TYT TH-7800

[Pricoxxx1]

I just bought one with the intent of setting it up as a repeater for our neighborhood watch group. I ain't stupid but I can be pretty dumb. I can't get it to function as a repeater. When I key a handheld the unit receives and passes it to transmit but I get a pulsating transmission indicated on the display with no audio out on another handheld or my Kenwood TK-805D. The two handhelds and the mobile work fine together but I am not getting anything out; it ain't repeat'n. I am hoping the problem is me and not the unit. Anyone got a handle on this?
Gary

 

[jonwienke]

You forgot about the CROSS-BAND part. If the input and output freqs are in the same band (UHF or VHF) then the repeater output will overload the input and mute it, when then turns off the output, which unmutes the input, which starts the cycle all over again.

On freq must be UHF, and the other must be VHF.

 

[Pricoxxx1]

Thanks for the reply jonwienke. According the TYT (sales propaganda) UHF to UHF is possible. That's the reason I bought it. If it isn't capable of full duplex (uhf-uhf) then why the setup instructions for "Offset" and "Shift"? That wouldn't exist cross-band. I'm stumped.

 

[jonwienke]

Offset and shift have nothing to do with cross-band repeat. They are for configuring a channel memory to use a conventional repeater so that the radio knows the correct input and output freqs on the repeater.

 

[N4GIX]

They work very well in cross-band repeat mode, but cannot do VHF/VHF or UHF/UHF repeat at all...

 

[Pricoxxx1]

Exactly so. Why then has TYT put these setup/programming instructions in their manual if the unit is not intended to function as a repeater in that same band mode?

 

[Pricoxxx1]

Bill, is this just false advertising? They say you can and that's supposed to be a big selling point feature. Did I get horn swaggled or is there something here for all of us to learn in the setup of this unit?

 

[Leelorr]

RE: Cross Band repeat

I have a TH7800 which I bought partly because of the Cross Band repeat capability. I have used it in this mode and it works very well. Can you tell me where you are seeing in the manual about doing "Same Band" repeat? (This function would take a huge duplexer, which would not fit in the radio...)
Sorry if you were expecting that function...

 

[Pricoxxx1]

Please read pages 18 and 24 and tell me what you think.
Gary

 

[Pricoxxx1]

They claimed in sales advertising I read before purchase that the duplexer is built in...... ?
Gary

 

[byndhlptom]

7800

Those pages appear to reference setting up the radio to operate (talk) to an external repeater.

Typical of both amateur and commercial operations, the input and output frequencies are different.

The duplexer mentioned in the manual is to allow both VHF & UHF operation at the same time (I believe that it properly is called a Diplexer?).

I saw nothing in the manual that suggested that in-band repeating was possible.

$.02

 

[Leelorr]

RE: Cross band repeat (manual)

Page 18 of the manual discusses how the radio can be used with either UHF or VHF on both sides of the radio (UHF<->VHF, UHF<->UHF, VHF<->VHF, or VHF<->UHF), This means that you can use the radio to monitor or transmit on either or both bands using both sides of the radio. It has no relationship to "Cross-Band" repeat functionality. For example, you can monitor two different frequencies or repeaters in the same band on the radio by putting one into each side. A lot of radios will only allow you to put a UHF frequency into one side of the radio for example.

Page 24 discusses the "Automatic Repeater Shift" (ARS) capability of the radio. This means that the TH7800 has been programmed to know the band plan for plus and minus shifts when setting it up to use an existing repeater. This keeps you from having to look up whether a certain repeater uses a "plus" shift or a "minus" shift for the input frequency when programming the radio.

Sorry, but neither of these functions are related in any way to the "Cross Band" repeat function.

The online manual can be found here:
http://aints.net/files/TH-7800英内0709.pdf

 

[Pricoxxx1]

I must be a little dense. Page 24 talks about Automatic Repeater Shift feature. #27 Shift on the Menu allows you to set the Offset. Please explain why you would need Shift and Offset in Cross Band repeater ops and why page 18 shows UHF-UHF Operation. Page 35 details Cross-band Repeater Operation and never mentions Shift and Offset. I don't get it......... I'll take all the $.02 I can get.....

 

[byndhlptom]

Repeater Shift and offset

Automatic shift references the radio automatically shifting either + or - depending on frequency settings.

On VHF most amateur repeater operate with a .600 MHz "shift", but there are other shifts in other countries. Commercial shifts can be all over the place. This means that when you are operating in repeater mode, the radio shifts frequency either up or down when transmitting depending on the shift direction.

Offset sets the shift value, i.e. for VHF it typically is .600MHZ, while UHF is typically 5MHz.

Per the previous response. If you have it set up for VHF-VHF, that only allows you to monitor two VHF frequencies at a time. If you tx on one, the opposite RX is muted (I hope!) or you may/will get RF feedback in the second VHF channel.

$.02

there is a pretty good explanation of repeater operation in several ARRL publications and in the Repeater Directory (both printed and online). Just do a search on "radio repeaters operation", you'll get a "boatload" of hits

 

[Pricoxxx1]

Thanks guys.
Gary

 

[N4GIX]

Frankly the only disappointment I have with the two TH-7800s that I own is that the same memory channels are shared between A and B sides.

In practical terms that makes it a bit useless to monitor a single frequency on A and scan channels in B at the same time, since unless you have A set on a VFO (tuned) frequency, whatever channel A is parked on will trigger side B also if the frequency is in use!

The radio my mobile TH-7800 replaced was the venerable Kenwood TMV-7A. On this radio you could assign a block of memory to A and the remaining block to B. Meaning that you could build two separate "scan lists" and scan on both A and B simultaneously with no doubled frequencies. I had set mine up with VHF on A and UHF on B.

 

[Pricoxxx1]

Thanks again, Bill.
Since the 7800 won't do what I bought it for.... I'll move one. I'm looking for a simple single frequency UHF repeater. Any suggestions welcome. Do you have an available CS800 controller? What do you think of the Bridgecom BCR-40U Repeater?
Gary

 

[N4GIX]

There's no such thing as a single frequency repeater. There are some 'boxes' on the market that will "store and forward" voice transmissions, but they aren't really very practical.

I'm not sure what you are asking about the CS800. It is a UHF DMR radio and the only fancy thing is a detachable face that can be installed remotely, which is how I have it installed my little Toyota Camry.

I have been running a BCR-40U for about eight months now. I like it well enough but honestly you can buy used commercial repeaters for about half the price if you are willing and able to get it tuned and set up.

The main thing that sold me on the BridgeCom is that it was delivered already tuned to my GMRS frequencies, so basically all I had to do was hook up the antenna, plug it in, and turn it on...

I had to send it back once because the duplexer they had installed wasn't filtering out the transmitter enough. The receiver was being heavily "de-sensed" because of that. They replaced the duplexer with a different brand and it's been running fine since.

I had a power surge a few months ago that killed the power supply. A quick phone call and I had a new power supply within two days. There was no charge either time because it was handled under warranty.

 

[Pricoxxx1]

You must excuse my novice naiveté and inability to speak the language.... please. I had a repeater all ready to go -- 463.5625/468.5625.... an old GE crystal fired transceiver with CS800 Controller and separate duplexer....... and then I did something stupid and killed it. That, to me, was a simple single channel repeater. That's what I'm looking to replace.

You wrote, "used commercial repeaters for about half the price". Any suggestions on where to go on that search?
Gary

 

[N4GIX]

You wrote, "used commercial repeaters for about half the price". Any suggestions on where to go on that search?
Gary

Search eBay with the key words "UHF Repeater" and you'll find dozens of listings. Read carefully.

Here is one I'd buy if I needed another one:
Motorola GR500 GM300 UHF 438-470Mhz 40W Base Repeater W/ Duplexer GMRS Warehouse
They will program your frequency pair and tune the duplexer before shipment.

Here is another one that's even portable. They too will tune before shipment:
http://www.ebay.com/itm/MOTOROLA-PO...293455?hash=item3f6c3419cf:g:ImEAAOSwNRdX7xGi