[K3CAL] [Norton AntiSpam]Re: 2 meter/70 cm Log Periodic Antenna Project...

[Rich Weaver]

Log periodic antennas offer a high impedance at the feed point. Just like a TV antenna.
Something like 200 to 300 ohms. You need a 4:1 balun and 75 ohm cable. 
The balun is the weak point in the design due to losses and power handling capabilities. 
The SWR may not be “flat” across the entire bandwidth. 
They are excellent broadband receive antennas but can be a little tricky as a transmitting antenna.
The Military and Government Services are the biggest users of these antennas.
There will be only a couple of ”active”  elements at best for a band range, two meters, 70cm etc..
I would not expect much gain. If you somehow get 3 DBd, that is nothing more than a 5/8 wave antenna.
Rich
WW3ZZ



From: Jim Tetlow 
Sent: Wednesday, October 29, 2014 5:41 PM
To: Calvert Amateur Radio Association - K3CAL 
Subject: [Norton AntiSpam]Re: [K3CAL] 2 meter/70 cm Log Periodic Antenna Project...

I was under the impression that it was 142 to 450 continuous. Wouldn't that mean 2 meters, 1 1/4 meters and 70cm?  Three amateur bands, thinking that be the case, it was exactly what I was looking for with one coax and no duplexers. If it doesn't cover 220, it isn't exactly what I was wanting, but would still be fun to build........if it doesn't cost more than $60 worth of materials.

Sent from my iPad, 73, 
Jim Tetlow
O!!!!!O
k3uga at comcast.net



On Oct 29, 2014, at 17:27, Edwin A Noell Jr <enoell at verizon.net> wrote:


  We're going to build them because we can.

  And want to.

  Ed
  KC3AEN



  On 10/29/2014 04:08 PM, Rich Weaver wrote:


    Log Periodic Beam Antenna that covers 142 - 450 MHz continuously....and with Gain
    What’s the purpose of the log periodic other than for a scanner? 
    We can’t transmit on the entire range.
    How much gain? Is that in DBi or DBd?
    If you are going to use it on 2 meters, then build a 2 meter yagi.
    If you are going to use it on 70cm then build a 70cm  yagi. 
    Why waste all the extra elements that are not in the ham band?
    Better yet build a 2 meter yagi with a 70cm yagi under it on the same boom.


    From: Monica Noell 
    Sent: Tuesday, October 28, 2014 11:05 PM
    To: Calvert Amateur Radio Association - K3CAL 
    Subject: Re: [K3CAL] 2 meter/70 cm Log Periodic Antenna Project...

    Hi Steve,

    Ed and I are interested in building two antennas (one for each of us).

    Thanks!
    Monica
    KC3DAS

    On 10/27/2014 5:44 PM, Steven Hempling wrote:

      Hi!... Any one interested in building a Log Periodic Beam Antenna that covers 142 - 450 MHz continuously....and with Gain... Boom is less than 4 feet... longest elements are 44 inches... we would buy materials in 20 foot lengths... think pop rivets..  drills..... SS hardware... Lexan/PVC........   Post interest.... I will work out $$  cost will be materials only... keeping receipts...Please post Interest.... thanks!   Steve   N3IPN...


      PS... It was a nice hamfest in St Mary's County! 
       

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