What Can I Expect From a MFJ Tuner?

[Robb]

This isn't a thread designed for trolls to bash MFJ.
:tongue:
However, it is meant to be a fact-finding search for using a Alpha Delta DX-CC antenna with a tuner. I currently own a MFJ-993B tuner and wonder if it is enough to make this fan dipole perform on all bands without damage. I do not run any more power than the 100 watt radio puts out, and the MFJ-993B is rated at 300 watts.

I am not trying to load a box spring mattress frame. So I am concerned about its ability to be able to go far out of the bands that the antenna was designed for. I understand the antenna will do 10-12-15-17-20-30-40 and 100khz on 80m. Can it do 60m? Ha - can it do 11m with this tuner?!?

Just what experience does anyone have with either the MFJ-993B OR the Alpha Delta DX-CC???

 

[n8fgb]

Just tune a minimum power. Then turn up the smoke. Sometimes you have to tell it to tune twice to get the SWR down. I am not a big fan of autotuners, but should be alright, until you get a manual one.
Rich

 

[Beetle]

I wouldn't use an autotuner if you're going to be making excursions well outside of the antenna's stated range. The tuner's ratings are for antennas that are already pretty close, but using 100 watts with a "300 watt" tuner, made by anybody, is about as much as I'd want to try, especially using an already-short antenna on 80M.

 

[Wire Weasel]

...............................

 

[Moleculo]

Try it and tell us what bands it worked good on and which ones didn't. Every auto tuner is a little different, so this will be a good reference for others thinking about buying this tuner.

Are you feeding that antenna with coax or ladder line? If I was a betting man, on that antenna I bet the tuner will not like 17 or 60 meters and parts of 80 when fed with coax. But I'm purely guessing, so tell us what it actually can do.

 

[mackmobile43]

This isn't a thread designed for trolls to bash MFJ.
:tongue:
However, it is meant to be a fact-finding search for using a Alpha Delta DX-CC antenna with a tuner. I currently own a MFJ-993B tuner and wonder if it is enough to make this fan dipole perform on all bands without damage. I do not run any more power than the 100 watt radio puts out, and the MFJ-993B is rated at 300 watts.

I am not trying to load a box spring mattress frame. So I am concerned about its ability to be able to go far out of the bands that the antenna was designed for. I understand the antenna will do 10-12-15-17-20-30-40 and 100khz on 80m. Can it do 60m? Ha - can it do 11m with this tuner?!?

Just what experience does anyone have with either the MFJ-993B OR the Alpha Delta DX-CC???

So by limiting this thread to POSITIVE comments and or opinions aren't you restricting collective knowledge of forum information to aid you in your quest?

You just might be pleased with how well it will tune a set of box springs.

 

[K8PG]

MFJ TUNER

Hello Rob-

I have to say that you will be over the capable power limits of that tuner on some of the
bands-due to current/voltage nodes and impedance of the feed line and the collective
currents in the tuners components,I would get a Manuel MFJ tuner -say the 500w pep
model,any antenna that is designed for a certain freq. it will play on a few bands -but not
all-I would say this antenna will work on 80/60/40/and 20 mtrs-the components in that
antenna coupleris going to get warm/hot.

Paul K8PG I Have never had many problems with
MFJ/Ameritron eqp.with all new equipment
you must look at the build quality-before
the smoke test !

 

[N0NB]

My philosophy regarding tuners, especially when contemplating a tuner for an "all band antenna" where impedances are likely to be quite high or quite low is to buy the biggest baddest tuner your budget allows even when running 100 Watts. The high power capable tuners will have larger components which translate to lower losses which become even more important as QRP power levels are approached. My current manual tuner is a Palstar AT1500DT (no longer made) which tunes my 200' doublet on the low end of 160m without complaint whereas the MFJ-986 it replaced was at the limit of the roller inductor (the Palstar still has turns to go).

One sign of being at a tuner's limit is the reflected power to the radio increases as power is turned up or during a longer transmission. It's likely that some component is heating up and it's losing the match.

You could always use it until it smokes and then you have an excuse, errr, reason to buy a new one!

 

[W5LZ]

If it's strictly a matter of -can- it be done, then I would guess the answer would be yes. If it's a matter of 'can' it, and be worth doing, that 'yes' turns into a 'maybe'. I only know of one way of finding out for sure...
- 'Doc


(That "biggest" and "baddest" is a very good suggestion. I don't care who makes that tuner.)

 

[Captain Kilowatt]

I was using only 100 watts when I burned up the toroidal inductor in my Ten Tec tuner which is rated for 200 or 300 watts. I forget but either way if the inductor burned up it was not even close to handling it. BTW when I say it burned up I mean that. When I hit the tuner with 100 watts there was a SNAP! followed by smoke coming from the inside of the tuner. When I opened it up and keyed the mike again there was another SNAP! and the plastic form holding the inductor caught fire and continued to burn until I blew the flame out. I suspect it self extinguished inside the closed case due to lack of air. The smoke was really black and putrid. I can't imagine what the caps/inductors and switching relays in an auto tuner would react like. A 3:1 ratio is not nearly as good as I would like when it comes to reactance voltages which can hit several thousand volts in a tuner when trying to match some impedances.

 

[KE5MC]

My take...

Robb,

You have the tuner that is going to do the heavy lifting. Depending on power levels it will match 6-3200 ohms which is a wide swing for a tuner compared to a transceiver that has a built-in tuner. One reason an external turner has an advantage over internal.

For 1/3 the cost you can buy a DX Engineering dipole/doublet antenna. It will have all the hardware and the 300 ohm feed-line for the balanced input to the tuner. 70 foot for 40m and up and 135 foot for 80m and up if you have the room. You can tune a lower band for that length, but the loses will be higher and the antenna efficiency will be lower.

I don't have a fan-dipole, but all the reading suggest a tuned antenna setup and no tuner. That's the reason I believe the information for the two together will be limited.

My setup is an SG-237 coupler and DX Engineering 70 foot antenna extended by 15 feet on each end. The feed-line to coupler is somewhat unconventional. One side of the feed-line to the ground stud on the tuner and the other side to the ceramic stud on the tuner. Tuner is under the eves of the roofline and the 9 foot coax from the tuner enters the house via a window.

You have a balanced line output so you are in better position than my setup. I don't believe a fan-dipole will improve your setup. So hang some wire and see what happens. Theory is great and it keeps from making poor choice, but in the end most setup are a compromise from the optimum configuration.

I made a contact with CE4CT yesterday evening (gray-line) with the above setup using a IC-7000 set to about 85-90 watts PEP on 15m. Likely he has a huge beam pointed North, but the contact was made. According to QRZ he is 5000 miles out on the tip of South America.