Near Intersection of I-35 & I-90 Southern Mn. | The above posts are correct.
In a nutshell for Ag GPS combinations using various pieces from different vendors the following rule generally applies: If the connections are opposite sex and will mate then plug them together. If the connectors are the same sex (both male or both female) than obviously an adapter is needed. This adapter will need to be the null modem type where pins 2 & 3 are crisscrossed.
The exceptions are that when working with an Ag Leader product Pin 4 & 6 were bastardized to be 12 V power and ground out to potentially power a GPS. This is what is meant by the warning message on the PF3000. This Power and Ground out can be very handy so that a GPS can be powered by the Ag Leader product and communicate the GPS and setup information all in one cable.
This can be dangerous as this powered pin can cause damage to SOME GPS receivers. If the GPS recieves its power through another source which many do then it is unnecessary to have any pins other than Pins 2,3 & 5.
If the connectors on the two devices would mate but are too short (such as connecting an EZ-Guide 500 to an Insight) then a common M-F extension can be used. Clipping off all male Pins but 2,3 & 5 will insure that you do not have any problems with the powered pin.
As far as the definition of the Pins involved - Pin 5 is always Signal Ground. Pins 2 &3 are Transmit (information from the GPS to the device) and Recieve (information from the device to the GPS). Depending on how you view the Pins these may be reversed.
Another example - If we wish to install a Raven Phoenix GPS in a combine with an Insight we need a special cable with the following requirements: 1) it must increase the total length to reach 2) it must have Male 9 Pin connectors on both ends 3) it must have the null crixsscross mentioned above 4) it should provide power and ground to the Phoenix.
We make up this cable which could be called a Male to Male Null modem extension with separate power & Ground. The end that goes into the Insight has 5 Pins in it using Pins 2,3,4,5 & 6. The other end is also a 9 Pin male with Pins 2,3 & 5 but with a separate WeatherPak two pole for Power & Ground to the Phoenix. The cable is not symmetrical so the first end is labelled Ag Leader and the other end GPS.
As far as your question about hooking two null modems back to back - this would effectively make an extension since the first null modem would swap some pairs of wires and the second would reswap them. This is the old "double negative" concept.
Concerning the Thumbscrew vs nut problem. As has been stated this has no bearing on the wiring. Sometimes it is necessary to connect a Male to Female but both may have thumbscres. It is possible to use a "standoff" which has the proper thread to connect the two. Often these standoffs are too long and will not allow the the Pins to fully mate. The standoffs can be shortened with a grinder but this often messes up the threads.
A solution to this situation is to just mate the connectors fully and then wrap electrical tape around the connection to insure that the two ends stay mated. This is not a very professional approach but seems to work fine.
Edited by tedbear 12/7/2008 09:41
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What does a null modem cable do? Will I fry my Insight or Mojo?
