开云体育

-----Original Message-----
From: ic7000@... [mailto:ic7000@...] On Behalf Of
Steve W3AHL
Sent: Saturday, December 22, 2012 2:08 PM
To: ic7000@...
Subject: [IC-7000] Re: ALC question

Yes, the ALC indicator does tend to go to full scale and into the red zone
with compression on, but that doesn't mean it isn't creating splatter. Here
is what I see on an Agilent 8924C analyzer hooked to the 7K's HF antenna
output via a 30 dB attenuator, with 300 Hz sample bandwidth with a span of
40 KHz. The audio source was a stock HM-151 mic with a long AHHHH. Mic
gain was set at 35% with two narrow bars of ALC showing when compression is
off.

With compression on, running 80 watts PEP on 14.2 MHz and with the ALC
showing all green bars on, I see splatter +/- 20KHz or more from the
sideband peak (carrier frequency + 1.5 KHz for USB) at -40 dBc (40 dB below
carrier, which is the peak sideband level in this case).

Assuming I was running a full 100 watts, which is 50 dBm, then the IMD
products are 50 dBM -40dB = 10 dBm. Free space path loss at 30 miles from
the antenna is aobut 90dB, so stations within 30 miles would receive my
splatter at 10 dBm-90dB = -80 dBm, which is a little more than S9 on the
S-meter on a 7k with the pre-amp on. If you are running an amplifier, the
problem is of course worse.

This splatter exists when the ALC exceeds 50% of the green bars on. At 50%
ALC, the splatter is below about -55 dBc. Below 30% ALC I could not see any
splatter above -65 dBc.

Which is why I don't use compression often and am very careful with the mic
gain and background noise levels when I do. I have too many ham friends
that share the bands within a 30-mile radius.

Steve, W3AHL

--- In ic7000@..., "P.C." <pcsalley@...> wrote:

Okay Captain, The ALC indicator is only meaningful when the speech

processing (compression) is off, then ALC is adjusted with microphone gain.
Power setting changes should have not affect. Follow the manual guidance
for best result. Regards, K4PO

--- In ic7000@..., "flashover_photography" <captain206@>

wrote:

ok is the any way to adjust the ALC? and or how does it work? If I

reduce the output power from 100W the ALC goes into the red?

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