I've struggled with what type of antenna to replace the broken original with.  I first tried an 11" rubber ducky that didn't work very well, as well as a hidden antenna that mounted to the window; again not working too well.  I decided it was time to investigate how to repair or replace the old semi-automatic antenna that Datsun included originally. 

The great feature of the Datsun antenna is that it is controlled by the radio head unit with a switch, allowing the driver (or passenger) the ability to raise or lower the antenna to the proper level to tune in stations.  

 

The original Datsun antenna had a modulator box already installed that allowed the switch to power one wire for up, the other for down, and use the body of the antenna for a ground; this is how the switch works too.  The modern semi-automatic that I sourced just reverses the polarity to have it go up and down.

 

I was able to find a diagram of a door lock actuator that would allow me to use the original Datsun radio switch and wiring while making the new antenna work by means of two relays.  Essentially reversing the polarity of the output wires.  

 

The results are great! I can accurately tune into any station in my '72 240z's radio that I can in a modern car with a digital tuner (meaning the antenna performs as good).

 

Full Write-Up with Pictures:

http://jarvas240z.blogspot.com/2015/05/amfm-antenna-upgrade.html

Great write up. A good solution for adapting a modern power antenna. Now if you could just find the elongated tip.

This is what I like to see. Upgrades using a combination of old and new technology.  For those of you who would like to listen to pandora or mp3 player on their ancient but period correct original radio's you may be interested to know you can add mp3 functionality to the later model hitachi radio that have the round 7 pin din in

the back. All you need is a 7pin din to mp3 male adapter jack.

 

Sometimes technology can be a pain in the butt too. I have the automatic antenna feature on my 90 cressida and something went haywire in the antenna.

When i turn the radio on the antenna motor keeps going after the antenna is fully extended. The only way to kill it is disconnect the battery.

Edited May 25, 20159 yr by hr369

Might be a good package for Dave Irwin to put together as one of his technology upgrades.  Just the parts end up being about $30 (including antenna & relays)

Nice write up. Where did you mount relay?

Tamo3 -- Both relays are mounted to the strut that holds the antenna to the body.  This allowed me to keep them fairly hidden, only be powered when the switch energizes the antenna, and to keep the original wiring.  Take a look at the last couple pictures on my blog site.

Oh, I see. nicely done!