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Author Topic: Portable QRP Antenna for a Ten Tec Argonaut VI, plus more.  (Read 809 times)
VK3ZT
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Posts: 10




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« on: August 26, 2019, 10:43:59 PM »

Dear Forum Members.  This my first post here as I have used other Yahoo and such forth forums.  Please be kind as I know you will.

Portable operations with a 17' caravan with the XYL and her three dogs, 1 thirteen yearly English Bulldog, 1 seven year old pug and a 2 year old French Bulldog.  The caravan was intended to be our dark sky escape away from the bright lights of the country town to some where dark for the 8" Celestron Edge HD Evolution.  With our lives lived beneath clouds it has yet to have its first calibration.

Hence I am thinking of taking a few radios on holiday when we trip around Australia.  Though I do not know how practical this will be.  The Ham radio is a Ten Tec Argonaut VI and I will eventually purchase the Elecraft T1 Tuner.  It appears to be a good match.

As we will be mostly stopping in caravan parks and cattle stations and State Forest Parks where dogs are allowed.  I am after a quick set-up and pack-up antenna.  I am still at odds for transmitting as we have two receivers which may supply just as much fun.

1.  Sony ICF-SW7600GR for everyday around town and a bit of DX if I am so inclined with a PK Loop from Paul at PK Loops.  This antenna operates between 3.5MHz and 16MHz when applied with 12VDC.

2.  For shortwave listening I was thinking of the MFJ-1886 amplified loop.

3.  I also own a Palstar R30A and am in the position to purchase another one of a fellow Ham in Queensland for $500 AUD.  The brand new one in the shack can stay there whilst I take the other one bush in the caravan.  The Palstar Range come with so many accessory products that seem to fit the bill.  Though the may be acceptable in the Goodo'l USA with higher population densities,  though out in the Never Never where whole Continents could fit in.  I do not know which path to go down.  I do have a IC-7410 in the car via a nine foot stainless whip.  Though I prefer to be outside withe mozzies and a cold can of beer.

Yes I know.  Spoilt for choices.

Warm regards,

Paul, VK3ZT
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VK3ZT
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Posts: 10




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« Reply #1 on: August 28, 2019, 09:59:58 PM »

I have had some more thought on the subject and some local advice.  For the time being it is out with the loop antennas and the plan now is to:

1.  Ten Tec Argonaut VI connected to T1 Elecraft Tuner and that to a Fan Dipole for 40, 30 and 20 metres up 15 metres as a possible inverted V.  This is for TX/RX on the ham bands.

2.  For SWL listening.  I was going to use the Palstar R30A for with an amplified loop.  I am now looking at a 15 metre vertical endfed via a 9:1 balun and an earth stake whilst we are out bush clamping in our 17' caravan.  A Long and Lat that I will save for future reference some can come back to the same spot for the earth stake.

There is also the option of purchasing a more modern receiver than that of the Palstar R30A which must also have a low drain on the batteries.

3.  By keeping radios small may also allow us when the clouds break to open our telescope to view the nights heavens.  The telescope which we purchased last Christmas has yet to see first light.  (It is a long story).

4.  Possibly replacing the Sony ICFSW-7600GR with a Sangean ATS909x.

I find it helps to type, write things down for my own mind and also to allow others to have a read to add their two bits.

Warm regards,

Paul in OZ.
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WB6BYU
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Posts: 18535




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« Reply #2 on: August 29, 2019, 08:47:03 PM »

I did something quite similar years ago, hauling my original Argonaut 505 in my
backpack and setting up from campsites while hitchhiking around OZ.  It was
great fun, though I'll admit I was a bit younger then...

I used multiple dipoles on a common feedpoint (I reserve the term "fan dipole" for
a much older antenna by that name) and didn't even take a tuner with me - it wasn't
needed, even though the dipoles got installed in all sorts of odd ways depending
on available supports (it wasn't practical to carry my own).  But then, the 505
didn't shutdown power at high SWR.

I build my dipole center insulators with the feedline attached, holes for tying the wire
elements to for strain relief, and wing nuts to secure the ends.  I choose which
bands I want to attach each time I set it up, giving more flexibility (I've used a
40m dipole as a full wave loop on 10, for example).  The original used RG-174
coax and a slice of radiator hose for the insulator to save weight, while newer
ones to be transported by car use a chunk of PVC lattice (because it was available)
and RG-58 coax.  The exact materials aren't critical:  basically it needs to provide
strain relief for the wires and coax, and a convenient wat to connect them together.

Such an antenna should work fine for SWL use, even if it isn't resonant at the
specific frequency.  If you want something smaller for that purpose, consider
an "active antenna", basic a 1m or so whip with a built-in amplifier.  No need
to bother with an earth stake.  If it has a telescoping whip it takes little space
to store, and you can just set it on top of the caravan, so installation is simple.

I mostly hung my dipoles from trees, which isn't difficult, especially with a
throwing bucket, though I did disturb some roosting bats at one point.  Camped
on a rock ledge over the ocean near Cape York I had to prop the feedpoint up
a metre off the ground with a stick.  At Lake St. Clair I strung up dipoles for
all 5 bands in a tree in half an hour - in the dark, while holding a trout in one hand.
In fact, the only time I had time to operate but couldn't figure out how to
put up an antenna was riding the Indian Pacific back from Kalgoorlie.

However, I'd suggest carrying a 6-9m squid pole with you for those times
when you don't have a tree handy.  The tip section is often too weak to support
an antenna, but just leave it off.

I found 80m SSB great for meeting locals in the evenings (resulting in a nice lunch
on my way through Woolgoolga).  Even in a campground there was room to
string up an 80m dipole (at least in the area set aside for tents).  It's just another
set of wires you can carry and add to the feedpoint when appropriate.


One of the keys for fast set-up and take-down is to use small wire and learn to
wind it and your ropes so they don't tangle.  I wind them in a figure-of-8 across
my palm between thumb and little finger, though commercial winders and/or
reels are also available.  Practice everything before you go and find what
works best for you.  We are currently working on a better way to attach the
wires to the insulator without needing to tie knots, as that appears to be a
disappearing art.

Good luck!

      - Dale WB6BYU ex-VK2DJW
« Last Edit: August 29, 2019, 08:49:36 PM by WB6BYU » Logged
VK3ZT
Member

Posts: 10




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« Reply #3 on: August 31, 2019, 01:39:30 AM »

Dear Dale,

You have given me something to think about.  A dipole for the 80 metre band.  Sounds like more fun.

Warm regards,

Paul

VK3ZT
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WB6BYU
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Posts: 18535




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« Reply #4 on: August 31, 2019, 07:52:18 AM »

That is what I like about being able to attach whatever set of dipole wires
I want each time I set it up:  at a lunch stop in the middle of the day I might
only set up 10m or 20m, while overnight it might be 40m and 80m, without
the longer wires getting in the way at other times.  Then each additional
band simply requires an extra pair of wires.

I use stranded, insulated hookup wire, perhaps 22 AWG or so.  0.5 to 0.8mm
is probably a good range, though you can go somewhat smaller for backpacking.
My whole antenna kit, with coax, dipoles for 5 bands, and rope to install it,
fits in a small pouch and weighs less than 1 kg.


I should note that some of the local 80m SSB activity may have shifted to
2m repeaters in the ensuing ~40 years since I was there, but the point is
that there is no need to limit yourself to a small number of HF bands.
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ZENKI
Member

Posts: 1649




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« Reply #5 on: September 28, 2019, 04:43:30 PM »

If you have fan dipoles as transmit antennas I dont know why you would need loops? Unless you have a noise problem or some other issues. If you are operating  in quiet locations one of the better  high dynamic range "mini whip" designs  generally perform better for  listening to DX and shortwave stations. Small loops make great antennas  for reducing local noise and nulling noise  but for weak signal dx work you always run into the problem that the loops preamps noise floor  is much higher than say the ITU rural quiet  noise floor.  Loops need to be much bigger than the typical small 60cm to 1 meter diameter to really detect weak signals and all loops regardless if its a LZ1AQ, W6VLP, Wellbrook, PK, or MFJ will all have these limitations. Shielded loops  like the Moebius loop from DXengineering will also have this problem. The capacitance of the shielded design limits the loops performance.

A much better way to go is to make yourself a tuned loop with switched capacitors which will outperform any of the above  loops by a wide margin. I have access to EMC loops  that are calibrated from R&S and Teseq and even these 10,000 dollar loop antennas with calibration certificates are lousy antennas for  weak signal work because of the laws of physics. There is no loop design that is small that has overcome these design issues. The prices that these loops sell for especially the ham versions are ridiculous especially when you consider their performance. In most cases a  dipole even severely miss matched will have a better signal to noise ratio than these loops. Even crappy bits of end fed wire will outperform these loops. The only advantage of loops is noise reduction

If it was me doing this. I would go this way.

80 meter doublet open wire fed with a simple balanced antenna tuner.
A fiberglass 40 meter vertical with a 4:1 unun at the base with a automatic  remote tuner. You can attach this to your caravan and push it up as needed. You will get excellent performance from 5 to 30mhz and just use your dipoles for NVIS work.
Use elevated radials on the vertical and life will be good.

 A Miniwhip for general purpose receive across the HF spectrum.

For mobile work one of thoe Aussie type multitap whips will do the job.
If you can find a Codan 9350 you can use this as the active antenna since it has a receive pre-amp in it  making it a active antenna like a miniwhip.  Codan makes excellent stuff. But the Codan is a base loaded design and is  typically down 3 to 6 db over the better ham mobile antennas.

I would also  think about a small amplifier. For SSB work the ideal power for  QRP is 20 to 30 watts to have the same signal to noise advantage as CW. A 30 watt station  is the ideal QRP portable all  round power limit. There is no law that says you cant turn it down if you dont need to use it! But what can you do with a useless 5 watt radio when you cant increase the power to get the message out. Most stations will not notice the difference when you reduce the power from 100 watts to 25 during a conversation and its reason why most Military HF manpack radios run this power output. Check out the new Codan HF manpack design, its 30 watts output for very good design reasons not stupid contest rules that pick power levels out of thin air.

With lower power efficiency is the main objective from antennas and power. The next objective is having gain at the right take off angle and since height is out of the equation (ie 1 wavelength above ground) You have no choice to use either NVIS or use good low angle radiations like verticals. if you can pick a seawater location and be less that wavelength from  the water thats the ideal, I am sure finding seawater should not be a problem in Australia!
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WB6BYU
Member

Posts: 18535




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« Reply #6 on: September 28, 2019, 07:06:32 PM »

Quote from: ZENKI

 ...I am sure finding seawater should not be a problem in Australia!



Depends, of course, where you are on the continent.  There are a lot of
parts that are a long ways from salt water, though he bulk of the population
live near the coast.
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KB1GMX
Member

Posts: 1830




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« Reply #7 on: September 29, 2019, 08:40:10 AM »

I'm with Zenki on much of this.

At lower power and especially current solar conditions its about the antenna.
At QRP power levels an efficient antenna is a must.

Loops are not efficient.  As a loop designer physics always wins, they are inefficient.
Loaded whips are not efficient, especially those short relative to wavelength.
A 1/4 or longer (under 5/8th) vertical over a really good ground
  (more than 24 radials or salt water) is efficient other wise not efficient.
Dipole(s) of suitable size are efficient.

Antennas that require a tuner are always less efficient.
However a 3/8ths with a decent ground is better due to
less ground loss.

All loaded antennas are inefficient.  Some are an acceptable
compromise for mobile operation (size) and generally center loaded
is better than base loaded.  Always, taller is better.

Pair of mobile whips as dipole, ok if its really high and tuned but
very very narrow band even on 20M.  Ok most bands 80-20 barely
cover the CW segment. 

That leaves half wave antennas generally center fed as best and
height determines length and pattern.  Low dipole below about
 5mhz can be good for NVIS or general operating.  Under current
solar conditions NVIS is likely to be limited to 80m and on a good
day 60M.  For 160 and 80  you can't get your antenna high enough
so the defacto radiation is UP and the predominant modes are
NVIS and luck.

For convenience end fed half wave antennas are very useful
as they can be easier to deploy but useless in the flat lands.

If all else read MCRP 3-40.3B, especially chapters 3,4 and 6.

Rule 3:  Any antenna deployed is better than a bunch of
stuff in storage (trunk).

To that I offer the K3MT grasswire, long dipole with matching
transformer stretched out on the ground.  its advantage is easy
deployment anywhere and works on 160M. 

Allison

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WB6BYU
Member

Posts: 18535




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« Reply #8 on: September 29, 2019, 11:32:26 AM »

You'll want to keep an eye on current propagation, of course.  A convenient way to do that is via the
Australian Space Weather Services website.  Under current conditions, for contacts less than
about 500km (if you are in Darwin) you'll want 80m (or 60m) during the day and 160m at night for
NVIS.  During the day the skip zone on 40m should pull into 500-600km or so, and 30m may get as
short as 800 - 900 km at mid-day.  Conditions can vary significantly depending on latitude and current
ionospheric conditions.

For local contacts (out to 1000 km), their Local Area Mobile Prediction (LAMP) chart is convenient
(though it is designed for commercial circuits that generally want a higher confidence than random
ham contacts).  They have a built-in option for the ham bands so you don't have to enter all the
specific frequencies.  There are a number of other forecast models that may be useful as well.
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