Luc, When using a preamp in any metropolitan area a band pass filter is needed. Helicoil types are very good for VHF. DCS makes them or build one out of the RSGB Book. QFH antennas can be made 1/4 turn to 1 turn, 1/4 wave to 1 wave all with different patterns. If done right they are a very effective antenna.
NOAA Tiros N satellites run 5 watts on 137 MHz. On 70 cm AO-51 is 1/2 W and you lose 9 dB more for the increase in frequency. You have 3dB less galactic noise on 70 cm, and another 3 dB for reduced bandwidth 37 KHz to 16 KHz. Doing the math you are comparing 5 watts of (NOAA-18) to .250 effective watts on AO-51 adjusted for noise power and frequency. A huge difference! Art, KC6UQH -----Original Message----- From: amsat-bb-boun...@amsat.org [mailto:amsat-bb-boun...@amsat.org] On Behalf Of Luc Leblanc Sent: Tuesday, June 09, 2009 8:43 AM To: amsat-bb@amsat.org Subject: [amsat-bb] Re: Another satellite-receiver option I try also to receive NOAA APT transmission with an helix but i got very marginal results even with a preamp for 137khz. The signal was better but the pagers QRM was also boosted by about a factor of 5... The only one viable solution was to use my VHF satellite beam with a PAR electronics vhf notch filter part number 5602516. Of course you should have a 50khz band pass below that results are also very marginal. I don't know if the PCR-100 is able to received at this bandwidth but the PCR-1000 can and it can be driven by WXtoimg software. P.S. My home made helix is available for 35$ plus shipping but a bit hard to securely fit inside a shipping box. pics available if needed. On 8 Jun 2009 at 23:14, Jerry Clement wrote: > I use a Hamtronics R139 Weather fax Receiver with a QFH antenna that I built for receving and decoding images from the weather birds such as NOAA 18. I never had any luck with any of my other receivers such as my Icom R20, being to narrow for this purpose, although I know of guy's who have modified receivers successfully for just this purpose. My set up may be seen on my website: www.stormchaser.cjb.net click on: Quadrifilar Helix Antenna. The page needs to be upgraded, as I use a newer laptop than the one shown. > > Jerry VE6AB > www.ve6ab.blogspot.com > _______________________________________________ "-" Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE _______________________________________________ Sent via amsat...@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 __________ Information from ESET NOD32 Antivirus, version of virus signature database 4142 (20090609) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 4142 (20090609) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com _______________________________________________ Sent via amsat...@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
