Portable dipole ?'s for QRP setup

[K4HYJ]

I have just purchased an MFJ-9420x from a gentleman here on the forums (it hasn't arrived yet). This is my first foray into low low power (10 watts). I am planning on doing some long hikes before the summer is over and want a SSB rig and simple antenna to drop in my pack - hoping to avoid an antenna tuner/meter for the weight. Is that doable if I roll my own dipole and trim it properly? Do I need a unun?

I realize that height, soil type, etc. effect the SWR of the antenna, but my experience is limited to placing antennas around my property and the SWR only varies by .1 to .3.

I will run 40' of RG-8x (because I have it) to the dipole and do my best to get it 35' off the ground with a rock and string and some tall pine trees. Is my expectation unrealistic to not use a tuner?

[KO6WB]

Not really. This is the simplest and most effective way to go when you consider the "Bang for the buck". The resonant dipole will present a low SWR for the phone portion of 20 meters so there is no need for an antenna tuner.
The RG8X is fine for the purpose and since you have it go ahead and give it a go.
I'm sure low power communications can be a lot of fun. It might get a bit hard to have to go up against those with multi-element beams and 1.5KW but there is a section of 20 that is supposed to be for the QRP stations at 14.285Mhz. Good luck with that.
Have fun
73
Gary

[WX7G]

it will work well without a tuner and without a balun.

[WB2WIK]

I agree with the others.

I've operated portable for many years from lots of places including ones you can only hike/pack to, and the added weight of things like tuners and SWR bridges would be silly to pack. A 20m dipole cut to the formula 468/f = feet, using lightweight string to tie off the ends and hopefully a lightweight center insulator, installed at least 20' above ground, will work fine without a tuner. The MFJ is pretty forgiving (I've used them) and won't "cut back" on output power until the mismatch is pretty bad. I'll bet you can be within SWR = 2:1 just by "winging it," and at that match, in my experience it won't cut back at all.

[WB2WIK]

It might get a bit hard to have to go up against those with multi-element beams and 1.5KW but there is a section of 20 that is supposed to be for the QRP stations at 14.285Mhz. Good luck with that.

It can be surprising. When operating /p QRP I've never used 14.285 or any other particular spot in the band. Most of my QRP DXing has been on CW, but now and then I've done okay on SSB, and I never identify as "QRP" or anything like that. Just jump in, pile on, and get through.

From the beach in Malibu, and also from some very good mountaintops, I've "competed" with home stations using beams and high power and beaten them in many instances. It's just having the perfect location for the path, and good timing.

The MFJ, while not very feature-rich nor as stable or as accurate as most modern gear, does have something going for it: It has a good speech compressor built in which works and is very low distortion. Adds a lot of "punch," and can make its low power sound like more. I've compared "getting through" with the MFJ vs. my Yaesu FT-817ND (which is more stable, more accurate, and does more stuff) and there's absolutely no comparison. I can be heard with the MFJ when people don't even acknowledge a caller with the MFJ. The "talk power" difference is probably at least 6 dB, probably more than that.

[VU2CDW]

Just put 4 legs below the MFJ to raise it a little so that you have all around air circulation to keep the drift minimum- I did it with mine and was successful in controlling the drift to a great extent

Have fun

73

VU2CDW

[KO6WB]

In someways the MFJ has advantages of the old tech stuff. An analog VFO and simple straight through circuits. No phase noise and some remarkable audio that sounds good as well. Sometimes these types of rigs can be amazing. Even a simple analog S-meter. Drift is aways a problem and been responsible for some very interesting encounters. Good timing and location are a great help. Like being on the edge of a massive ocean, they call it a salt water linear.
Have fun and as Steve already indicated he didn't ever sign QRP. I would follow that example. Some ops can be very strange in the presence of what they consider an inferior setup.
Just have fun with it.
73
Gary

[KB7NRN]

Below is a photo of a ham I know in N. California. QRP QSO's with JA's & VK's. He's using his 9420 with a crapy pole antenna attached to a back pack. You can just see the countpoise wire behind him. He was able to walk around trailing the wire while in QSO.
And yeah, that the Pacific Ocean beyond him, his "salt water linear".

John

[K4HYJ]

How small of a wire (AWG) should I use? Stranded or not? I was thinking about 22 AWG enameled armature wire for weight savings. Too small?

[KO6WB]

The wire size is fine as long as it doesn't break easily. Some wire made out there breaks if you look cross eyed at it. Stranded would be good and there are some manufacturers that have very fine stranded wire that is extermely flexable and very easy to work with. Solid wire tends to start breaking after a while and doesn't take well to repeated coiling up and uncoiling.
Check the listings for these wires at; http://www.thewireman.com/antennap.html. There is some wire that has like 126 strands that is very difficult to tangle or kink and they have a #26 wire that weighs less than 1 pound per 1000 feet. It breaks at 25 lbs and that might be a bit too fragile for your operations.
Good luck and remember you're only using 32-33 feet of wire.
73
Gary