41C on packet radio?

[Dave Britten]

I was just curious of any of the hams have ever gotten a 41C onto packet radio. I can see from the manual of the 82164A RS-232 interface that you also need the Extended IO module to use it with a 41C. This is obviously in addition to a TNC with an RS-232 port and a radio to connect it to. Can the 41C handle data fast enough to do 1200 bps packet, or do you have to step it down to 300 bps?

[Garth Wilson]

How big are the packets? I've never really looked into packet radio; but I assume that what you're considering a potential problem is the receive-buffer size. The 41 can supposedly do 150 bytes per second on HP-IL, about 3% as fast as the 71 can. Actually doing something with those bytes might be another matter.

I have the FSI164A rather than the HP82164A. It seems to be pretty rare. They two are mostly compatible, but there are some minor pros and cons to each. One advantage to the FSI unit is that the default receive-buffer size is 1024 bytes, and the manual says the max size is about 10 times as big as that of the HP unit's. With a quick scan, it has been difficult to tell if the 1024-byte default size is the max or not. (It also says you can extend the max by adding memory inside.) What is the max size of the HP unit's receive buffer?

Regarding the requirement for the Extended I/O module, I don't remember ever having to use the HP-IL commands manually. I think I've always just used the REMOTE commands. I have the XIO built into the HP-IL module, so together the two only take one port. I bought them that way, brand new, from EduCALC; and since they're together, I tend to forget which module certain instructions are in. As I look in the XIO manual now, I do see that the REMOTE, LOCAL, and NOTREM commands are in the XIO.

[Dave Britten]

Yeah, I suspect speed will be the limiting factor, unless the TNC itself provides some amount of buffering. It sounds like the packet size can be variable - I've seen numbers ranging from 256 bytes to 30KB. Would be an interesting experiment, though a rather pricey one, since I'd have to buy a TNC, an HP-IL/RS-232 adapter, and an Extended IO module.

[bbergman]

(06-25-2021 12:39 PM)Dave Britten Wrote:  Yeah, I suspect speed will be the limiting factor, unless the TNC itself provides some amount of buffering. It sounds like the packet size can be variable - I've seen numbers ranging from 256 bytes to 30KB. Would be an interesting experiment, though a rather pricey one, since I'd have to buy a TNC, an HP-IL/RS-232 adapter, and an Extended IO module.

I never tried it, even in the heydays of packet and while the 41c was still a hot item. Just seemed like easier paths (even the TRS Model 100 was easier) to success. Most TNC's honor CTRL-S/Q for stop start, so if you send those characters from the 41c, you should be able to do you own buffering. Find a Pico TNC and play around. Good luck!

Bruce AI6KL

[Dave Britten]

(06-25-2021 04:11 PM)bbergman Wrote:  I never tried it, even in the heydays of packet and while the 41c was still a hot item. Just seemed like easier paths (even the TRS Model 100 was easier) to success. Most TNC's honor CTRL-S/Q for stop start, so if you send those characters from the 41c, you should be able to do you own buffering. Find a Pico TNC and play around. Good luck!

Bruce AI6KL

My Tandy 102 will likely be the first thing I attempt to hook up if I buy a TNC. But I have to find out if there's any packet activity in my area first so I'm not just transmitting data to nobody.

[Bill (Smithville NJ)]

(06-25-2021 04:16 PM)Dave Britten Wrote:  My Tandy 102 will likely be the first thing I attempt to hook up if I buy a TNC. But I have to find out if there's any packet activity in my area first so I'm not just transmitting data to nobody.

Hi Dave,

I was a big fan of packet radio back in the day, especially TCP/IP jnos. But there really isn't much packet left in my area. The only packet is that by the APRS users.

I have used the TNC-PI on the Raspberry PI's. They work well and are reasonable in price. But you really don't need a TNC now days. You can use a software TNC modem - Direwolf Modem for the Linux system is a nice one. I have run it on Raspberry pi's to do APRS. I belive there are also sound modems for the Windows computers. You could use a software modem to see if there are any packet in the area, and then buy a real tnc if that's what you wish to use.

73
Bill WD9EQD
Smithville, NJ