Topics

PTT Overshoot

Philippe PARIS
 

Hudge one on 7000.

Test done on UHF 430 MHz, no test done on HF yet.

For information, same test done on FT1 and FTM-400 make no overshoot at all on UHF.

https://youtu.be/MidCA2EXktA

 

J.D. Barron
 

What is the point?
I think that we are looking at the overshoot of the power meter as much as anything.
It is possible that the ALC circuit is a little slow to reduce the power, but still what is the point?

Philippe PARIS
 

Hi,
As I explain I don’t see any with 2 others UHF trx, then I could imagine there is no microHam false display.
There is not point for me, except only to know they are there on my IC 7000 (perhaps it could a default in my unit).
If not only on mine, perhaps it could be a point for people using external PA, I don’t know if such peak could damage them ?
If you think this is false, then just forget my post and sorry for the disturbance done with my post. 73.

Joe
 

While I was testing a repeater amplifier I was trying to use a Wouxun KG-UV6D V2 handheld radio to provide a 1 watt signal. I noticed that it overshot the output power to a great degree until it settled down to 1 watt output.

So, there are rigs that do overshoot power output and MIGHT be a problem when driving an amplifier.

73, Joe, K1ike

On 5/26/2019 6:20 PM, Philippe PARIS wrote:
Hi,
As I explain I don???t see any with 2 others UHF trx,

Clive Jenner
 

Hi, Overshoot is important if you are driving a transverter. It could cook the input network of your transverter.

73 Clive GW0PPO

Steve W3AHL
 

Reports about the 7K's overshoot when keyed have been around since day one of production.  There are several causes.  One is due to the ALC circui's timing and is worse when running at lower power levels where ALC action is greater to reduce TX ppower output.

Another more serious case is when using compression and the click of the PTT switch on the HM-151 is greatly amplified and ALC doesn't limit it.  For examples of both see my uploaded files from 2012 & 2014:

https://groups.io/g/ic7000/files/7K%20PTT%20Spike%20with%20Compression.doc

https://groups.io/g/ic7000/files/7KCWKeyingSpike.pdf

I haven't looked at what happens in constant carrier modes, like FM.  But power spikes can certainly caused many solid state amplifiers to trigger protective circuits (or fail).

I was going to change the .doc file above to a .pdf, but don't seem to have file upload permissions.  I probably haven't uploaded anything since the Group changed to groups.io, so will contact the group owner.


Steve, W3AHL