Re: in the adjustment menu i can not get the driver idle current down to the 1 amp setting


davebb123456
 

Hi 
I have ordered a new UHF fet, it should be with me in about 2weeks time,
I will let you all know when it arrives and I have fitted it,
I hope it will not be a fake,
Thanks all for your help
Thanks Dave 2E0DMB

On Mon, 25 Apr 2022, 17:59 Pasquale S via groups.io, <iw0hex=yahoo.it@groups.io> wrote:

I agree with Steve.

 

When you can not get 2.5 Ampere with UHF Adj, you have UHF mosfet with any issue. You can get power (often 15-25 watt….) but you need to fix with new mosfet RD60HUF.

 

73s Pasquale IW0HEX

 

 

Inviato da Posta per Windows

 

Da: Steve W3AHL
Inviato: lunedì 25 aprile 2022 18:14
A: ic7000@groups.io
Oggetto: Re: [ic7000] in the adjustment menu i can not get the driver idle current down to the 1 amp setting

 

Dave,
The UHF Idle Current definitely needs to be set to 2.5 amps for minimum distortion and spurious emissions.  I would suggest replacing the UHF PA FET.  There are other possible causes, but diagnosing them would be more difficult that replacing the PA.  

Setting the Idle Current establishes the FET's operating set point so that the positive and negative peaks of the RF signal aren't clipped.  There is no or minimal signal applied (thus the term "Idle"), so ALC should not be an issue.  

If you do replace the UHF PA FET, you will should perform all of the TX adjustments for the UHF band, since the newer FETs seem to have different gain than the original ones used, in my experience.  This requires applying the correct audio drive signal at seveal different levels.

Steve, W3AHL

 

Join ic7000@groups.io to automatically receive all group messages.