kenwood TM700

kenwood TM700

[chappaz alexandre]

hi guys

I am a newbie in ham radio, and for my job I use 2 Kenwood TM700 transceivers 
for a numeric packet radio transmission (Kenwood TM700 has an build-in TNC),

 For the moment the TNC-radios are discussing in an half duplex mode - that 
means one radio emmits a packet and stops, the second radio receives the 
packet and answers and so on and so on... My problem is that in that case, 
the maximum speed is  only one packet ever half second is emmited. This is 
due (to me) to the time the radio emettor needs to bring the power up and 
running for emitting the packet. The problem is that once the packet is sent, 
the radio stops the emission, that  means it has to start up again for the 
next packet. I didn't find any mode for telling the emetor to stay up even if 
there's no packet to transmit....... So I'd like to know if someone could 
help me eather for configuring properly the built-in TNC or to use a 
soundcard modem in the same purpose 
( have numeric transmission with the less delay possible in fact ).


Thank a lot
(sorry for the not perfect english i am french)
Alex Chappaz

Re: kenwood TM700

[Dennis Boone]

 > For the moment the TNC-radios are discussing in an half duplex mode
 > - that means one radio emmits a packet and stops, the second radio
 > receives the packet and answers and so on and so on... My problem
 > is that in that case, the maximum speed is only one packet ever half
 > second is emmited. This is due (to me) to the time the radio emettor
 > needs to bring the power up and running for emitting the packet. The
 > problem is that once the packet is sent, the radio stops the emission,
 > that means it has to start up again for the next packet. I didn't
 > find any mode for telling the emetor to stay up even if there's no
 > packet to transmit.......

I've been told that the D7 radios limit window size to 1 frame.
This may or may not be true of the D700.

You probably want to experiment with the MAXFRAME command to enlarge
the window size.  Apparently the command exists on the D7, but does
nothing, so your mileage may vary.

You may also wish to check the TXDELAY setting, which comes set at
500 ms from the factory, though the radio works fine at 200-300 ms.

To the best of my knowledge, there's no way to get the radios to
transmit if there's no packet in the transmit queue.  This would
cause problems due to the way channel busy is detected.

Dennis Boone
KB8ZQZ

Re: kenwood TM700

[chuck gelm]

chappaz alexandre wrote:

>hi guys
>
>I am a newbie in ham radio, and for my job I use 2 Kenwood TM700 transceivers 
>for a numeric packet radio transmission (Kenwood TM700 has an build-in TNC),
>
> For the moment the TNC-radios are discussing in an half duplex mode - that 
>means one radio emmits a packet and stops, the second radio receives the 
>packet and answers and so on and so on... My problem is that in that case, 
>the maximum speed is  only one packet ever half second is emmited. This is 
>due (to me) to the time the radio emettor needs to bring the power up and 
>running for emitting the packet. The problem is that once the packet is sent, 
>the radio stops the emission, that  means it has to start up again for the 
>next packet. I didn't find any mode for telling the emetor to stay up even if 
>there's no packet to transmit....... So I'd like to know if someone could 
>help me eather for configuring properly the built-in TNC or to use a 
>soundcard modem in the same purpose 
>( have numeric transmission with the less delay possible in fact ).
>
>
>Thank a lot
>(sorry for the not perfect english i am french)
>Alex Chappaz
>  
>

Dear Alex Chappaz:

 I think that I understand your situation and your english is
1000 times better than my french.  ;-)

However, you did not describe your goal.  Are you trying to
increase your throughput?  It is the radio that is half-duplex
and not the TNC or computer.

 It is the TNC that is reducing the size of a packet and the
number of packets that can be sent.  The TM-700 has a
'micro' TNC and not a TNC-2 clone.  I think that it has
a limit of 128 bytes and one frame per packet.  This is
0.125 kilobytes per packet.

 A regular TNC-2 can send frames up to 256 bytes and up
to seven (7) frames for a total of 1.75 kilobytes.

 So, if you are trying to increase your data throughput,
you may need to:
Use radios capable of 'full duplex'.
Use a TNC capable of full duplex and full TNC-2 standard
 frames size and number of frames (256x7).

 Since you only mention your two radios and noboby else;
would using 802.11b devices help?

Regards, Chuck