[Skimmertalk] 160M Skimmer Observations

[Ron Castro]

I use Skimmer with the Perseus SDR and while the combo shows excellent
sensitivity and copies barely audible signals on all bands, I have noticed a
problem with dynamic range.  The Perseus has excellent dynamic range, but on
strong signals, the display seems to 'smear' vertically, looking like
extreme key-clicks or wide signals many kHz wide.  This might not be a
Skimmer problem since the Perseus has to be run through RateMonkey which
uses a sample rate converter to change the 125/250/500 kHz sample rate
scheme of the Perseus to the more familiar 48/96/192 scheme used by CW
Skimmer.  On 160, I generally use 30 dB of attenuation in the Perseus and
have tried as much as 50 dB and it still copies fairly weak signals on a
simple 1/4 wave sloper.

I use Skimmer with the Perseus SDR and while the combo shows excellent
sensitivity and copies barely audible signals on all bands, I have noticed a
problem with dynamic range.  The Perseus has excellent dynamic range, but on
strong signals, the display seems to 'smear' vertically, looking like
extreme key-clicks or wide signals many kHz wide.  This might not be a
Skimmer problem since the Perseus has to be run through RateMonkey which
uses a sample rate converter to change the 125/250/500 kHz sample rate
scheme of the Perseus to the more familiar 48/96/192 scheme used by CW
Skimmer.  On 160, I generally use 30 dB of attenuation in the Perseus and
have tried as much as 50 dB and it still copies fairly weak signals on a
simple 1/4 wave sloper.


            Ron  N6IE
       www.N6IE.com

----- Original Message ----- 
From: "H Lawrence Serra" <hlserra at sbcglobal.net>
To: "Rick Walker" <rnwalker at bellsouth.net>; <skimmertalk at contesting.com>
Sent: Friday, December 04, 2009 7:12 AM
Subject: Re: [Skimmertalk] 160M Skimmer Observations


> Rick-
>
> I have the same problem with the SDR-IQ on 160m and above 15 MHz (15m and
> 10m bands). With the Skimmer, it copies very few sigs. Skimmer and SDR-IQ
> work great on 40m and 20m. I sent the SDR-IQ back to Pieter after
> performing some diagnostics with him, he changed out the above-15 MHz
> filter ckt and relay, but it still shows the same insensitivity on the 15m
> and 10m bands with the Skimmer.
>
> I use a 23 ft marine vertical with a motor-driven coil for the
> Skimmer/SDR-IQ combo. I just now tuned it to lowest SWR (1.4:1) for 160m
> for the contest this weekend. With the Skimmer on 160m all last night, it
> only copied about 20 calls. I will see if it is any more sensitive tonight
> with the ANT tuned best it can be for 160m. Since I am in San Diego right
> above the Pacific, if it is working right it should copy a lot of JAs and
> other PAC stations. You can log into its telnet spots at:
>
> n6ncskimmer.ath.cx 7300
>
> Could the lower sensitivity be an algorithm problem in Skimmer as opposed
> to an SDR-IQ sensitivity problem?
>
> 73, Larry N6NC (San Diego)
>
>
>
>