df antennas on van

[brasda91]

Sorry for the brain-fart.

For those that have the front/right, rear/left, and center antennas that mount on the van roof, how far apart are the front/right, left/rear antenna's placed?  The length of the center antenna or the length of the front/right, left/rear antenna?

I know the center antenna is centered between the two outside antenna's, but I'm having a brain-lock on how far apart the front, rear antenna's are spaced from each other.

[lordmonar]

For best results they should be at least 1 wave lenght apart....but van roofs are ususally not large!

For practical purposes....about the length of the antenna to the center antenna should be good.

[SarDragon]

Here are the manufacturer's instructions. Go to page 16.

[lordmonar]

Here are the manufacturer's instructions. Go to page 16.

INSTRUCTIONS!  WE DON'T NEED NO STINKING INSTRUCTIONS! 

[IceNine]

CAUTION, DANGER, DANGER Will Robinson.

If you have a CAP or any other transmitting radio for that matter in the vehicle you will fry the discriminator circuit in the antenna's.  I learned this the hard way. 

Moral of the story either turn the radio off or don't use the antenna's.

You have to be something like 15 ft away from a radio that transmits with 25 watts.

[SarDragon]

CAUTION, DANGER, DANGER Will Robinson.

If you have a CAP or any other transmitting radio for that matter in the vehicle you will fry the discriminator circuit in the antenna's.  I learned this the hard way. 

Moral of the story either turn the radio off or don't use the antenna's.

You have to be something like 15 ft away from a radio that transmits with 25 watts.

How close were your antennae? I have my DF antennae about 8 ft from my airband antenna, and have had no problems. The DF antennae are about 2 ft from my Stealth antenna, and I worry more about whacking the airband radio, than I do about the DF antennae.

Here are the specs from the manual linked above:

[ltcmark]

I use a homemade antenna fore/aft -  left/right array and mounted it permanently on our Corporate van.  I made the switch boxes using small metal project boxes and breadboard.  I used industrial diodes instead of the diodes that you can order from the DF factory.  They can take a lot more abuse and they are a lot cheaper.  Not to mention you can get them from local electronics store.  I also used ¼ wave 2 meter antennas for the array.  Total cost was about $50 at the time.

As far as mounting, the VHF antenna is about 4 feet from the front DF antenna.  The array is mounted towards the back of the vehicle.  I do not use a center antenna.  When you have 12 antenna's on a van, you run out of real estate fast.  I do try to keep the transmitting antennas towards the front of the vehicle.

Now before everyone chastises me, I have been using this system for 16 years, never replaced a diode and I have 79 actual and 57 practice finds.   99.5 percent of the time, I can drive right up to the ELT unless the gate is locked.

I also installed a Cessna VOR/Glideslope head in the van.  This is hooked up as an external meter to the DF unit.  It is a lot easier to see than the little meter on the DF.  To make it more interesting I put a switch on the VOR head to use the Glideslope part in the fore/aft mode.  Needle up - signal in front of you, needle down - signal hehind you.

[Tubacap]

^Can you provide pictures?  This seems like a fairly simple setup, that can still be accomplished fairly easily.

[notaNCO forever]

 mashcraft your system sounds awsome. Please post a picture.

[ltcmark]

I will take a couple of pictures and post in the next day or so.

[ltcmark]

Here are the pictures.  The first one shows our equipment set up. 

The antenna switching is done manually.  When you switch the antenna you also have to manually switch the VOR head with the external meter switch.  It is hidden behind the BNC connector.

I used a 1/4" stereo connector for the jack to the VOR head.  You can use a smaller 3 conductor connector of any type that would fit.  I used this type of connector so that it would break the connection to the internal meter when the plug was installed.

I will caution you, if you take your unit apart to make this modification, be very careful of all the small wires.  They break with very little force.



For the a larger view:
http://www.inwg.org/184/photo/df.jpg


Here is the antenna set up on the van:



For a larger view of the van:
http://www.inwg.org/184/photo/van.jpg

Enjoy!

[Tubacap]

Thanks!