[OZAPRS] MFJ1270 won't key up FT8100, but ok with FT897?

[Steven Heimann]

Hi Damien

I don't know if you solved this.  Sorry for the delay in replying.  I
started typing a reply some time ago but got distracted, didn't finish
it, and then forgot all about it.  Your email just got back to the top
of the pile.

I had a slightly different but, I think, related problem about a year
ago with a home brewed PC interface.

The PTT would work with some rigs but not others.  I tested the PTT on
the rigs that refused work with the PC interface by shorting the
appropriate pins on the radio's 6 pin DIN connector and they worked
fine.  I surmised the same as you that the optocoupler I was using to
control PTT was not pulling the PTT close enough to ground.  I was using
a 4N25 from Jaycar.  The 4N25 seems to be recommended on a few sites
giving info about PC interfaces.  After a bit of Googling I switched to
a CNY17-4 and all my problems disappeared.  The -4 indicates bin
selection for a current transfer ratio of >160%.  I think the CTR of the
4N25 is in the 20-50% range.

Hope this helps.

Regards
Steven  VK2BOS

On Sun, 2011-01-23 at 20:46 +1100, Damien Gardner Jnr wrote:
> Hey Folks,
> 
> This has been driving me nuts for aaages - I thought my trusty old 1270 had died, because despite pulling the PTT line low, it wasn't keying up my FT8100.. So I kept an eye out on ebay, and finally managed to snag a 1278.  That's been sitting around for a while now..  I finally plugged it in, and what do you know? That won't key up the 8100 either!   Pulling the 5-pin DIN out of the back of the MFJ, and shorting the PTT pin to ground with a pair of pliers, keys up the radio, so I know the radio *will* key up..  A small brainwave had me unplugging the cable to the laptop, from my FT897, and plugging in the cable from the MFJ.. and what do you know? It keys it up fine!  
> 
> So now I'm totally stumped!  I don't suppose anyone has come across anything like this?  Are the MFJ's for some reason not pulling the PTT 'low enough' for the 8100?  Has the 8100 gotten a little old, and is wanting 'more' of a low than the MFJ's will put out?  Or have I inadvertently bumped something at some stage on the 8100, and there's a setting I don't know about, relating to the PTT on the data port?
> 
> Any thoughts muchly appreciated, this is driving me nutso!
> 
> Cheers,
> 
> DG
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