[Moon-net] IC746 transient output spikes

[LANCE COLLISTER]

Many thanks to the many fine folks who replied with assistance to my inquiry.  It 
seems that the Icom rigs are notorious for these transients.  I know when I chatted 
with the TE Systems people yesterday, they said they had tested an IC746 recently and 
found very strong spikes on it.  Their recommendation was to drive their solid state 
amps at half power rating.

Most of the replies I received suggested running the IC746 at full output and using 
attenuators to reduce the power to the desired level of drive for the solid state 
amplifier.  This is what I have been doing in the past, and I probably will go back 
to this.  I have purchased some nice high power non-inductive resistors (amazing what 
is available these days!) and plan to build a new attenuator for the exciter.  My 
primary application with the solid state amplifier is for the 6m band, so it is not 
quite so simple as conrolling the power on 2m, where RG-58U coax is very convenient 
for that purpose ;-)

On 2m, I already use the rig on highest ouput power, and use a long length RG-58 coax 
over to my 8877 (which is quite forgiving of such power spikes anyway).  I already 
use a sequencer with my rig, but in order to protect my relays and preamps, the IC746 
is the LAST thing to turn on, so the spikes often get through the system :-(

Thanks also for the clarification regarding the ALC pin on the accessory jack on the 
rear panel of the rig.  I recall this was discussed years ago as a way to lower the 
power down below what is the normal minimum for the front panel RF control.  I think 
this is a very interesting approach, and I hope to be able to have time tomorrow 
afternoon to experiment with that.

I am investigating the Elecraft K3 for possible purchase, and this is a good question 
to ask about that rig.  Hopefully, as Leif suggested, a rig like that which is so 
highly controlled by a built in computer processor will have such spikes well 
suppressed.

Thanks again to everyone for your guidance!  It always seems there are SO MANY 
projects to do, and just not enough time to get all of them done!

Good DXing and VY 73, Lance


-- 
Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8)
P.O. Box 73
Frenchtown, MT  59834  USA
QTH: DN27UB
TEL: (406) 626-5728
URL: http://www.bigskyspaces.com/w7gj
2m DXCC #11/6m DXCC #815