[App_rpt-users] Quad Radio PCI Card & Icom IC-F221s

[Stephen Rodgers]

On 02/26/2011 08:49 PM, John (WB5NFC) wrote:
> Is anyone else using a Quad Radio PCI Card with a pair of Icom IC-F221s 
> configured as a repeater? 
> 
> 
> I've worked my way through the need for a COS pull-up resistor, but I can't seem 
> to get the audio right. After setting proper deviation, I hear what sounds like 
> a lot of computer-generated hash on the transmitter and a 'ghost' signal from a 
> local commercial broadcast station in the background.  I suspect that one of my 
> problems is not using shielded cable from the Quad Card to the ICOMs. I could 
> not find the appropriate shielded cable locally, so I had hoped to get by by 
> sacrificing an old twisted-pair jumper. I crimped on a new RJ-45 with the 
> following pin-outs: 
> 
> 
> ICOM Receiver Discriminator Audio (330 mVRMS @ 100 k ohms --> Pin 1Quad Radio 
> RJ-45 
> 
> ICOM Tramsmitter (Radio Modulation IN) (330mV RMS) --> Pin 7 Quad Radio RJ-45 
> ICOM PTT -->  Pin 5 Quad Radio RJ-45 
> 
> ICOM COS  (when radio is properly programmed and a pull-up resistor is used) --> 
> Pin 2 Quad Radio RJ-45 
> 
> ICOM Ground --> Pin 8 RJ-45 
> 
> RX de-emphasis jumper is enabled and the best results seem to be obtained with 
> TX pre-emphasis enabled (even though it is not recommended). 
> 
> 
> I will be ordering shielded cable for RJ-45s Monday, but is there anything else 
> I have missed?
> 
> Thanks for any suggestions.
> 
> John / WB5NFC
> 
> 
> 
>       
> 
> 
> 
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1. Try a 20:1 attenuator on the  input capacitor to ground on the radio side. And crank up the TX audio
to get the same deviation on the TX without the attenuator.

2.If the computer is powered from the same +13.8V source as the radio you might
have a ground loop which could be causing the computer hash issue. Try powering
the computer from a separate power source to see if what you have is a ground loop.

The reason why the Pre-emphasis setting is not recommended is there is no limiting
on the Quad Radio PCI card.

Steve
WA6ZFT