CVS remoterx

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CVS remoterx

Ad-3
Hi,
 
I am testing the current CVS and see a new application named remoterx
Can you tell somthing about it.
I hope it is to run a second receiver on another pc with linux so you can connect to the svxlink repeater via TCP,
because that's what i'm looking for.
 
Grtz Ad PA3DPL.
 

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Re: CVS remoterx

Tobias Blomberg
On Monday 13 November 2006 22:27, Ad wrote:
> Hi,
>
> I am testing the current CVS and see a new application named remoterx
> Can you tell somthing about it.
> I hope it is to run a second receiver on another pc with linux so you can
> connect to the svxlink repeater via TCP,
> because that's what i'm looking for.

Then I can make you happy. The remoterx application is doing just that. It is
a bit experimental but worked well when I tested it a couple of months ago.
There is no audio compression so you will need more than 128kbps of
bandwidth.

Configure remoterx using the remoterx.conf (/etc/remoterx.conf or
~/.svxlink/remoterx.conf) configuration file. It looks a lot like the SvxLink
server configuration file. The RX section is exactly the same. Start remoterx
and it will sit and wait for an incoming TCP-connection. Note: There is no
access control.

It is the SvxLink server that connect to the remoterx application so in
svxlink.conf create a new receiver section.

[MyRemoteRx]
TYPE=Net
HOST=remoterx.some.domain

Then you point this out as a receiver in the logic core RX configuration
variable (RX=MyRemoteRx).

That is the simplest setup but you probably want to use the voter
functionality as well if you have more than one receiver. The voter need some
sort of signal strength detector. You might have noticed that a number is
printed after every squelch open/close. This is a signal strength estimation.
For the voter to work the estimation must be the same on all receivers. You
use two configuration variables in an RX section to calibrate the signal
level estimation, SIGLEV_SLOPE and SIGLEV_OFFSET. The goal is to make the
squelch estimation show 100 for full signal strength and 0 for no signal.
Calibrate in the following way.

1. Set SIGLEV_SLOPE to 1 and SIGLEV_OFFSET to 0 (restart SvxLink)
2. Open the squelch on the receiver and make sure it's just hearing a nice
background noise. If you are in a noisy environment, disconnect the antenna
(also disconnect the PTT) or connect to a dummy load.
3. Use another transmitter to transmit an unmodulated signal. This will be the
reference full signal strength signal. Press and release the PTT a couple of
(5) times. You will get a signal strength reading for each squelch open and
close.
4. Calculate the mean diff (open level - close level) and the mean lower
(squelch close) value
5. SIGLEV_SLOPE = 100 / (mean diff)
6. SIGLEV_OFFSET = -(mean lower) * SIGLEV_SLOPE

Note: The remote RX does not unmute until connected to the SvxLink server.

Good luck!

73 de SM0SVX / Tobias

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Re: CVS remoterx

Ad-3
Hi Tobias,
 
That is exactly what i was searching for,
because my brother is also radioamateur and lives in the same village here, we want to add there the second receiver and connect it to my repeater via internet.
About the accesscontrol we can use the firewall, what port(s) use the remoterx system?
I saw port 5210 TCP, are ther also UDP ports used?
I have also to play with the Voter signal strengths because i saw some strange behaviors like a long tx without a signal.
Thanks anyway, I have again a lot to experiment.
 
Grtz Ad PA3DPL

 
2006/11/14, Tobias Blomberg <[hidden email]>:
On Monday 13 November 2006 22:27, Ad wrote:
> Hi,
>
> I am testing the current CVS and see a new application named remoterx
> Can you tell somthing about it.
> I hope it is to run a second receiver on another pc with linux so you can
> connect to the svxlink repeater via TCP,
> because that's what i'm looking for.

Then I can make you happy. The remoterx application is doing just that. It is
a bit experimental but worked well when I tested it a couple of months ago.
There is no audio compression so you will need more than 128kbps of
bandwidth.

Configure remoterx using the remoterx.conf (/etc/remoterx.conf or
~/.svxlink/remoterx.conf) configuration file. It looks a lot like the SvxLink
server configuration file. The RX section is exactly the same. Start remoterx
and it will sit and wait for an incoming TCP-connection. Note: There is no
access control.

It is the SvxLink server that connect to the remoterx application so in
svxlink.conf create a new receiver section.

[MyRemoteRx]
TYPE=Net
HOST=remoterx.some.domain

Then you point this out as a receiver in the logic core RX configuration
variable (RX=MyRemoteRx).

That is the simplest setup but you probably want to use the voter
functionality as well if you have more than one receiver. The voter need some
sort of signal strength detector. You might have noticed that a number is
printed after every squelch open/close. This is a signal strength estimation.
For the voter to work the estimation must be the same on all receivers. You
use two configuration variables in an RX section to calibrate the signal
level estimation, SIGLEV_SLOPE and SIGLEV_OFFSET. The goal is to make the
squelch estimation show 100 for full signal strength and 0 for no signal.
Calibrate in the following way.

1. Set SIGLEV_SLOPE to 1 and SIGLEV_OFFSET to 0 (restart SvxLink)
2. Open the squelch on the receiver and make sure it's just hearing a nice
background noise. If you are in a noisy environment, disconnect the antenna
(also disconnect the PTT) or connect to a dummy load.
3. Use another transmitter to transmit an unmodulated signal. This will be the
reference full signal strength signal. Press and release the PTT a couple of
(5) times. You will get a signal strength reading for each squelch open and
close.
4. Calculate the mean diff (open level - close level) and the mean lower
(squelch close) value
5. SIGLEV_SLOPE = 100 / (mean diff)
6. SIGLEV_OFFSET = -(mean lower) * SIGLEV_SLOPE

Note: The remote RX does not unmute until connected to the SvxLink server.

Good luck!

73 de SM0SVX / Tobias

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Re: CVS remoterx

Tobias Blomberg
On Tuesday 14 November 2006 23:20, Ad wrote:
> About the accesscontrol we can use the firewall, what port(s) use the
> remoterx system?
> I saw port 5210 TCP, are ther also UDP ports used?

Yes, it use TCP port 5210. No UDP ports at the moment. The audio is also sent
via TCP. A firewall would make the system a bit more secure. Also, remoterx
only accept one client so if another try to connect, the connection will be
rejected. Since your SvxLink server will be connected most of the time, noone
else can connect. So there's just a tiny bit of security ;-)

> I have also to play with the Voter signal strengths because i saw some
> strange behaviors like a long tx without a signal.

The signal strength measurement is totally separate from the squelch
indication. The only time the signal strength estimation is done is directly
after squelch open. That is the time SvxLink choose which receiver to use. So
a bad configuration of the SIGLEV configuration variables or the voter cannot
keep the squelch open. Bad SIGLEV settings will cause the wrong receiver to
be selected.

The only thing you might have to tweak in the voter configuration is the
VOTING_DELAY. This parameter must be set sufficiently high to allow all
receivers to report their signal strength.

Note that the signal strength estimation is in no way perfect. It is affected
by if the signal is modulated or not, so for best voting push the PTT and be
quiet for maybe half a second. This will allow the signal strength estimation
to be done on an unmodulated signal. This is due to how the estimation is
done.

Basically, I have a high pass filter at 3500Hz and then I calculate the audio
energy left in the signal after the filter. The idea is that if the incoming
signal is strong, there will be little audio energy but if it is a weak
signal there will be noise which will then result in more audio energy. The
high pass filter is of course used to remove such things as speech and CTCSS
tones. Unfortunately the speech energy also spill over above 3500Hz so speech
will affect the estimator. There is room for improvement here but I must say
it work amazingly well in all its simplicity.

Normal analogue voters work in the same way but have the advantage that they
work on signals that is time synchronous. This make it possible to compare
the signals directly to eachother, removing the common part of the signal
(speech) and only leave the noise. Synchronous sampling in a loosly coupled
system, like something linked via TCP/IP, is a bit harder to accomplish.


> Thanks anyway, I have again a lot to experiment.

I hope you'll get it right :-)

73 de SM0SVX / Tobias

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