Sunday 18 April 2010

Dead Mice in the Shack!

Well - not those kind of mice, obviously.

Having spent a king's ransom (in my terms) on a used FT817ND at the NARSA Rally in Blackpool, I was unwilling to squeeze any more shekels out of the m0xpd wallet for a data cable. What's worse, I was even reluctant to buy a new Mini-DIN plug to make one up (available at Maplins under code JX04E for the princely sum of £1.39).

Fortunately, these 6-way Mini-DIN plugs -

are used on computer mice so they litter the land, ready molded to a nice length of cable! All I had to do was check that the correct connections are available and find some dead mice...

The relevant connections are as follows...

PinPS/2 MouseFT 817 Data
1DataData In
4+5VData Out (9600)
5ClockData Out (1200)

The pins of the Mini-DIN plug are numbered as follows (in this drawing, we're looking at the female jack on the back of the FT 817)...

As you can see from the table above, there are two pins labelled as "reserved" in the PS2 Mouse connections - these might be "no connections" in a mouse cable. This won't be too much of a panic for me in the case of the squelch status line (pin 6), but having no ground connection certainly would be an issue! Fortunately, this pin is paralleled with the plug "shield" on the FT817, so even if there's no cable to the mini-DIN pin 2, there is likely to be one to the plug shield.

I found a few "dead mice" (actually, the XYL found them for me)...

and examined the cabling - fortunately, of two cables investigated (one an un-shielded 6-core and the other a shielded 4-core), both gave me access to the pins on the Mini-DIN plug I needed (see table above). I ended up using the un-shielded cable, as it was easier (don't tell anybody).

I made audio connections via phone sockets, which I mounted in a small Maplins box (code FK72), found lying in the junk bin...

Then for the tricky part - I needed to hook up the cable to the COM port of my shack PC to control the PTT. Unfortunately, I hadn't any DB9 female connectors (and certainly wasn't going to spend any money, having come this far). Fortunately, the XYL came to the rescue again - for, when I said "can you find me some dead mice", she found an old three-button serial mouse with a molded female 9-pin on the end! Checking the pins on a serial mouse revealed that I had access to the two pins on the connector I needed - Ground and RTS. Phew!

I intended to make the PTT control according to the design on Jim's 2e0jps website . Unfortunately, on trying it, it didn't work (the PTT was pulled low when the RTS was at logic 0 (-11 V)). So, I had to make a trivial modification (the addition of a diode!)...

This system works for me - if you choose to copy it, you do so at your own risk (as it is neither warranted nor implied to be fit for any purpose). I have enough trouble being responsible for my own actions - I certainly won't be responsible for yours!

Here's the final cable - I added a clamp-on ferrite near the rig end to keep RF where it is allowed to be...

I tried the cable using MultiPSK and BPSK31 and had an immediate qso with Anne, oz1agn - it seems to work fine!

The FT 817 nd is certainly living up to its billing as a "do anything" rig - the only frustration is the need for a Collins filter for CW, which will require the wallet to be dusted off again!

...-.- de m0xpd

1 comment:

  1. I got my FT-817 CW filter from K8DRN. It cost $89, which is a lot less than you'll pay over here, though that was a few years ago. I don't know if he still does them.