On Mar 26, 2010, at 12:04 AM, kd8biw wrote: > Hello everyone, > > Wondering if anyone has been able to implement a Motorola Maxtrac as a > "frequency agile" remote base on a repeater. What I would like to do is have > a 16 channel VHF mobile hooked to our repeater, and be able to select a > channel at will. I'm sure it can be done, i'm just overlooking something > here. Our controller has a 4 pin hex output that I think could do the > necessary stuff to make it work, just not sure about how it needs hooked to > the radio. Has anyone done something similiar to this? I was looking at > NO6B's RBI, and that would fit the bill, just wondering if I could make it > work with our controller (MCC RC-100) or would I have to get a different > controller (CAT or LinkCom)? Thanks all! > > Steve KD8BIW > > KD8BIW/R 224.580 > N8IHI/R 147.105 > W3YXS/R 146.745 > KD8JBF/R 444.325
Don't know about Maxtracs, but plenty of folks have done channelized remote bases and even completely frequency-agile ones. A couple of things to watch out for: - If you're repeater is VHF and your remote base is VHF... look out! You're putting a (relatively) high power transmitter very near your repeater input frequency. If you don't directly desense your repeater input, you can certainly hit "mixes" with nearby transmitters on the site and do it, and/or just clobber other mountain-top "neighbors" with repeaters in your target band. Be as careful picking the frequencies you'll ALLOW your remote base to operate on, as the site manager would when doing a transmitter site survey and calculating all of the mixes, 3rd and 5th order harmonics, etc. - If your repeater is in another band other than your remote base, that's better for you, but calculate and think about the "neighbors" if there are any, same as the above. Also watch out for 3rd order harmonics if you're doing VHF on one and UHF on the other. - I've read articles about radios LIKE the Maxtrac that have a microphone up/down switch just being directly triggered by the controller with a single logic-level output line. No need for a fancy remote base interface. However, think about how to "find" channel 1 if you ever get the controller and rig out of "synch" on button-presses. Many rigs can be programmed to always power up on a particular channel in the commercial options (like the Maxtrac, I believe... but a Moto programming expert would have to clarify the options with that particular rig), and making sure to wire up a way to "bounce" the power to the remote base rig on top of the remote channel switching circuitry, is in order. - Similar to the above... if the RB radio locks up in TX or RX with some new mix or a bad "neighbor" at the site... make sure you don't just have a way to disconnect it's audio from the controller, make sure you have a way to POWER IT OFF remotely, if any sort of failure occurs. There's nothing madder than a site manager calling saying your remote base mobile in your cabinet has been determined to be the culprit, is stuck in transmit, and the only way to the site is a snow-cat or snowmobile in the dead of winter. (I know, you're probably in 8-land if your callsign matches your district still, and don't have that limited access to your repeater site... but think it through if you have anything that limits access as to how you'll "failsafe" the whole system. (Applies to the repeater itself, too... really.) - Mobiles have terrible shielding, typically. Many sites here BAN mobile rigs used in cabinets completely. The reason? IF leakage can mix with other IF's on site and create havok. Commercial quality repeaters typically have GOOD shielding with a metal box all the way 'round the exciter, receiver, and everything but the Power Amplifier stage. It can then, of course, be grounded, and act as a mini Faraday Cage around the noisy microprocessor (inevitable) of a synthesized rig, the IF of the rig, etc. At the very least, make sure the CASE of whatever mobile you use (if you must use a mobile) is grounded properly. Keep the RF noise INSIDE the radio. Granted many Amateur repeaters (here's looking at you Icom/D-STAR!) have even less shielding than a typical commercial mobile rig, and/or have leaky internal coax jumpers that will both let RF out, and into, the repeater... Those are just some thoughts about using mobiles (and worse, ham mobiles) as remote bases at busy RF sites. If you're at a site with few radios, and know the other repeater/system operators well, have them give you a heads up as to what frequencies they're using, and stay away from their input frequencies, harmonics/multiples there-of, etc... and likewise, pre-plan your frequencies appropriately when trying not to wipe yourself out, too. Hopefully that helps spark your thoughts as to how to properly engineer a remote base. I know nothing about your MCC, but perhaps the note about pulsing a single pin will bring some thoughts about whether or not you can use it, to mind... Have fun. -- Nate Duehr, WY0X [email protected]
