# LPDA orientation when receiving GPS signals on USRP2

**URL:** <https://www.ruby-forum.com/t/lpda-orientation-when-receiving-gps-signals-on-usrp2/201764>\
**Category:** GNU Radio\
**Created:** [January 14, 2011, 4:09am UTC](https://www.ruby-forum.com/t/lpda-orientation-when-receiving-gps-signals-on-usrp2/201764 "2011-01-14T04:09:41Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\
**Post date:** [January 14, 2011, 4:09am UTC](https://www.ruby-forum.com/t/lpda-orientation-when-receiving-gps-signals-on-usrp2/201764/1 "2011-01-14T04:09:41Z")

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Hi everyone,

Does anyone know what the orientation of an LPDA (log periodic dipole  
antenna) should be when receiving GPS signals?

Should the up-most element be the longest one, or should it be the  
shortest  
one? In other words

* * *

```
           ___________

```

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_-  
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_  
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_  
OR  
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

* * *

```
       ____________________________

```

* * *

* * *

Nick

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**Author:** ![trout](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e9bcb4/32.png) [@trout](https://www.ruby-forum.com/u/trout)\
**Post date:** [January 14, 2011, 4:38am UTC](https://www.ruby-forum.com/t/lpda-orientation-when-receiving-gps-signals-on-usrp2/201764/2 "2011-01-14T04:38:28Z")

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On Thu, 2011-01-13 at 22:08 -0500, Nick O. wrote:

> * * *
> 
> Nick
> 
> * * *
> 
> Discuss-gnuradio mailing list  
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> [Discuss-gnuradio Info Page](http://lists.gnu.org/mailman/listinfo/discuss-gnuradio)

> From ARRL Antenna Handbook (1988) the ‘forward’ direction is towards the  
> smaller elements on an LPDA. Don’t think that JCM equations have changed  
> since '88.

```
     Kind Regards,

                 John

```

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**Author:** ![trout](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e9bcb4/32.png) [@trout](https://www.ruby-forum.com/u/trout)\
**Post date:** [January 14, 2011, 5:42am UTC](https://www.ruby-forum.com/t/lpda-orientation-when-receiving-gps-signals-on-usrp2/201764/3 "2011-01-14T05:42:53Z")

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On 01/13/2011 07:08 PM, Nick O. wrote:

> Hi everyone,
> 
> Does anyone know what the orientation of an LPDA (log periodic dipole  
> antenna) should be when receiving GPS signals?
> 
> Should the up-most element be the longest one, or should it be the  
> shortest one? In other words

Point the short side (with the connector) towards the source you are  
trying to receive from.

A log periodic antenna is not ideal for receiving GPS since GPS is  
circularly polarized and the LPDA is linear.

Matt