mfj-2990/mfj-986

[N5XO]

And of course all day all you get when you call MFJ tech support is a voice mail box that says "I'm sorry but the person you called has a voie mail box that is not setup".

Great PR there.

[N5XO]

Well I see everyone likes to spout their opinions but not answer the question.
I two am looking at the antenna 15 years as a Tech and just upgraded to General. How is the antenna quality ect. Would appreciate an honest answer
Doug
N2PLR

I was pleased with the build quality and easy assembly, so from that aspect it is a nice antenna.

[N0MKH]

I just got me a house with a backyard for the first time ever! I`m now very excited about getting on the air. I`ve been a ham since 1988 and never really had the chance to operate. I`m looking for a multiband verticle antenna I can put up and this MFJ-2990 or Hy-Gain 6160 (same-thing? HyGain $40 more?) has caught my eye. Especially since it appears it would blend in with the trees. I`ve read the instructions (pdf format)and they do say that this antenna needs at least 16- 43ft long radials for proper performance on 160-20 meters. 17-6 meters the antenna needs to be shortend for a 5/8th wavelength. I think I might give this antenna a shot. But first I need to finish moving. I would like to hear more about this antenna.

[KA5S]

My first impressions with the MFJ 2990 are not that positive. Granted I do not have a lot of experience with Verticals, using mostly mono band beams on HF for 10, 15, 20 and 40.

I do use an AV-6/40 vertical and it is mounted 25ft and has worked well, I recently purchased the new MFJ-2990 to get 80 and 160 meter capability on a limited city lot. So far I can not make this antenna work.

If you think of a watch face......I have an 80ft radial run in the 12:noon, a 45ft at the 11, a 25ft in the 9, a 50ft in the 8, a 50 ft in the 7 and 20ft in the 6:30 and a 20ft in the 6,

It will not tune at all on 160 {using an MFJ 989D}, it tunes on 80 to a perfect flat SWR, but I can not get a signal out on either band....switch to my AV640 and the station I am testing with on 80 and 160 which is about 15 miles away as the crow flies is S 20 on 80, go to the 2990 and his signal drops down to below S4 and in the noise, on 160 I cant hear him at all on the 2990, but if I listen on the AV640 {which stops at 40 meters} He is an S10 or better. On my 80 meter dipole we have no problems communicating

Is this antenna crap, or am I doing something wrong. Like I said this is my first ground mounted vertical and only my 2nd HF vertical in 30 years. But heck my 80 meter mobil ham stick on a mag mount on my truck out performs this thing.

We are lucky here that we have some real antenna experts -- I'm not one of them -- among us. Their opinions about using an antenna like that on the lower bands are worth listening to, and most recently relevant are discussions involving automatic tuners on the lower bands, which I believe was the intended market for these 43-foot sticks. While we might get a "match," loss in a tuner on 160 and even 80 can be quite high.

Trying to match it from the shack and over a length of coax insures poor performance. By way of analogy, imagine that setup on 80 with the antenna as 100 pF capacitor (SWAG number as I can't lay my hands on the Antenna Book just now), and 50 feet of coax (at 25 pF/ft) as 1250 pf of capacitive shunt. There's 92 percent of the RF current staying in (and heating up) the coax, with only 8 percent in the the antenna!

See if putting your tuner temporarily at the antenna base isn't better.

Even base loading would still make a large difference on 160 and 80. The MFJ-1792 ("33 feet of ruthless radiating power") uses top loading for 80 with an inductor and a 54 inch top hat. Or put a loading coil just under the whip.

FWIW, what throws me off on the 43-footers is the cost. A (18 foot) Gotham was $22!


Cortland
KA5S

[N5XO]

We are lucky here that we have some real antenna experts -- I'm not one of them -- among us. Their opinions about using an antenna like that on the lower bands are worth listening to, and most recently relevant are discussions involving automatic tuners on the lower bands, which I believe was the intended market for these 43-foot sticks. While we might get a "match," loss in a tuner on 160 and even 80 can be quite high.

Trying to match it from the shack and over a length of coax insures poor performance. By way of analogy, imagine that setup on 80 with the antenna as 100 pF capacitor (SWAG number as I can't lay my hands on the Antenna Book just now), and 50 feet of coax (at 25 pF/ft) as 1250 pf of capacitive shunt. There's 92 percent of the RF current staying in (and heating up) the coax, with only 8 percent in the the antenna!

See if putting your tuner temporarily at the antenna base isn't better.

Even base loading would still make a large difference on 160 and 80. The MFJ-1792 ("33 feet of ruthless radiating power") uses top loading for 80 with an inductor and a 54 inch top hat. Or put a loading coil just under the whip.

FWIW, what throws me off on the 43-footers is the cost. A (18 foot) Gotham was $22!


Cortland
KA5S

Well I noticed a direct electrical short in my antenna at the coax end, so traced it back to the antenna and the 1:1 balun they provide was wired with a direct short on it, I know some say this is RF invisible, but since the antenna would not tune on any band and switching from my AV-640 to the MFJ-2990 would cost me as much as 8 S units of signal strength on recieve I figured what the heck. I cut the short out, and retained the balun as a choke, now the antenna tunes like a champ on 160 and 80 {have not tried it on the other bands as 160 and 80 was what I was wanting} and I've worked a few stations with it. Performance was fair on local contacts working friends between 14 to 40 miles seperation. That evening I worked two stations in Dallas {about 400 miles with 100 watts} I was reported to be weak but was copied.

I have since taken the 1:1 balun fully out, and built a home made coil and with antenna analizer have tapped it with the best SWR on 160 I could get which is 2.7. I then used the tuner and still running only 100 watts have now worked 2 states with decent signals.

So the 43ft is a nice STARTING point but for Freakin the price I expect it to be doing more than starting me off as a expermental kit.

Still working on this project, so any thoughts are most welcome.

[K8JD]

My first impressions with the MFJ 2990 are not that positive
15 miles away as the crow flies is S 20 on 80,} He is an S10 or better. On my 80 meter dipole we have no problems communicating

But heck my 80 meter mobil ham stick on a mag mount on my truck out performs this thing.

I think the S10 and S20 is an interesting concept.
.Can you stick a 40 ft vertical on a mag mount and use a metal pie plate as a counterpoise ??? Sure but will it get a signal out of the back yard ?????????
./
Seriously this test distance is too far for direct wave at the low angle of a big vertical, the ground wave peters out after a few miles ( AMBC is a better freq for ground wave and you need 5-50 kw to do it) So the high angle of the dipole is ideal for the short hop anyway.
Not a valid test.
Try someone 1500 miles away instead of 15 miles for your test, late at night !!
Let us know how it comes out !

[KA5S]

... I cut the short out, and retained the balun as a choke, now the antenna tunes like a champ on 160 and 80 {have not tried it on the other bands as 160 and 80 was what I was wanting} and I've worked a few stations with it. Performance was fair on local contacts working friends between 14 to 40 miles seperation. That evening I worked two stations in Dallas {about 400 miles with 100 watts} I was reported to be weak but was copied.

I have since taken the 1:1 balun fully out, and built a home made coil and with antenna analizer have tapped it with the best SWR on 160 I could get which is 2.7. I then used the tuner and still running only 100 watts have now worked 2 states with decent signals.

So the 43ft is a nice STARTING point but for Freakin the price I expect it to be doing more than starting me off as a expermental kit.

Still working on this project, so any thoughts are most welcome.

You are making some progress.

FWIW, you need to use an antenna analyzer to check out the match and see things like that short circuit (that might be a discharge path for static and induced lighting effects).

I don't know what the ground conductivity is like down in Converse and that affects performance. It's poor in the FW area, but I once worked 90 stations in 30 states from that area during a 160m CW contest, using an eight foot CB whip homemade base loaded antenna with a coil of number 22 wire. Mobile!

A bunch of us did some informal experiments* while I was working in the FW area in the 90's, between mobiles and a station North of town, and found that NBFM (<1 KHz deviation) and 100W mobile setups gave better coverage to his location on 160 than a FW 2m repeater did.

*Driving to work we'd do 75m antenna shootouts to the station in (IIRC) Boyd as we crossed the Belknap St. bridge. Just the usual drive time nets. If you don't count goat reports. Heh!

Agree on the price being too high.

Cortland
KA5S

[K3ROJ]

Yes the price is very high for the aluminum used but sometimes it is worth the investment instead of scrounging around for the masts, ground mount and pipe clamps. Perhaps I am doing something different but by using 95 feet of RG11 direct burial cable and a Heathkit SA2060 tuner in the shack, I am able to work everything I hear on 160 meters. 80 meters is even better and of course 40, 20, 15 and 10 meters doesn't require a tuner. 17 meters is finicky and needs a tuner however. This vertical antenna is ideal for someone who cannot install a halfwave dipole on 160 meters. I installed mine 2 days ago using only a ground rod at the base and running #10 wire to my chain link fence 10 feet away. Many stations have commented that my signal compares to other stations in my area and I use only CW.