Coax / Wire Antennas; Curiouser and Curiouser

[WQWI871]

Okay, so.

 

For quite a while, I've seen people using homemade antennas of coaxial, or, wire, which could just be some stranded insulated wire cut to the length of band / frequency, soldered to a fitting, connected directly to the radio, or, those coaxial dipoles with the negative and positive (braid / center) stripped and spaced out, cut to desired length.

What's the idea of using, say for example, a coax cut to the desired length, unstripped? Quarter or half?

[n4gix]

They make quite excellent quarter wave "emergency" antennas. They can roll up compactly and fit into a "Go Bag" for rapid deployment in the field.

[WQWI871]

I'm confused, though, if It's necessary to strip the outer insulation of the desired length and fold the braid back if the coax is already cut to the appropriate length?

[n4gix]

Yes! The center conductor becomes the "radiating element" and the folded-back braid becomes the "counterpoise" for this simple vertical dipole antenna.

 

Watch this video: https://youtu.be/N-rUeIMYXbg?t=2m58s

[WQWI871]

I know, It's just lol. The center and braid is just covered with insulation. I didn't see why the insulation would really make a difference. The braid and center are already separated from each other, so, folding the braid back from the center didn't make much sense to me, either.

 

Edit: An offtopic note, by the way, do you know when that 2017 sale is over, or, am I too late? I'm still trying, but, that's kind of bad timing. I may have to wait for christmas, but, someone wants an iPhone for christmas, and, I won't be selfish.

[n4gix]

Well, if the braided shield isn't separated from the center conductor, they the two halves of the dipole would effectively cancel each other out. Worse though would be a situation where there is no load on the transmitter, which at worst could cause severe damage, and at best would mean zero signal going out...

 

I have no idea when the sales price of the MD-2017 from R&L will change. Whether it is merely an introductory offer or their regular price they haven't said.

[WQWI871]

Okay, thank you.

[WQWI871]

Does anyone have ideas on how to get a counterpoise on to an SMA fitting without using an adapter? I tried bending and filing the terminal, it won't fit right. I always use the screws on the belt clip, but, sometimes I'm too lazy to use a philips screwdriver for that.

 

Edit: I also considered taking a tiny (maybe about one inch) wire, connecting a but plug terminal to one end. and, perhaps a ring terminal to the other end. The ring terminal (or spade) would be connected to the negative screw, and, the butt plug would allow me to connect and disconnect a counterpoise that has the other butt plug to one end. But, I didn't know about the swr or if that would be a good idea with the one ice wire and three terminals instead of a direct connection.

[mainehazmt]

When your talking a portable radio the practicality of putting crap on a portable is foolish. Get a mobile radio proper antenna and coax and be done with it. 1 you won't be taken serious in public with it. A good portable with a good antenna working on a good system doesn't require anything special. 2 miles with a portable should be it in planning..anything else is gravy

[WQWI871]

This topic was regarding a stationary mobile or base radio. The last comment was a side note referring to a thin 30G, maybe about 11" of wire used on a portable / handheld as a counterpoise which is discreet and not noticeable, certainly more discreet than a whip that is 15 inches or more. But, wasn't the focus of the topic. I have resolved the last comment, though and accepting any more comments for the focus of the topic.

[chiefeis]

This topic was regarding a stationary mobile or base radio. The last comment was a side note referring to a thin 30G, maybe about 11" of wire used on a portable / handheld as a counterpoise which is discreet and not noticeable, certainly more discreet than a whip that is 15 inches or more. But, wasn't the focus of the topic. I have resolved the last comment, though and accepting any more comments for the focus of the topic.

Actually I think all you need for a counterpoise is around 6".  I have one hooked on my, uh, "X brand radio", and it seemed to produce better results.

[WQWI871]

Actually I think all you need for a counterpoise is around 6".

For GMRS or 70cm, yes, about 6-7 inches is okay. For 2m or MURS, about 11-12 inches. But, I suppose 6-7 inches is better on 2m or MURS than not at all, unless someone can verify that. I won't do 19-20 inches, but, 11-12 inches is discreet if It's thin gauge and located in a good spot. I have a small terminal, It's no more noticeable than those wrist straps that come with some radios.