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Antennas

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craigb(at)onthenet.com.au
Guest

Posted: Fri Sep 11, 2009 7:56 pm Post subject: Antennas

For those interested I have constructed and fitted a full wave loop antenna

as per Dave Morris's

designs located here.



http://www.davemorris.com/dave/MorrisDFLoop.html



I hooked up my hand held scanner to the loop comm antenna today, and the

initial results

are excellent. I appear to be getting better reception on the ground in my

closed workshop

than i have had in most of the aircraft i have flown, while airborne. the

ATIS

info from the airport 40km away is so strong I cannot cut it out even with

FULL

squelch, likewise aircraft transmissions from areas 25km the other side of

the airport

(based on airspace freq, Parachute drop at a field I know well) are nice and

clear.

The antenna  still has to SWR'ed in yet, and is approximately 2 inches too

long.

oh the aircraft is presently facing more or less east, and the airport is

due south

of me, so the ATIS and the aircraft mentioned is virtually all side lobe

reception.

The loop fits neatly round the fuselage about 100mm behind the baggage bay

bulkhead



total cost for this was about $5 if you are counting your pennies that hard.



Craig

kit 577

VH-XSV

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gregoryf.flyboy(at)comcas
Guest

Posted: Sat Sep 12, 2009 8:55 pm Post subject: Antennas

Nice Craig!  It would be interesting to set up a bunch of different style

antennas and compare them all, with the same feed line and radio. Not too

much matter if they all work adequately. Let us know how it works in the

air. 



Maybe I will play around with one of these, while working on the others too.



Regards,

Greg

 >For those interested I have constructed and fitted a full wave loop

antenna

 	  Quote: 	
		  as per Dave Morris's

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frans(at)paardnatuurlijk.
Guest

Posted: Sun Sep 13, 2009 10:24 am Post subject: Antennas

craig bastin wrote:

 	  Quote: 	
		   

 

 For those interested I have constructed and fitted a full wave loop antenna

 as per Dave Morris's

 designs located here.

 

 http://www.davemorris.com/dave/MorrisDFLoop.html

 

 I hooked up my hand held scanner to the loop comm antenna today, and the

 initial results

 are excellent. I appear to be getting better reception on the ground in my

 closed workshop

 than i have had in most of the aircraft i have flown, while airborne.


	


Basic physics dictate that if you get "gain" somewhere, there must be a

loss elsewhere. If I have a lightbulb, I can certainly increase the

light in certain directions (by using reflectors and/or lenses) but this

always comes at the price of a loss somewhere else (behind the

reflector, or outside the aim of the lenses).



Now, in an aircraft, you probably favour an omnidirectional radiation

pattern (like a naked light bulb). If someone claims a "gain", I would

like to know where the losses are.



So, my question is: "Where are the losses?"

(If someone is brave enough to tell me that there ain't any losses, my

next question will be where the extra energy of the gain is coming from,

and whether it is possible to save the earth with this magical extra

energy that seems to spring into live from nowhere.  )



Frans

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craigb(at)onthenet.com.au
Guest

Posted: Mon Sep 14, 2009 3:52 am Post subject: Antennas

Frans, I dont believe I mentioned "gain", If i remember correctly, there was

much

conjecture over how effective and how "directional" an antenna of this type

would be

a while ago on the forum. I was simply posting what I have done, and my

observations

on how well it "appears" to work, even when the source of the transmission

is in the apparent

worst location, in an attempt to answer some of the questions raised.



For all I know the transmission qualities of the antenna I built will be

very poor, with very high

SWR that cannot be corrected making it totally useless , but not having a

comm radio I

can hook up to the antenna i wont know until I actually test it's transmit

qualities.



The whole thing took about 10 minutes to make, and cost about $5, maybe if

you have a radio

you can use you could make one and see if your results are simmilar to mine.

BTW the wire

I used for the loop is .7mm stainless 316 grade, from a MIG welder spool, I

fashioned "clamps"

to hold the wire from the brass inserts in an old light switch, that have

the screws in them.

I simply cut the co-axial cable to length stripped it back and soldered the

outer copper braid

to the outside of one of brass clamps, and the inner copper core to the

other brass clamp, and then

crimped the BNC connector on the other end of the cable. The stainless wire

can then just be slipped

into the brass clamp and the screws tightened. I did drill a small hole in

the end of one of the

brass clamps to allow the loop wire to pass right through, which should

allow easy adjustment

of the length of the loop to get the SWR as good as it can be.



I dont expect the be buying any avionics until my baby is ready to fly, so

if anyone has the time

and a radio to test this I would love to hear from them, on or off list.



craig

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