| 9H1GW |
Rating:      |
2004-09-02 | |
| Excellent Antenna ! |
Time Owned: 0 to 3 months. |
I chose the MFJ 10 Bander because of it's compactness and coverage. I had NO IDEA of it's performance untill it was constructed and installed..
Now all I can say is "Well done MFJ!" For the best vertical I have ever used !!
I had a full sized 102ft G5RV at about 50ft AGL and was reasonably pleased with the performance.
As soon as the vertical arrived I built it (Pretty easy) and mounted it on the roof of the house on a short 3M Pole so it is around 60ft to the base.. The comparison is UNBELIEVABLE !!!
The MFJ 1798 gives me easily 5 to 6 S points better than the G5RV on All bands except 80M (but that's probably because I didn't even tune it for 80 as I dont generally use it)
I can que jump a dx pile up with ease and the stations I hear on it kick the G5RV into next week !
I Would recommend this vertical to anyone who wants to work (or even HEAR) DX .. it's like having a huge pre-amp stuck in the back of the rig !!!!! |
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| OE1SOW |
Rating:     |
2003-07-26 | |
| not easy to assemble... |
Time Owned: 0 to 3 months. |
The manual is the worst I ever read...some things they forgot to mention, really not easy, especially when your english isn't that perfect :-)
But it is now performing ok, but...forget 6m !
Even the tuner of my 756 ProII isn't able to tune the antenna for 6m...sad 'bout that...
80m a bit narrow, also 10m.
But it is performing better than my CP-6, except 6m and 10m.
Waiting for the first storm after raising up the antenna...will see what happens ;-)
73 !
Othmar, OE1SOW
http://www.qsl.net/oe1sow
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| KA8URX |
Rating:    |
2003-06-11 | |
| independent of ground |
Time Owned: more than 12 months. |
Difficult to tune the low bands.KA8NID had purchased this antenna in 1999 and two or three attempts by other local amateurs had been made trying to achieve a low vswr on 80,40 and 30 meters.The antenna is mounted about six feet above the ground on a city lot right between two 2-story homes(wood construction).So I started with new 3 foot long capacitance spokes,as we began trimming I make note of VSWR,R and X (MFJ-249B).I noticed that trimming the spokes moved the resonance point toward the center of the band but the VSWR kept rising.Initially we found the antenna to be resonante just below 80 meters(3.49MHz)with an vswr of 1.2:1 ,as we trimmed the spokes and got closer to 3.8MHz the vswr climbed to 3.0:1.
I called MFJ(1-800-973-6572)and spoke to Tom Stone,he told me that I needed to change out the four 130PF capacitors that are mounted at the top of the antenna(matching network).Tom sent me four replacement capacitors(390PF,1000V,silver mica),thats right,an increase of three times the original design value.After taking the antenna down and soldering the new capacitors in,we were able to tune the antenna and achieve VSWR values of 1.3:1 or lower on 80,40 and 30 meters.We did find that 17/6 meters was a compromise and the antenna is still very narrow banded on 80 and 40 meters.
Time and the sunspot cycle will tell how good of a performer the antenna really is,you'll need to ask KA8NID.
Mods and tuning completed on 6-6-2003. Tom KA8URX |
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| KD5LNO |
Rating:     |
2002-08-24 | |
| Works As Advertised |
Time Owned: 0 to 3 months. |
This was the first antenna I have ever assembled. The assembly directions were not always very clear, but with a little study it was not too difficult. I assembled it by myself in about 8 hours. I did run into a part problem, but MFJ sent me a replacement after a brief e-mail request.
The performance seems to be as advertised. I use a tuner as the bandwidth is very narrow on the lower bands. Signal reports are as good as can be expected with a ground mounted vertical. It doesn't work magic, but it does work as advertised ! I would encourage anyone looking for a vertical to consider the 1798. The price is right and it performs well. |
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| W7FL |
Rating:      |
2001-03-04 | |
| Great Vertical Antenna |
Time Owned: 0 to 3 months. |
| When I bought this antenna I was looking for the lowest priced multiband vertical I could find. The MFJ-1798 fit that bill but I didn't expect the performance that it's delivered. It took me about 5 hours to assemble and put up on an 8 foot pole. I operate mostly CW and I've done no tuning as I found low SWR on all CW bands that I operate, 80 - 10. Over the past two months I've been working DX and busting pileups with ease using 100 watts or less. I couldn't be more pleased. A single feedline, instant bandswitching, no lossy traps, broad.... it's a well engineered piece of equipment that works very well. W7FL |
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| AB8HM |
Rating:     |
2000-08-14 | |
| Good HF multiband vertical |
Time Owned: 0 to 3 months. |
| This antenna works very well on 20-10. I have worked 40 countries, mostly running barefoot on 20M SSB, but a few on RTTY as well as 17M, 15M, and 10M in the one month it has been up. Receive good reports, not great, but good. Mostly 55-58. However, on 40M resonance is 2.5:1, with a very narrow 3:1 bandwidth of 30kHz(the rated 2:1 bandwidth) 75M seems OK, I have received good reports (57 to 59 across Michigan) on a statewide net in the daytime, but have not worked any 75M at night. 2:1 bandwidth on 75/80 is 50kHz. 2M capability is perfectly adequate for most simplex and packet use as well as repeater use, but it is only 1/4 wave. The 2M portion is simply a quarterwave vertical above the counterpoise on the top of the antenna, at my QTH, this gives it a height well above all surrounding trees. I would reccomend this antenna for the person who wants to work DX on 20-10, check into nets on 75M, ragchew on 40M and 75M, and get on his local repeater and simplex channel on 2M. |
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| NT8N |
Rating:   |
2000-06-03 | |
| Good performer but bad mechanical construction |
Time Owned: more than 12 months. |
Complete Review with photos at:
http://http://www.qsl.net/nt8n/mfj1798review.htm
I was looking for a good all-purpose antenna for my station. See the posted comparison. After much examination, the MFJ 1798 became the antenna of choice, because of:
Top loading
Wide bandwidth (no traps),
Full radiators on 20 meters and up,
No radials required,
Balum inline (no feedline radiation).
Diagram of MFJ 1798 PDF format.
After deciding, I talked with MFJ about doing a review on their antenna, The following is an excerpt from my letter to them.
"What I want to do now is post another page describing the performance of the antenna, construction, and listing the contacts made with it. "
"I assure you that this will be a quality page, but I will be honest with my comments and numbers."
MFJ agreed to the terms, and I was to pick the antenna at Dayton.
As I was leaving Mr. Jue made the comment, " If you have any problems give us a call and we will help in any way we can". This was very refreshing coming the president of the company.
Theory of Design from MFJ 1798 Instruction manual
"The MFJ-1798 is an 80 through 2 meter ground independent vertical antenna. This antenna has several unique features including an inverted radiating element, a fully elevated counterpoise, lumped constant end loading, and linear Stub decoupling. These unique features eliminate the traditional problems encountered in ground independent mulit-band vertical designs.
Established antenna theory dictates that maximum radiation occurs in the high current portion of the antenna. While conventional antennas generally place the highest current at the bottom or center of the radiating element, the MFJ-1798's unique design places the highest current and the maximum radiation point at the very top of the radiating element. This feature produces the lowest wave angle possible for a given antenna height, and elevates the radiating section away from the lossy earth.
It is a well-documented fact that bending or folding a radiating element at a high current point reduces antenna system efficiency. The MFJ-1798 eliminates all bending or folding of the important high current areas by using linear decoupling stubs on frequencies above 14 MHz. These linear decoupling stubs provide low loss operation without compromising bandwidth. Efficient lumped constant end loading produces the highest efficiency possible on frequencies below 14 MHz.
Counterpoises must be an appreciable fraction of a wavelength above ground if losses are to be minimized. The MFJ-1798 design places the counterpoise at the top of the radiating element. This provides maximum separation between the counterpoise and the lossy earth. For example, a ground mounted MFJ-1798 has a counterpoise elevation of one half wavelength on 10 meters."
Back at home on Sunday May 15, 1999, we started assembling the antenna, Charles Randy Adams -- NT8N (me) and Albert Huffman -- KB4SAF. Beginning about 11:30 a.m. and finishing 8 hours later at 7:45 p.m. This is a very long time for assembling an antenna, but the manual needs some clarification to make assembly faster. Overall, the assembly of the antenna went well, everything fit and there where no missing parts. All parts where packed nicely. Parts lists are included in each bag of materials for easy identification. Markings on each bag would have made finding groups of parts faster. Such as group A, B etc.
On page 12 of the manual number 12, the text refers to the "edge lip facing up". What the manual is trying to say is the aluminum side of the top plate faces down, and the brackets are attached to the bottom or aluminum side of the top plate.
The most difficult section to understand was page 13 number 15. The section on how to: assemble and install the "I" bracket. This does not seem such a task reading the manual, but if not assembled correctly the linear decoupling stubs will not be straight.
If you will assemble the "I" beam as shown in the picture above, making sure your right is the bottom of the antenna. This will assure alignment of the decoupling stubs. Pay close attention to the direction and placement of the angle bracket. See picture below.
In the step on page 14 number, 19 you will need a small round file; the couplers are not de-burred, and will not fit on the rods without filing them down.
Pay close attention to the alignment of band stubs with respect to main radiator. The 17 meter stub ( the longest stub) is located on the same side as the balun coil. A bit off center from the coil. You can see this diagram on page 14 section 22.
On page 17 section 37 the manual does not make clear, without close inspection, as to what side the counterpoise tubes attach too. They sit on top of the plate and the brackets inserted from the bottom. See the pictures below.
Tuning of the 12,17,15,10 and 2 meter, bands are accomplished via shorting or lengthening respective stub. This is done by the hold down nuts as shown in the above picture
The antenna can be assembled and tuned on the ground. Although, MFJ says in to use a five foot pole when tuning, I installed it on a 3-foot pole and tuned the antenna with no problems. The spokes you see in the picture below are the means of tuning the antenna on the 30,40 and 80 meter bands.
The antenna is initially resonate at:
3.416.7
6.832
9.885
13.971
18.141.2
21.101.6
24.900
28.690
All frequencies are at the low end of the band.
Tuning of the bands above 30 meters are easily done by means of the stubs. 30-meters and below are accomplished by trimming spokes on the loading coils. These bands must be tuned in succession, starting with the 80-meter band. See page 22 of the manual for complete details
If you would like a MFJ1798 manual before purchase, you can get one from MFJ's web site.
The final installation is on a 30-foot tower with no ground radials. I found this antenna to be very good performer and works well on all bands with less than 2:1 SWR. I can work the entire band from 2 meter - 20 meters, 65 kHz on 80 meters and 100 kHz on 40 meters with no trouble.
Update 5-19-2000
I installed the antenna on 6-25-99 and have now used it for almost a year. Some problems accrued over the winter months with the antenna. Sometime in December my SWR went up over 10. Upon examination of the MFJ-1798 I found that the So-239 connector at the bottom of the antenna was not making contact. Again in January my SWR went up, this time it was varying with weather conditions. I found that the top section of the antenna was icing and causing the problem. Then again at the last of January, first of February when ice was accumulated at the top the wind managed to bend the main section, not a very strong wind just about 20 mph. The MFj-1798 is a very good performer for a vertical. It just needs beefed up a bit.
So, I have finally decided to go with a proven performer and manufacture. The A3S w/40 meter add on kit by Cushcraft. Installation of the antenna is scheduled for June 3, 2000. I will be posting pictures of the antenna assembly and raising here.
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