[VHFcontesting] Gremlins and this weekend's contest

[kr7o at vhfdx.com]

I battled this for a while with my 706mkII.  The problem is that 
Vsend/Hsend are bidirectional.  Depending on the keying circuit in your 
external device, that device could look like a ground to the accessory jack 
and key the radio.  You need to add a protection diode or build a small 
buffer keying circuit (which helps protect your accessory port also).  A 
couple of 2N3904's and a couple of resistors will do it.  The circuit at 
http://www.k6xx.com/radio/ic706amp.html solved my 706 keying issues.




>I set about making the cord.  I am 100% sure that I have isolated and used
>the #3 HSEND pin.  However, when I plug it into the transverter, it keys up
>immediately.  I wasn't hitting the PTT button.  I switched bands.  I changed
>menu settings.  I even turned the radio off and the thing is still keyed.  I
>tried the same thing with the 144 amp with the same result.  It appears that
>the pin is always grounded and therefore, any device attached to it is
>keyed.
>

73, Robert KR7O/YB2ARO, DM07ba/OI52ee  (ex.  N7STU)
kr7o at vhfdx.com

www.vhfdx.com (KR7O/YB2ARO homepages)