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80m/160m trap dipole



 
 
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  #1  
Old June 21st 09, 01:43 AM posted to rec.radio.amateur.antenna
maxpower
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Posts: 2
Default 80m/160m trap dipole

Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You.
Cheers
Max
  #2  
Old June 21st 09, 02:10 AM posted to rec.radio.amateur.antenna
Ed
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Posts: 256
Default 80m/160m trap dipole


. . . . I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.


I'll leave the home-brewing to others... its relatively easy, but if
you want to take the simple but more expensive route, there are traps
available commercially... Amateur Radio Electronics carries a fine line
made by Reyco. Their 75 and 80 meter traps sell for $53.00 a pair. I
just sold a pair of 75M traps a few months ago on EHam for $25.00.


Ed K7AAT

  #3  
Old June 21st 09, 02:44 AM posted to rec.radio.amateur.antenna
Roy Lewallen
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Posts: 1,374
Default 80m/160m trap dipole

maxpower wrote:
Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You.
Cheers
Max


The function of a trap is to automatically shorten an antenna for use on
higher frequencies. For example, 80 meter traps can be added to a 160
meter dipole to make it usable on 80 meters. But it doesn't work in
reverse -- traps won't make your 80 meter dipole work on 160.

You can add loading coils to an 80 meter antenna to make it work after a
fashion on 160. But then it won't work on 80 unless you have some way to
switch the traps out.

Roy Lewallen, W7EL
  #4  
Old June 21st 09, 06:19 AM posted to rec.radio.amateur.antenna
Jim Lux[_2_]
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Posts: 25
Default 80m/160m trap dipole

maxpower wrote:
Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You.
Cheers
Max


Would a switchable network at the feedpoint work for you? You could
send power to operate a relay up the feedline. The gain/efficiency of
a half length dipole (e.g. 40 m long for use on 160m) isn't all that
bad compared to full size. It's only when you get down in the tenth
of a wavelength or less that you start seeing big changes.
  #5  
Old June 21st 09, 02:06 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_]
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Posts: 3,522
Default 80m/160m trap dipole

maxpower wrote:
Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You. Cheers Max


It is not clear to me whether you are talking about:

1. Increasing the length of your dipole to ~246 feet
and adding 80m traps or

2. "Making your" existing ~123 foot "80m dipole usable
on 160m" by adding 160m loading coils.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com
  #6  
Old June 21st 09, 02:18 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_]
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Posts: 3,522
Default 80m/160m trap dipole

maxpower wrote:
I have an 80m dipole that I wish to use on 160m as well.


Something else to consider is shorting the transmission
line at the tuner and feeding the 80m dipole as a single
wire against ground on 160m where "ground" is ideally a
good radial system.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com
  #7  
Old June 21st 09, 02:52 PM posted to rec.radio.amateur.antenna
Dave
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Posts: 797
Default 80m/160m trap dipole


"maxpower" wrote in message
...
Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You.
Cheers
Max


'traps' are normally meant to cut up a big antenna into smaller pieces for
user on higher frequency bands. that is, if you had a 160m dipole you could
put 80m traps in it to make the inner part resonant on 80m. to get an 80m
dipole to resonate on 160m you need to add loading coils to make it look
longer, that will of course make it not resonant on 80m. with some more
complex loading and trapping combined you could probably make something that
would force it to resonate on 160m and 80m... but its probably easier to
just put a tuner at the radio end and got with that.

  #8  
Old June 22nd 09, 06:21 PM
KE5LDO KE5LDO is offline
Junior Member
 
First recorded activity by RadioBanter: Jan 2009
Location: East Texas
Posts: 13
Thumbs up

There is an out of print book, "Easy up Antennas for Radio Listeners and Hams", by Ed Noll. It has plans in there for doing EXACTLY what you are looking for. Amazon has it for $13.50. Others may also have it. Good reference.
KE5LDO










Quote:
Originally Posted by maxpower View Post
Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You.
Cheers
Max
__________________
Extra Class
Volunteer Examiner
ARRL Instructor
  #9  
Old June 23rd 09, 10:01 AM posted to rec.radio.amateur.antenna
Ian Jackson[_2_]
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Posts: 395
Default 80m/160m trap dipole

In message , Dave
writes

"maxpower" wrote in message
...
Hello All,
I have an 80m dipole that I wish to use on 160m as well. I am
considering using traps on the existing dipole. I have searched the
web and have not found any 80m/160m trap dipoles. Has anyone added
traps to their 80m dipole to make it usable on 160m? Or could anyone
point me in the right direction towards homebrewing traps to suit. I
have made traps in the past for 40m/80m dipoles but I am unsure what
dimensions, length, turns etc I would need for homebrewing a trap to
make my 80m dipole useable on 80m and 160m.
Thank You.
Cheers
Max


'traps' are normally meant to cut up a big antenna into smaller pieces
for user on higher frequency bands. that is, if you had a 160m dipole
you could put 80m traps in it to make the inner part resonant on 80m.
to get an 80m dipole to resonate on 160m you need to add loading coils
to make it look longer, that will of course make it not resonant on
80m. with some more complex loading and trapping combined you could
probably make something that would force it to resonate on 160m and
80m... but its probably easier to just put a tuner at the radio end and
got with that.


If you already have an 80m halfwave dipole, you will need to add your
80m traps at the ends. Anything added beyond the traps will 'not be
seen' on 80m.

You will then need to extend the dipole beyond the traps, adding
sufficient wire to make it resonant on 160m.

If there were no traps, the additional length of wire needed would be
around 67'. However, below their 80m parallel resonance, the 'effective
inductance' of 80m traps will act as loading coils, and the length of
wire needed will be less than 67'. [Note: The effective inductance will
be greater than the physical inductance of the coil itself.]

How long (or 'short') the additional wire will need to be will depend on
the L/C ratio of the traps. A large L/C will require less additional
wire). You might get away with (say) 30'. If you can't accommodate this
amount of wire, you could always cheat by winding some of it,
effectively as another loading coil.

Note that, because your 160m dipole has inductive loading (from the 80m
traps alone, plus any additional loading you have to add), it will have
less bandwidth than a full-size 160m dipole.

Of course, an easier alternative approach might be simply to use an open
wire feeder, and a tuner in the shack. The existing 80m dipole will be
reasonably efficient on 160m as it is, but it could be improved by
extending the existing dipole (assuming you have the space available).
--
Ian
  #10  
Old June 23rd 09, 12:44 PM posted to rec.radio.amateur.antenna
maxpower
external usenet poster
 
Posts: 2
Default 80m/160m trap dipole

Thank You all for the replies.
Ian, what you haved written is what I am trying to do. I have an 80m
dipole up at the moment that needs to be relocated.
I thought I might as well put it up where I could put some 80m traps
inline and extend it for 160m. I haven't got enough room for a half
wave 160m dipole, but I could possibly squeeze in an 80/160m trapped
dipole, depending on how much extra length (with the 80m traps) I need
to add to get it to resonate on 160m. I have since found a drawing for
a 40/80/160m trapped dipole. I will make up the 80m traps from that
plan, add it to my 80m dipole and see how I go.
Cheers
Max
 




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