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@videotron.ca To: amsat-bb@amsat.org Cc: eu-amsat@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@comcast.net Subject: [amsat-bb] AO-51 V/S To: amsat-bb@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 www.qsl.net/ve2dwe DSTAR urcall VE2DWE WAC BASIC CW PHONE SATELLITE
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On 20 Apr 2010 at 17:38, Bob- W7LRD wrote:
Date sent: Tue, 20 Apr 2010 17:38:07 +0000 (UTC) From: Bob- W7LRD w7lrd@comcast.net Subject: Re: [amsat-bb] Re: AO-51 V/S To: Luc Leblanc lucleblanc6@videotron.ca Copies to: eu-amsat@yahoogroups.com, amsat-bb@amsat.org
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
Hi Bob
I have the same DC but my IF is on 123mhz and i got no desense at all on 2M but that's the 2.4Ghz RF your "snapping, popping" who i think is could be reducing the RF sensitivity of the DC. The AIDC was design to received MMDS TV where channels where isolated from each other and they was no other QRM on the original band this downconverter was design for. How he's performing on a band full of QRM that i don't know and it will be something to test to see if the DC keep his same sensitivity when is QRMed on 2.4Ghz.
Adding some sort of flitration is could be a way to reduce any 2.4Ghz desense if any and what the noise blanker does is to suppress the pops and clicks but he cannot reduce the overall QRM level.
Our regular Ham receiver can be tweaked for the best reception possible but with a DC we are stuck with a static passband, no way to reduce the RF level and so on.
I don't know how wide the AIDC 3731AA front end was but to be able to receive TV signals it should be quite wide and he should pass a lot more than 15KC?
"-"
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe DSTAR urcall VE2DWE WAC BASIC CW PHONE SATELLITE
participants (2)
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Bob- W7LRD -
Luc Leblanc