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Author Topic: QRP and antennas  (Read 24885 times)
W1VT
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Posts: 862




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« Reply #15 on: May 16, 2014, 06:15:58 AM »

QRPers get to use resonant voltage fed antennas--usually not an option for those hams running high power--as the voltages become excessive.  Wink

When I got started with QRP, I used both a beam and a simple antenna--a 2 element Quad on 10/15 and a half wave vertical on 20 meters.  Both were quite effective in working DX--I worked lots of stuff you haven't been able to work for years...

Zack W1VT

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W2UIS
Member

Posts: 36




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« Reply #16 on: May 27, 2014, 12:18:29 AM »

I've used Ham sticks successfully but using a G5RV Junior (40-6) provides better results but requires a bit more work to set up.
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NO2A
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Posts: 824




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« Reply #17 on: May 27, 2014, 01:12:22 PM »

How about 5 watts to an 80m Hamstick? That would certainly qualify as being QRPp.     Wink Cheesy
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W4FID
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Posts: 137




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« Reply #18 on: June 01, 2014, 07:13:49 AM »

signal out is WAY more dependent on antenna than power.

Whatever rig you use do the very most antenna you can. Higher, longer, tuned to resonance (Vs letting a tuner fol the rig into low SWR), in the clear, are all major factors in how many QSOs you have, how easy to make they are, and how solid you're copied. If the best you can do is a very small (short) and simple antenna then by all means do it and enjoy whomever you work.

Minimalist means the most you can carry and use in a given circumstance and environment ............... it doesn't have to mean a deliberate strategy or choice to shoot yourself in the foot the day before the race ............ unless your slant on the hobby is to see how poor your set up can be and still have a QSO. And that's fine too if it's how you enjoy the hobby and challenge yourself to see what you can do. We all have our favorite things we like to do.

As a rule of thumb do as much antenna as the circumstances allow to maximize the performance you get from the rig.
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W1AJO
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Posts: 108




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« Reply #19 on: June 09, 2014, 05:26:28 PM »

When I was in Florida I was able to set up my Cushcraft MA-5B mini-beam and use it with my FT-817.  Worked very well and mostly I ran 5 watts into it.

I can't set it up at my current QTH so I spend lots of time tuing my stealth antennas with an MFJ 259B analyzier.  Really helps get a signal out.

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VU2NAN
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Posts: 253




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« Reply #20 on: June 09, 2014, 08:23:44 PM »

Here's my version of a 'minimalist' antenna.

http://nandustips.blogspot.in/2011/02/low-cost-dipole-antenna-for-hf-qrp-rigs.html

73,

Nandu.
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N3PM
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Posts: 31




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« Reply #21 on: June 10, 2014, 07:35:25 PM »

 Been using a 250' at 20' random wire. Pretty low profile. Works good with my crystal sets, too.
Mike N3PM
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WB6BYU
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Posts: 13482




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« Reply #22 on: June 10, 2014, 09:48:12 PM »

Quote from: VU2NAN

Here's my version of a 'minimalist' antenna...



Look up "electrician's knot" to tie the wire to itself to keep it from splitting further.
Saves the need for the piece of string.
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VU2NAN
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Posts: 253




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« Reply #23 on: June 10, 2014, 11:06:54 PM »

Quote from: VU2NAN

Here's my version of a 'minimalist' antenna...



Look up "electrician's knot" to tie the wire to itself to keep it from splitting further.
Saves the need for the piece of string.

Hi OM Dale,

I've learnt a new trick, thanks to you, easily grasped through these sketches.

http://hope.edu/academic/engineering/labs/Electricity_Lab/Figures.html

73,

Nandu.

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KB2FCV
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Posts: 1298


WWW

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« Reply #24 on: June 12, 2014, 11:44:02 AM »

I think when at home inside the shack, I don't see any reason to switch to a lesser antenna just because you are operating QRP. If you have stacked monobanders on 20m or 40m at the home QTH, then have at it. If you are portable, you will probably be taking the best antenna you can transport easily. What you may transport in a car for use at a picnic bench might be entirely different what you may use hiking a few miles into the wilderness. I think the bottom line is use the best antenna you have available to you that is reasonable to use for the situation.
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WB6BYU
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Posts: 13482




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« Reply #25 on: June 12, 2014, 12:54:49 PM »

Quote from: KB2FCV

...I think the bottom line is use the best antenna you have available to you that is reasonable to use for the situation.

(My bold.)


And best antenna, of course, is a relative term.

For some it may mean the highest gain to a particular area.  For others the "best"
antenna might be the one with the flattest SWR curve, or that fits in their
backpack, or works with available supports, or allows for multiband operation
without manual readjustment, or doesn't require a tuner, or fits in their shirt
pocket, requires minimal setup effort and/or thought, something they can
buy ready-made from a catalog, or perhaps the one that best fits their prior
assumptions of what a portable antenna looks like.

Often QRP operators will want one with minimum losses because they don't have
a lot of extra power to waste, but this isn't always the case.  (I remember an
article on using a T2FD because the low SWR reduced feedline losses, conveniently
ignoring the fact that the inherent 4 to 6dB or more loss in the antenna itself was
much higher than the loss in any reasonable length of coax feeding it.)

Sure, efficiency and (to some extent) gain are important, but the other factors
may be just as important to some operators, or more so.  Hence the wide array
of antennas that get used in the field (and various commercial offerings.)


We had a portable antenna workshop a few years ago, and I may plan to hold
another one again.  We practiced skills for putting up antennas in the field
(such as tying knots, throwing ropes over tree branches, putting up portable
masts, etc.) and actually tried them out.  That's a great opportunity to compare
performance and other characteristics of different antenna options, as well as
broadening one's pictures of what is practical in the field.
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KV7W
Member

Posts: 136




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« Reply #26 on: June 13, 2014, 10:59:02 PM »

Been using a 250' at 20' random wire. Pretty low profile. Works good with my crystal sets, too.
Mike N3PM

I do the same; 203' and I've thought adding to 250' or 300' - it tends to act a little broadside on 20m. I like that I don't have to go very high with it. I also carry a 66' piece for counterpoise and to also use as a efhw on 40m, but I've never had a problem with finding things to throw the random wire over, so have never used as an efhw. Seems to work the best when I elevate the counterpoise a foot or two, but then I tend to trip over it in the dark.

Right now I'm working on some real simple clip on spreaders to take, so I can use my random as a loop if I need to without carrying a bunch of ladder line or cutting and splicing any wire. Had kind of a break through tonight - I've got them down to where they cost me about a penny a piece, I can build one in under a minute with a single bit in a dremel, and they weigh 0.05 ounces - 30 in a sandwich baggy will weigh about an ounce and a half.
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KV7W
Member

Posts: 136




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« Reply #27 on: June 14, 2014, 11:53:01 AM »

Here's a pic of my antenna. I have about 260 feet of wire and about 100 foot of backer line on the spool,  couple weights, and the spreaders. Doing random and loops, I don't need anything to launch my weight. The 10 ounce is nice when the trees have thick growth, it'll pull the backer line and sometimes I just tie the 20 gauge hookup wire to it. I can toss it 25 - 30' up pretty easy. I carry the lighter one for areas I don't want 10 ounces of lead flying around, like state parks or things like that.

My spreaders are 2.5" hobby sticks with bamboo skewers used to space the wire with rubber band hold downs. Trying to drill out Popsicle sticks splits them half the time. I found the dremel 194 high speed cutter can be used to plow a hole through the wood that is the perfect size for the skewers. (You know, those bits that come with the kits that you've really never found a good reason for?) I've done hundreds of holes and never split a stick - can't say that for drill bits. Doesn't look like it would work, but start at a bit of an angle and they pop right through - wear gloves. Yeah, rubber bands and hot ladder line don't usually mix, but work for qrp with teflon coated wire. The top spreader gets zip tied for strength. I notched the ends of the sticks, but it's not really needed, just in case. If I wanted something more permanent, I'd coat them in epoxy and spray paint - even zip ties about last forever doing this. I have some spreaders I made ten years ago out of those thin green bamboo garden sticks that have been left out and still not rotted, the only zip ties that wore out were the ones I put on as an afterthought, so weren't epoxied.   

I can rig up a lot of different antenna options with what I have here, without unnecessary extra stuff. I'm still trying to figure out a way to field splice where I don't need to solder, yet have the connector thin enough to slide through the tree branches and strong enough to really pull on.
     
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WB4TJH
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Posts: 193




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« Reply #28 on: July 21, 2014, 10:59:13 AM »

I have found that wire antennas are much better; I usually use a Par antenna or a VersaTenna end fed. They run rings about short, dummy load, portable verticals. When you handicap yourself with low power, it seems silly to squander it in an inefficient antenna.
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KB1GMX
Member

Posts: 815




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« Reply #29 on: July 22, 2014, 02:57:45 PM »

I friend reminded me that any wire antenna dipole or loop is useless if your hat is the highest thing on the island.

A good vertical system tall as possible whip or fiberglass pole with a wire and a counterpoise or two
plus loading coil as needed works when your in the middle of nothing.  How high, 20ft at least, of you can do 33
that a full halfwave on 20M (PAR EF hanging vertically), quarterwave on 40M with counterpoise and a decent
size on 80M (1/8th wave with load about 3db down).

Allison
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