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Author Topic: Light weight antenna ideas to match MFJ 9475 transceiver  (Read 3586 times)
VA3AEX
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Posts: 22




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« on: April 02, 2012, 12:00:58 PM »

While the MFJ 9475 is slightly outside of QRP SSB at 12W PEP, what antenna ideas are there to run it portable?  I have the matching MFJ 971 tuner: a T match tuner with a 4:1 balun for balanced line. 

Restrictions are weight/size (fit in a suitcase), and it has to pass through airport security.  Pluses of the site is that its right on the edge of salt water in Maine (though not a huge lot), and there are a few trees on site that I might be able to get the antenna up about 20' in the air.  I'm thinking that an NVIS 80M dipole fed with window line is probably the most flexible solution that would give me the biggest local signal?

How would this compare to an Inverted L?

73 Alex

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WB6BYU
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Posts: 13484




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« Reply #1 on: April 02, 2012, 12:35:01 PM »

Quote from: VA3AEX

I'm thinking that an NVIS 80M dipole fed with window line is probably the most flexible solution that would give me the biggest local signal?



I'd take it one step further - feed the antenna with RG-174 coax and forget
about the tuner.  The losses are less than 1dB in 50'.  Tune up your antenna
in a local park before you go.  This is what I've done for portable operation
with my venerable Ten-Tec Argonaut 505.

One method I've used for field adjustment is to tie the support ropes to the
antenna about 5' (1 - 2 m) from the end of the wire.  I then attached a plastic
clothespin or alligator clip to the end of the wire with a short piece of string.
That allows me to fold the end back towards the feedpoint (to raise the
resonant frequency) or out along the support rope (to lower it) depending
on where I put the clip.

Using #24 stranded, insulated hookup wire for the antenna and the RG-174
you may be able to squeeze the whole antenna kit in the same space as the
tuner.  My antenna kit is a 2" x 4" x 6" pouch which contains my feedline
plus dipole wires for all 5 pre-WARC HF bands and enough rope to put them
up.  (Mason's cord is useful for light antennas.)

If you have enough weight and space you can use RG-58 instead of RG-174.


The dipole will give you high angle radiation for local work around New England
and Nova Scotia / New Brunswick / Quebec.  An inverted L will have more
vertical polarization which is better if you are trying to work across the Pond,
though with a maximum height of 20' it will still have some high angle radiation
as well.  (It might also give you good ground wave coverage to Yarmouth.)

Another accessory to consider is a Parafoil kite, made entirely of fabric without
any sticks.  That would lift your wire when you want to try vertical polarization
and take up little space in your suitcase.
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K4FMH
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Posts: 259




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« Reply #2 on: April 03, 2012, 03:49:21 PM »

I'd take a look at the new MFJ 'Big Stick'. It has a telescoping vertical whip made of stainless steel which screws into a loading coil via a 3/4" adapter...includes a set of radial wires, all for about $100. Mine works very well for portable ops. You can get either a stake with a 3/4" adapter, a tripod, or a "claw" clamp. YMMV!

Frank
K4FMH
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VA3AEX
Member

Posts: 22




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« Reply #3 on: April 03, 2012, 05:08:30 PM »

Thank you both for your replies.  I'm going to try building the light weight dipole and I like the RG  174 coax idea.  Light weight and thin so that I can snake it through a window or under a door jam.

73  Alex
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W1JKA
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Posts: 1816




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« Reply #4 on: April 04, 2012, 04:56:32 AM »

    Alex,as WB6BYU states,,a dipole will work fine.I regularly work qrp cw/ssb from from maine coast and islands.Horizontal,L or inverted v will all work about the same,whatever your location dictates and you can usually get part of antenna over water at least at high tide.No problem for local contacts in N.England,Maritimes, and gulf of Maine.Lots of fun to chat with coastal cruising and schooner fleet hams.Also almost limitless supply of 20-30 ft. antenna mast  from small diameter deadfall spruce trees along shore or in woods.I can not comment on tuners and baluns as my radiatorsl are cut to frequency and do not need to mess with either. Have fun.  Jim                        
« Last Edit: April 09, 2012, 02:01:11 PM by W1JKA » Logged
KG6BRG
Member

Posts: 119




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« Reply #5 on: April 04, 2012, 06:52:07 AM »

I have great results, and have had for years just using a random length of wire and a "L" network tuner.  Simple and light weight.   I do also connect a counterpoise to the tuner to push against.  Really works.  Cheers
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N4MJR
Member

Posts: 7




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« Reply #6 on: April 26, 2012, 11:10:15 AM »

You could try a 88' doublet fed with a balanced, line since you already have the tuner.  But I think WB6BYU has the best idea.  if you are operating just one area of the band a resonant antenna makes the most sense.  Good luck and 73, Michael N4MJR
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