[amsat-bb] Re: searching advice on low pass filter for 146 MHz
Hi Domenico, I8CVS, I am grateful that you took the time to look at my measurements und send me valuable advice. I have today sent our correnspondence to my contact person in SSB and keep you informed about their answers. I will also study the diagram you attached, to understand, how you solved a similar problem. This project is for me a great educational adventure ! We have a great hobby ! 73 Werner, HB9BNK Am 04.05.2011 00:36, schrieb i8cvs: Hi Werner, HB9BNK I have seen your measurement on spectrum analyser with and without the passband cavity filter but the result is not satisfactory because you need to add a notch cavity filter tuned to suck the - 20 dBm offending POCSAG signal at 147.300 MHz By the way you can solve the problem using a less know Front End Crystal Antenna Filter The above filter is a passband filter to be placed between the antenna and the preamplifier input and it's passband is very sharp and narrow and only flat for about 30 KHz after that the responce belove and upper the passband drops down for about -60 to -70 dB For example you can order a passband from 145.925 to 145.955 MHz or from 145.955 to 145.975 MHz to work OSCAR-7 You can install the filter inside the SSB Electronics preamplifier between the input coax relay and the gate of the GaAsFET and this allow you to transmit in 2 meters because on transmit the crystal filter is swithed OFF from the TX line. Alternatively you can place the crystal filter at the antenna but outside the preamplifier on a PCB into a separate box with two coax relays in order to switch OFF the filter with the purpose to transmit and to receive the full 2 meters band. There are many manufacturers as you can see on Google searching with Front End Crystal Antenna Filters but they must be ordered on request and specifications of the customer and I believe that it is a difficult task to get only one prototype. In your situation I suggest you to call by telephone Mr Barkoviak at the SSB Electronic factory because he know many crystal manufacturers in Germany and I am sure he can order the filter for you under your specifications. I know Mr Barkoviak very well and he has ordered many not standard crystals for me to be used into my SSB Electronics converters and transverters. In additions I am confident that Mr Barkoviac will be interested to know the results of your experimentation using his SSB Electronic preamplifier. Best 73 de i8CVS Domenico - Original Message - From: Werner Kullmann, HB9BNKhb9...@uska.ch To:amsat-bb@amsat.org Sent: Tuesday, May 03, 2011 12:10 PM Subject: [amsat-bb] searching advice on low pass filter for 146 MHz I received several suggestions, when I stated my problem lasst week. While exercising, I started to document my 'case' and now I would be glad, if you could have a look at my measurements: http://www.hb9bnk.ch/index.php?id=59L=1 and let me have your opinion ! I guess, that Domenico had the ultimate answer: two huge filters (if the problem can be solved at all) or Power-off of the preamplifier Thanks and 73 Werner, HB9BNK ___ Sent via AMSAT-BB@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 ___ Sent via AMSAT-BB@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
[amsat-bb] Re: searching advice on low pass filter for 146 MHz
Hi Werner, HB9BNK I have seen your measurement on spectrum analyser with and without the passband cavity filter but the result is not satisfactory because you need to add a notch cavity filter tuned to suck the - 20 dBm offending POCSAG signal at 147.300 MHz By the way you can solve the problem using a less know Front End Crystal Antenna Filter The above filter is a passband filter to be placed between the antenna and the preamplifier input and it's passband is very sharp and narrow and only flat for about 30 KHz after that the responce belove and upper the passband drops down for about -60 to -70 dB For example you can order a passband from 145.925 to 145.955 MHz or from 145.955 to 145.975 MHz to work OSCAR-7 You can install the filter inside the SSB Electronics preamplifier between the input coax relay and the gate of the GaAsFET and this allow you to transmit in 2 meters because on transmit the crystal filter is swithed OFF from the TX line. Alternatively you can place the crystal filter at the antenna but outside the preamplifier on a PCB into a separate box with two coax relays in order to switch OFF the filter with the purpose to transmit and to receive the full 2 meters band. There are many manufacturers as you can see on Google searching with Front End Crystal Antenna Filters but they must be ordered on request and specifications of the customer and I believe that it is a difficult task to get only one prototype. In your situation I suggest you to call by telephone Mr Barkoviak at the SSB Electronic factory because he know many crystal manufacturers in Germany and I am sure he can order the filter for you under your specifications. I know Mr Barkoviak very well and he has ordered many not standard crystals for me to be used into my SSB Electronics converters and transverters. In additions I am confident that Mr Barkoviac will be interested to know the results of your experimentation using his SSB Electronic preamplifier. Best 73 de i8CVS Domenico - Original Message - From: Werner Kullmann, HB9BNK hb9...@uska.ch To: amsat-bb@amsat.org Sent: Tuesday, May 03, 2011 12:10 PM Subject: [amsat-bb] searching advice on low pass filter for 146 MHz I received several suggestions, when I stated my problem lasst week. While exercising, I started to document my 'case' and now I would be glad, if you could have a look at my measurements: http://www.hb9bnk.ch/index.php?id=59L=1 and let me have your opinion ! I guess, that Domenico had the ultimate answer: two huge filters (if the problem can be solved at all) or Power-off of the preamplifier Thanks and 73 Werner, HB9BNK ___ Sent via AMSAT-BB@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 ___ Sent via AMSAT-BB@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
[amsat-bb] Re: searching advice on low pass filter for 146 MHz
Hi Werner, HB9BNK In addition to my previous message I found that KVG in Germany make Frontend crystal filters upon customer specification in the range 100 to 200 MHz. The only problem is that they are large and flat only +/- 7 KHz (14 KHz total) and the insertion loss is 7 dB http://www.kvg-gmbh.de/8.0.html?L=3 Since the gain of the SSB preamplifier is about 20 dB you can try to use the above filter for a test between the output of the SSB preamplifier and the input of tranceiver IC 910H In this configuration the gain of the preamplifier will be reduced only by the filter insertion loss of 7 dB but having available about 13 dB of preamplier gain the overall Noise Figure of the receiving system will be not deteriorated. If all goes well and the preamplifier is not overload by the POCSAG 147.300 MHz signal you can order four crystal filters to cover about 50 KHz to work OSCAR-7 By the way I believe that the above crystal filters are very costly and that two huge cavity one connected as passband filter and the other one as notch filter is less expensive for you and this is exactly what I did in my 2 meters receiver system using both cavities after a high dinamic range Norton type antenna mounted preamplifier to clean up the garbage at 145.200 MHz in my location. 73 de i8CVS Domenico - Original Message - From: Werner Kullmann, HB9BNK hb9...@uska.ch To: amsat-bb@amsat.org Sent: Tuesday, May 03, 2011 12:10 PM Subject: [amsat-bb] searching advice on low pass filter for 146 MHz I received several suggestions, when I stated my problem lasst week. While exercising, I started to document my 'case' and now I would be glad, if you could have a look at my measurements: http://www.hb9bnk.ch/index.php?id=59L=1 and let me have your opinion ! I guess, that Domenico had the ultimate answer: two huge filters (if the problem can be solved at all) or Power-off of the preamplifier Thanks and 73 Werner, HB9BNK ___ Sent via AMSAT-BB@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
[amsat-bb] Re: searching advice on low pass filter for 146 MHz
Werner Kullmann, HB9BNK expunged (hb9...@uska.ch): What an amazing responsetime on this list ! (post the question, go shopping, find valuable advice !) thank you all very much ! Since you have plenty of gainr, one cheap alternative might be to try a tuned stub inline with the feedline. -Steve N1JFU - http://n1jfu.blogspot.com - smeuse@twitter ___ Sent via AMSAT-BB@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
[amsat-bb] Re: searching advice on low pass filter for 146 MHz
Hi Steve, N1JFU A tuned stub 1/4 wave long open to the other end and inline with the feedline will be too large in responce and it will attenuate the same amount of dB both 145.900 MHz and 147.300 MHz 73 de i8CVS Domenico - Original Message - From: Steve Meuse sme...@mara.org To: Werner Kullmann, HB9BNK hb9...@uska.ch Cc: amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 8:35 PM Subject: [amsat-bb] Re: searching advice on low pass filter for 146 MHz Werner Kullmann, HB9BNK expunged (hb9...@uska.ch): What an amazing responsetime on this list ! (post the question, go shopping, find valuable advice !) thank you all very much ! Since you have plenty of gainr, one cheap alternative might be to try a tuned stub inline with the feedline. -Steve N1JFU - http://n1jfu.blogspot.com - smeuse@twitter ___ Sent via AMSAT-BB@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 ___ Sent via AMSAT-BB@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
[amsat-bb] Re: searching advice on low pass filter for 146 MHz
Werner: I EMPHATICALLY agree with the advice to turn down the gain. Improving your IMD will provide much more bang for the effort than trying to find a filter with a loaded Q of over 100 at 2m. An easy way (if imperfect) to get it right is to maximize the RF gain in the Icom radio and then adjust gain down until the preamp-on noise is only SLIGHTLY higher than preamp off. This gets you enough gain to let the preamp set system noise figure, although you still have a bit of excess. Good luck and please share your results! 73, Jim wb4...@amsat.org On 4/27/2011 1:15 PM, Werner Kullmann, HB9BNK wrote: What an amazing responsetime on this list ! (post the question, go shopping, find valuable advice !) thank you all very much ! It will be a few days, until I can get at the antenna. I will report my findings here Thanks and 73 Werner, HB9BNK ___ Sent via AMSAT-BB@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 ___ Sent via AMSAT-BB@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
