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Old 02-09-2008, 04:23 PM
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Default Hi, my name is Hants...

... and I'm a gadget freak.

I'm in the market for a mobile radio & HT. I'm pretty sure I want the following features:

2M & 70cm (is there significant utility to having additional mobile bands?)
50W (power is good, is more power better?)
Cross-band repeat (full duplex to/from HT)
APRS (I already have the GPS; does anyone here have first hand experience?)

I curious about the following features/technologies:

Echolink
D-Star

Has anyone here used them? How widespread are repeaters that support them, particularly in the backcountry? Internet anywhere would be the goal.


Thoughts? Recommendations?
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  #2  
Old 02-09-2008, 04:38 PM
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Hi Hants

Congrats on your being passing your test.

You aced it and then passed your General and all I have to say is

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Damn you Hants White..........
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  #3  
Old 02-09-2008, 05:04 PM
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DaveInDenver DaveInDenver is offline
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Quote:
Originally Posted by Hants View Post
... and I'm a gadget freak.

I'm in the market for a mobile radio & HT. I'm pretty sure I want the following features:

2M & 70cm (is there significant utility to having additional mobile bands?)
50W (power is good, is more power better?)
Cross-band repeat (full duplex to/from HT)
APRS (I already have the GPS; does anyone here have first hand experience?)

I curious about the following features/technologies:

Echolink
D-Star

Has anyone here used them? How widespread are repeaters that support them, particularly in the backcountry? Internet anywhere would be the goal.
That's a pretty long list.

First Echolink and D-STAR. D-STAR is thus far only on ICOM radios and not particularly wide spread. Echolink, not familiar with it other than having heard of it. IOW, never used it. This could be handy if you want to talk to someone at home, since it's a way to talk to someone on a computer. But the person on the computer has to be a licensed ham I think, since their voice will be coming over a radio. Although that might fall into the auto patch provision, where it's legal to have a non-licensed person on the phone. I dunno, not familiar with it too much and couldn't tell you the number of repeaters around that might have access to it.

Cross band repeat will lock you into a few radios. Yeasu 8800 and 8900, Alinco DR-635T or Kenwood TM-V71A. All of those can accept a TNC for packet radio, but none have it built-in. For APRS the best radio is the Kenwood TM-D710A, which is dual band but not cross band repeatable. the D710A has APRS functions built in and those make it the most friendly. But any radio with a TNC capable port will be adaptable to packet radio. For that the best TNC option is a Kantronics MT1200G, which has a port for a GPS receiver and so you don't need the PC if all you are doing is APRS. If you want to do packets, then you need the terminal, which is most often a laptop. Some people have rigged up dumb terminals with a keypad and LCD display, but there's nothing commercial for that really.

Power wise, most every dual band does 50W on VHF. Most are less on UHF, in the 35W range. Don't worry about that too much, the difference between 35W and 50W is not huge. Range goes approximately by the square root of the power increase. So the difference in approximate range from 5W to 50W is SQRT(50/5) = SQRT(10) = 3.2 times the range. So the difference between 50W and 35W is SQRT (50/35) = SQRT (1.43) = 1.2 times, so just 20%. Also remember you will spend most of your time at 5W or 10W, since that's about all you need to get into the repeaters around town. Having 50W for simplex is good, but you shouldn't be concerned with more than about 50W or 60W. Also remember as you increase power, you increase your RF exposure and so you want to be careful about antenna placement with higher and higher powers, even at 50W you need to make sure to keep about 6 feet or so between you and the antenna when transmitting to stay below accepted FCC exposure levels.

Bands. Sure, more bands the better. But only if you have someone to talk to. Probably 75% of the time you will be on 2m (and primarily all the time in the club, some people have single band 2m radios). UHF is handy for caravans, but only if everyone has the band. Having 6m can be OK to mess around with, but not heavily used. Then 10m, well mobile radios only do 10m FM and that's not all that common, either. There are some 10m repeaters, so that could be OK. Mostly 2m and 70cm will get you 99% of the stuff we do as 4WD'ers, the rest depends on how much you want to tinker with it as a hobby.
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Old 02-09-2008, 11:42 PM
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Thanks for the detailed response, Dave!

Echolink & D-STAR are out.

I'm looking at the specs on the Kenwood TM-D710A, it says it does crossband repeat, and it appears to have 2 receivers..... I just found the manual and it gives instructions for setting up cross-band repeat (VHF/UHF) and locked-band repeat (same band).

Sounds like UHF & VHF are all I need at this time -- no Quad-banders for now.

I think I'll start looking for a deal on a D710A.

Quote:
Originally Posted by DaveInDenver View Post
Also remember as you increase power, you increase your RF exposure and so you want to be careful about antenna placement with higher and higher powers, even at 50W you need to make sure to keep about 6 feet or so between you and the antenna when transmitting to stay below accepted FCC exposure levels.
Hmmmmm. I thought that, at 50W, I basically didn't need to worry about RF exposure. At 6ft, the bumpers would be the only option? I'll need to do some antenna & mount research now. I understand that ground plane & SWR becomes a real issue once you get off of the roof or the hood.

Then again, we're not making any more kids here, so I could just ignore it.

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Old 02-10-2008, 07:51 AM
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Quote:
Originally Posted by DaveInDenver View Post
Echolink, not familiar with it other than having heard of it. IOW, never used it. This could be handy if you want to talk to someone at home, since it's a way to talk to someone on a computer. But the person on the computer has to be a licensed ham I think, since their voice will be coming over a radio. Although that might fall into the auto patch provision, where it's legal to have a non-licensed person on the phone. I dunno, not familiar with it too much and couldn't tell you the number of repeaters around that might have access to it.
Echolink and IRLP both require the operator to be licensed. Each of these can be used with a radio from any manufacturer and because of this are very popular and widespread. Your radio will need to be capable of DTMF, i.e. numbers to dial with on your microphone, which most new radios today are. One other thing to keep in mind is that these features are typically provided as benefits to the radio club members and are protected by access codes.

The Colorado Repeater Association Club has Echolink and IRLP repeaters.

The Rocky Mountain Radio League Club has an IRLP repeater - they had the first IRLP node in the state.

The Denver Radio Club has an Echolink repeater.

There are several other clubs in the metro area and I did not check their repeaters this morning, they may also have these capabilities.
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Old 02-10-2008, 12:52 PM
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Hmmmmm. I thought that, at 50W, I basically didn't need to worry about RF exposure. At 6ft, the bumpers would be the only option?
The FCC recommends that on VHF you evaluate your exposure at 50W and higher. There is no perfect good/no good power, it depends on the antenna gain, transmitter power, distance and what's between you and the radiating antenna. An omnidiectional 1/4 wavelength antenna has a closer safe distance than a 1/2 wavelength, for example. A highly directional antenna like a yagi or a horn will have a high exposure zone and a much reduced off axis zone where exposure is much lower. Anyway, the roof is very good since you have the sheet metal between you and the antenna. You only need to give it some thought if there isn't a shield between you and the antenna. The bumper is generally OK exposure wise from the cab at 50W, but is something of a compromise depending on the antenna design.
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Old 02-10-2008, 05:29 PM
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My understanding is that a 1/2 wave doesn't have quite the gain of a 5/8. However, it doesn't need a groundplane.

My concern with the roof is breaking it off pulling into the garage late at night. I've hit my mag-mount CB hard enough to tip it over.

Knowing what I know right now, I'm seriously considering a 1/2 wavelength antenna on the front bumper.

I need to do some more antenna homework...
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"Damn you, Hants White!" - CruiserDan

"Wanna race?" - Bill Morgan

"Live long, love lots, cruise often." - Robert Fortune
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Old 02-10-2008, 05:30 PM
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Thanks for the additional info on Echolink & IRLP.

I may get into Echolink and IRLP at some point (I am a gadget freak, after all), but I'm going to table them for now.
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"Damn you, Hants White!" - CruiserDan

"Wanna race?" - Bill Morgan

"Live long, love lots, cruise often." - Robert Fortune
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Old 02-10-2008, 09:30 PM
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Quote:
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My understanding is that a 1/2 wave doesn't have quite the gain of a 5/8. However, it doesn't need a groundplane.
It's not that simple. Are you planning on coming to the ham classes this month? I figured the question about 1/4, 1/2, 5/8, monopoles, dipoles, SWR, gain, impedances, efficiency, etc. would come up in there... The short answer is that all monopoles work better with a ground plane, although some antennas can work satisfactorily without one.
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