[OZAPRS] TNC

Norm, VK3XCI vk3xci at aanet.com.au
Wed Jan 13 10:05:10 EST 2010


Interesting,

I've been using a 2M Quansheng for APRS for some time and I'm well aware of the 
Sleep problem. I've just never quantified it so thank you James.

The DC effect is a new one to me, but does explain some odd things. We have our 
local digi set with a TXDelay in the order of a couple of hundred milliseconds. 
My own digi(when it's running... so many things, so little time!)has 700ms. In a 
mobile situation I receive most of my  digi'd packets and occasional other 
packets. Obviously transmitting also wakes up the rx.

Those od missed packets puzzled me a bit, wonder if it's a DC audio proble? Im 
using an OT+ tracker and an old Garmin GPS12 so not rxing accurately doesn't 
really matter a lot.

BTW, defeating the sleep mode with the monitor switch really kills the battery 
life on rx as it runs the receiver and audio. Wonder if there's a 
software/firmware way of defeating it and still having a squelch




73 de Norm, VK3XCI
Mildura, Australia
The Wintersun City
QF15bt.

James Cameron wrote:
> On Tue, Jan 12, 2010 at 07:26:23PM +1030, Terry Neumann wrote:
>> There were rumours that some of the newer ultra cheap HH's apparently
>> will go into sleep mode in some APRS situations  - check this out
>> before you commit to buying one for this purpose.
> 
> For what it may be worth, I've tested a few Quansheng TG-25AT units in
> various ways a few weeks ago, and the standby mode can affect APRS on
> receive because the radio can take a while to notice the transmission
> ... because it only periodically powers the receiver.  The following
> measurements were made:
> 
> - time after mute close before radio enters standby is 7 to 8 seconds
>   (limit of reading one second),
> 
> - time between receiver activation events during standby is 0.70 seconds
>   (limit of reading 0.02s),
> 
> - times are independent of supply voltage.
> 
> If you are operating a private APRS link the delay between PTT and data
> should be 800ms more than normal, if there has been no activity for more
> than 7 seconds.  This isn't too difficult to code if you are in full
> control of your TNC firmware.
> 
> To allow the unit to work with the rest of the APRS traffic (not that I
> have any here), you can hold down the Monitor key or short it
> internally.
> 
> There's also a minor series capacitor effect on audio output that
> corrupts the curve ... it happens when the mute opens and the audio amp
> engages ... measured using Linux arecord and audacity on two units,
> settling time is 25ms before the curve has lost the DC component.
> 
> No effect on transmit.
> 
> 
> 
> ------------------------------------------------------------------------
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com 
> Version: 9.0.725 / Virus Database: 270.14.136/2616 - Release Date: 01/12/10 18:35:00
> 


More information about the OZAPRS mailing list