Icom IC-756 Pro 2 and ALS-600

[G0ORC]

Hi all,

Recently I have interfaced an Ameritron ALS-600 with a recently acquired IC-756 PRO 2 seemingly successfully - no initial problems at all.

Whilst making some antenna adjustments the other day I noticed that when the 756 keys the amp there is an initial slight kick of the SWR meter on the 756 - its not much and not observable on an external meter between the rig and the amp.  On a dummy load it maybe kicks to about 1.3:1 and then drops back. When the amp is on standby, the kick is not there.

I'm a little concerned on two counts - that the amp might be "hot switching" if you can use that term with a solid state amp, and two, I presume the meter of the 756 is damped somewhat and may actually be seeing a transient very high SWR for a very short time.

On a cw signal there doesn't seem to be any initial clipping of the first dot or dash, on keying in FSK RTTY the deflection seems slightly higher than if it keys the amp in AM or FM.

I don't have this problem at all with a FT-2000 attached to the same amp - so it the RF "attack" from the 756 too quick for the TX relay to completely close on the amp or is there some other issue?

Vince G0ORC

[W1QJ]

The problem is the radio seems to be putting rf before the antenna relay switches over to the amp.  It is a form of hot switching for a split second.  You should be able to go into the menu and change the delay on the rf output of the radio to give the amp relay a bit of time to switch before the rf comes out of the radio.  Surely it is a matter of milliseconds and it takes a fast meter to even see it.  An anolog meter would never catch it.

[G0ORC]

Hello,

Thanks for that - unfortunately Icom do not provide a menu item to delay the production of RF unlike Kenwood & Yaesu.  A little bit of digging around reveals that the relay on the amp needs a delay around 12 to 15ms - I can't find a definitive time for the rig but it looks like I'm goinf to need an amp sequencer, as included in the Microham Microkeyer 2.

Thanks again,

Vince G0ORC

[AD5X]

I measured the "amp-enable-to-RF out" delay on an IC-706MKIIG at about 12ms, and on an IC-7000 at about 8-10ms.  I'm guessing that the '756P2 is in that ballpark as well.  The open-frame relays in non-QSK amps take typically 15ms as you've discovered, and Icom doesn't provide an adjustable delay.  You might want to take a look at the relay-based QSK mod I did on my ALS-600 (info in the "Equipment Modifications" section of my website at www.ad5x.com).  This improves amplifier switching time to 3-5ms.

But then with faster switching you need to worry about whether the '756P2 unkeys the amp before RF has completely gone away (a problem if you operate QSK - not when operating semi break-in).  I know this can be a problem in the IC-706MKIIG, the IC-7000 and the IC-7600 - but don't know about the '756P2.  I have an article on how I solved this (ALS-600 Flexible QSK Keying Interface) in that same "Equipment Modifications" section of my website.

Phil - AD5X

[G0ORC]

Phil,

Thanks very much and a very interesting response - I suppose it was what I suspected.

I'll take a look at your website for the mod - thanks again very much....

Vince G0ORC

[NA7U]

Just FYI, I just finished Phil's relay mod to my ALS-600, which is using a K2 for the exciter, and all seems to be working quite well. Pretty easy mod to make though I had to wince a little when I was jerking out the old open frame relay, hi.

My mod described here: http://cloud-warmer.blogspot.com/2012/08/the-ameritron-als-600-qsk-mod-is-done.html

73,

Casey, TI2/NA7U