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Author Topic: Newbie Question  (Read 310 times)
KC2MLE
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Posts: 2




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« on: January 29, 2004, 09:25:14 AM »

Hi Everyone,

I just got my license and have been researching radios and I think I have decided on a Kenwood TH-G71A as a first radio.  I noticed in the brochure a comment about DTMF remote control stating "you can turn your car's tranciever into a repeater at any time".  I don't really understand what this means or what mobile radios it would work with.  I think it says it will work with Kenwoods TM-V7A but that radio doesn't get great review here.  I was thinking of getting the TM-G707A as a mobile unit but I don't think this will accept the DTMF codes?  Can someone try to explain what this means to me.  I like the idea of maybe using my mobile unit as a repeater at some point down the road....it sounds like it could be fun.

Thanks,
Kevin
73's
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VA3WXM
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« Reply #1 on: January 29, 2004, 11:38:28 AM »

Congratulations on the new ticket!

The comment made in the Kenwood brochure is referring to cross-band repeat capability. The V7A has this function in which a signal received on the 70cm band is repeated by the radio on the 2m band, or vice versa. Cross-band repeating is a useful tool if you're away from your car but want to keep in contacted with whomever using your HT. The car radio receives your weaker HT signal and repeats it on the other band using higher power. The neat thing that Kenwood has done is to allow some controlling of certain function remotely using DTMF. Specifically, the V7A understands certain DTMF strings to turn the repeater on/off, adjust power, etc.

I wish the other radio manufacturers had included this functionality in their own dual-band mobile rigs!

This is one caveat. There are some FCC regulations that place restrictions on uncontrolled, remote stations -- which a cross-band repeater technically is. We in Canada don't have the same restrictions on operating cross-band repeaters. Others on this board will explain the legalities a bit more for you I'm sure!
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WA2JJH
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« Reply #2 on: January 29, 2004, 11:49:37 AM »

This is not some new. Many dual bander of past could be turned into either a SIMPLEX repeater.

  Your simplex repeater user's input on VHF and receive the output on UHF. Or visa-versa

  Yes, your user's would have to use a few touch tones to turn on the repeater funtion in your rig.

  I had a phone patch connection with the one I had.
Please be advised that your are  not frequency coordinated. So make sure that if you are using much power and a high gain antenna with decent height, you may cause interference.

  We would set up a mobile repeater at DAYTON for our little group.

Enjoy and 73 MIKE
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AC4FD
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« Reply #3 on: January 29, 2004, 04:37:38 PM »

I would just like to make a clarification regarding Simplex repeaters so that there is not any confusion.  Basically... Simplex means... 1 Frequency... or you receive and transmit on the SAME frequency.  Simplex repeaters use a recording device to record a message... then later after the message is complete.. play it back for everyone to hear.

The type of repeater described here is actually Semi-Duplex. You will Receive(VHF) and Transmit(UHF) on different frequencies although not at the same time (Your Cross band repeater actually does the opposite receiving on UHF and transmitting on VHF).

Full Duplex is the ability to Receive and Transmit at the same time... such as on your telephone... in other words... someone could interrupt you while you were talking. One might argue that the repeater itself is actually Full-Duplex since it is Receiving and Transmitting at the same time, however from the users perspective... only one action can be performed at a time (receive or transmit).
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KC2MLE
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« Reply #4 on: January 29, 2004, 06:01:38 PM »

Thanks for the help everyone.  I think I understand better now.  I understand the discussion about the radio being a crossband repeater but I was wondering if any mobile radios can operator as a repeater like this on a single band (2m).  I know I would need to control the repeater station through UHF but could I control the station through UHF and communicate on 2m?  I was thinking that 2m band would have better range than 440.  Maybe they all do this.....it's all new to me.  Other than the TM-V7A what would be good units to look at for operation as a mobile repeater.

Obviously, if I was near a "real" repeater that would be the way to go.  However, I thought this might be useful if we were at a large event and simplex between HT's was not working that a mobile repeater might be great.

Thanks,
Kevin
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KC0MDC
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Posts: 58




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« Reply #5 on: January 29, 2004, 11:07:26 PM »

I have the Kenwood 700A as my mobile rig and have only recently discovered the advantage of the repeater functions.  I moved farther from town, farther from our 440 repeater, so I can't hit the 440 repeater with my HT from the comfort of the couch.  I can use the mobile rig as a repeater allowing me to get into the 440 machine in town.  Certainly an interesting advantage that could be used in remote locations!

73 Tim
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AB8BC
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« Reply #6 on: January 30, 2004, 11:15:34 PM »

Kevin----I had one of the first TM-V7A's off the belt.  I think the other fellas may not understand what you are asking.  Yes cross banding is nothing new, but controlling the rig via DTMF codes is (as far as I know)is exclusive at this time with Kenwood.  I never had much luck with my TM-V7A, but since the time I've owned mine they may have made improvements.  Personally, I had a TM-733a and THAT worked with the functionality Kenwood  described in TM-V7A manual.  Try this webpage---->
http://www.hamradio.cz/rigs/Dilna/kenwood/tmv7armt.htm
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VE7NGR
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« Reply #7 on: February 01, 2004, 02:27:19 AM »

Icom has had the ability to control crossband repeat with DTMF for quite a few years.

http://www.icomamerica.com/support/documents/crossband_repeat_info.pdf
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AC4FD
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« Reply #8 on: February 02, 2004, 11:48:59 AM »

Hi Again Kevin,

I think what you are asking is if this can function as a 2 meter repeater.   And the answer would be no.

To operate a repeater on 2 meters for example... you need to have a way of separating the RF transmit from the receive.  This is because the transmit and receive frequencies are so close to each other and the Repeater will be both transmitting and receiving at the same time.

Normally this is done in either one of two ways:

- Spacing....   Physically locating both the transmit and receive antennas a good distance apart. On a repeater... the receive and transmit sections will have their own separate antenna connect to make this possible.

- Cavity Filter. Cavatiy filters are filters which exhibit a very High Q (Quality) in that only the desired frequency is rejected while the other frequencies are alowed to pass. Several Cavity filter are connected together together to achieve the desired results.  Cavity filters are very large and would be difficult to lug around for portable repeater operation unless you had a truck or something to carry them in.  Use of cavity filters enables you to Run both the Transmit and Receive sections of a Repeater from the Same Antenna.

For Cross band repeating... the Receive and Transmit frequencies are spaced much further apart.  A device called a Duplexer give you enough RF separation to allow the repeat capabilities.

I hope that maybe I at least understood your question correctly and I hope that this helps you understand a little better what you are trying to do.

73,

Randy
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