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Author Topic: Multiple Mobile 2M transmitters in one vehicle?  (Read 354 times)
KG4OJB
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« on: October 25, 2004, 02:32:14 PM »

I'm not really terribly familiar with the dynamics of multiple transmitters and antennas in close proximity. I would like to have two tranceivers in one vehicle (one 2m, one 2m/70cm). The 2m only rig is for purpose of APRS at the moment. What are my antenna options? I currently use a 2m/70m dual-band glass mount; would it be possible to utilize this antenna on both tranceivers, or will I be required to mount a second antenna? Thanks!

KG4OJB
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K0BG
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« Reply #1 on: October 25, 2004, 02:57:35 PM »

You cannot use one antenna with two radios at the same time without some rather sophisticated equipment like cavities and isolators. You can use two antennas. You'll get a lot of de-sense depending on how and where you mount the antennas, but the chances of burning one up is slim. In any case, I'd get rid of the glass mount in favor of a good-quality NMO unit correctly mounted.

Alan, KØBG
www.k0bg.com
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KG4OJB
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« Reply #2 on: October 25, 2004, 04:58:03 PM »

Thanks; this is as I suspected. So, my best plan will be to mount 2 non-glass mount antennas with as much seperation as feasible (i.e. on on roof, one on trunk) and cope with the desense (which I suppose won't be too big of an issue, as the APRS radio will only be involved in brief packet transmissions).
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K1CJS
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« Reply #3 on: November 06, 2004, 03:03:07 PM »

Two antennas separated as much as possible are best for those purposes.  I'd recommend the APRS rig on low power using the antenna on the roof and the other rig using the trunk mounted antenna.  Also, setting the roof antenna as far forward as possible for separation purposes is adviseable, say about 20 inches back from the front edge of the roof.

Also, regular 19-20 inch quarter wave antennas on both would be better than using gain antennas on either--using gain antennas on either ups the probability of desense on either rig when the other transmits.

I've done a two rig setup on occasion for public service events and have switched out my gain antenna on a NMO mount for a 19 inch whip, with another 19 inch whip on a mag mount for the second rig, and I've had minimal problems with desense on either rig.

Good luch with your setups.  
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