[Antennas] QRP rig and Mini Antenna; Mini Tin Questions

[NPAlex at aol.com]

Nick,
 
I have responded to some of your questions below with my thoughts in  
CAPITAL LETTERS.  Others have responded and all have made good suggestions  
regarding wire type etc.  One point that you have to clarify is the  frequency of 
operation - 40 meters as the transmitter implies, or 20m which you  mention 
as a band of interest.  It may not do both.
 
Good luck
Norm W4QN
===============================================================
Subject: [Antennas] a few portable antenna questions
excerpts-

Background:
I bought a 40m RockMite from SmallWonders Laboratories to  experiment with 
and I'm really excited by the possibility that I might be able  to store a 
whole 20m *station* into an Altoids tin. Sounds crazy maybe, but I  would 
then be able to take it backpacking with me. That, and I'll never turn  down a 
good project.

==============================
Questions:
(1)  The RockMite is solid-state. Does this mean that the RF output is 
balanced or  unbalanced? 
===>IT IS MOST LIKELY UNBALANCED, THE ANTENNA CONNECTION POINT WILL TELL  
YOU WHICH.==== 

(2) Is a (small diameter) coax-fed dipole a good antenna system to use,  or 
will anyone suggest something better/simpler/smaller?
====> IN YOUR CASE AND BASED ON YOUR REQUIREMENTS I WOULD NOT RECOMMEND  
IT. TOO FRAGILE, YOU WON'T HAVE IT HIGH ENOUGH.  IF YOU ARE WILLING TO  CARRY 
A COLLAPSIBLE SUPPORT IT MAY BE ABLE TO WORK (SEE BUDIPOLE FOR AN  IDEA).  I 
WOULD CONSIDER A QUARTER WAVE LENGTH OF COPPER WIRE, A STAINLESS  SKEWER AS 
A ANCHOR, GROUND AND FEED POINT FOR MINI TEFLON COAX. ADD TO THE  OPPOSITE 
END OF THE WIRE A MONO-FILIMENT EXTENSION TO TOSS OVER A TREE OR A ROCK  
OUTCROPPING ABOVE YOUR CAMP SITE.  YOU MAY HAVE TO BUILD A SIMPLE "L"  MATCHING 
NETWORK.  ===> 

(3) My tent is about 4.5 feet high and has aluminum support rods so I'm  
thinking that 3m of feedline ought to get my wire far enough away from those?  
(It's tempting to use the support rods as a counterpoise for a vertical, 
but I  still would like to be able to use this setup if I'm without the tent. 
Two  interchangeable antennas maybe?)
===> SAME AS ABOVE SHOULD SATISFY THIS REQUIREMENT====

(3) Are dipoles best driven by a balanced or an unbalanced signal? And  if 
I need to drive it with a balanced signal can I do that with something like  
miniature ladder-line?
====> IT MAKES LITTLE REAL DIFFERENCE, AND IN YOUR SITUATION IT MIGHT BE  
BETTER UNBALANCED AND ALLOW THE COAX TO BE PART OF THE ANTENNA. =====

(4) Would it help if the station were tied to ground? If so, I have six  
eight-inch aluminum tent stakes at my disposal. 
===> ONE PROBLEM WILL BE RF GETTING INTO THE CIRCUITS, A GROUND WILL  HELP, 
AS WILL A RF CHOKE IN THE FEED LINE. ABOUT 10 OR 15 FERRITE BEADS SLIPPED  
ONTO RG-174 COAX WOULD BE EFFECTIVE.=====

(5) All other things being equal, the shorter the wavelength, the  happier 
I will be, because the antenna will be less of a hassle to put up and  take 
down. Is 20m a good band? I will have only one crystal.
===> 20M IS A GOOD BAND, BUT IN YOUR OPENING STATEMENT YOU SAID YOU  BOUGHT 
A 40M ROCKMITE - IF THAT IS THE ONLY BAND, THEN YOU ARE COMMITTED TO THE  
40M BAND.===

(6) Do they make really tiny straight keys?
===> YES, AND YOU CAN MAKE YOU OWN FROM A MICRO SWITCH
.
(7) Has anyone tried anything like this before?
====>  I HAVEN'T COMMON, BUT THERE IS NOTHING TOO UNUSUAL IN WHAT  YOU ARE 
TRYING TO DO.  YOUR CHOICE OF MATERIALS, AND THE CONFIGURATION WILL  BE KEY 
TO YOUR SUCCESS.  A STRANDED, JACKETED WIRE IS MORE DURABLE THEN  SOLID AND 
UN INSULATED WIRE, (PENALTY IS A LITTLE SIZE AND WEIGHT). =====  

Sorry for all the questions, but I'm trying to plan this out as much as  
possible. I admit that allowing myself even one extra Altoids tin would make  
this much easier, but I like the challenge and even though this might not be 
the  most practical setup, I'm hooked on the idea of simplicity and think 
it would be  lot of fun to build and tweak. Now, if I could only finish 
learning CW...  :-)
====> A SECOND TIN MAY BE NECESSARY TO HOUSE A TUNING UNIT TO GIVE YOU  
MORE FLEXIBILITY IN MATCHING A VARIETY OF ANTENNAS.  FOR THE ANTENNA AND  COAX, 
USE A ZIP LOCK BAG TO CARRY THOSE PARTS. ===== 
 
REMEMBER YOU ARE QRP TO START WITH, SO THE BETTER THE ANTENNA PERFORMANCE  
THE BETTER YOU CAN EXPECT TO HEAR AND BE HEARD.  
 
ANOTHER ANTENNA THOUGHT, I WOULD CARRY AS MUCH LIGHT GAGE WIRE AS POSSIBLE, 
 END FEED IT (NEEDS A MATCHING CIRCUIT) AND STRETCH THE WIRE AS FAR AND 
HIGH AS  YOU CAN GET.  BRING A SLING SHOT OR A "TOSSING" WEIGHT TO GET AN  END 
UP IN THE AIR.

Answers, questions, concerns, and comments are all very  welcome.

Thanks for the bandwidth,
Nick Hecker  (KI4YSP)
------------------------------

Message: 3
From: "Richard  (Rick) Karlquist" <richard at karlquist.com>
Subject: Re: [Antennas] a few  portable antenna questions
fourninefour at yahoo.com wrote:
>  I  think that a dipole made from thin steel "thread" will be strong,
small, quick, lightweight, and a good performer.
> Nick Hecker  (KI4YSP)

At 10 MHz, 30 gauge copper wire has 1/3 ohm of resistance
per  foot.  Steel has many times that loss, especially if
it is "music wire",  which I suspect is what you are
thinking about.  Stick with  copper.

Rick N6RK
------------------------------

From:  iam at pmug.org (DavidE Benedict)
Subject: [Antennas] Mint Tin Questions  Answers

Basic dipoles are naturally balanced and need a transformer  inserted to be
fed w/ coax.

Basic verticals are naturally  unbalanced.

Transistorized equipment can be designed as balanced or  unbalanced.
Simplest circuitry is usually unbalanced.

Some have used  zip cord as balanced line. There is very light/small zip
cord  available.

Use 30ga copper wire, not steel.

There are a few  miniature straight-key  designs.

David
W7DBH



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