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Author Topic: Looking for mobile rig suggestions  (Read 5547 times)
KB8UAQ
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Posts: 24




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« Reply #15 on: October 04, 2010, 01:19:28 PM »

Many of today's mobile rigs are programmable to shut the radio off after a specified period of inactivity.  That's the method I use.  It not only avoids inadvertently running the battery down, but also avoids questions from the wife like, "Who is talking in our garage?" ;-)

If the radio you choose does not have this feature, consider a solenoid after the radio's positive lead fuse (should be right at the battery).  These solenoids look virtually identical to a starter solenoid, but are rated 100% duty cycle and are commonly used in light aircraft.  You will probably have to get one from an aircraft parts supply company, such as Aircraft Spruce or Chief's.  DO NOT USE a car starter solenoid.

73 de John - WB0KSL


So, if I'm understanding you correctly, what you're suggesting is that the solenoid could act as a 'switch' in the radio circuit, and the solenoid would be activated by the ignition switch (so that when you turn the ignition switch 'on' or to 'acc', current flows from the ignition switch to the solenoid, which then switches on the radio [by closing the positive lead])?

Could you do basically the same thing with a simple transistor? I'm not completely sure I understand transistors, but if I understand correctly, a voltage on one of the terminals of the transistor will allow current to flow through the other terminal, to the ground (well, that is I think current flows through both terminals to the common ground, but only if voltage is applied to both terminals, otherwise it doesn't flow through either, is that right)? Or, in Boolean logic terms, a transistor implements the AND operation, with the 'result' being output on the ground, where a non-zero voltage potential is (logical) 1, and a zero potential is (logical) 0?

(I ask that last bit, because I know a lot more about computer programming than electric circuits, at the moment, but I remember taking a couple courses which relate the physical circuits to mathematical logic - they teach programmers this so we can start to understand how the hardware implements computational logic).

EDIT: I've been reading a page with more info about transistors, and they mention transistors are usually only good for switching circuits with max 5A current. I'll have to see what kind of current the radio would draw - I'm guessing it might be more than 5A while transmitting 50W signal? Well, when I get a radio, the manual should tell me. The page mentions using a relay to switch higher amp power, so I might compare the solenoid idea to a relay, see which will be cheaper and simpler.
« Last Edit: October 04, 2010, 01:33:18 PM by Jeff Schmidt » Logged
K0BG
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« Reply #16 on: October 04, 2010, 03:30:06 PM »

For whatever reason, everybody seemingly suggests some sort of cure, mod, and other circuitry to shut radios off when you start the vehicle, or if you forget to shut one down. Universally, this involves a relay. Well, that's about as passé as tubes will be sooner than we all think. There are certainly better ways.

While not all mobile transceivers have an auto shutoff feature, about 90% of them do. If they do, then use it! If they don't, then use an aftermarket device which does it for you. About the best one out there is the PowerWerx APO3.

What you don't want to do, is go to the trouble of trying to protect a transceiver from voltage spikes when you start the engine. Anyone who tells you that this has to be done, is ignorant of the facts.

If you wire your installation correctly, the chances of a voltage spike damaging a modern-day transceiver, are as remote as finding Big Foot—anecdotal information to the contrary!
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WB0KSL
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« Reply #17 on: October 04, 2010, 08:43:46 PM »

I think Alan probably has the best solution, if your radio does not have an auto power off function.  The PowerWerx APO3 sells for around $60 and is an easy plug n play, with Anderson Power Pole connectors.  I have the auto power off function on my radio(s), so I don't need the PowerWerx or solenoid.  It's an issue only with leaving the radio running inadvertently, as far as I'm concerned.  I wouldn't spend one minute worrying about having the radio on when the car is started, either.  I do think the master solenoid is a viable low tech solution, though.  Aircraft Spruce sells one for $24.85.  Not plug n play, but not hard to install.  As far as reliability goes, I have two airplanes that use master switch solenoids in their electrics, and I have flown hundreds of hours in each with no worry/no problem (at least from the solenoids ;-)....  Nothing succeeds like success!

73 de John - WB0KSL
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KB8UAQ
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« Reply #18 on: October 15, 2010, 11:08:28 AM »

Hey, I've been giving some more thought about what radio to choose, and looking into a few different models. Something just occured to me today - are there any mobile rigs that are designed as 'replacement' for your car stereo? I suppose most hams have their AM/FM radio, and a separate amateur radio. But, I've been trying to think where I would actually physically put my amateur mobile when I get it, and it occurred to me it would be great if I could just pull out the factory radio and put the mobile ham radio in there. . . but I don't want to lose AM/FM Stereo broadcast band receive. It would also be nice to have at least an aux line-in jack (for hooking up an mp3 player, CD player, etc).

I'm thinking it might be kind of nice to have the ham radio be able to output audio to the car's built-in speakers (instead of using either a built-in speaker, or a separate external speaker).

Has anyone marketed such a radio, with 2M/70cm dual-band operation?  In some of the manuals I've been checking, it looks like a lot of models have a very wide-band receiver - that is, you can only transmit on the ham bands, of course, but receive covers a lot more bands than just 2M/70cm, including the 88-108Mhz (FM Broadcast), but when they receive FM Broadcast, do they receive and output stereo, or just mono? Has anyone seen any models with an aux line-in jack for using the unit as an amplifier for hooking up other audio equipment to listen to on your car speakers?
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K0BG
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« Reply #19 on: October 15, 2010, 11:33:32 AM »

Everybody tries to use their stereo speakers at least once. If they're still using them, they haven't used a decent quality mobile communication speaker. While it works passably for FM where there isn't any high frequency hash to put up with, it becomes a disaster when using HF.

As for the DIN sized radio.... Actually, that was one of the original design parameters behind the Icom IC-706. It never materialized into a DIN mount, however. The biggest problem with most DIN holes is the lack of air circulation, and even if it has some, it is usually directly from the heater.

You could build anything. You could have 10 kHz to 1 GHz receive coverage, with all of the mods. But in order to sell something like that at a reasonable price, you'd have to leave out a lot of stuff. Even then, very few amateurs would bite the bullet. Heck, they complain paying $400 for a used 7000!
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KB8UAQ
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« Reply #20 on: October 15, 2010, 01:45:33 PM »

Everybody tries to use their stereo speakers at least once. If they're still using them, they haven't used a decent quality mobile communication speaker. While it works passably for FM where there isn't any high frequency hash to put up with, it becomes a disaster when using HF.

Yeah, even as I was writing that, I was thinking that amateur radio signals through car stereo speakers might not work the best - might have sort of the wrong 'sound' response.

Quote
As for the DIN sized radio.... Actually, that was one of the original design parameters behind the Icom IC-706. It never materialized into a DIN mount, however. The biggest problem with most DIN holes is the lack of air circulation, and even if it has some, it is usually directly from the heater.

That seems a solvable problem - make the electronics of the radio small enough to use only part of the DIN space, then have some vent holes or ducts to the passenger compartment, with an inexpensive CPU Fan (which I believe universally run on 12VDC) to force some airflow. Even if the fan fails, they're cheap to replace.

Quote
You could build anything. You could have 10 kHz to 1 GHz receive coverage, with all of the mods. But in order to sell something like that at a reasonable price, you'd have to leave out a lot of stuff. Even then, very few amateurs would bite the bullet. Heck, they complain paying $400 for a used 7000!

Well, yes, price could be an issue. From a little looking around, it looks like a lot of receivers at least include FM Broadcast anyhow (I guess because it's so close to 2M, that capability is basically 'free' to engineer into the unit) - do most receivers, if they can tune in FM, do they have stereo decoders (stereo probably wouldn't be 'free' from an engineering standpoint, except stereo tuners are so cheap, why not just use the same stereo chip to receive mono FM ham transmissions, right? I mean, you can find FM radio's at any department store for like $10, so it can't be too expensive to put stereo decoding into a receiver chip).
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