QRP & Antenna Tuner

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Harlock

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Hello All -

I'm trying to hash out a portable QRP rig, and am not finding much info on the below question I have.

Is there a need to use an antenna tuner with a rig if:

1) You are using a properly cut dipole antenna
2) You are operating between 5w - 20w

I appreciate the help - thanks!
 

Kb2Jpd

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Hello All -



I'm trying to hash out a portable QRP rig, and am not finding much info on the below question I have.



Is there a need to use an antenna tuner with a rig if:



1) You are using a properly cut dipole antenna

2) You are operating between 5w - 20w



I appreciate the help - thanks!


I'd make this suggestion. Use a magnetic loop. It is small, highly selective, and since it uses the magnetic component of the radio wave less interference with electric noise.

Adam Kb2Jpd

We have a Facebook group. Look us up.


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jwt873

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Woodlands, MB
Hello All -

Is there a need to use an antenna tuner with a rig if:

1) You are using a properly cut dipole antenna
2) You are operating between 5w - 20w

I appreciate the help - thanks!
Up near 10 - 20 watts, I'd be considering a tuner if the rig has no self protection circuit... But a resonant dipole with less than 3:1 should be OK.
 

wrath

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With a decent 40 M dipole , you should be good to go on most HF, I do agree with Adam mag loops are real nice to have in the toy box , if your handy with a slobbering iron a tunable mag loop is pretty easy , buying one on the other hand is $400+ , it's an antenna for god sake they should come in gold plated for that.

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AK9R

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If your antenna is resonant on the frequency you are transmitting on, you do not need an antenna matching unit, aka tuner.
 

Kb2Jpd

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A quick education.

Magnetic loops are tuned to the frequency you desire. Anything else is rejected. You are basically using a tuned circuit to get the best reception possible. You can build one any size but most are about the size of 1 yard or 1 meter. You can purchase a mfj loop tuner and then tune for maximum noise if you desire. You just have to use coax cable to feed to your receiver.
Now you decide how you want to do.

Have fun. 73 de Kb2Jpd


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SCPD

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Hi Harlock
.
You ask'd good questions... the answers to which, I am sure you will find, are filled with a lot of emotion. Hams are quite passionate about antennas..... (smiles :) )
.
If you have a really good antenna, one that you know the SWR is low, and can be assembled in a temporary location with such confidence- then your need for an external tuner should not be necessary. Just throw it up and operate. Chances are, it won't work the same as it did in your design environment....
.
....So: a Tuner.... but remember, a tuner only cheats the transmitter into thinking it has a 1:1 match with the antenna and the feed line... what happens after the tuner is anyone's guess. Yes, a tuner does improve things, but it a compromise, plain and simple. You should strive to not need one, ever, in your antenna designs.
.
To that end, and from one who is hardly an Angel when it comes to Perfect Antennas (I use tuners all the time, both as a 'ham' and professionally)-- I suggest you construct the best dipole(s) for the band(s) you intend to operate. Adjust them for the lowest SWR's, having erect'd them to the the approximate heights they will be used at the temporary locations. Coil them up, take off for the hills-- and then, when you operate at these locations, use your tuner to 'tweak' the SWR to 1:1.
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It really doesn't matter that you are operating low power- the rules apply regardless. Also, don't sweat anything that is SWR 2:1 or less-- in some cases even 2.5:1-- though that ratio is in the 'Stink Zone'-- you should always try to do better-- and you should be able to. If not, something is definitely wrong and you can correct it by looking things over carefully-- feed line connections, solder joints, too close to something RF- active (metallic etc)??... get the SWR down to 2:1 or better.
.
I hope this gives you some pointers... good luck!
.
.........................................CF
 
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prcguy

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I've run some finicky radios with little tolerance to high VSWR and have had antennas that worked great in one location and not in another, where the radio was unusable without a tuner. I've also been burned by portable auto tuners (LDG in one case) where it tuned a G5RV at home but would not tune the freq I needed for a net while traveling with the same antenna.

So, to cover all bases its a good idea to have some kind of tuner in your portable kit and if its really important to be on the air without fail, get a manual tuner.

I've also gone through most every kind of antenna for portable QRP work and finally settled on a resonant half wave end fed. With a very small 64:1 matching transformer in a box a little bigger than a Zippo lighter and about 63ft of wire that rolls up inside a plastic chalk line reel, it works the same as a full size dipole on 40m and also works great on 20, 15 and 10m. This antenna usually has a great match and does not require a tuner.

The 64:1 transformer will also tune any half wavelength of wire from about 5MHz on up, so you can easily get on WARC or odd bands with the right length of wire. So far no other antenna has been able to cover all the bands with full size dipole performance that packs into such a small package.
prcguy
 

Harlock

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Thank you all so much for your input. As someone who always wants to operate properly, and not harm my gear, I'll be taking the tuner on my adventures based on your advice. For those of you interested in knowing what I'm currently leaning towards, here's the link:

Yaesu FT 857d portable amateur ham radio battery packs and carrying systems

Really didn't want to take the 857d out of the house, but can't justify spending hundreds more than what this upgrade would cost on another radio (that would pale in comparison) + other necessary equipment.
 
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