Tuning a spider quad is very fussy (at least at my location). Splitting the feed line would eliminate some of this.
Having said that, it has been up for a couple of weeks and I love the antenna. Get great responses and I think it looks great too. For the price it is well worth it, but be prepared... "some assembly required" would be an understatement. I would buy from them again though. |
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| NU7J |
Rating: |
2001-03-12 | |
| Excellent, light weight antenna |
Time Owned: more than 12 months. |
I've used a 2 element Gem quad for approx. 10 years here in western WA, and I also owned one for several years at a previous QTH (IL). Mine is configured for 10, 12, 15, 17 and 20 meters, and it works great on all bands. I'm in the process of adding 6M elements. The antenna is very strong and light weight. I recommend against following the manufacturer's recommended feeding method. (They recommend feeding it on multiple bands with only one or two feed lines). I feed each band separately, with a 1/4 wave matching section of 75 ohm coax, to a 5 position coax switch (Ameritron), which is mounted on the mast. This method minimizes interaction.
Quads work amazingly well at low heights. Mine is mounted at 64 feet, but I've worked plenty of DX while it's hanging from the tower, with the 20 meter element only a foot or two off the ground. (It's been in that position all winter, while I find time to add the 6 meter elements and fix my rotator).
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| K5PSO |
Rating: |
2000-03-13 | |
| Anyone familiar with these quads? |
Time Owned: unknown months. |
| Anyone have one of these and want to tell me about it? Dan, K5PSO e-mail me dnyboy2k@aol.com Thanks & 73 |
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