zhl 1010 before or after ZBSF-95+ fm filter

[yellingsoftly]

Originally I was planning to place the ZBSF-95+ fm filter before the zhl 1010 amplifier next to the antenna when I put my new dpd miltenna up this weekend for airband monitoring but I got to thinking with the high +45 ip3 of the zhl 1010 would it make more sense to put the zhl 1010 before the fm filter to counteract the 1.5 db loss of the fm filter? Suppose I could test this but was trying to decide which way to initially put it up and was curious if there was anyone else that had thoughts.

 

[prcguy]

The whole point of a filter is to protect the amplifier and receiver from out of band junk, put the filter before the amplifier. Typical insertion loss of the filter is about 0.6dB from 125 to 1000MHz.

 

[yellingsoftly]

The whole point of a filter is to protect the amplifier and receiver from out of band junk, put the filter before the amplifier. Typical insertion loss of the filter is about 0.6dB from 125 to 1000MHz.

ok thanks, thats what i was originally thinking but thought i would ask

 

[Ubbe]

would it make more sense to put the zhl 1010 before the fm filter to counteract the 1.5 db loss of the fm filter?

Test it at the scanner. Having both the amplifier and filter directly accessible at the scanner will make it possible to try how the scanner and amplifier reacts when you have the filter before or after the amplifier. Remember to use at least a 6dB attenuation before the scanner, one fixed 6dB or a 1-4 splitter. When you have tried monitoring different bands with the filter at different positions you can then move them to the antenna installed in the most favorable position.

I've tried this when 100 meters from a big site with 20-30 transmitter channels and using a 6dB gain antenna on the roof and never noticed the amplifier getting overloaded, it where always the scanner if the attenuation where not dialed in so didn't matter where the filter where placed but I prefer to overcome any insertion loss by using any filters after the amplifier. But test first down at the scanner.

That ZHL-1010 have an internal noise figure of 3dB, so I would try a PGA103+ with 0,8dB NF as they are only $25 and compare. Perhaps you do not need more strong handling than that and will then have 3dB more sensitivity.

/Ubbe

 

[yellingsoftly]

Test it at the scanner. Having both the amplifier and filter directly accessible at the scanner will make it possible to try how the scanner and amplifier reacts when you have the filter before or after the amplifier. Remember to use at least a 6dB attenuation before the scanner, one fixed 6dB or a 1-4 splitter. When you have tried monitoring different bands with the filter at different positions you can then move them to the antenna installed in the most favorable position.

I've tried this when 100 meters from a big site with 20-30 transmitter channels and using a 6dB gain antenna on the roof and never noticed the amplifier getting overloaded, it where always the scanner if the attenuation where not dialed in so didn't matter where the filter where placed but I prefer to overcome any insertion loss by using any filters after the amplifier. But test first down at the scanner.

That ZHL-1010 have an internal noise figure of 3dB, so I would try a PGA103+ with 0,8dB NF as they are only $25 and compare. Perhaps you do not need more strong handling than that and will then have 3dB more sensitivity.

/Ubbe

Ok thanks for the explanation. I wasn’t aware of the pga103+ I may have to keep that in mind and try it sometime after my wallet recovers lol