[amsat-bb] Re: AO-51 V/S

Bob- W7LRD w7lrd at comcast.net
Tue Apr 20 10:38:07 PDT 2010

Hi Luc and all 

I am using a Transystem 3731AA downconverter.  Also an old Kenwood TS-700A for the tunable IF.  I have compared Keps 13LNC-PH downconverter against the 3731.  The 3731 is virtually immune to desense to 2M tx as well as wifi etc.  However the Keps (pricey) is affected by the 2M tx.  Without the noise blanker turned on in the TS-700 I get lots of snapping, popping from wireless phones, wifi etc.  The noise blanker in this old 700 is superb, better that the one in my 910!  Go figure!  Mind you this is all empirical evaluation using nothing but my ears.  I have heard the filter in the 3731 is better than most.  I will be shipping some of my dc's soon to a fellow who can give a very accurate evaluation on these devices.  Hope this helps Luc, see you on S band! 

73 Bob W7LRD 

----- Original Message ----- 
From: "Luc Leblanc" <lucleblanc6 at videotron.ca> 
To: amsat-bb at amsat.org 
Cc: eu-amsat at yahoogroups.com 
Sent: Tuesday, April 20, 2010 6:14:17 AM GMT -08:00 US/Canada Pacific 
Subject: [amsat-bb] Re: AO-51 V/S 

On 20 Apr 2010 at 2:24, Bob- W7LRD wrote: 

Date sent:              Tue, 20 Apr 2010 02:24:55 +0000 (UTC) 
From:                   Bob- W7LRD <w7lrd at comcast.net> 
Subject:                [amsat-bb]  AO-51 V/S 
To:                     amsat-bb at amsat.org 

> This last pass worked W6YX and heard Kerry, WC7V.  Noticed some very deep fades. 
> 73 Bob W7LRD 

Did anyone ever tested their downconverter who is basically a receiver to measure the amouint of desense the WI-FI , spread spectrum and 
frequency hopper device and so on produce on 2.4Ghz? 

Desense is very noticeable on VHF and UHF when a transmitter is transmitting near a receiver as per i can see on a PCR-1000 scope screen 
there is always a 10db noise floor but i'm not sure if this level is not really much higher as the scope seems to not be fast enough to 
display the real peak level of all the signal on 2.4Ghz. 

If a fairly high amount of desense is always present this could explain why the downconverter is lacking sensitivity and why some normal 
fades appears deeper than they really are. And what is worse is the WI-FI QRM is also right on the received 2.4Ghz amateur band. 

Here i have to switch off my WI-FI router and my 2.4Ghz camera when i want to listen on 2.4Ghz and the camera is the worse as she give 30 
over 9 very wide  spread signal. 

Opinions are welcome. 


Luc Leblanc VE2DWE 
Skype VE2DWE 
DSTAR urcall VE2DWE 


Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author. 
Not an AMSAT-NA member? Join now to support the amateur satellite program! 
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb 

More information about the AMSAT-BB mailing list