20 meter dipole for QRP

[K4YND]

This weekend Im going to put together a 20 meter dipole for portable operating with a HW8. Im going to order 25 feet of coax today. What coax (or other feed line) should I use and what guage wire can I use. Output is 2 watts.

Thanks
KJ4QKN

Don

[WA4FNG]

Don,

You probably want 50 ohm feedline for your antenna. This could be RG58, RG8X or as many QRPers use, RG174 or mini-coax. RG174 is small and lightweight, but has greater loss. I doubt 25' would be a problem. Research using RG174 before you order it as you may want to consider buying it with connectors attached. BNC connectors are used frequently with this and you may need an adapter to a PL259. For me, RG58 or RG8X is just fine.

I have a QRP dipole for 40m made from 22ga. stranded wire - actually small speaker wire. For 2W most any small wire will work as long as it can support the antenna without breaking. Depend on how you plan to erect it. My 40m dipole is used as an inv vee so the wire doesn't have to support any weight.

Hope this helps.
73,
Milt

[NA0AA]

I would go with any standard, RG-58, or RG-8x are plenty for a 25' feedline, as the earlier posted noted, if you are going to carry this [AN HW8?] in the field, perhaps the thinner stuff would be better.

With only two watts, any wire strong enough to hold up the antenna will work FB - again, 20 gauge or 18 gauge would be more robust and a trifle easier to handle.

You might consider a second length of coax in case you have the opportunity to put the antenna up even higher - with QRP you can use all the help available.

[K8JD]

For effective QRP operation you want to reduce losses as much as possible, Using RG174 and Hair fine element wire is not the way to do this.
Using #14 wire for the dipole element and the heavier RG213 type coax is the way to go.
If this is for a permanent home station, I would even start looking for a good Yagi and rotor.

[KB9BVN]

The HW-8 is looking for 50 ohm impedance on the antenna.

I like the suggestion of a heavier wire, like maybe 20 or 22 gauge for the dipole, and then feed it with 300 ohm or 450 ohm ladder line or balanced line. You could even make your own.

Then use a simple LC matcher to mate it to the HW-8

I prefer to use a 1/2 wave 20m end fed with a homebrew matcher.

Easy to deploy, lightweight, and good match.

[KE5FRF]

For monoband operation, I would be tempted to use an end fed 1/2 wave antenna with an appropriate matching network. You might even get away with a balun and enough coax to get the radiating part of the system away from the transceiver. If a commercial antenna is desired, I've read some good things about the "end-fedz" antenna.

AA5TB has some good info on his website about end feeding antennas.

[W0IS]

For portable QRP use, I just use a piece of coax with a PL-259 on one end, and two alligator clips on the other end. I usually turn it into a dipole.

For wire, I use whatever wire is available. Honestly, it doesn't make much difference, as long as it's adequate to hold it in the air. I usually go with some kind of inverted vee setup, so the strength isn't an issue--I just secure the end of the coax to whatever is convenient, and then run the two pieces of dipole away from that.

If I'm in the mood to use wire that's simply disposable, I just use some thin steel wire. For short runs (such as on 20 meters), it's not too difficult to work with, and when I'm finished, I just pull it down and throw it away.

For longer runs, I often use speaker wire. For the first time I use it, I measure out a single piece, and then unzip it. It can be reused many times, but if you have to destroy it while taking it down (or don't feel like winding it up), it's not much of a loss to just yank it down and throw it in the trash.

I can usually get most of the wire I need at the dollar store.

[K0RGR]

Twenty five feet of RG-174 (Belden 8216) will yield 0.7 dB loss at 14 Mhz..
That means your 5 watts will be 4.2 watts at the antenna. A good grade of RG-8X will reduce the loss by about 50% on that run, giving you 4.6 watts at the antenna. The big stuff, RG-213, will raise that to almost 4.8 watts. The difference will be imperceptible! For anything longer than 25 feet, RG-174 would not be a good idea. Make it shorter if you easily can.

I would not use very small wire for the dipole itself. Small wire will stretch or break. On this band, it's only 16 feet each side of center, so the weight of the wire is not that important. Be sure the wire is heavy enough to support the center insulator and the coax.

[KU3X]

For great portable fun, you'll find a simple dipole made from somewhere between #16 and #20 insulated wire will do great. Use about 35 feet of RG-8X. It's not a big deal to use a short length of RG-174 but it is more lossie. Don't get carried away with coax loss and wire size. Just get out and have some fun. Before you know it you'll be told to use 1-1/2" hard line with "N" connectors and make your antenna out of 1" copper tubing. Oh My !

[K8JD]

Twenty five feet of RG-174 (Belden 8216) will yield 0.7 dB loss at 14 Mhz..
That means your 5 watts will be 4.2 watts at the antenna. .

Almost 20 % loss of signal Makes a big difference for a QRP station (or a KW)....Maybe not if you are already S9..I just like to get more efficiency if it is as easy as using good feedline.