hi

i've been studying around trying to get info to build a small dipole and
found 'too much' info ended up confused thought perhaps someone
could help

I am going to be traveling around , (hotels , etc) and want to build or
buy a small as poss dipole for 40-10m.

my main goal would be aside from small, to minimize giving off RFI.

I am not certain in general if a trap design or not is best

and rfi wise, not certain if adding a balun(1:1/4:1) is going to min any
problems, same for ladder line vs coax

(my tuner can take coax, or ladder)


any tips/suggestions to designing a total solution would be greatly
appreciated,, i'd like to perhaps build 1 or 2 kinds and experiment
but got confused alot of posts seem to contradict each other
technology wise


thanks

I am going to be traveling around , (hotels , etc) and want to build or
buy a small as poss dipole for 40-10m.

Hi, Is it your intention to have the antenna inside the Hotel room? If it is,
I can tell you from experience that you will not have very good results. I
assume it is due to the amount of metal used in the building, especially the
newer ones. The best resuslts I have had operating from a Hotel is running
coax out to the pretty good mobile antenna mounted on my vehicle. This is not
always possible, for a number of reasons, but when you can, it is your best
bet.
If you could run a loaded vertical out a window, or mount it on a balcony.
You will have to use a counterpoise or radial wire with the verticals. If the
balcony is large enough you might be able to string a small loaded dipole.
When I did the above, the results were dissapointing. When I have tried
anything inside the room, the results were poor.
73 Gary N4AST

I have had some experience of this. I used a home-brew, transportable,
aluminium, attache-case 30-watt transceiver. Still got it. It still works.
But these days it is only of strong sentimental value.

In hotel bedrooms the best antenna by far, is a length of thin, plastic
insulated, flexible, multi-strand wire. tossed out of the bedroom window.
Allow it to dangle down alongside the wall for as far as possible,
consistent with your ideas of what the neighbourhood will put up with before
complaints are heard.

I always asked, with a nice smile when I had gleaming teeth, the young lady
hotel receptionist for a room on the highest floor possible, at the rear of
the hotel. The wire could then dangle down as far as just above the trash
bins outside the open rear door of the hotel's kitchen.

If one is staying at the hotel for several days its a good idea to make
friends with the Chef, buy him a drink or two in the bar in his off-duty
hour. This ensures there will be no interference to arrangements at the
lower end of the antenna in the vicinity of the trash bins.

To feed the top end of a vertical wire still requires a ground connection.
So use one or more copper pipes in the hotel's plumbing and central heating
system. Don't forget to include in the tool kit a big alligator clip, with
flexible wire already soldered to it, or two clips, to make the desired
connection to ground.

On one occasion, from a high multi-floor building, I was able to tell the
disbelieving fellow at the other end of the QSO I was using a top-fed
3/8-wave vertical antenna on the 160 metre band. Which was quite true.

But if you like experimenting with small, hotel-room antennas, without
opening the windows, then try a very short, centre-loaded, horizontal
dipole. The loading coil is the most awkward component to pack into your
travelling bag when you walk into the hotel. Use drawing pins or small nails
to anchor the dipole ends to the wall-paper, door posts or ceiling. Don't
forget to take with you a small hammer.

Seriously now, a short centre-loaded dipole is the electric counterpart of
the small magnetic loop. Like the magloop it can be most effective at one
particular resonant frequency although it cannot be tuned except by pruning
the overall length of the wire loading tails.

Download program MIDLOAD from website below for design of a centre-loaded
antenna, including coil design, diameter and length of coil former and
number of turns. There are several different ways of feeding it, either with
coax or balanced-twin feedlines.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

"ml" wrote in message
...
hi

i've been studying around trying to get info to build a small dipole and
found 'too much' info ended up confused thought perhaps someone
could help

I am going to be traveling around , (hotels , etc) and want to build or
buy a small as poss dipole for 40-10m.

my main goal would be aside from small, to minimize giving off RFI.

I am not certain in general if a trap design or not is best

and rfi wise, not certain if adding a balun(1:1/4:1) is going to min any
problems, same for ladder line vs coax

(my tuner can take coax, or ladder)


any tips/suggestions to designing a total solution would be greatly
appreciated,, i'd like to perhaps build 1 or 2 kinds and experiment
but got confused alot of posts seem to contradict each other
technology wise


I have seen folks use 2 -or 4 toy slinkies (the metal kind)
what holds them up ? plastic trimmer line like on a weed-eater
The plastic trimmer line is threaded through the slinkies and stretched
across the room
, and the slinkies acted like a continouusly-loaded dipole
as short as you need it - and it can s-t-r-e-t-c-h a little too.



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Well, you could always stick a TS-2000 rig in the car, and run "sky command"
with a TH-D7a.

I run APRS in a similar manner, HT on flea power, talking through the car's
transponder which I configure into a temporary digipeater. It's got a nice
antenna, and 50W output, and a nice big battery. Makes life much easier.