900Mhz serial radio (MDR292A) - stops transmitting after x number of chars. Why?

[flyingfishfinger]

Hi,
Not sure if this is the correct forum but I'm hoping for some takers. I recently picked up a pair of old Blackbox MDR292A RS232 radios in an effort to get some data through a couple miles of forest. It's a tall order, but I'm having issues just getting them set up.

They "work" in that I can type text back and forth between two serial terminals, but if I try to send a bulk transfer (i.e a raw file through the serial terminal) the data stream stops in the same place every time.

The radios are right next to each other, so I doubt bad signal is an issue. The configuration tool only lets me adjust a handful of settings (hardware handshaking from host to modem, but NOT flow control OTA; full / half duplex, baud rate and number of retries on packet error) which I've been through to no avail.

The weird part is that for sending the same file, the data transfer always stops in the same place regardless of what baud rate I choose so it does NOT seem like a buffer overflow issue.

The company still exists, but stopped making this modem about 10 years ago so they don't have much expertise left. I do have the manual which doesn't quite go into all the details one could want, so it's also not very helpful. Apparently it also supports some set of AT commands which the manual doesn't mention (but the configuration tool has a tab for).

Does this sound familiar to anyone?

Cheers,
R

[thm_w]

What are you using for a RS232 connection, cheap USB adapter or physical port?
After how many bytes does it stop? You tried another file right.

[flyingfishfinger]

Hi,
I actually semi-solved this, I thought I deleted the topic.

I'm using Prolific USB-serial adapters. Enabling hardware flow control improves things by quite a lot, I actually succeeded in loading some basic websites using Lynx & ppp protocol over the link. It's still extremely slow for that (~1 kB/s??)  and I'm not sure where the issue is, but at least it works consistently.

R

[thm_w]

Counterfeit adapters exist, but yeah either way you'd need flow control if you are transmitting at a greater rate than the system is capable of achieving.

They say RF data rate is up to 76.8kbit so 10kB/s would be the maximum speed you'd see with a good connection.

[flyingfishfinger]

Adapters seem fine as far as I can tell. These radios require true RS232 voltages and the adapters work so I'm assuming they are OK. For the datarate, there's TCP & PPP overhead so maybe it's working as it should be.

I'm going to try SLIP as well to see if it reduces the overhead meaningfully enough to increase the speeds a bit...

R