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  #11  
Old 02-20-2008, 12:04 AM
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Originally Posted by corsair23 View Post
Thanks gents

Hants I'm with you on the CBR w/ HT thing. I chatted with UB and Romer about this at Monday's HAM class. Before I knew anything about HAM (and I don't know much now either), I remember on the BOWAGWR last year watching Nakman working his rig while we were stopped. He kept having to run back to his 40 like those of us with CBs have to and I thought "Boy it would be nice if you didn't have to do that" - At the time I was thinking of those little walky talking dealyos some of us have or had in the past.

How many times are we out of our rigs on a trail for one reason or the other when we find it would be nice to still be in communication with others without having to run back to our vehicles? I can think of a dozen plus cases and I've been on maybe 6 or so club runs.

But, maybe just having a HT in addition to a mobile rig would serve that purpose well enough on the trail to not warrant the CBR functionality. Cost wise getting a rig that has that seems to really escalate the cost. If you really need the extra power to DX (trying to use the terminology here ) then back into the rig you go.

Judging by cost (from my quick glance at ICOM and Kenwood stuff) it appears I'll end up with something made by Yaesu. ICOM and Kenwood seem to average about double a comparable Yaesu rig

Thanks for the spreadsheet as well Hants

Jeff,
In your scenario here, CBR would not be needed. An HT will reach further than most CB's! A scenario that would work would be a mobile set up on CBR at Slickrock with one side set at a powerful VHF band, running simplex and squelch coded, that would be a prearranged "home" or campground freq. The other side would be set at a very low (1 watt) unused UHF freq set with a unique squelch code. Anybody in the campground would have their HT set at that same unique uhf freq on minimum power and on the same squelch code. Anyone, anywhere. on any trail out there could tune in to that home VHF signal and the CBR will allow the HT(s) in camp to communicate easily with the caller in normal and very clear communication. The mobile unit supply's the high power for reaching out there at the same time allows a very low power link to the HT's in camp. Essentially a small scale repeater that isn't easily used by anyone but the operator of the HT's. I also just discovered that the 8800's can be set up to self identify themselves on CBR (I think....haven't done it yet). Also, If the "home" freq was duplex with a repeater the HT's don't need no stinking CBR!
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  #12  
Old 02-20-2008, 05:48 AM
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Jeff,
In your scenario here, CBR would not be needed. An HT will reach further than most CB's!
Just to reinforce what UB said, Romer and I chatted over the weekend, both of us on our handhelds via a repeater. Both at home via the 145.145 repeater, which is on Squaw Mt, which is west in the foothills. So Romer was reaching probably 40 miles and me probably about 30 miles using handhelds at 5W. This was to a repeater, which has height, good antennas and higher power TX. But holding simplex conversations with 5W HTs is not unusual at 10 and 15 miles. From the White Crack Overlook on the White Rim, I could talk to Moab with my HT. I do have a pretty good antenna on it, so that helps. But that's probably 20 miles line of sight and a pretty ideal spot to operate to Moab.
Quote:
A scenario that would work would be a mobile set up on CBR at Slickrock with one side set at a powerful VHF band, running simplex and squelch coded, that would be a prearranged "home" or campground freq. The other side would be set at a very low (1 watt) unused UHF freq set with a unique squelch code. Anybody in the campground would have their HT set at that same unique uhf freq on minimum power and on the same squelch code. Anyone, anywhere. on any trail out there could tune in to that home VHF signal and the CBR will allow the HT(s) in camp to communicate easily with the caller in normal and very clear communication. The mobile unit supply's the high power for reaching out there at the same time allows a very low power link to the HT's in camp. Essentially a small scale repeater that isn't easily used by anyone but the operator of the HT's.
This is using the x-band repeat as a range extender and is really the only legal use without self ID. Also V-V or U-U repeating really should be coordinated with the local band plan person so that it does not interfere with an existing repeater. But doing simplex to simplex or simplex to a repeater input does not need to be coordinated because you don't need the input/output offset.
Quote:
I also just discovered that the 8800's can be set up to self identify themselves on CBR (I think....haven't done it yet). Also, If the "home" freq was duplex with a repeater the HT's don't need no stinking CBR!
Interesting. How? The only thing remotely like it is the ARTS CW ID'er. That only sends your call sign when it's made an ARTS contact as near as I can tell.
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Old 02-20-2008, 05:54 AM
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Originally Posted by corsair23 View Post
Judging by cost (from my quick glance at ICOM and Kenwood stuff) it appears I'll end up with something made by Yaesu. ICOM and Kenwood seem to average about double a comparable Yaesu rig
The ICOM 208 and Yaesu 7800 are pretty comparable price and features. The Alinco 635, Yaesu 8800 and Kenwood 708 are about in the same league. There are a lot of options and differences, so prices for things are all over. Hant's Kenwood is a very complex radio and Yaesu doesn't make a VHF/UHF rig anywhere similar to it. Also don't forget used! Hams tend to mess with their systems and are selling them all the time and they are rarely all beat up like CBs.

I would also add that Hant's Kenwood is really not that expensive because it's got the TNC and GPS interface built-in. The Kanrtronicx MT1200G (an external interface with a built-in GPS controller) is $300. So to replicate what Hants has with in Yaesu would be say a 8800 at $375+$300 = $675 and most places sell the Kenwood for around $590~$620.
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Old 02-20-2008, 08:33 AM
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I'm confused, Dave. My understanding is that with CBR, the only way to be legal is to have the mobile self-identify on both frequencies (mobile-to-repeater, AND mobile-to-HT). Without that, there is no identification, in particular, when the mobile transmits to the HT.

What am I misunderstanding?

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This is using the x-band repeat as a range extender and is really the only legal use without self ID. Also V-V or U-U repeating really should be coordinated with the local band plan person so that it does not interfere with an existing repeater. But doing simplex to simplex or simplex to a repeater input does not need to be coordinated because you don't need the input/output offset.
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  #15  
Old 02-20-2008, 09:17 AM
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What am I misunderstanding?
There's a lot of misunderstanding with this feature. When talking about cross band repeating most people think of a regular repeater like we use all the time. That NOT a cross band repeater technically since it's using an input offset on the same band. The transmitting radio must be identified, be that automatically or by the operator. The FCC requires you to identify your transmitting station every 10 minutes with your call sign.

So you set up your mobile to cross band repeat from UHF to VHF. You TX with your walkie talkie on a UHF simplex frequency, the mobile receives that and re-transmits (across bands) it on VHF. That could be a VHF simplex or VHF repeater input frequency. What the mobile is doing is allowing you to increase your TX range only. This is called half duplex cross band repeating. Your HT still receives on the VHF side of the conversation, just like you would if the mobile was not involved. This is legal as long as you say "KC0DEF on 446.225 talking through a cross band repeater to 147.525" when you transmit.

The next option would be to have the mobile retransmit your UHF TX and additionally do the flip side and retransmit the other party to your remote UHF frequency. This is called a full duplex cross band repeating. The difference is that your HT only needs to talk to your mobile. But now you have two transmitters working on two different input and output frequencies. This means you have to ID both radios and since you don't know when someone might trip the input to the mobile, it's not technically being ID'd properly. DOING THIS BLINDLY IS ILLEGAL UNLESS THE RADIO SELF IDENTIFIES! If the radio can self ID (with your call sign) when it happens to transmit, this is OK to use as an RX range extender. Also if both hams using the full duplex cross band announce what is going on, that could be fine.

The other type of repeater is the VHF-VHF or UHF-UHF repeater with an offset input/output pair. These are essentially the same as the full duplex cross band above, but are a special case because you need to make sure to coordinate the frequencies so that you don't stomp on someone else's repeater. Also a same band repeater needs some special attention on equipment, depending on what you are doing. But in theory the operation is similar to the full duplex example.

Add to that the control, you have to be able to shut the radio down if it goes haywire. This is true of all repeating, so leaving a radio running in a truck while you go on a few mile hike means that it could be hours before you get back to the radio. That is illegal. Being in control of a station does not mean you have to sit in front of the rig, but does mean that you can reasonably operate the radio by means of physical or remote control. If you set up a cross band repeat and are in your house or around camp, it's not a big deal to get to the radio to shut it down and that's OK. Oh, also, the FCC only allows you to do remote control tones on the UHF side AFAIK. I've never verified that in the FCC Rules, so that may only be hear-say. But I do believe that doing remote control via an HT on the UHF side is fine, so set up cross band remote controls going UHF-to-VHF and you should never be non-compliant.

Your Kenwood can do both, self ID and remote control via a DTMF keypad. The bulk of cross band repeating mobiles CAN NOT do that. So the only legal use of a 88/8900 for example is as a local TX range extender. Setting it up as a 50W TX extender so that you can use a 100mW HT to walk around camp. Perfectly OK as long as you announce what you are doing periodically. Leaving an unattended, uncontrollable radio that does not ID is no question illegal. A 8800 can never be used as a full duplex repeater unless both parties know to ID the repeater. So for emergency use, say parking your truck at a high spot so that two HTs down in valleys can be connected would be fine. Both operators would have to call both frequencies when doing that, does that make sense?

That's a lot of words. More or less confused. Your Kenwood has all the right features to be legal.
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Last edited by DaveInDenver; 02-20-2008 at 09:38 AM.
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Old 02-20-2008, 09:31 AM
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Thanks!

That confirms what I had "learned"... gotta like book lern'n.

With half-duplex CBR, you potentially have an issue that your HT doesn't have the gain/power/location to RX/TX to the distant party.

Once I figured that out, I focused on full-duplex CBR. But I wasn't very clear about that above.

We're ALL doing a bunch of learning! It is GREAT to be associated with a group with so many diverse talents!
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Last edited by Hants; 02-20-2008 at 09:55 AM. Reason: Clarification
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Old 02-20-2008, 10:20 AM
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Dave and Hants,
When I first played with the CBR on my 8800 I assumed it was 1/2 duplex and used the second band on the HT for receiving. After reading the 8800's manual again and also Hant's article he posted I realized I might have sold my 8800 short so I played around again. It does go full duplex! The HT can RX and TX on the same UHF freq and the CBR will shuffle all communication between the two selected bands both ways! I also noted that when the 8800 is in CBR mode it is completely locked out of any other feature until CBT is shut off which means the mic is useless as is all buttons except the "set" and "power." Even though most modern radios can scan for codes I really doubt someone will find the low power simplex uhf unique coded freq your using with the HT and CBR! The 88 and 8900's will ONLY cross band repeat however so it will only work as VHF/UHF-UHF/VHF and will not do UHF/UHF or VHF/VHF.
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  #18  
Old 02-20-2008, 10:35 AM
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After reading the 8800's manual again and also Hant's article he posted I realized I might have sold my 8800 short so I played around again. It does go full duplex!
This is true, the 8800 and 8900 x-band repeat are full duplex. One way I've heard to stay legal (assuming my read of the Rules is right about full duplex) is to set the UHF side to TX on a non-ham frequency. This assumes you have not gone and modified your radio to free band, which I'm sure no one has, right? That way when the VHF side receives it tries to repeat to a non-legal frequency and the radio will not do it. The display will say TX ERROR and it won't be transmitting. My assumption is that these radios have the cross band repeat function for countries with different rules or maybe just as a sales feature that is "For Offroad Use Only" as they say with like 90% of the junk we bolt on our trucks...
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Old 02-20-2008, 01:32 PM
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The Kenwood TM-V71A has all of the features of the TM-D710A, except for the TNC for APRS. It does support Remote Control (via DTMF) and self-identification in CBR mode. It is about the same price as the Yaesu FT-8800R.

The TM-V71A was my radio-of-choice until I asked Caroline. I showed her this link:

http://aprs.fi/

then asked her if it was worth the price difference to be able to tell where the rig is when we're in the backcountry. Her response : "<puzzled look> That's a safety feature. Of course its worth it.... as long as its not $1000 more or something."

Bingo -- budget increase!
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  #20  
Old 02-20-2008, 01:49 PM
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The Kenwood TM-V71A has all of the features of the TM-D710A, except for the TNC for APRS. It does support Remote Control (via DTMF) and self-identification in CBR mode. It is about the same price as the Yaesu FT-8800R.

The TM-V71A was my radio-of-choice until I asked Caroline. I showed her this link:

http://aprs.fi/

then asked her if it was worth the price difference to be able to tell where the rig is when we're in the backcountry. Her response : "<puzzled look> That's a safety feature. Of course its worth it.... as long as its not $1000 more or something."

Bingo -- budget increase!
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