Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old November 29th 06, 03:01 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 14
Default Feeding a 4 bay vertical folded dipole

I need to build a 4 bay folded dipole like the one use on vhf/uhf
repeaters. The folded dipole is easy
enough to figure out but how do you get the 4 - 300ohm dipoles to
combine to one 50ohm feedline,
I have looked close as i can at these and there is no combiner but it
looks like maybe some coax
phasing stubs or lengths of coax inside the antenna support mask?


  #2   Report Post  
Old November 30th 06, 04:28 AM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Oct 2006
Posts: 134
Default Feeding a 4 bay vertical folded dipole

"N4aeq" wrote in message
ups.com...
I need to build a 4 bay folded dipole like the one use on vhf/uhf
repeaters. The folded dipole is easy
enough to figure out but how do you get the 4 - 300ohm dipoles to
combine to one 50ohm feedline,
I have looked close as i can at these and there is no combiner but it
looks like maybe some coax
phasing stubs or lengths of coax inside the antenna support mask?


The ARRL book, FM and Repeaters (1970s) included information on building a
"phasing harness".

Kevin Custer, K3KKC has some of this information at his Repeater Builder web
site:
http://www.repeater-builder.com/rbti...seddipole.html

w9gb


  #3   Report Post  
Old November 30th 06, 04:39 AM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Oct 2006
Posts: 134
Default Feeding a 4 bay vertical folded dipole

"N4aeq" wrote in message
ups.com...
I need to build a 4 bay folded dipole like the one use on vhf/uhf
repeaters. The folded dipole is easy
enough to figure out but how do you get the 4 - 300ohm dipoles to
combine to one 50ohm feedline,
I have looked close as i can at these and there is no combiner but it
looks like maybe some coax
phasing stubs or lengths of coax inside the antenna support mask?


Here is a great UHF solution (DB Products commercial 4-bay antenna) -- nice
price
DB Products phasing harness for 4 bay UHF dipole, New in box. 455.0 MHz
center frequency. $50.
http://www.ipass.net/hockaday/com.html

gb


  #4   Report Post  
Old November 30th 06, 01:59 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Nov 2006
Posts: 85
Default Feeding a 4 bay vertical folded dipole

There are quite a few possibilities

The first that comes to mind is that 300 ohm ribbon feed from all 4
antennas joined at one point will give you 75 ohms. The ribbons should
be the same length.

You can also use a lower Z line in odd multiples of 1/4 wave to
translate the Z down to a lower value. This is commonly called a Q
section and is worth getting your head into! (you can also translate up
in Z)

You will find that with mast coupling issues the antenna feed Z will
probably be lower than 300 ohms anyway. If for example it gets to 200
ohms a tuned half wave of 300 ohm ribbon on each will translate the same
impedance back to where you combine them. You would then get 50 ohms.

Coaxially you could make a 4:1 balun from 75 or 50 ohm coax. This is a
nice way of feeding 200/300 ohm antennas from coax.

I think in my case I would be concerned what coax/ribbon/joiners/T's etc
I had available for feeding the thing, then work out how to use them..

Cheers Bob

N4aeq wrote:

I need to build a 4 bay folded dipole like the one use on vhf/uhf
repeaters. The folded dipole is easy
enough to figure out but how do you get the 4 - 300ohm dipoles to
combine to one 50ohm feedline,
I have looked close as i can at these and there is no combiner but it
looks like maybe some coax
phasing stubs or lengths of coax inside the antenna support mask?

  #5   Report Post  
Old November 30th 06, 08:23 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 148
Default Feeding a 4 bay vertical folded dipole

On Wed, 29 Nov 2006 21:28:06 -0600, w9gb wrote:
"N4aeq" wrote in message
ups.com...
I need to build a 4 bay folded dipole like the one use on vhf/uhf
repeaters. The folded dipole is easy
enough to figure out but how do you get the 4 - 300ohm dipoles to
combine to one 50ohm feedline,
I have looked close as i can at these and there is no combiner but it
looks like maybe some coax
phasing stubs or lengths of coax inside the antenna support mask?


The ARRL book, FM and Repeaters (1970s) included information on building a
"phasing harness".


IIRC -- without running down to the ham shack and diggng through my old
copies -- some ARRL Handbook (and/or Antenna Handbook) editions back
then had a complete project description for the whole shee-bang: folded
dipoles, matching/phasing harness, mounting technique(s), etc.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: http//jonz.net/ng.htm


  #6   Report Post  
Old November 30th 06, 08:36 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 1,614
Default Feeding a 4 bay vertical folded dipole

Allodoxaphobia wrote:
IIRC -- without running down to the ham shack and diggng through my old
copies -- some ARRL Handbook (and/or Antenna Handbook) editions back
then had a complete project description for the whole shee-bang: folded
dipoles, matching/phasing harness, mounting technique(s), etc.


Available on eznec.com, I have used EZNEC in
combination with SIMPFEED.ZIP to design phased
systems that worked well.
--
73, Cecil, http://www.qsl.net/w5dxp


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Inverted ground plane antenna: compared with normal GP and low dipole. Serge Stroobandt, ON4BAA Antenna 8 February 24th 11 11:22 PM
Why Tilt ? - The Terminated Tilted Folded Dipole (TTFD / T2FD) Antenna RHF Shortwave 2 April 18th 06 10:21 PM
ABOUT - The "T" & Windom Antenna plus Twin Lead Folded Dipole Antenna RHF Shortwave 0 November 4th 05 07:13 PM
Workman BS-1 Dipole Antenna = Easy Mod to make it a Mini-Windom Antenna ! RHF Shortwave 0 November 2nd 05 12:14 PM
QST Article: An Easy to Build, Dual-Band Collinear Antenna Serge Stroobandt, ON4BAA Antenna 12 October 16th 03 07:44 PM


All times are GMT +1. The time now is 05:52 PM.

Powered by vBulletin® Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright ©2004-2017 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017